Chapter 1: The Living World: Ecosystems

1.1: Introduction to Ecosystems

• Ecosystem: A community of living (biotic) organisms interacting with the non-living (abiotic) components of their environment as a system through various nutrients and energy cycles.

Biological Populations and Communities

• Organism: A living thing that can function on its own.

• Species: Organisms that resemble each other; are similar in genetic makeup, chemistry, and behavior; and are able to interbreed and produce fertile offspring.

  • Interspecific: Means between different species.

• Population: Organisms of the same species that interact with each other and occupy a specific area.

• Community: Population of different species.

Ecological Niches

• Ecological Niche: A particular area within a habitat occupied by an organism, as well as the function of that organism within its ecological community.

• Physical environment: It influences how organisms affect and is affected by resources and competitors.

• Niche: It reflects the specific adaptations that a species has acquired through evolution.

• Characteristics of a niche include:

  • Habitat.

  • Interactions with living and nonliving factors.

  • place/role in the food web.

  • Types and amounts of resources available.

Generalists vs. Specialists Species

Interactions Among Species

• Symbiosis: A term used to describe any type of close and long-term biological interaction between two different biological organisms of the same or different species.

Symbiotic Interactions

• Amensalism: The interaction between two species whereby one species suffers and the other species is not affected.

  • Example: The black walnut tree releases a chemical that kills neighboring plants.

• Commensalism: The interaction between two species whereby one organism benefits and the other species is not affected.

  • Forms of commensalism include:

    • using another organism for transportation

    • using another organism for housing, and

    • using something that another organism created.

• Competition: It can be either intraspecific and interspecific.

  • It is the driving force of evolution whether it is for food, mating partners, or territory.

  • Intraspecific: Competition between members of the same species.

  • Interspecific: competition between members of different species.

  • Competition is prominent in predator–prey relationships, with the predator seeking food and the prey seeking survival.

• Mutualism: The interaction between two species whereby both species benefit.

• Parasitism: The interaction between two species whereby one species is benefited, and the other species is harmed.

• Predation: Predators hunt and kill their prey.

  • Opportunistic predators kill and eat almost anything.

  • Specialist predators only prey upon certain organisms.

• Saprotrophic: Saprotrophs obtain their nutrients from dead or decaying plants or animals through the absorption of soluble organic compounds.

Law of Tolerance

• Law of Tolerance: It states that the existence, abundance, and distribution of species depend on the tolerance level of each species to both physical and chemical factors.

  • Some factors can control an organism's abundance or distribution if they exceed its tolerance limits.

Limiting Factors

• Limiting Factor: Any abiotic factor that limits or prevents the growth of a population.

• Limiting factors in terrestrial ecosystems may include:

  • the level of soil nutrients,

  • the available amount of water and light, and

  • the temperature

• In aquatic ecosystems, major limiting factors may include:

  • the pH of the water,

  • the amount of dissolved oxygen, light, or

  • the degree of salinity.

Predator-Prey Relationship

• Predator-prey cycles are based on a feeding relationship between two species:

  • If the prey species rapidly multiply, the number of predators increases until the predators eventually eat so many of the prey that the prey population dwindles again.

Resource Partitioning

• Morphological partitioning: It occurs when two species share the same resource but have evolved slightly different structures to utilize the same resource

• Spatial partitioning: It occurs when competing species use the same resource by occupying different areas or habitats within the range of occurrence of the resource

• Temporal partitioning: It occurs when two species eliminate direct competition by utilizing the same resource at different times

1.2: Terrestrial Biomes

• Biomes: These are major regional or global biotic communities characterized by dominant forms of plant life and the prevailing climates

  • Temperature and precipitation are the most important determinants of biomes.

• Many places on Earth share similar climatic conditions despite being located in different areas.

• Most terrestrial biomes are identified by the plant life primarily found within them.

• The geographical distribution of the various terrestrial biomes is controlled primarily by the average air temperature and the amount of rainfall the biome receives.

Deserts

• Deserts: Defined in terms of the amount of rainfall they receive, not temperature.

  • They cover about 20% of Earth’s surface and occur where rainfall is less than 20 inches (50 cm) per year.

  • Daily extremes in temperature result from exceptionally low humidity as water vapor tends to block solar radiation.

  • Most deserts are located between 15° and 35° north and south latitudes.

  • Arctic tundra is a cold desert due to the low amount of rainfall it receives yearly.

• Succulents

  • Plants that have fleshy leaves or stems that store water.

  • They have:

    • deep roots to tap groundwater;

    • open stomata at night;

    • shallow roots to collect and store water after short rainfalls;

    • small surface areas exposed to sunlight;

    • vertical orientation to minimize exposure to the sun; and

    • waxy leaves to minimize transpiration.

• Cactus

  • They have sharp spines that create shade, reduce drying airflow, discourage herbivores and reflect sunlight.

  • They also secrete toxins into the soil to prevent interspecific completion.

• Wildflowers

  • They are are dependent on water for germination;

  • They have short life spans;

  • They perform their entire life cycle from seed to flower to seed within a single growing season; and

  • They store biomass in seeds.

• Desert animals:

  • They are generally small.

  • They are often nocturnal.

  • They have small surface areas.

  • They spend time in underground burrows where it is cold.

• Aestivation: A summer hibernation.

Forests

• Forests cover about one-third of Earth's land surface, mostly in North America, the Russian Federation, and South America, and account for 75% of gross primary productivity and plant biomass.

• Ecozones like boreal forests near the poles and tropical forests near the equator are formed by forests at different latitudes and elevations.

• Forest Layers

  • Closed canopy: Tree crowns cover more than 20% of the ground’s surface.

    • The majority (80%) of the forest biome.

  • Open canopy: Tree crowns cover less than 20% of the ground surface.

Tropical Rainforests

• Animals include numerous birds, bats, small mammals, and insects.

• Decomposition is rapid and soils are subject to heavy leaching.

• Distinct seasonality where winter is absent and only two seasons are present.

• The length of daylight is 12 hours and varies a little year-round

• Large diversity of species.

• Occur near the equator.

• Annual rainfall exceeds 80 inches (200 cm) and is evenly distributed.

• Plants are highly diverse.

• Most nutrients are rapidly assimilated and stored in plant tissue, leaving soil nutrient-poor.

• Temperature is warm to hot and varies little throughout the year.

• Tree canopy is multilayered and continuous, allowing little light penetration.

• Trees have buttressed trunks, shallow roots, and large, dark green leaves.

Temperate Deciduous Forests

• Occur in eastern North America, northeastern Asia, and western and central Europe.

• Have a distinct winter, moderate climate, and a 140–200-day growing season during four to six frost-free months.

• Temperature varies from –20°F to 85°F (–30°C to 30°C).

• Precipitation averages 30–60 inches (75–150 cm) per year.

• Fertile soil is enriched by decaying leaf litter.

• The tree canopy allows light to penetrate, resulting in well-developed and diverse understory vegetation and animal stratification.

• Oaks, hickories, beeches, hemlocks, maples, cottonwoods, elms, willows, and spring-flowering herbs are deciduous trees.

• Birds, squirrels, rabbits, skunks, deer, mountain lions, bobcats, timber wolves, foxes, and black bears live there.

• Development, land clearing, and timbering have left few temperate forests.

Temperate Coniferous Forest

• Found in temperate regions with warm summers, cool winters, and enough rainfall to support forests.

• Common in coastal areas with mild winters and heavy rainfall, or inland in drier climates or mountains.

• These forests have cedar, cypress, fir, juniper, pine, redwood, and spruce.

• These forests have two layers:

  • Overstory: The uppermost trees in a forest.

  • Understory: Layer made up of young trees, short species of trees, shrubs, and soft-stemmed plants.

• Some forests have a shrub layer.

• Grassy understories in pine forests often burn in ecologically important wildfires.

• The understory has many herbaceous and shrub species.

• Conical trees shed snow and protect branches.

• Dark green needles absorb more light for photosynthesis.

• As temperatures rise, trees can start photosynthesis with their year-round needles.

  • Needles have thick waxy coatings, waterproof cuticles, and sunken stomates.

  • Needles reduce transpiration by reducing surface area.

• In winter, when food is scarce, many animals hibernate to conserve energy and build fat in summer.

• Birds have feathers and many animals have thick fur to protect them from cold weather.

• Some animals migrate to warmer climates during the winter months.

Taiga

• Taiga: Largest terrestrial biome; found in northern Eurasia, North America, Scandinavia, and two-thirds of Siberia.

• Southern Taiga: Also known as boreal forest, consists primarily of cold-tolerant evergreen conifers with needle-like leaves, such as pines, spruces, and larches.

• Northern Taiga: It is more barren as it approaches the tree line and the tundra biome.

• The harsh climate in the taiga limits both productivity and resilience.

  • Cold temperatures, wet soil during the growing season, and needle and moss acids slow organic matter decay.

• Seasons are divided into:

  • Short, moist, moderately warm summers

  • Long, dry, freezing winters.

• Soil is thin, nutrient-poor, and acidic.

• Animals include woodpeckers, hawks, moose, bears, weasels, lynxes, deer, hares, chipmunks, shrews, and bats.

Grasslands

• Grasslands are characterized as lands dominated by grasses rather than by large shrubs or trees.

• There are two main divisions of grasslands:

  • savannas or tropical grasslands; and

  • temperate grasslands.

Savannas

• Savannas: These are grasslands with scattered individual trees and cover almost half the surface of Africa and large areas of Australia, South America, and India.

• Savannas are found in warm or hot climates with an annual rainfall of 20 to 50 inches (50–130 cm) concentrated in six to eight months, followed by a long drought when fires can occur.

• Savanna soil drains quickly and has a thin layer of humus to nourish vegetation.

  • Grass and small broad-leafed plants dominate.

  • Deciduous trees and shrubs are scattered across the open landscape.

  • Seasonal fires help savannas' biodiversity during dry and rainy seasons.

• Animals include buffaloes, elephants, giraffes, ground squirrels, hyenas, kangaroos, leopards, lions, mice, snakes, termites, and zebras.

Temperate Grassland

• Temperate Grasslands: Here grasses are the dominant vegetation, while trees and large shrubs are absent.

• Examples of temperate grasslands include

  • the veldts of South Africa,

  • the pampas of Argentina,

  • the steppes of Russia, and

  • the plains and prairies of central North America.

• Climate is characterized by hot summers and cold winters, and rainfall is moderate.

  • Taller grasses grow in wetter areas.

  • Drought and fires affect biodiversity in the savanna.

• Deep, multi-branched grass roots grow and decay in the dark, fertile soil, enriching it.

  • Rotted roots bind to soil and feed plants.

• Seasonal drought, fires, and large mammal grazing prevent woody shrubs and trees from establishing.

  • In river valleys, cottonwoods, oaks, and willows grow, along with some flowers.

• Animals include gazelles, zebras, rhinoceroses, lions, wolves, prairie dogs, rabbits, deer, mice, coyotes, foxes, skunks, badgers, blackbirds, grouses, meadowlarks, quails, sparrows, hawks, owls, snakes, grasshoppers, and spiders.

Tundra

• Tundra: It has extremely low temperatures, large repetitive population changes, limited soil nutrients, little precipitation, low biotic diversity, poor drainage, short growing and reproductive seasons, and simple vegetation structure.

• Due to the Arctic tundra's unique conditions, the biota is highly specialized and sensitive to environmental change.

  • Dead organic material functions as a nutrient pool in the tundra.

Arctic Tundra

• Arctic tundra: It circles the North Pole and extends south to the taiga, is cold, dry, and desert-like.

• Organic matter and pollutants decompose slowly in cold, dry conditions.

  • The very short growing season averages around 50 days per year.

• This biome survives because summer temperatures range from 37°F to 54°F (3°C to 12°C) and winter temperatures average –30°F (–34°C).

  • Yearly precipitation, including melting snow, is 6 to 10 inches (15 to 25 cm).

• The thin, shallow, easily compacted, nutrient-poor soil forms slowly.

  • Permafrost: A layer of permanently frozen subsoil.

  • Bogs and ponds form when water saturates the upper surface, providing moisture for cold-resistant plants like low shrubs, mosses, grasses, approximately 400 flower varieties, and lichen.

• All plants are adapted to sweeping winds and disturbances of the soil.

  • Short, clumped plants survive winter snowfall.

  • They can photosynthesize in low light and temperatures.

  • Most plants reproduce by budding and division, not by flowering.

• Food webs are simple and characterized by low biodiversity.

  • Animals are highly specialized for long, cold winters and quick breeding and raising young in summer.

  • Mammals and birds also have additional insulation from fat.

  • Due to the scarcity of food in the winter, a lot of animals hibernate or move south.

• Animals:

  • Herbivorous mammals include lemmings, caribou, Arctic hares, and squirrels.

  • Carnivorous animals include Arctic foxes, wolves, and polar bears.

  • Migratory birds include ravens, falcons, terns, snowbirds, and various species of gull. Insects include mosquitoes, flies, moths, grasshoppers, and bees.

  • Reptiles and amphibians are few or absent.

  • Fish include cod, salmon, and trout.

Alpine Tundra

• Alpine tundra: It is located on mountains throughout the world at high altitudes where trees cannot grow.

  • The growing season is approximately 180 days, with nighttime temperatures usually falling below freezing.

  • The soil in the alpine tundra is well-drained.

• Plants are very similar to those of the Arctic tundra and include grasses, dwarf trees, and small-leafed shrubs.

• Animals living in the alpine tundra include mountain goats, sheep, elk, birds, beetles, grasshoppers, and butterflies.

1.3: Aquatic Biomes

• Antarctic, marine, lakes, wetlands, and rivers and streams comprise aquatic biomes.

• Aquatic organisms get nutrients from water.

• Water allows for the effective dispersal of gametes and larvae to new areas.

• Water's thermal capacity is high, most aquatic organisms don't need to regulate temperature.

• Water buoyancy reduces the need for legs and trunks.

• Water screens out UV radiation.

Antarctic

• Antarctica has the coldest climate on Earth.

• The interior averages −70°F (−57°C), while the coast averages 14°F (−10°C).

• Antarctica's total precipitation (mostly snow) averages ~6.5 inches (166 mm) per year, with deserts in the interior receiving less than 10 inches (~250 mm).

• Rainfall is rare and usually occurs in coastal and island areas during summer.

• Antarctica's dry air and low temperatures reduce humidity.

• The ice sheet is formed from compressed snow that rarely melts.

• Winters are dark, cold, and phytoplankton-free.

• Antarctic seas are productive because summer phytoplankton grows abundantly.

  • This massive primary-producer population supports large populations of krill.

  • Krill: These are key food sources in this ecosystem and serve as food for many predators.

Marine

• Oceans cover approximately 75% of Earth’s surface and have a salt concentration of about 3%.

• Evaporation of seawater is the primary source of most of the world’s rainfall.

• Ocean temperatures affect cloud cover, surface temperature, and wind patterns.

• Marine algae and photosynthetic bacteria absorb carbon dioxide and produce oxygen in the oceans.

• Oceans have the highest net primary productivity per unit area of Earth.

Ocean Circulation

• Land dominates the Northern Hemisphere and oceans the Southern.

• Summer and winter air temperature differences are greater in the Northern Hemisphere.

  • Air and oceanic currents carry heat from the equator to the poles.

• Convection: The circular motion that occurs when warmer air or liquid rises, while the cooler air or liquid sinks.

• Wind patterns caused by tropical air flowing to the polar regions drive surface ocean currents.

• Temperature and density control deep-water, density-driven currents.

• Deeper ocean waters are colder and denser than near-surface waters.

• In the Northern Hemisphere, north-flowing ocean currents from the equator are warmer than south-flowing ones.

• Thermohaline currents drive a conveyor belt of ocean water that moves constantly, unlike most surface currents, which are driven by winds.

  • Cold, salty water sinks, while warmer water rises.

  • The Gulf Stream heats northern latitudes by entering the Norwegian Sea.

  • This water sinks because it loses heat and becomes cooler and denser.

  • Cold bottom water flows south to Antarctica and warms and rises to the surface in the Pacific and Indian Oceans.

Ocean Zones

• Littoral Zone: Also known as the intertidal zone, it is the part of the ocean that is closest to the shore.

• Neretic Zone: Also known as the sublittoral zone, this zone extends to the edge of the continental shelf.

• Photic Zone: The uppermost layer of water in a lake or ocean that is exposed to sunlight down to the depth where 1% of surface sunlight is available.

  • The layer just above the depth where the rate of carbon dioxide uptake by plants is equal to the rate of carbon dioxide production by animals.

Corals

• Corals: These are marine invertebrates that typically live in compact colonies of many identical individual polyps.

  • Polyps: Small, sac-like animals with a set of tentacles surrounding a central mouth opening and an exoskeleton made of calcium carbonate at the base.

• Most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates, commonly known as zooxanthellae, that live within their tissues.

Types of Coral Reefs

• Fringing reefs

  • They grow near the coastline around islands and continents and are separated from the shore by narrow, shallow lagoons.

  • They are the most common type of reef.

• Barrier reefs

  • These are also parallel to the coastline but are separated by deeper, wider lagoons.

  • At their shallowest point, they can reach the water’s surface, forming a “barrier” to navigation.

• Atolls

  • These are rings of coral that create protected lagoons and are usually located in the middle of the sea.

  • They usually form when islands, often the tops of underwater volcanoes, surrounded by fringing reefs, sink into the sea, or the sea level rises around them.

Lakes

• Lakes: These are large natural bodies of standing freshwater formed when precipitation, runoff, or groundwater seepage fills depressions in Earth’s surface.

• Most lakes on Earth are located in the Northern Hemisphere at higher latitudes.

• Processes that form lakes include the following:

  • Advance and retreat of glaciers that scrape depressions in Earth’s surface where water can accumulate.

  • Crater lakes formed in volcanic craters and calderas.

  • Oxbow lakes formed by erosion in river valleys.

  • Salt or saline lakes that form where there is no natural outlet or where the water evaporates rapidly.

  • Tectonic uplift of a mountain range that creates a depression that accumulates water.

• Lake Inputs include:

  • Manmade sources from outside the catchment area

  • Precipitation

  • Runoff is carried by streams and channels from the lake’s catchment area, groundwater channels, and aquifers.

• Lake Outputs include:

  • Evaporation

  • Extraction of water by humans

  • Surface waters and groundwater flow.

• Artificial lakes: These are constructed for hydroelectric power generation, recreational purposes, industrial and agricultural use, and/or domestic water supply.

• The depth to which light can reach in lakes depends on turbidity or the amount and type of suspended particles in the water.

• The material at the bottom of a lake can be composed of a wide variety of

  • inorganic materials, such as silt or sand, and/or

  • organic materials, such as decaying plant or animal matter.

Lake Zones

• Benthic Zone: The bottom of lake, organisms can tolerate cool temperatures and low oxygen levels.

• Limnetic Zone: A well-lit, open surface water, farther from shore, extends to a depth penetrated by light, occupied by phytoplankton, zooplankton, and higher animals; produces food and oxygen that supports most of a lake’s consumers

• Littoral Zone: It is shallow, close to shore, extends to depth penetrated by light; rooted and floating plants flourish

• Profundal Zone: It is deep, no-light regions, too dark for photosynthesis; low oxygen levels; inhabited by fish adapted to cool, dark waters

Types of Lakes

• Oligotrophic (Young Lake): Deep, cold, small surface area relative to depth; nutrient-poor, phytoplankton are sparse; not very productive; doesn’t contain much life; waters often very clear; and sediments are low in decomposable organic matter.

• Mesotrophic (Middle-Aged Lake): Moderate nutrient content and moderate amounts of phytoplankton; reasonably productive.

• Eutrophic (Old Lake): Shallow, warm, large surface area relative to depth;

  • Nutrient-rich, phytoplankton more plentiful and productive;

  • Waters often murky;

  • High organic matter content in benthos, which leads to high decomposition rates and potentially low oxygen.

  • Eutrophication occurs over long periods of time as runoff brings in nutrients and silt.

  • Pollution from fertilizers often causes algae populations to dramatically increase causing a decrease in the oxygen content of the water, with detrimental consequences for life in the lake.

Lake Stratification

• The stratification or layering of water in lakes is the result of density changes caused by shifts in temperature.

• The density of water increases as temperature decreases until it reaches its maximum density at about 39°F (4°C), causing thermal stratification—the tendency of deep lakes to form distinct layers in the summer months.

• Deep water is insulated from the sun and stays cool and denser, forming a lower layer called the hypolimnion.

• The surface and water near the shore are warmed by the sun, making them less dense, so that they form a surface layer called the epilimnion.

Seasonal Turnover

• Seasonal turnover: Refers to the exchange of surface and bottom water in a lake or pond that happens twice a year.

• During the summer, the sun heats water near the surface of lakes, which results in a well-defined warm layer of water occurring over a cooler one.

  • As summer progresses, temperature differences increase between the layers, and a thin middle layer, or thermocline, develops, where a rapid transition in temperature occurs.

• Fall Turnover

  • With the arrival of fall and cooler air temperatures, water at the surface of a lake begins to cool and becomes heavier.

  • During this time, strong fall winds move the surface water around, which promotes mixing with deeper water.

• As the winter approaches in areas where subfreezing temperatures are common, the lake surface temperatures approach the freezing mark.

  • Thus, as lake waters move toward freezing and reach 4°C, the water sinks to the lake bottom.

  • Colder water remains above, potentially becoming capped by an ice layer, which further prevents the winds from stirring the water mass.

• Spring Turnover

  • With spring, the surface ice begins to melt, and cold surface waters warm until they reach the temperature of the bottom waters, again producing a fairly uniform temperature distribution throughout the lake.

  • When this occurs, winds blowing over the lake again set up a full circulation system.

Wetlands

• Wetlands: These are areas that are covered with water at some point in the year and that support aquatic plants.

• High plant productivity supports a rich diversity of animal life.

• The water found in wetlands can be saltwater, freshwater, or brackish

Ecological Services of Wetlands

• Absorbing excess water from flooding or storm surges.

• Acting as carbon sinks.

• As sediment flows through a wetland from the surrounding watershed, it becomes trapped, reducing the siltation into lakes, rivers, and streams.

• Providing areas for agriculture and timber

• Providing recreational trees.

• Recharging groundwater.

• Serving as nurseries for fishes and shellfishes.

Anthropogenic Causes of Wetland Degradation

• Agriculture

  • Wetlands have been drained to utilize the rich organic soil.

  • Wetlands are drained by digging ditches.

  • This lowers the water table and dries out the wetland.

  • Consequences include salinization and soil compaction.

• Commercial Fishing

  • The depletion of native species of fish and shellfish affects the wetland food webs.

  • It may hurt marine life, habitats, and human communities that depend on ocean for survival.

• Dams and levees

  • Dams and levees block nutrient-rich sediments from entering the floodplain, harming wetlands' food webs.

  • Dam sediments prevent them from replenishing barrier islands and beach sediments.

• Development

  • Draining wetlands destroys habitats, causing bank erosion and pollution.

  • Dredging streams lowers the water table and dries nearby wetlands.

  • Water is diverted around wetlands, lowering the water table and increasing anthropogenic pollution.

  • Freshwater is depleted from wetlands for residential and commercial purposes.

• Grazing

  • Compaction, vegetation loss, and streambank destabilization result.

  • Wetland vegetation removes water through evapotranspiration, alters water and soil chemistry, provides wildlife habitats, and reduces erosion.

  • Vegetation removal can permanently alter wetland function.

• Invasive species

  • Native species cannot always compete with introduced species.

  • Common invasive species traits include:

    • fast growth,

    • rapid reproduction,

    • high dispersal ability,

    • tolerance of a wide range of environmental conditions,

    • ability to live off of a wide range of food types,

    • association with humans, and

    • prior successful invasions.

• Logging

  • Logging decreases biodiversity in wetlands as natural habitats are destroyed.

  • It can increase flooding.

• Mining

  • Mine wastes are often deposited in the floodplain.

  • It eliminates the water source of wetlands through land fractures.

• Oil exploration and spills

  • Oil exploration and spills cause a disruption in wildlife both on land and in the sea.

  • It causes pollution and erosion as part of the drilling process.

• Pumping groundwater

  • Pumping large quantities of water from springs lowers nearby groundwater.

  • It can result in the loss of wetland vegetation.

• Recreation

  • Boating, all-terrain vehicles, etc., disturb sediments.

  • It affects breeding grounds for fish and other wildlife and also produces noise pollution, which affects wildlife behavior.

• Roads and Railroads

  • Roads and railroads narrow the floodplain, increase flooding, and create low-quality wetlands upslope of the roads by interrupting surface water and groundwater flows, which reduces sediment renewal and depletes nutrients for native vegetation and higher trophic levels.

  • Lack of sediment renewal also affects fish nurseries and bird breeding grounds.

  • Dumping fill material buries hydric soil, which is permanently or seasonally saturated by water, resulting in anaerobic conditions, and lowers the water table so that water-loving plants cannot compete with upland plants.

Rivers and Streams

• The nutrient content of rivers and streams is largely determined by the terrain and vegetation of the area through which they flow and is also determined by adjacent and overhanging vegetation, the weathering of rocks in the area, and soil erosion.

• Rivers and streams move continuously in a single downhill direction, and their inputs include

  • groundwater recharge;

  • precipitation;

  • springs;

  • surface runoff; and

  • the release of stored water in ice and snowpack.

River Zones

• Source Zone

  • Contains headwaters or headwater streams and often begins as springs or snowmelt of cold, clear water with little sediment and relatively few nutrients.

  • Narrow rocky channels, creating swift currents.

  • The water has relatively high oxygen levels and may include freshwater species such as trout.

• Transition Zone

  • Contains slower, warmer, wider, and lower-elevation moving streams, which eventually join to form tributaries.

  • The water is less clear as it contains more sediment and nutrients, with the substrate beginning to accumulate silt.

  • Species diversity is usually greater than in the source zone.

• Floodplain Zone

  • As a result of large amounts of sediment and nutrients, the water is murky and warmer.

  • Tributaries join to form rivers, which empty into oceans at estuaries.

Riparian Areas

• Riparian areas: These are lands adjacent to creeks, lakes, rivers, and streams that support vegetation dependent upon free water in the soil.

• Vegetation consists of hydrophilic (water-loving) plants and trees.

1.4: Carbon Cycle

• Carbon: It is exchanged among the biosphere, geosphere, hydrosphere, and atmosphere and is the basic building block of life and the fundamental element found in carbohydrates, fats, proteins, and nucleic acids.

  • It is also found in carbon dioxide, which makes up less than 1% of the atmosphere.

• Carbon can precipitate into the ocean's deeper, more carbon-rich layers as dead soft tissue or calcium carbonate in shells.

• Carbon enters the ocean mostly by dissolving atmospheric carbon dioxide.

• One-third of soil carbon is stored in organic form.

• The creation of coral reefs and the viability of externally fertilized egg cells are disrupted by ocean acidification caused by carbon dioxide absorption.

• Due to rising CO2 concentrations, oceanic acidity may slow the natural precipitation of calcium carbonate, reducing the ocean's capacity to absorb CO2.

• The major reservoirs or “sinks” of carbon include the following:

  • Plant Matter: A portion of atmospheric carbon (~15%) is removed through photosynthesis.

  • Terrestrial Biosphere: Forests store about 90% of the planet’s above-ground carbon and about 75% of the planet’s soil carbon.

    • Old-growth forests, limestone (CaCO3), and peat store carbon long-term.

  • Oceans: The carbon in carbon dioxide dissolved in seawater is utilized by phytoplankton and kelp for photosynthesis.

    • Marine organisms also require carbon for the production of shells, skeletons, and coral.

  • Sedimentary Deposits: Limestone (CaCO3) is the largest reservoir of carbon in the carbon cycle.

    • The calcium comes from the weathering of calcium-silicate rocks, which causes the silicon in the rocks to combine with oxygen to form sand or quartz, leaving calcium ions available to form limestone.

• Carbon is released back into the atmosphere through the following:

  • Burning fossil fuels

  • Cellular respiration of plants and animals break down glucose into carbon dioxide and water.

  • Decay of organic material by the action of decomposers.

  • Incineration of wastes

  • Release of carbon dioxide by warmer ocean waters.

  • Strip mining and deep plowing

  • Volcanic eruptions

  • Weatherization of rocks.

  • When oxygen is not present, anaerobic respiration occurs and releases carbon into the atmosphere in the form of methane.

Carbon Sinks

Human Impact on the Carbon Cycle

• Before the Industrial Revolution, CO2 transfer rates through photosynthesis, cellular respiration, and fossil fuel burning were balanced.

• After the Industrial Revolution, the deforestation of old-growth forests and the combustion of fossil fuels released carbon stored in long-term carbon sinks, causing climate change and the following environmental impacts:

  • increased acidity of oceans

  • increase in atmospheric particulate matter

  • increased rate of melting of long-term water storage

  • stronger and more frequent storm events

1.5: Nitrogen Cycle

• Nitrogen makes up 78% of the atmosphere.

  • It is an essential element needed to make amino acids, proteins, and nucleic acids.

  • Other nitrogen stores include the organic matter in the soil and the oceans.

  • Though atmospheric nitrogen (N2) is abundant, it has limited use biologically, which leads to a scarcity of usable forms of nitrogen in terrestrial and aquatic ecosystems.

  • Fossil fuel combustion, inorganic fertilizer use, and wastewater and sewage production have drastically altered the nitrogen cycle.

  • Nitrogen increases water acidification, eutrophication, and toxicity.

  • It is needed for photosynthesis and plant growth in chlorophyll.

  • It’s availability affects primary production and decomposition.

  • Nitrogen is a key component in nucleic acids (DNA and RNA) and proteins.

  • It is a limiting nutrient in terrestrial ecosystems, so its presence often limits food production.

• The natural cycling of nitrogen, in which atmospheric nitrogen is converted to nitrogen oxides by lightning and deposited in the soil by rain, where it is assimilated by plants and either eaten by animals or decomposed back to elemental nitrogen by bacteria, includes the following processes:

  • Nitrogen Fixation: Atmospheric nitrogen is converted into ammonia (NH3) or nitrate ions (NO3–), which are biologically usable forms of nitrogen.

    • The key participants in nitrogen fixation are legumes, such as alfalfa, clover, and soybeans, and nitrogen-fixing bacteria known as Rhizobium.

  • Nitrification: Ammonia (NH3) is converted to nitrite (NO2–) and nitrate (NO3–), which are the most useful forms of nitrogen to plants.

  • Assimilation: Plants absorb ammonia (NH3), ammonium ions (NH4+), and nitrate ions (NO3–) through their roots.

  • Ammonification: Decomposing bacteria convert dead organisms and wastes, which include nitrates, uric acid, proteins, and nucleic acids, to ammonia (NH3) and ammonium ions (NH4+)—biologically useful forms.

  • Denitrification: Anaerobic bacteria convert ammonia into nitrites (NO2–), nitrates (NO3–), nitrogen gas (N2), and nitrous oxide (N2O) to continue the cycle.

Effects of Excess Nitrogen

• Fossil fuel combustion has sevenfold increased atmospheric nitrogen oxides (NOx), particularly nitrogen dioxide.

  • NOx produces tropospheric ozone, smog, acid rain, and nitrogen inputs to ecosystems.

• Ammonia (NH3) in the atmosphere has tripled as a result of human activities since the Industrial Revolution.

  • Ammonia acts as an aerosol and decreases air quality.

• Nitrous oxide (N2O): This greenhouse gas breaks down and destroys atmospheric ozone in the stratosphere.

  • N2O is in a large part emitted during nitrification and denitrification processes that take place in the soil.

    • Nitrification: Reduced nitrogen compounds are sequentially oxidized to nitrite and nitrate.

    • Denitrification: Reducing nitrate and nitrite to gaseous forms of nitrogen.

  • In agriculture, nitrogen-containing fertilizer emits the most N2O.

• Human activity has more than doubled the annual transfer of nitrogen into biologically available forms through:

  • biomass burning;

  • cattle and feedlots;

  • extensive cultivation of legumes;

  • industrial processes; and

  • the extensive use of chemical fertilizers and pollution emitted by vehicles and industrial plants (NOx)

1.6: The Phosphorus Cycle

• Phosphorus is essential for the production of nucleotides, ATP, fats in cell membranes, bones, teeth, and shells.

• Phosphorus is not found in the atmosphere; rather, the primary sink for phosphorus is in sedimentary rocks.

  • It is found in the form of the phosphate ion or the hydrogen phosphate ion.

  • It is slowly released from terrestrial rocks by weathering and the action of acid rain and then dissolves into the soil and is taken up by plants.

  • It is often a limiting factor for soils due to its low concentration and solubility, and it is a key element in fertilizer.

• Humans have impacted the phosphorus cycle in several ways, as follows:

  • Allowing runoff from feedlots, fertilizers, and municipal sewage plants to collect in lakes, streams, and ponds increases cyanobacteria, green algae, and aquatic plants.

    • This growth results in decreased oxygen content in the water, which then kills other aquatic organisms in the food web.

  • Applying phosphate-rich guano and other fertilizers containing phosphate to fields.

  • Clearing tropical habitats for farming, which reduces the amount of phosphorus that is readily available because it is contained in the vegetation.

  • Large-scale phosphorus-rich rock mining for inorganic fertilizers and detergents.

1.7: The Hydrologic Cycle

• Water cycle: It is powered by energy from the sun, which evaporates water from oceans, lakes, rivers, streams, soil, and vegetation.

• The oceans hold 97% of all water on the planet and are the source of 78% of all global precipitation.

• Oceans are also the source of 86% of all global evaporation, with evaporation from the sea surface keeping Earth from overheating.

• The water cycle is in a state of dynamic equilibrium by which the rate of evaporation equals the rate of precipitation.

  • Warm air holds more water vapor than cold air.

• Processes involved in the water cycle include the following:

  • Condensation: The conversion of a vapor or gas to a liquid

  • Evaporation: The process of turning from a liquid into vapor

  • Evapotranspiration: The process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants

  • Infiltration: The process by which water on the ground surface enters the soil

  • Precipitation: Rain, snow, sleet, or hail that falls to the ground

  • Runoff: Part of the water cycle that flows over land as surface water instead of being absorbed into groundwater or evaporating

Human Impact on Water Cycle

Water Distribution

• Over 70% of Earth’s surface is covered by water, with oceans holding about 97% of all water on Earth, and freshwater making up only about 3%.

• Of the freshwater that is available, most of it is trapped in glaciers and ice caps, with the rest found in groundwater, lakes, soil moisture, atmospheric moisture, rivers, and streams.

Water Properties

• A lot of energy is needed to evaporate water.

• Strong hydrogen bonds hold water molecules together.

• The temperature of water changes slowly due to its high specific heat capacity.

• Water expands when it freezes.

• Water filters out harmful UV radiation in aquatic ecosystems.

• Water has a high boiling point.

• Water is a polar molecule, which means the following:

  • Capillary action: A result of hydrogen bonding, helps tree roots take up water, allowing trees to grow as large as they do.

  • Floating ice: Essential to life near the poles, results from the different ways water molecules arrange themselves at different temperatures.

  • The polarity of water helps to dissolve many compounds.

  • Water’s polarity allows interaction with non-polar molecules.

Freshwater

• The renewal of Earth’s freshwater supply depends on the regular movement of water from Earth’s surface into the atmosphere and back again.

Freshwater Renewal Rates

Aquifers

• Aquifer: A geologic formation that contains water in quantities sufficient to support a well or spring.

• Confined “artesian well” aquifer: An aquifer below the land surface that is saturated with water.

  • As a result of impermeable material above and below the aquifer, the water is under pressure.

• Recharge zone: The surface area above an aquifer that supplies water to the aquifer.

• Unsaturated zone: The zone immediately below the land surface where the open spaces in the soil contain both water and air, but are not totally saturated with water.

• Water table: The level below which the ground is saturated with water.

Factors that Threaten Aquifers

• Aquifer depletion is primarily caused by sustained groundwater pumping.

  • When the rate of groundwater extraction is greater than the rate of aquifer recharge, the net effect is a drop in the water table.

  • Though agriculture is the largest sector responsible for aquifer depletion, domestic and municipal withdrawals also affect groundwater levels in many areas around the world.

• As human populations increase, the rates of groundwater extraction likewise increase.

• Changes in global weather patterns also reduce aquifer inputs, jeopardizing groundwater levels.

Effects of Groundwater Depletion

• Increased costs as more energy is required for pumping

• Land subsidence: The sinking of land that results from groundwater extraction.

• Water shortages: Since groundwater is the main water source for many populations, residents of these areas may experience water insecurity for domestic and agricultural needs.

• Lowering of the water table.

• Overgrazing and the resulting erosion

• Reduction of water in lakes, ponds, and streams

• Saltwater intrusion: The movement of saltwater into freshwater aquifers, which can lead to contamination.

1.8: Primary Productivity

• The ultimate source of energy is the sun.

  • Plants are able to use this light energy to create food through the process of photosynthesis.

  • Photosynthesis: The plants remove carbon dioxide from the atmosphere and use light energy to produce carbohydrates and other organic compounds:

• Plants capture light primarily through the green pigment chlorophyll, which is contained in organelles called chloroplasts.

• The energy derived from the oxidation of glucose during cellular respiration is then used to form other organic compounds such as cellulose, lipids, amino acids, and eventually proteins.

• Oxygen gas is released into the atmosphere during photosynthesis, and plants emit carbon dioxide during respiration.

• Since plants produce less carbon dioxide than they absorb, they, therefore, become net sinks of carbon.

• Factors that affect the rate of photosynthesis include:

  • carbon dioxide concentration;

  • the amount of light and its wavelength;

  • the availability of water; and

  • temperature.

1.9: Trophic Levels

• Trophic Level: The position an organism occupies in a food chain and is the number of steps it is from the start of the chain.

• Food web: The natural interconnection of food chains.

Ecological Pyramids

• Ecological pyramids: These show ecosystem properties by placing primary producers at the base and decreasing energy as species move away from them.

• In some instances, biomass pyramids can be inverted, and are often seen in aquatic and coral reef ecosystems.

  • Zooplankton has a longer lifespan than phytoplankton, so its biomass is higher.

  • One generation of zooplankton may consume several generations of phytoplankton.

  • Only 10% of a generation's biomass is transferred.

• Primary consumers have longer life spans and slower growth rates and accumulate more biomass than the producers they consume.

  • Phytoplankton lives just a few days.

  • Zooplankton eats the phytoplankton live for several weeks.

  • The fish eating the zooplankton live for several years.

• Aquatic predators also tend to have a lower death rate than the smaller consumers, which further contributes to the inverted pyramid pattern.

• Energy pyramids will always have an upright pyramid shape if all sources of food energy are included.

  • Second Law of Thermodynamics: States that as energy is transferred or transformed, more and more of it is wasted.

  • Entropy: A natural tendency of any isolated system to degenerate from an ordered state into a more disordered state.

1.10: Energy Flow and the 10% Rule

Cellular Respiration

• Heterotrophs: Organisms dependent on photosynthetic organisms.

• Cellular respiration is the opposite of photosynthesis.

  • In respiration, glucose is oxidized by the cells to produce carbon dioxide, water, and chemical energy.

  • This energy is then stored in the molecule adenosine triphosphate (ATP).

Ecological Pyramids and the 10% Rule

• Only about 10% of the energy used to move from one trophic level to the next is used to turn organic matter into tissue.

  • The remaining energy is typically lost as heat during metabolic reactions, temperature control, incomplete digestion, and waste product decay.

• Sunlight is the ultimate source of energy required for most biological processes.

  • 35% of Earth's solar energy heats water, land, and evaporates water.

  • 8% of solar energy is available to plants, 1% of which is used for photosynthesis. 15% is reflected back into space, and 80% is absorbed by Earth.

  • 10% Rule: It states that energy is lost mostly as heat from one stage to the next.

• Productivity: Refers to the rate of generation of biomass in an ecosystem and is expressed in units of mass per unit surface area (or volume) per unit time, with mass referring to dry matter or to the mass of carbon generated.

  • Productivity of autotrophs is called primary productivity.

  • Productivity of heterotrophs is called secondary productivity.

• Secondary production: The generation of biomass by heterotrophic consumers in a system, is driven by the transfer of organic material between trophic levels, and represents the quantity of new tissue created through the use of assimilated food by organisms responsible for secondary production.

Biomass Pyramids

• Biomass pyramid: It shows how much organic mass is within each trophic level.

• Marine pyramid of biomass is inverted because:

  • trophic level biomass depends on member longevity;

  • the biomass of zooplankton is greater than that of phytoplankton and predatory fish are much larger than zooplankton; and

  • the producers in ocean or aquatic ecosystems are phytoplankton and have lower mass than zooplankton.

Energy Pyramids

• Energy Pyramids: These show the proportion of energy passed from one trophic level to the next-level consumers in an ecosystem

  • The energy temporarily “trapped” within the mass of the trophic level is not counted.

Ecosystem Productivity

• Photosynthesis uses only 3% of Earth's sunlight for land plants and 1% for aquatic plants.

• Heterotrophs at all trophic levels have limited energy due to the low efficiency of solar energy conversion into carbon compound energy.

Gross Primary Production (GPP)

• Gross primary production (GPP): The rate at which plants capture and fix a given amount of chemical energy as biomass in a given length of time.

  • Primary producers use some fixed energy for cellular respiration and tissue maintenance.

Net Primary Production (NPP)

• Net primary production (NPP): The remaining fixed energy is the rate at which a ll the plants in an ecosystem produce net useful chemical energy.

  • NPP is equal to the difference between the rate at which the plants produce useful chemical energy known as gross primary productivity (GPP) and the rate (R) at which they use some of that energy during respiration.

• Open oceans collectively have the highest net primary productivity.

Chapter 2: The Living World: Biodiversity 

2.1: Introduction to Biodiversity

• Biodiversity: The variability among species, between species, and of ecosystems.

• It can be described and defined at the genetic, species, and ecosystem levels.

  • Genetic diversity: It describes the range of all genetic traits, both expressed and recessive, that make up the gene pool for a particular species.

  • Species diversity: It is the number of different species that inhabit a specific area.

  • Ecosystem diversity: It describes the range of habitats that can be found in a specific area.

• Ecosystems that have high biodiversity are characterized by the following:

  • Abundant natural resources

  • Large genetic diversity

  • Complex food webs involving a variety of ecological niches

  • Large numbers of organisms of different species

  • Large numbers of different species

• Biodiversity is important because it helps keep the environment in a natural balance.

Anthropogenic Activities That Can Reduce Biodiversity

Population Bottleneck

• Population Bottleneck: It is a large reduction in the size of a single population due to a catastrophic environmental event.

  • As a result of the smaller population, there is less genetic diversity in the gene pool for future generations.

• Minimum Viable Population Size: The number of individuals remaining after the bottleneck and how that compares to the smallest possible size at which a population can exist without facing extinction from a natural disaster.

Loss of Habitat = Loss of Specialist Species

• Generalist Species: Species that live in different types of environments and have varied diets.

  • Ex.: Raccoons: They are classified as omnivores as they are able to survive on a large variety of food types.

• Specialist Species: These species require unique resources and often have a very limited diet; they often need a specific habitat in which to survive.

  • Ex.: Giant Panda Bear: They survives almost entirely on bamboo and lives in remote bamboo forests in China.

Species Richness

• Species Richness: The number of different species (diversity) represented in an ecological community or region.

  • If individuals are drawn from different environmental conditions or different habitats, the species richness can be expected to be higher than if all individuals are drawn from similar environments.

2.2: Ecosystem Services

• Cultural Benefits

  • Sustainable fisheries and aquaculture can directly support recreational services.

  • Recreational fishing is linked to healthy aquatic ecosystems.

• Provisioning Benefits

  • Ecosystems provide diversity of materials and products

  • Livestock provide different types of raw material such as fiber (wool), meat, milk

• Regulating Benefits

  • Keep pest populations in balance through natural predators.

  • Keeps food prices lower

  • Reduces the need for pesticides

  • Achieved in ecosystems through the actions of predators and parasites as well as by the defense mechanisms of their prey.

• Supporting Benefits

  • Form new soil and renew soil fertility

  • Allows for greater crop yields, which can feed more people.

  • Reduces the need for fertilizers.

2.3: Island Biogeography

• Island: A suitable habitat for a specific ecosystem that is surrounded by a large area of unsuitable habitat.

• Island Biogeography: It examines the factors that affect the richness and diversity of species living in these isolated natural communities.

• Theory of Island Biogeography: It proposes that the number of species found on an “island” is determined by immigration and extinction of isolated populations.

• Island Biogeography is influenced by the following:

  • Degree of Isolation: Distance to the nearest island or mainland.

  • Habitat fragmentation: It occurs when a habitat is broken into pieces by development, industry, logging, roads, etc., and can cause an edge effect.

  • Habitat suitability

    • Climate

    • Initial plant and animal composition

    • The current species composition.

  • Human activity and subsequent level of disruption

  • Location relative to ocean currents

• Important Points:

  • Closer islands are also easier to find for migrating species.

  • Habitat fragmentation is currently the main threat to terrestrial biodiversity.

  • Islands closer to the mainland have more biodiversity.

  • Island biogeography is used to predict biodiversity and extinction rates in habitat fragmentation on the continents.

  • Larger islands are bigger targets, so migrating species can find them more easily.

  • Larger islands have more biodiversity.

  • Larger islands have higher populations of species and therefore lower extinction rates.

2.4: Ecological Tolerance

• Earth’s ecosystems are affected by both biotic and abiotic factors, and are regulated by the Law of Tolerance.

• Law of Tolerance: It states that the existence, abundance, and distribution of species depend on the tolerance level of each species to both physical and chemical factors within its environment.

• Each organism's success depends on a complex set of conditions, including minimum, maximum, and optimum environmental factors.

• Biological, climatic, and topographic factors affect an organism's abundance and distribution. If these exceed the organism's tolerance, species numbers will decline.

2.5: Natural Disruptions to Ecosystems

• Ecosystem: A community of organisms that interact with each other and their environment and that can change over time.

• Natural and sudden disruptions dramatically affect which species will thrive in an environment and which species will not and will possibly become extinct.

Flooding

• Kills wildlife and their food source

• Soil is no longer held in place by roots.

• Flooding can result in water-saturated soils.

  • Plant roots need oxygen, so saturated soils drown them.

• Flooding may also cause water and nutrients to run off across land surfaces.

  • Burrows, dens, and nests can be destroyed by rushing water, forcing animals to move.

• Floodplain species have adapted to occasional flooding.

  • The flooding deposits nutrient-rich sediment along stream banks.

Volcanic Eruptions

• Kills wildlife and their food source.

• Soil is no longer held in place by roots.

• Volcanic materials break down and weather to form some of Earth's richest soils, which have fed civilizations.

• Over 4.5 billion years, volcanoes and cooling magma condensed steam to create all of Earth's water.

• Volcanoes also contributed to a large portion of Earth’s early atmosphere.

• Sulfur gas and water in the atmosphere form microscopic droplets that stay in the atmosphere for years, cooling the troposphere by 2–3 degrees.

Wildfires

• Kills wildlife and their food source

• Soil is no longer held in place by roots.

• Helps the ecosystem by clearing out dead and dying vegetation to give surviving plants more light.

• Ash and charcoal left from burnt vegetation can help add nutrients to depleted soil. These nutrients provide a rich environment for surviving vegetation and sprouting seeds.

• Several plants actually require fire in their life cycles.

Earth system processes operate on a range of scales

• Episodic Process: Occurring occasionally and at irregular intervals. — El Niño and La Niña

• Periodic Process: Occurring at repeated intervals. — Tide

• Random Process: Lacking a regular pattern. — Meteorite impacts

Sea Levels

• Global sea level has changed significantly over Earth’s history, with sea level being affected by the amount and volume of available water and the shape and volume of the ocean basins.

• The temperature of ocean water, the amount of water retained in aquifers, glaciers, lakes, polar ice caps, rivers, and sea ice, the changing shape of ocean basins, tectonic uplift, and land subsidence all affect sea level.

• The primary reason for changes in sea level today is glaciers and sea ice melts caused by global warming.

• ~30% of sea-level change is due to the melting of glaciers and ice sheets on land.

• ~30% of sea-level change is due to thermal expansion—as the oceans warm (climate change), water expands.

• ~40% of sea-level change is due to coastal land subsidence (sinking).

Wildlife Migrations

• Escaping harsh weather like seeking warmer water for breeding and raising young but returning to colder water for feeding as there is more food available.

• Escaping natural disasters and their environmental aftermaths like wildfires, floods, and storm events.

• Finding natural resources for food.

2.6: Adaptations

• Adaptation: The biological mechanism by which organisms adjust to new environments or to changes in their current environment.

  • Behavioral Adaptation: Such as instincts, mating behavior, or vocalizations.

  • Physiological Adaptation: Such as methods of temperature control or how food is digested

  • Structural Adaptation: Involves physical features such as body coverings.

• Short Term Adaptations

  • Develops in response to temporary changes in the environment;

  • Involves temporary changes;

  • It is not inherited, nor does DNA change; and

  • Plays no role in evolutionary processes.

• Long-term adaptations may involve DNA changing over long time periods in response to natural selection involving evolutionary processes.

2.7: Ecological Succession

• Ecological succession: The gradual and orderly process of ecosystem development brought about by changes in community composition and the production of a climax community and describes the changes in an ecosystem through time and disturbance.

• Facilitation: When one species modifies an environment to the extent that it meets the needs of another species.

• Inhibition: When one species modifies the environment to an extent that is not suitable for another species.

• Tolerance: When species are not affected by the presence of other species.

• Pioneer Species: Earlier successional plants, generalists.

  • Pioneer Plants have short reproductive times.

  • Pioneer Animas have low biomass and fast reproductive rates.

Characteristics of Succession within Plant Communities

Primary vs. Secondary Succession

• Ecological succession: The process of change in the species structure of an ecological community over time, which can be millions of years in the case of primary succession or decades in the case of secondary succession.

• Primary succession: The evolution of a biological community’s ecological structure in which plants and animals first colonize a barren, lifeless habitat.

• Secondary succession: A type of ecological succession in which plants and animals recolonize a habitat after a major disturbance.

Ecological Succession in a Disturbed Ecosystem

• Ecological disturbance: An event or force that can result in mortality to organisms and changes in the spatial patterns in their ecosystem and plays a significant role in shaping the structure of individual populations within the ecosystem.

• The impact that a disturbance has on an ecosystem depends upon:

  • Intensity and frequency

  • Season

  • Size and spatial pattern

  • Topography

• Succession: A directional, non-seasonal, cumulative change in the types of plant species that occupy a given area over time, involving colonization, establishment, and extinction, shows how an ecosystem changes after an ecological disturbance.

• Species Richness generally increases as succession proceeds and generally peaks when it reaches the climax community, but the diversity growth rate gradually slows down as succession advances to the climax community.

  • Species richness: The number of different species represented in an ecological community.

• In the early stages of succession, gross productivity is low due to the initial environmental conditions and low numbers of producers.

• In later stages of succession near the climax community, gross productivity (GP) may be high, but increased respiration (R) balances it, so net productivity approaches zero and the gross production respiration (GP:R) ratio approaches 1:1.

• Changes that occur during succession include the following:

  • Biodiversity increases and then falls as the climax community is reached.

  • The biomass production respiration ratio falls.

  • Early stages of succession have few species.

  • Energy flow becomes more complex.

  • NPP and GPP rise and then fall.

  • Soil depth, humus, water-holding capacity, mineral content and cycling increase.

  • Species-diversity increase continues until a balance is reached between:

    • existing species to expand their range;

    • possibilities for new species to establish; and

    • local extinction.

  • Species diversity increases with succession.

  • The size of organisms increases.

Keystone Species

• Keystone species: A species whose very presence contributes to a diversity of life and whose extinction would lead to the extinction of other forms of life.

• Examples:

  • Certain bat species pollinate critical trees in the rainforest and help disperse their seeds.

  • Grizzly bears transfer nutrients from oceanic to forest ecosystems.

  • Prairie dog burrowing aerates the soil and improves soil structure, while other animals use prairie dog burrows for shelter and hibernation.

  • Sea stars prey on sea urchins, mussels, and other shellfish that have no other natural predators, keeping their populations in check.

Indicator Species

• Indicator species: These are organisms whose presence, absence, or abundance reflects a specific environmental condition and can indicate the health of an ecosystem.

• Examples:

  • Caddisflies, mayflies, and stoneflies require high levels of dissolved oxygen in the water

  • Lichens —some species indicate air pollution

  • Mollusks indicate water pollution

  • Mossesindicate acidic soil

  • Sludge worms indicate stagnant, oxygen-poor water

Chapter 3: Populations

3.1: Generalists and Specialists Species

3.2: K-Selected & R-Selected Species

3.3: Survivorship Curve

• Survivorship curves: It show age-distribution characteristics of species, reproductive strategies, and life history.

• Reproductive success: It is measured by how many organisms are able to mature and reproduce, with each survivorship curve representing a balance between natural resource limitations and interspecific and intraspecific competition.

Survivorship Curves Table Guide

• Type I - Late Loss

  • Reproduction occurs fairly early in life, with most deaths occurring at the limit of biological life span.

  • Low mortality at birth with a high probability of surviving to advanced age.

  • Death rates decrease in younger years due to advances in prenatal care, nutrition, disease prevention, and cures, including immunization.

  • Examples: humans, annual plants, sheep, and elephants.

• Type II - Constant Loss

  • Individuals in all age categories have fairly uniform death rates, with predation being the primary cause of death.

  • Typical of organisms that reach adult stages quickly.

  • Examples: rodents, perennial plants, and songbirds.

• Type III - Early Loss

  • Typical of species that have great numbers of offspring and reproduce for most of their lifetime.

  • Death is prevalent for younger members of the species due to environmental loss and predation and declines with age.

  • Examples: sea turtles, trees, internal parasites, fish, and oysters.

3.4: Carrying Capacity

• Carrying capacity (K): It refers to the number of individuals that can be supported sustainably in a given area.

  • It varies from species to species and is subject to changes over time. As an environment degrades, the carrying capacity decreases.

• Factors that keep population sizes in balance with the carrying capacity are called regulating factors and include the following:

  • Amount of sunlight available

  • Food availability

  • Nutrient levels in soil profiles

  • Oxygen content in aquatic ecosystems

  • Space

3.5: Population Growth and Resource Availability

Population Dispersal Patterns

• Population dispersal pattern: It is how individuals or species of animal become distributed in different spaces over certain periods of time.

• Clumped: Some areas within a habitat are dense with organisms, while other areas contain few members.

  • Found in environments with “patch” resources.

  • Living in groups provides advantages and is common for animals.

  • Examples include the following:

    • Animals living in social families.

    • Animals that feel safer living in groups

    • Animals that serve as prey

    • Animals that work together to trap or corner prey.

    • Animals with inability of their offspring to independently move from their habitat.

• Random: Occurs in habitats where environmental conditions and resources are consistent.

  • There is little interaction among members of the population.

  • Individuals are distributed randomly; occurs with dandelions and other plants that have wind-dispersed seeds.

• Uniform: Space is maximized between individuals to minimize competition.

Biotic Potential

• Biotic potential: The maximum reproductive capacity of an organism under optimum environmental conditions.

• Environmental Resistance: Any factor that inhibits an increase in the number of organisms in the population.

Factors That Influence Biotic Potential

J-Curves and S-Curves

• J-Curve: It represents a population growth occurs in a new environment when the population density of an organism increases rapidly in an exponential or logarithmic form, but then stops abruptly as environmental resistance or another factor suddenly impacts the population growth.

  • This type of population growth rate is known as “density dependent,”a the regulation of the growth rate is not tied to the population density until the resources are exhausted and the population growth crashes.

• S-Curve: It occurs when, in a new environment, the population density of an organism initially increases slowly but then stabilizes due to the finite amount of resources available.

  • This slowing of the growth rate reflects the increasing environmental resistance, which becomes proportionately more significant at higher population densities.

  • This type of population growth is termed “density dependent” since the growth rate depends on the number of organisms in the population.

  • This point of stabilization is known as the carrying capacity of the environment, and it denotes the point at which the upward growth curve begins to level out

Feedback Loops

• Positive feedback loops stimulate change and are responsible for sudden or rapid changes within ecosystems.

  • When part of the system increases, another part of the system also changes in a way that makes the first part increase even more.

• Negative feedback loops often provide stability.

  • Limiting factors can cause a negative feedback loop because populations cannot exceed the ecosystem's carrying capacity.

  • Predators and prey maintain population stability by keeping animal populations within the carrying capacity of their environment.

  • More prey means more energy for predators, which leads to more predators and fewer prey.

Limiting Factors

• Limiting Factor: It can be any resource or environmental condition that limits the abundance, distribution, and/or growth of a population.

• Based on Liebig’s law of the minimum, even if all other factors are favorable, the one that is least favorable will dictate the growth, abundance, or distribution of the population of a species.

• Density-dependent limiting factors: These are factors whose effects on the size or growth of the population vary with the density of the population.

• Density-independent factors: These are factors that limit the size of a population, and their effects are not dependent on the number of individuals in the population.

Rule of 70

• Rule of 70: It helps to explain the time periods involved in exponential population growth occurring at a constant rate.

• Doubling time: It is the amount of time it takes for a population to double in size.

• To find how long it takes for a population to double in size we can use the following formula: dt= 70/r

• Key points to remember about population doubling times are as follows:

  • Populations cannot double forever.

  • The growth rate varies considerably among organisms.

  • The larger the growth rate (r), the faster the doubling time.

Important Population Formulas

• Birth Rate (%) = [(total births/total population)] × 100

• Crude Birth Rate (CBR) = [(b ÷ p) × 1,000]

• Death Rate (%) = [(total deaths/total population)]× 100

• Crude Death Rate (CDR) = [(d ÷ p) × 1,000]

• Doubling Time = 70/% growth rate

• Emigration = number leaving a population

• Global Population Growth Rate (%) = [(CBR – CDR)]/10

• Immigration = number entering a population

• National Population Growth Rate (%) = [(CBR + immigration) – (CDR + emigration)]/10

• Percent Rate of Change = [(new # - old #)/old #] × 100

• Population Density = total population size/total area

• Population Growth Rate (%) =

Impacts of Population Growth

• Biodiversity

  • Biodiversity sustains agriculture and medicine.

  • Yet, two-thirds of the world's species are in decline due to human activity.

• Coastlines and Oceans

  • High population densities and urban development stress half of coastal ecosystems.

  • Ocean fisheries are overexploited, estuaries (sea nurseries) are being drained and filled in due to population growth, and fish catches are down.

• Forests

  • Nearly half of the world's original forest cover has been lost, and 16 million hectares are cut, bulldozed, or burned annually.

  • Forests sustain ecosystems and contribute $400 billion to the global economy.

  • However, demand for forest products may exceed sustainable consumption by 25%.

• Food Supply and Malnutrition

  • 25% of the world is malnourished.

  • In 64 of 105 developing countries, especially in Africa, Asia, and parts of Latin America, population growth has outpaced food supply.

  • Population pressures have degraded two billion hectares of arable land—the size of Canada and the US combined.

• Freshwater

  • The supply of freshwater is finite.

  • The demand is soaring as the population grows and per-capita use rises.

• Global Climate Change

  • Earth’s surface is warming due to greenhouse gas emissions, largely from burning fossil fuels.

  • If the global temperature rises as predicted, sea levels will rise by several meters, causing widespread flooding, droughts, and agricultural disruption.

• Public Health

  • Over 12 million people die each year from dirty water and poor sanitation, mostly in developing nations.

  • Air pollution kills nearly three million more.

  • Heavy metals and other contaminants also cause widespread health problems.

  • Tobacco-related diseases kill more people than AIDS, tuberculosis, road accidents, murder, and suicide combined.

• Unequal distribution of wealth and governmental priorities

  • Due to government priorities, financial constraints, and special interest groups, rapid population growth can make it politically difficult for countries to raise living standards and protect the environment.

  • As a country's population grows, wealth must be redistributed, lowering GDP per capita.

3.6: Age-Structure Diagrams

• Age-structure diagrams: These are determined by birth rate, generation time, death rate, and sex ratios.

• Pyramid-shaped age-structure diagram: It indicates that the population has high birth rates and the majority of the population is in the reproductive age group

• Bell shape age-structure diagram: It indicates that pre-reproductive and reproductive age groups are more nearly equal, with the post-reproductive group being smallest due to mortality.

  • This is characteristic of stable populations.

• Urn-Shaped age-structure diagram: It indicates that the post-reproductive group is largest and the pre-reproductive group is smallest, a result of the birth rate’s falling below the death rate, and is characteristic of declining populations

3.7: Total Fertility Rate

• Total fertility rate (TFR): The average number of children that each woman will have during her lifetime.

• Declines in fertility rates can be attributed to several factors, as follows:

  • As developing countries transition to developed countries, there is greater access to primary healthcare and family-planning services.

  • Female educational opportunities are increasing.

  • Many “millennials” are postponing marriage until their careers are established.

  • More individuals desire to increase their standard of living by having fewer children.

  • The number of females in the workforce has increased.

  • There is greater personal acceptance and government encouragement of contraception.

  • Urbanization results in a higher cost of living and reduces the need for extra children to work on farms.

Worldwide Total Fertility Rate

3.8: Human Population Dynamics

• Several factors have reduced human death rates, as follows:

  • Increased food and more efficient distribution, resulting in better nutrition

  • Improvements in medical and public health programs, resulting in better access to anesthetics, antibiotics, and vaccinations

  • Improvements in sanitation and personal hygiene

  • Improvements in the safety of water supplies

• The human population has had four surges in growth as a result of the following:

  • The use of tools (3.5 million years ago)

  • The discovery of fire (1.5 million years ago)

  • The first agricultural revolution, which allowed the change from hunting and gathering to crop growing (~ 10,000 B.C.E.)

  • The industrial and medical revolutions (within the last ~ 200 years).

Human Population Growth

• Before Agricultural Revolution

  • ~ 1 million to 3 million humans.

  • Hunter-gatherer lifestyle.

  • Earth Wisdom: Natural cycles that can serve as a model for human behavior.

• 8000 B.C.E. to 5000 B.C.E.

  • ~ 50 million humans.

  • Increases due to advances in agriculture, domestication of animals, and the end of a nomadic lifestyle.

  • Earth Wisdom

• 5000 B.C.E. to 1 B.C.E.

  • ~ 200 million humans.

  • Rate of population growth during this period was about 0.03 to 0.05%, compared with today’s growth rate of 1.3%.

  • Frontier Worldview: Viewed undeveloped land as a hostile wilderness to be cleared and planted, then exploited for its resources as quickly as possible.

• 0 C.E. to 1300 C.E.

  • ~ 500 million humans.

  • Population rate increased during the Middle Ages because new habitats were discovered.

  • Factors that reduced population growth rate during this time were famines, wars, and disease

  • Frontier Worldview

• 1300 C.E. to 1650 C.E.

  • ~ 600 million humans.

  • Plagues reduced population growth rate.

  • Up to 25% mortality rates are attributed to the plagues that reached their peak in the mid-1600s.

• 1650 C.E. to present

  • Currently ~ 7.5 billion humans.

  • In 1650 C.E., the growth rate was ~ 0.1%.

  • Today it is ~ 1.2%.

  • Healthcare, health insurance, vaccines, medical cures, preventative care, advanced drugs and antibiotics, hygiene and sanitation, agriculture and distribution, and education have increased growth.

  • Planetary Management: Beliefs that as the planet’s most important species, we are in charge of Earth.

    • We will not run out of resources because of our ability to develop and find new ones.

    • The potential for economic growth is essentially unlimited.

    • Our success depends on how well we manage Earth’s life-support systems mostly for our own benefit.

• Present to 2050 C.E.

  • Estimates are as high as 9.8 billion.

  • Earth Wisdom: Beliefs that nature exists for all Earth’s species and we are not in charge of Earth; resources are limited and should not be wasted.

    • We should promote Earth-sustaining economic growth and learn from nature how Earth sustains itself.

3.9: Demographic Transition

• Demographic transition: It is the transition from high birth and death rates to lower birth and death rates as a country or region develops from a pre-industrial to an industrialized economic system.

• Stage 1: Pre-Industrial (High Stationary)

  • Poor agricultural practices, pestilence, and living conditions make food scarce and medical care is poor.

  • High birth rates replace high mortality, resulting in low population growth.

  • Sub-Saharan Africa has 54% of the world's AIDS-HIV cases but only 6% of the population.

  • Since 2010, drug therapy has reduced new infections by 28% and death rates by 44% in the region.

• Stage 2: Transitional (Early Expanding)

  • This stage occurs after the start of industrialization.

  • Hygiene, medical advances, sanitation, cleaner water, vaccinations, and higher education lower the death rate, resulting in a significant population increase.

  • Population rises rapidly.

• Stage 3: Industrial (Late Expanding)

  • Urbanization reduces economic incentives for large families.

  • Urban families are increasingly discouraged from having large families as costs rise.

  • Female education and employment lower birth rates.

  • Leisure time and food are not priorities.

  • Retirement safety nets reduce parents' need for more children.

  • Economic pressures lower the birth rate until it approaches the death rate.

• Stage 4: Post-Industrial (Low Stationary)

  • Population growth is zero when birth and death rates are equal.

  • The standard of living is higher, and birth and death rates are low.

  • In some countries, birth rates are lower than mortality rates, resulting in population losses.

• Stage 5: Sub-Replacement Fertility (Declining)

  • Some theorists believe a fifth stage is needed to represent countries with sub-replacement fertility.

  • Death rates exceed birth rates in most European and East Asian nations.

  • Unless mass immigration continues, population aging and decline will occur in this stage.

Chapter 4: Earth Systems and Resources

4.1: Plate Tectonics

• Plate tectonic theory: It states that Earth’s lithosphere is divided into a small number of plates that float on and travel independently over the mantle, with much of Earth’s seismic activity occurring at the boundaries of these plates.

Continental Drift

• In 1915, Alfred Wegener proposed that all present-day continents originally formed one landmass he called Pangaea.

• Wegener believed that this supercontinent began to break up into smaller continents around 200 million years ago.

• He based his theory on the following six factors:

  • Fossils of extinct land animals were found on separated landmasses.

  • Fossilized tropical plants were discovered beneath Greenland’s ice caps.

  • Glaciated landscapes occurred in the tropics of Africa and South America.

  • Similarities existed in rocks between the east coasts of North and South America and the west coasts of Africa and Europe.

  • The continents fit together like pieces of a puzzle.

  • Tropical regions on some continents had polar climates in the past, based on paleo-climatic data.

Seafloor Spreading Theory

• During the 1960s, alternating patterns of magnetic properties were discovered in rocks found on the seafloor.

• Similar patterns were discovered on either side of mid-oceanic ridges found near the center of the oceanic basins.

• Dating of the rocks indicated that as one moved away from the ridge, the rocks became older, and suggested that new crust was being created at volcanic rift zones.

• The lithosphere is the solid, outer part of the Earth and is broken into huge sections called plates, which are slowly moving.

  • When one plate moves beneath another (subduction) or when two plates converge, it can result in earthquakes and volcanoes.

• Subduction zones: These are areas on Earth where two tectonic plates meet and move toward each other, with one sliding underneath the other and moving down into the mantle.

Types of Boundaries

• Convergent Boundaries: These occur where two plates slide toward each other.

  • Commonly forming either:

    • a subduction zone, where one plate moves underneath the other; or

    • an orogenic belt, if the two plates collide and compress.

  • When a denser oceanic plate subducts a less dense continental plate, an oceanic trench may form on the ocean side and a mountain range on the continental side.

  • Ex.: Cascade Mountain Range

• Divergent Boundaries: These occur when two plates slide apart from each other.

  • It can create massive fault zones in the oceanic ridge system and areas of frequent oceanic earthquakes.

    • Examples:

      • Oceanic Divergent Boundary — Mid-Atlantic Ridge and the East Pacific Rise;

      • Continental Divergent Boundary — East African Great Rift Valley

  • When two oceanic plates converge, they create an island arc — a curved chain of volcanic islands rising from the deep seafloor and near a continent.

    • They are created by subduction processes and occur on the continental side of the subduction zone.

    • Their curve is generally convex toward the open ocean.

    • A deep undersea trench is located in front of such arcs where the descending plate dips downward.

  • When two continental plates collide, mountain ranges are created as the colliding crust is compressed and pushed upward.

• Transform boundaries: These occur where plates slide past each other in opposite directions.

  • The friction and stress buildup from the sliding plates frequently causes earthquakes, a common feature along transform boundaries.

  • Example: The San Andreas fault.

  • 4.2: Soil Formation and Erosion

    Soil

    • Soils: These are a thin layer on top of most of Earth’s land surface.

      • This thin layer is a basic, natural resource, and its characteristics deeply affect every other part of the ecosystem.

    • Soils are composed of three main ingredients:

      • Minerals of different sizes

      • Open spaces that can be filled with air or water

      • Organic materials from the remains of dead plants and animals

    • Soil Profile

      • Surface Litter: Leaves and partially decomposed organic debris.

      • Topsoil: Organic matter, living organisms, and inorganic materials; it is very thick in grass lands.

      • Zone of leaching: Dissolved and suspended materials move downward.

      • Subsoil: Tends to be yellowish in color due to the accumulation of iron, aluminum, humic compounds, and clay leached from A and E horizons.

      • Weathered Parent Material: Partially broken-down inorganic materials.

    • Soils develop in response to the following factors:

      • Climate: Measured by precipitation and temperature, which results in partial weathering of the parent material, which forms the substrate for soil.

      • Living organisms: Include the nitrogen-fixing bacteria Rhizobium, fungi, insects, worms, snails, etc., that help to decompose litter and recycle nutrients.

      • Parent material: Refers to the rock and minerals from which the soil derives. The nature of the parent rock, which can be either native to the area or transported to the area by wind, water, or glacier, has a direct effect on the ultimate soil profile.

      • Topography: Refers to the physical characteristics of the location.

    Soil Erosion

    • Soil erosion: It is the movement of weathered rock and/or soil components from one place to another caused by flowing water, wind, and human activity.

      • It decreases the soil’s water-holding capacity, destroys the soil profile, and increases soil compaction.

    • Poor agricultural techniques that lead to soil erosion include the following:

      • Improper plowing of the soil

      • Monoculture

      • Overgrazing

      • Removing crop wastes instead of plowing the organic material back into the soil

    Landslides and Mudslides

    • Landslides: These occur when masses of rock, earth, or debris move down a slope.

      • These occur when water rapidly collects in the ground, causing a surge of water-soaked rock, earth, and debris. They can occur after heavy rains, droughts, earthquakes, or volcanic eruptions.

    • Mudslides: It is also known as debris flows or mudflows, are a common type of fast-moving landslide that tends to flow in channels.

      • It usually begin on steep slopes and can be triggered by natural disasters in areas where wildfires or construction have destroyed vegetation.

    • Some areas are more likely to experience landslides or mudslides, including the following:

      • Areas where landslides have occurred before

      • Areas where surface runoff is directed

      • Areas where wildfires or construction have destroyed vegetation

      • Channels along a stream or river

      • Slopes that have been altered for the construction of buildings and roads

      • Steep slopes and areas at the bottom of slopes or canyons

    Rock Types

    • Igneous Rocks: These are formed by cooling and classified by their silica content.

      • Intrusive igneous rocks: Solidify deep underground, cool slowly, and have a large-grained texture.

      • Extrusive igneous rocks: Solidify on or near the surface, cool quickly, and have a fine-grained smooth texture.

      • Igneous rocks are broken down by weathering and water transport.

    • Metamorphic Rocks: These are formed by intense heat and pressure, high quartz content.

      • Common examples: diamond, marble, asbestos, slate, and anthracite coal.

    • Sedimentary: These are formed by the piling and cementing of various materials over time in low-lying areas.

      • Fossils form only in sedimentary rock.

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  • 4.2: Soil Formation and Erosion

    Soil

    • Soils: These are a thin layer on top of most of Earth’s land surface.

      • This thin layer is a basic, natural resource, and its characteristics deeply affect every other part of the ecosystem.

    • Soils are composed of three main ingredients:

      • Minerals of different sizes

      • Open spaces that can be filled with air or water

      • Organic materials from the remains of dead plants and animals

    • Soil Profile

      • Surface Litter: Leaves and partially decomposed organic debris.

      • Topsoil: Organic matter, living organisms, and inorganic materials; it is very thick in grass lands.

      • Zone of leaching: Dissolved and suspended materials move downward.

      • Subsoil: Tends to be yellowish in color due to the accumulation of iron, aluminum, humic compounds, and clay leached from A and E horizons.

      • Weathered Parent Material: Partially broken-down inorganic materials.

    • Soils develop in response to the following factors:

      • Climate: Measured by precipitation and temperature, which results in partial weathering of the parent material, which forms the substrate for soil.

      • Living organisms: Include the nitrogen-fixing bacteria Rhizobium, fungi, insects, worms, snails, etc., that help to decompose litter and recycle nutrients.

      • Parent material: Refers to the rock and minerals from which the soil derives. The nature of the parent rock, which can be either native to the area or transported to the area by wind, water, or glacier, has a direct effect on the ultimate soil profile.

      • Topography: Refers to the physical characteristics of the location.

    Soil Erosion

    • Soil erosion: It is the movement of weathered rock and/or soil components from one place to another caused by flowing water, wind, and human activity.

      • It decreases the soil’s water-holding capacity, destroys the soil profile, and increases soil compaction.

    • Poor agricultural techniques that lead to soil erosion include the following:

      • Improper plowing of the soil

      • Monoculture

      • Overgrazing

      • Removing crop wastes instead of plowing the organic material back into the soil

    Landslides and Mudslides

    • Landslides: These occur when masses of rock, earth, or debris move down a slope.

      • These occur when water rapidly collects in the ground, causing a surge of water-soaked rock, earth, and debris. They can occur after heavy rains, droughts, earthquakes, or volcanic eruptions.

    • Mudslides: It is also known as debris flows or mudflows, are a common type of fast-moving landslide that tends to flow in channels.

      • It usually begin on steep slopes and can be triggered by natural disasters in areas where wildfires or construction have destroyed vegetation.

    • Some areas are more likely to experience landslides or mudslides, including the following:

      • Areas where landslides have occurred before

      • Areas where surface runoff is directed

      • Areas where wildfires or construction have destroyed vegetation

      • Channels along a stream or river

      • Slopes that have been altered for the construction of buildings and roads

      • Steep slopes and areas at the bottom of slopes or canyons

    Rock Types

    • Igneous Rocks: These are formed by cooling and classified by their silica content.

      • Intrusive igneous rocks: Solidify deep underground, cool slowly, and have a large-grained texture.

      • Extrusive igneous rocks: Solidify on or near the surface, cool quickly, and have a fine-grained smooth texture.

      • Igneous rocks are broken down by weathering and water transport.

    • Metamorphic Rocks: These are formed by intense heat and pressure, high quartz content.

      • Common examples: diamond, marble, asbestos, slate, and anthracite coal.

    • Sedimentary: These are formed by the piling and cementing of various materials over time in low-lying areas.

      • Fossils form only in sedimentary rock.

    4.3: Soil Composition and Properties

    Soil Components

    • Gravel

      • Coarse particles.

      • Consists of rock fragments.

    • Sand

      • Sedimentary material coarser than silt.

      • Water flows through too quickly for most crops.

      • Good for crops and plants requiring low amounts of water.

    • Loam

      • About equal mixtures of clay, sand, silt, and humus. Rich in nutrients.

      • Holds water but does not become waterlogged. Particle size can vary.

    • Silt

      • Sedimentary material consisting of very fine particles between the sizes of sand and clay.

      • Easily transported by water.

    • Clay

      • Very fine particles.

      • Compacts easily.

      • Forms large, dense clumps when wet. Low permeability to water; therefore, upper layers become waterlogged.

    Humus

    • Humus: It is the dark organic material that forms in soil when plant and animal matter decays.

      • The thick brown or black substance that remains after most of the organic litter has decomposed

    • As this material decays, it breaks down into its most basic chemical elements and compounds, which are important nutrients for plants and animals that depend upon soil for life.

    • Earthworms often help mix humus with minerals in the soil.

    • Soil containing humus will crumble, allowing air and water to move easily through the loose soil, making root growth easier, reducing erosion, and stabilizing the pH.

    Components of Soil Quality

    • Aeration: Refers to how well a soil is able to absorb oxygen, water, and nutrients.

      • Aeration, which reduces soil compaction, involves perforating the soil with small holes to allow air (especially oxygen), water, and nutrients to penetrate to the roots.

      • This helps the roots grow deeply and produce a stronger, more vigorous plant.

      • When there’s little or no light, plants require oxygen to break down the plant’s sugar(s) to release CO2, water, and energy.

    • Degree of Soil Compaction: It is measured by dry unit weight and depends on the water content and compaction effort.

      • Heavily compacted soils contain few large pores and have a reduced rate of both water infiltration and drainage from the compacted layer.

    • Nutrient-Holding Capacity: The ability of soil to absorb and retain nutrients so they will be available to the roots of plants.

      • The process of weathering greatly influences the availability of plant nutrients.

      • Initially, as soil particles begin to weather, primary minerals release nutrients into the soil.

      • As these particles decrease in size, the soil is able to retain greater amounts of nutrients.

      • The capacity to hold and retain nutrients is greatly reduced in highly weathered soils since most nutrients have been lost due to leaching.

      • Primary plant nutrients are nitrogen (N), phosphorus (P), and potassium (K).

    • Permeability: The measure of the capacity of the soil to allow water and oxygen to pass through it.

      • Low permeability can lead to soil salinization.

    • pH: It is the measure of how acidic or basic soil is.

      • Various plants have different soil pH requirements.

      • Acidic soils can be caused by pollutants, such as acid rain and mine spoiling, and are most often found in areas of high rainfall.

      • Alkaline (basic) soils have a high amount of potassium (K+), calcium (Ca²+), magnesium (Mg² +), and/or sodium (Na+) ions.

    • Pore Size: Describes the space between soil particles.

      • It determines how much water, air, and nutrients are available for plant roots.

    • Size of soil and particles: It determines the amount of moisture, nutrients, and oxygen that the soil can hold along with the capacity for water to infiltrate.

      • The particles which constitute the inorganic portion of soil and which are 2 mm or less in diameter.

    • Water holding capacity: It is controlled primarily by the soil texture and the soil organic matter content.

      • Soil texture: A reflection of the particle size distribution of soil.

      • After the soil is saturated with water, all of the excess water and some of the nutrients and pesticides that are in the soil solution are leached downward in the soil profile.

      • Formula: Where Vw is the volume of the water required to saturate the soil and Vt is the total volume of the saturated soil (1 cm³ = 1 mL).

    Soil Food Web

    • Soil Food Web: It is the community of organisms living all or part of their lives in the soil, and it describes a complex living system in the soil and how it interacts with the environments, plants, and animals.

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    4.4: Earth’s Atmosphere

    Early History

    • Atmospheric carbon dioxide (CO2) produced by volcanoes and methane (CH4) produced by early microbes, both greenhouse gases, likely produced a strong greenhouse effect and allowed the earliest life forms to develop.

    • Great Oxidation Event (GOE) 2.5 billion years ago killed almost all life on Earth.

      • It was a time period when the Earth’s atmosphere and the shallow ocean experienced a rise in oxygen.

    • As oxygen began to accumulate in the atmosphere, it is believed that there were two major consequences:

      1. Free oxygen oxidized atmospheric methane (GWP 25) to carbon dioxide (GWP 1), weakening Earth's greenhouse effect and causing planetary cooling and ice ages.

      2. Increased oxygen concentrations allowed biological diversification and major chemical changes between Earth's clay, rocks, and sand, atmosphere, and oceans.

    Atmosphere’s Current Composition

    • Nitrogen (N2) — 78%

      • Fundamental nutrient for living organisms.

      • Found in all organisms, primarily in amino acids and nucleic acids.

      • Makes up about 3% of the human body by weight.

      • Deposits on Earth through nitrogen fixation and reactions involving lightning and subsequent precipitation.

      • Returns to the atmosphere through combustion of biomass and denitrification.

    • Oxygen (O2) — 21%

      • By mass, the third most abundant element in the universe, after hydrogen and helium.

      • The most abundant element by mass in Earth’s crust, making up almost half of the crust’s mass as silicates.

      • Free elemental oxygen (O2) began to accumulate in the atmosphere about 2.5 billion years ago.

      • Highly reactive nonmetallic element that readily forms compounds.

      • Product in photosynthesis and reactant in cellular respiration.

    • Water Vapor (H2O) — 0% to 4%

      • Largest amounts are found near the equator, over oceans, and in tropical regions.

      • Polar areas and deserts lack significant amounts of water vapor.

      • Besides evaporation, other sources of atmospheric water include combustion, respiration, volcanic eruptions, and the transpiration of plants.

    • Carbon Dioxide (CO2) < 1%

      • Produced during cellular respiration, the combustion of fossil fuels, and the decay of organic matter.

      • Required for photosynthesis

      • Major greenhouse gas contributing to global warming

      • Average lifetime of a CO2 molecule in the atmosphere is ~100 years.

    Atmosphere’s Structure

    • Troposphere: The lowest portion of Earth’s atmosphere, 0–6 miles (0–10 km) above Earth’s surface.

      • 75% of the atmosphere’s mass and almost all of the water vapor on the planet is contained within the troposphere, with weather also occurring in this layer.

      • The atmospheric pressure within the troposphere is highest at the surface and decreases with height, whereas the temperature of the troposphere decreases with height.

    • Stratosphere: It is located 6–30 miles (10–50 km) above Earth’s surface.

      • In the stratosphere, ozone (O3) absorbs high-energy ultraviolet radiation from the sun and is broken down into atomic oxygen (O) and diatomic oxygen.

      • Temperature increases with altitude in the stratosphere.

    Weather and Climate

    • Weather: It is caused by the movement or transfer of heat energy, which results from the unequal heating of Earth’s surface by the sun.

      • It describes whatever is currently happening outdoors.

      • It influences the following physical properties:

        • Air pressure

        • Air temperature

        • Humidity

        • Precipitation

        • Sunlight reaching Earth affected by cloud cover

        • Wind direction and speed

    • Climate: The average weather conditions prevailing in an area in general or over a long period.

      • The statistical description in terms of the mean and variability of relevant quantities over a period ranging from months to thousands or millions of years.

    • Convection: It is the primary way energy is transferred from hotter to colder regions in Earth’s atmosphere and is the primary determinant of weather patterns.

      • Warmer, more energetic air molecules move vertically and horizontally.

      • Air rises when it becomes warmer and less dense than the air above it, creating pressure differences that cause wind.

    • Heat Index (HI): The measure of how warm it feels when factoring in relative humidity.

    Climate and Factors that Influence it

    • Air Mass: A large body of air that has similar temperature and moisture content.

      • These can be categorized as equatorial, tropical, polar, Arctic, continental, or maritime.

    • Albedo: An expression of the ability of surfaces to reflect sunlight.

      • Materials like ocean water have low albedo, whereas landmasses have moderate albedo.

      • Snow and ice have the highest albedo.

    • Altitude: The distance above sea level.

    • Carbon Cycle: The process in which carbon atoms continually travel from the atmosphere to the Earth and then back into the atmosphere.

    • Distance to Oceans: Oceans are thermally more stable than landmasses; the specific heat of water is five times greater than that of air.

      • Because of this, changes in temperature are more extreme in the middle of the continents than on the coasts.

    • Fronts: When two different air masses meet, the boundary between them forms a “front.”

      • The air masses can vary in temperature, dew point and wind direction.

      • Cold Front: The leading edge of an advancing mass of cold air and is associated with thunderhead clouds, high surface winds, and thunderstorms.

      • Warm Front: The boundary between an advancing warm air mass and the cooler one it is replacing.

      • Stationary Front: A pair of air masses, neither of which is strong enough to replace the other, that tend to remain in essentially the same area for extended periods of time.

    • Greenhouse Effect: Without this effect, Earth would be cold and inhospitable.

      • The most important greenhouse gases are water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

      • If taken too far, however, Earth could evolve into a hothouse.

    • Heat: Climate is influenced by how heat energy is exchanged between air over the oceans and the air over land.

    • Human Activity and Climate: Climate can also be influenced by human activity.

      • Increased pollution alone tends to increase the amount of rainfall in urban areas by as much as 10% when compared with undeveloped areas.

      • Climate is also influenced by urbanization and deforestation.

    • Latitude and Location

      • Latitude: The measurement of the distance of a location on Earth from the equator.

        • The farther away from the equator, the less sunlight is available.

      • At the poles, the sun’s rays strike Earth at an acute angle, which spreads the heat over a larger area.

      • Climate is influenced by the location of high and low air pressure zones and where landmasses are distributed.

    • Moisture Content of Air: It is a primary determinant of plant growth and distribution and is a major determinant of biome type.

    • Pollution: Greenhouse gases are emitted from both natural sources and anthropogenic sources.

    • Rotation: Daily temperature cycles are primarily influenced by Earth’s rotation on its axis.

      • At night, heat escapes from Earth’s surface, and daily minimum temperatures occur just before sunrise.

    • Volcanoes

      • Sulfur-rich volcanic eruptions: It can eject material into the stratosphere, potentially causing tropospheric cooling and stratospheric warming.

      • Volcanic aerosols: These exist in the atmosphere for an average of one to three years.

        • Volcanic aerosols injected into the stratosphere can also provide surfaces for ozone-destroying reactions.

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    4.5: Global Wind Patterns

    Land and Sea Breezes

    • Land Breeze: It occurs during relatively calm, clear nights when the land cools down faster than the sea, resulting in the air above the land becoming denser than the air over the sea.

    • Sea Breeze: It occurs during relatively calm, sunny days, the land warms up faster than the sea, causing the air above it to become less dense.

    Atmospheric Circulation-Pressure

    • Air closer to Earth's surface is warmer and rises due to Earth's rotation on its axis, revolution around the sun, and tilt.

      • Cooler, denser, higher-elevation air sinks, causing convection and winds.

      • Low-pressure weather systems have lower pressure at their centers than elsewhere.

      • Where winds meet low pressure, air rises.

      • Air rises, condensing water vapor into clouds and precipitation.

    • High-pressure weather systems: They have higher pressure at their center than around them, so winds blow away from them.

      • They blow clockwise north of the equator and counterclockwise south of it, with air from higher in the atmosphere sinking down to fill the gaps left by outward-blowing air.

      • Cool, dense air descends toward Earth's surface and warms in high-pressure masses, which are usually associated with fair weather.

    • Trade Winds: These are the prevailing pattern of easterly surface winds found in the tropics near Earth’s equator, within the troposphere or lower portion of Earth’s atmosphere.

      • It have been used by captains of sailing ships to cross the world’s oceans.

    • Wind Speed: It is determined by pressure differences between air masses.

      • The greater the pressure difference is, the greater the wind speed.

    • Wind Direction: It is based on the direction from which wind originated.

      • Easterly: Wind coming from the east.

      • Westerly: Wind coming from the west.

    • Coriolis Effect: A phenomenon wherein earth’s rotation on its axis causes winds to not travel straight, which causes prevailing winds in the Northern Hemisphere to spiral clockwise out from high-pressure areas and spiral counterclockwise toward low-pressure areas.

    Hadley Air Circulation

    • Air heated near the equator rises and spreads out north and south.

    • After cooling in the upper atmosphere, the air sinks back to Earth’s surface within the subtropical climate zone.

    • Surface air from subtropical regions returns toward the equator to replace the rising air.

    • The equatorial regions of the Hadley cells are characterized by high humidity, high clouds, and heavy rains.

    • Subtropical regions of the Hadley cell are characterized by low relative humidity, little cloud formation, high ocean evaporation due to the low humidity, and many of the world’s deserts.

    • The climate is characterized by warm to hot summers and mild winters. The tropical wet and dry (or savanna) climate has a dry season more than two months long.

    Ferrel Air Circulation Cells

    • Ferrel cells develop between 30° and 60° north and south latitudes.

    • The descending winds of the Hadley cells diverge as moist tropical air moves toward the poles in winds known as the westerlies.

    • Mid-latitude climates can have severe winters and cool summers due to mid-latitude cyclone patterns.

    • Defined seasons are the rule, with strong annual cycles of temperature and precipitation.

    • Climates of the middle latitudes have a distinct winter season.

    Polar Air Circulation Cells

    • Polar cells originate as icy-cold, dry, dense air that descends from the troposphere to the ground.

    • This air meets with the warm tropical air from the mid-latitudes and then returns to the poles, cooling and then sinking.

    • Sinking air suppresses precipitation. As a result, the polar regions are deserts.

    • Very little water exists in this area because it is tied up in the frozen state as ice.

    • The amount of snowfall per year is relatively small.

    Polar Vortex

    • Polar Vortex: A low-pressure zone embedded in a large mass of very cold air that lies atop both poles.

    • The bases of the two polar vortices are located in the middle and upper troposphere and extend into the stratosphere.

    • Due to the equator-pole temperature difference, these cold, low-pressure areas strengthen in winter and weaken in summer.

    • There is also a relationship between the chemistry of the Antarctic polar vortex and severe ozone depletion.

    Hurricanes

    • Hurricanes, cyclones, and typhoons are all the same weather phenomenon.

      • Hurricanes: Term used in the Atlantic and Northeast Pacific.

      • Cyclones: Term used in South Pacific and Indian Ocean.

      • Typhoons: Term used in Northwest Pacific.

    • Hurricanes begin over warm oceans in areas where the trade winds converge.

      • A subtropical high-pressure zone creates hot daytime temperatures with low humidity that allow for large amounts of evaporation, with the Coriolis effect initiating the cyclonic flow.

    • Hurricane development requires tropical ocean thunderstorms and cyclonic circulation that starts to rotate them.

      • This cyclonic circulation allows them to pick up moisture and latent heat energy from the ocean.

    • In the center of the hurricane is the eye, an area of descending air and low pressure.

    • Storm Surge: A rise in sea level that occurs during tropical cyclones, typhoons, or hurricanes.

      • These storms produce strong winds that push the seawater toward the shore, which often leads to flooding.

    Tornadoes

    • Tornadoes: These are wirling masses of air with wind speeds close to 300 miles per hour (485 kph).

      • The center of the tornado is an area of low pressure.

    • Formation of Tornadoes

      • Thunderstorm or hailstorm creates strong winds.

      • The strong winds begin to rotate (due to updrafts and downdrafts) and form a column of spinning air called a mesocyclone.

      • The mesocyclone meets warm air moving up and cold air moving down and creates a funnel.

      • The funnel, made up of dust, air, and debris, reaches the ground, and a tornado is formed.

    Tornadoes vs. Hurricanes

    Tornadoes	Hurricanes
    Diameters of hundreds of meters	Diameters of hundreds of km
    Produced from a single convective storm	Composed of many convective storms
    Occur primarily over land	Occur primarily over oceans
    Require substantial vertical shear of the horizontal winds	Require very low values of vertical shear in order to form and grow
    Typically last less than an hour	Last for days

    Monsoons

    • Monsoons: These are strong, often violent winds that change direction with the season.

    • Monsoon winds: These blow from cold to warm regions because cold air takes up more space than warm air.

    • Monsoons blow from the land toward the sea in winter and from the sea toward land in the summer.

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    4.6: Watershed

    • Watershed: A land area that drains rainfall and snowmelt into a lake, ocean, or aquifer.

    • Mississippi River watershed: The largest watershed in the United States, which drains more than one million square miles or land.

    • Watershed management: It reduces pesticides and fertilizers that wash off farm fields and into nearby waterbodies by using land, forest, and water resources in ways that don't harm plants and animals.

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    4.7: Solar Radiation and Earth’s Seasons

    Angle of Sunlight

    • The amount of heat energy received at any location on Earth is a direct effect of the angle of the sunlight reaching the Earth’s surface.

    • The angle at which sunlight strikes Earth varies by location, time of day, and season due to Earth’s orbit around the sun and its rotation around its tilted axis.

    • Seasonal changes in the angle of sunlight are caused by the tilt of Earth’s axis, which is the basic mechanism that results in warmer weather in summer than in winter.

    • Sunlight shining on Earth at a lower angle spreads its energy over a larger area, making it weaker than if the sun were higher overhead.

    Solar Intensity

    • Factors that affect the amount of solar energy at the surface of Earth (which directly affects plant productivity) include the following:

      • The tilt of Earth’s axis (23.5°)

      • Atmospheric conditions

      • Earth’s rotation around the sun (once per year)

      • Earth’s rotation on its axis (once every 24 hours)

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    4.8: Earth’s Geography and Climate

    Bodies of Water Moderate Climate and Regulate Precipitation

    • Over 70% of the Earth’s surface is covered in water.

    • Oceans and lakes store solar radiation (heat), and as the water heats up it adds moisture to the air above it, beginning a process that drives the major air currents around the world.

    • Large water bodies also tend to stabilize the climate of adjacent land masses by absorbing extra heat during warm periods and releasing it during cooler periods.

    • Warm, moist ocean air is a driving force for precipitation patterns around the world as it is carried over cooler land masses.

    Higher Elevations Have Cooler Climates

    • Climates become cooler and the cold season lasts longer as elevation increases.

    • Higher elevations have lower air pressure due in part to there being fewer atoms and molecules per unit of air and, thus, cooler temperatures.

    • Many high-altitude plains are technically deserts because they are on the downwind (leeward) side of a mountain range or continental mass.

    • Latitude: A measure of distance either north or south from the equator.

    • Tropic of Cancer: The northernmost latitude reached by the overhead sun.

    • Tropic of Capricorn: The southernmost latitude reached by the overhead sun.

    Mountains Affect Air Flow

    • Mountain ranges: These are barriers to the smooth movement of air currents across continents.

      • When an air mass hits mountains, it slows down and cools because the air is forced up into cooler parts of the atmosphere to move over the mountains.

      • The cooled air can't hold as much water anymore, so it rains on the side of the mountain range that faces the wind.

    • The mountain range's leeward side is drier than the windward side because air on this side has less moisture.

      • Rain Shadow Effect: The drier situation which is directly responsible for the plants that grow there, which in turn affects the animals that live there.

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    4.9: El Niño and La Niña

    La Nada (Normal Conditions)

    • During normal conditions, easterly trade winds move water and air toward the west.

      • The ocean is generally around 24 inches (60 cm) higher in the western Pacific, and the water there is about 14°F warmer.

    • The trade winds, in piling up water in the western Pacific, make a deep warm layer in the west that pushes the thermocline down while it rises in the east.

      • Upwelling: It occurs when prevailing winds, produced through the Coriolis effect and moving clockwise in the Northern Hemisphere, push warmer, nutrient-poor surface waters away from the coastline

      • It is caused by winds pulling nutrient-rich water from below, increasing fishing stocks in this shallow eastern thermocline (90 feet or 30 m).

    El Niño (Warm Phase)

    • Air pressure patterns reverse direction, causing trade winds to decrease in strength.

    • This causes the normal flow of water away from western South America to decrease “pile up.”

    • As a result, the thermocline off western South America becomes deeper and there is a decrease in the upwelling of nutrients, which causes extensive fish kills.

    • A band of warmer-than-average ocean water temperatures develops off the Pacific coast of South America.

    • Effects are strongest during the Northern Hemisphere winter because ocean temperatures worldwide are at their warmest.

    • Increased ocean warmth enhances convection, which then alters the jet stream

    La Niña (Cool Phase)

    • Trade winds that blow west across the tropical Pacific are stronger than normal.

    • This then results in an increase in the upwelling off of South America.

    • This then results in cooler-than-normal sea surface temperatures off of South America.

    • This then results in wetter-than-normal conditions across the Pacific Northwest, and both drier- and warmer-than-normal conditions in the southern United States.

    • This then results in an increase in the number of hurricanes.

    • The southeastern US has warmer winters and the northwest cooler ones, while India and southeast Asia have heavier monsoons.

    Environmental Effects of ENSO Weather Patterns

    • Warmer or cooler ocean temperatures

      • A decrease in upwelling, resulting in die-offs.

      • A negative impact on coral reefs.

      • Animal migration patterns may become disrupted.

      • Changes in weather patterns may increase insect-borne diseases.

      • Marine food webs and biodiversity may be disrupted by species that cannot tolerate warmer or cooler water temperatures.

      • Global warming decreases as warmer ocean water can hold less CO2.

      • Hurricanes and tornadoes may become stronger and more frequent.

      • Ocean currents and glacial melting may change with warmer ocean temperatures.

    • Increase or decrease in the amount of normal rainfall

      • Reduced rainfall may increase food competition, agricultural output, migration patterns, starvation, species die-offs, forest fires, and water shortages.

      • An increase in rainfall may result in an increase in flooding, soil erosion, and leaching of nutrients from the soil.

      5.1: The Tragedy of the Commons

      • Garrett Hardin wrote “The Tragedy of the Commons” in 1968.

        • The essay parallels what is happening worldwide in regards to resource depletion and pollution.

      • The seas, air, water, animals, and minerals are all “the commons” and are for humans to use, but those who exploit them become rich.

      • The following environmental issues echo "The Tragedy of the Commons" sustainability issues:

        • Air pollution

        • Burning of fossil fuels and consequential global warming

        • Frontier logging of old-growth forests and the practice of “slash and burn”

        • Habitat destruction and poaching

        • Over-extraction of groundwater and wastewater due to excessive irrigation

        • Overfishing

        • Overpopulation

      • Limits to “The Tragedy of the Commons” include the following:

        • Dividing a "commons" into privately owned parcels fragments its policies.

        • Different standards and practices on one parcel may or may not affect all parcels. Environmental decisions are long-term, while economic decisions are short-term.

        • Investors would be encouraged to pay a short-term price for a long-term gain by including discount rates in resource valuation.

        • Market pressure affects privately owned land.

        • Controlling some "commons" is easier than others. Air and the open oceans are harder to control than land, lakes, rangeland, deserts, and forests.

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      5.2: Clear-Cutting

      • Clear-cutting: It occurs is when all of the trees in an area are cut at the same time.

        • Environmental impacts of clear-cutting include the following:

          • Habitat loss reduces biodiversity.

          • Allows sunlight to reach the ground, making it warmer and drier, unsuitable for many forest plants.

          • Temporary wood availability followed by long periods without wood Reduction in long-term and short-term carbon sinks, which increases atmospheric CO2

          • Runoff increases soil erosion.

      • Edge Effect: It refers to how the local environment changes along some type of boundary or edge.

        • Forest edges: These are created when trees are harvested, particularly when they are clear-cut.

        • Tree canopies: It provide the ground below with shade and maintain a cooler and moister environment below.

      • Deforestation: It is the conversion of forested areas to non-forested areas, which are then used for grain and grass fields mining, petroleum extraction, fuel wood cutting, commercial logging, tree plantations, or urban development.

        • Impacts of deforestation include the following:

          • Runoff into aquatic ecosystems, climate change, and erosion decrease soil fertility.

          • Without shade, forest soils dry out quickly.

          • Degrading environment(s) with decreased biodiversity and ecological services.

          • Forests house 80% of land animals and plants.

          • Increasing habitat fragmentation and CO2 emissions from burning and tree decay.

          • Reducing migratory bird and butterfly habitats

          • Endangering niche-specialized species.

      

      Deforestation Mitigation

      • Adopting uneven-aged forest management practices.

      • Educating farmers about sustainable forest practices and their advantages.

      • Monitoring and enforcing timber-harvesting laws.

      • Growing timber on longer rotations.

      • Reducing fragmentation in remaining large forests.

      • Reducing road building in forests.

      • Reducing or eliminating the practice of clear-cutting.

      • Relying on more sustainable tree-cutting methods.

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      5.3: The Agricultural and Green Revolutions

      Agricultural Revolutions

      • First Agricultural Revolution (2000+ B.C.E.)

        • People went from hunting and gathering to the domestication of plants and animals, which allowed people to settle in areas and create cities.

        • Settled communities permitted people to observe and experiment with plants to learn how they grow and develop.

      • Second Agricultural Revolution (1700–1900 C.E.)

        • Occurred at the same time as the Industrial Revolution—mechanization had a major role in this revolution and changed the way people farmed.

        • Advances were made in breeding livestock.

        • Increased agricultural output made it possible to feed large, urban populations.

        • Methods of soil preparation, fertilization, crop care, and harvesting improved.

        • New banking and lending practices helped farmers afford new equipment and seed.

        • New crops came into Europe from trade with the Americas.

        • Railroads allowed distribution of products.

        • The invention of the seed drill allowed farmers to avoid wasting seeds and to plant in rows.

        • The invention of the tractor, combined with other farm machinery, improved efficiency on farms.

      • Third Agricultural Revolution (1900 C.E.–present)

        • Mechanization such as tractors and combines requires less labor and makes food prices more affordable.

        • Scientific farming methods such as biotechnology, genetic engineering, and the use of pesticides are now beginning to focus on more sustainable methods.

      Green Revolutions

      • First Green Revolution (1940s–1980s)

        • The introduction of inorganic fertilizers, synthetic pesticides, new irrigation methods, and disease-resistant, high-yielding crop seeds.

      • Second Agricultural Revolution (1980s–Present)

        • In the mid-1980s, new engineering techniques and free-trade agreements involving food production property rights shaped agricultural policies and food production and distribution systems worldwide.

        • This revolution saw the development and spread of genetically modified organisms (GMOs)—animals, plants, and microorganisms—with genes that don't exist in nature.

        • BT corn and Golden Rice, modified with daffodil genes to produce more beta-carotene (converts to Vitamin A), are examples (corn modified with a bacterial insecticide gene that produces insect toxins within the cells of the corn).

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      5.4: Agricultural Practices

      • Agricultural productivity: It implies greater output with less input.

        • As farms become more efficient, they are able to produce more products at a lower cost, which tends to stabilize food prices and make more food available to more people, which is vital for developing countries.

      • Desertification: It is the conversion of marginal rangeland or cropland to a more desert-like land type.

      • Overgrazing: A plant is considered overgrazed when it is re-grazed before the roots recover, which can reduce root growth by up to 90%.

      • Fertilizers: These provide plants with the nutrients needed to grow healthy and strong.

        • Inorganic Fertilizers: A fertilizer mined from mineral deposits or manufactured from synthetic compounds.

        • Organic Fertilizers: Any Any fertilizer that originates from an organic source, such as bone meal, compost, fish extracts, manure, or seaweed.

      • Genetically modified foods: These are foods produced from organisms both animal and plant) that have had changes introduced into their DNA.

        • Genetic engineering techniques: These allow for the introduction of new traits as well as greater control over traits when compared to previous methods.

      • Rangelands: These are native grasslands, woodlands, wetlands, and deserts that are grazed by domestic livestock or wild animals.

        • These are managed through livestock grazing and prescribed fire rather than more intensive agricultural practices of seeding, irrigation, and the use of fertilizers.

      • Slash-and-Burn Agriculture: It is a widely used method of growing food or clearing land in which wild or forested land is clear-cut and any remaining vegetation is burned.

      • Soil Erosion: It is the movement of weathered rock or soil components from one place to another and is caused by flowing water, wind, and human activity.

      • Soil degradation: It is the decline in soil condition caused by its improper use or poor management, usually for agricultural, industrial, or urban purposes.

        • Desertification: Productive potential of arid or semiarid land falls by at least 10% due to human activity and/or climate change.

        • Salinization: Water that is not absorbed into the soil evaporates, leaving behind dissolved salts in topsoil.

        • Waterlogging: Saturation of soil with water, resulting in a rise in the water table.

      • Tillage: An agricultural method in which the surface is plowed and broken up to expose the soil, which is then smoothed and planted.

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      5.5: Irrigation Methods

      • Irrigation: The application of controlled amounts of water to plants at needed intervals and has been a necessary component of agriculture for over 5,000 years.

      • Ditch: Dug and seedlings are planted in rows.

        • The plantings are watered by placing canals or furrows in between the rows of plants.

        • Siphon tubes are used to move the water from the main ditch to the canals.

      • Drip: Water is delivered at the root zone of a plant through small tubes that drip water at a measured rate.

      • Flood: Water is pumped or brought to the fields and is allowed to flow along the ground among the crops.

        • Being simple and inexpensive, it is the method most widely used in less-developed countries.

      • Furrow (Channel): Small parallel channels are dug along the field length in the direction of the predominant slope.

        • Water is applied to the top of each furrow and flows down the field under gravity, infiltrating the ground more at the beginning and less at the end.

      • Spray: Uses overhead sprinklers, sprays or guns to spray water onto crops.

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      5.6: Pest-Control Methods

      • Pesticides: These can be used to control pests, but their use has drawbacks.

        • Integrated Pest Management (IPM): It is an ecologically based approach to control pests.

      Types of Pesticides

      • Biological Pesticides: Living organisms used to control pests.

      • Carbamates: Also known as urethanes, affect the nervous system of pests, which results in the swelling of tissue in the pest.

      • Fumigants: These are used to sterilize soil and prevent pest infestation of stored grain.

        • Inorganic pesticides: These are broad-based pesticides that include arsenic, copper, lead, and mercury. They are highly toxic and accumulate in the environment.

        • Organic pesticides: These are natural poisons derived from plants such as tobacco or chrysanthemum.

        • Organophosphates: These are extremely toxic but remain in the environment for only a brief time.

      Persistent Organic Pollutants (POPS)

      • Persistent organic pollutants (POPS): These organic compounds can pass through and accumulate in living organisms' fatty tissues because they don't break down chemically or biologically.

        • They also biomagnify food pyramids.

      The Pesticide Treadmill

      • Pesticide resistance: It describes the decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest.

      • Pest species: They evolve pesticide resistance via natural selection.

      • In response to resistance, farmers may increase pesticide quantities and/or the frequency of pesticide applications, which magnifies the problem.

      • Pesticide Treadmill: Also known as pest traps; farmers are forced to use more and more toxic chemicals to control pesticide-resistant insects and weeds.

      Integrated Pest Management (IPM)

      • IPM: It is an ecological pest-control strategy that uses a combination of biological, chemical, and physical methods together or in succession and requires an understanding of the ecology and life cycle of pests.

      • Methods used in IPM include the following:

        • Construction of mechanical controls.

        • Developing genetically modified crops that are more pest-resistant.

        • Intercropping: A farming method that involves planting or growing more than one crop at the same time and on the same piece of land.

        • Natural insect predators

        • Planting pest-repellant crops

        • Polyculture: The simultaneous cultivation or raising of several crops or types of animals

        • Regular monitoring through visual inspection and traps followed by record keeping

        • Releasing sterilized insects

        • Rotating crops often to disrupt insect cycles

        • Using mulch to control weeds

        • Using pheromones or hormone interrupters

        • Using pyrethroids or naturally occurring microorganisms

      • When used effectively, IPM can reduce the following:

        • Bioaccumulation and biomagnification of pesticides

        • Pests’ becoming resistant to a particular pesticide

        • Genetic resistance: An inherited change in the genetic makeup of the pests that confers a selective survival advantage.

        • The destruction of beneficial and non-targeted organisms.

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      5.7: Meat Production Methods

      Concentrated Animal Feeding Operations (CAFOs)

      • CAFO: It is an intensive animal feeding operation in which large numbers of animals are confined in feeding pens for over 45 days a year.

      • The large amounts of animal waste from CAFOs present a risk to water quality and aquatic ecosystems.

      • States with high concentrations of CAFOs experience on average 20 to 30 serious water-quality problems per year as a result of manure management issues.

      • Manure discharge from CAFOs can negatively impact water quality.

      • The two main contributors to water pollution caused by CAFOs are

        • soluble nitrogen compounds

        • phosphorus

      • Water pollution from CAFOs can affect both sources if one or the other is contaminated.

      • CAFOs release several types of gas emissions—ammonia, hydrogen sulfide, methane, and particulate matter.

      • The primary cause of gas emissions from CAFOs is the decomposition of animal manure being stored in large quantities.

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      5.8: Overfishing

      • Fishing is an important industry that is under pressure from growing demand and falling supply.

      • Marine life, including fisheries, as well as terrestrial life, depends upon primary producers.

      • Aquatic plants require sunlight and are therefore largely restricted to shallow coastal waters, which make up less than 10% of the world’s ocean area yet contain 90% of all marine species.

      • Aquaculture: Mariculture or fish farming. It includes the commercial growing of aquatic organisms for food and involves stocking, feeding, protecting from predators, and harvesting.

        • For aquaculture to be profitable, the species must be marketable, inexpensive to raise, efficient at converting feed into fish biomass, and disease resistant.

      Methods to Manage Marine Fishing

      • Eliminate government subsidies for commercial fishing.

      • Increase the number of marine sanctuaries.

      • Prevent the importation of fish products from countries that do not adhere to sustainable fishing practices.

      • Require and enforce labeling of fish products that were raised or caught according to sustainable methods.

      • Require fishing licenses and open inspections, which limit the number and kind of fish caught per year, and trade sanctions should these limits be exceeded.

      Methods to Restore Freshwater Fish Food Webs

      • Control erosion.

      • Control invasive species.

      • Create or restore fish passages.

      • Enforce laws that protect coastal estuaries and wetlands.

      • Plant native vegetation on stream banks.

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      5.9: Mining

      • Mining: Removing mineral resource from the ground.

        • Can involve underground mines, drilling, room-and-pillar mining, long-wall mining, open pit, dredging, contour strip mining, and mountaintop removal.

      • Surface Mining

        • Contour mining: Removing overburden from the seam in a pattern following the contours along a ridge or around a hillside.

        • Dredging: A method for mining below the water table and usually associated with gold mining.

          • Small dredges use suction or scoops to bring the mined material up from the bottom of a body of water.

        • In situ: Small holes are drilled into the Earth and toxic chemical solvents are injected to extract the resource.

        • Mountaintop removal: Removal of mountaintops to expose coal seams and disposing of associated mining overburden in adjacent “valley fills”

        • Open pit: Extracting rock or minerals from the Earth by their removal from an open pit when deposits of commercially useful ore or rocks are found near the surface

        • Strip mining: Exposes coal by removing the soil above each coal seam

      • Underground Mining

        • Blast: Uses explosives to break up the seam, after which the material is loaded onto conveyors and transported to a processing center

        • Longwall: Uses a rotating drum with “teeth,” which is pulled back and forth across a coal seam—the material then breaks loose and is transported to the surface

        • Room and pillar: Approximately half of the coal is left in place as pillars to support the roof of the active mining area.

          • Later, the pillars are removed and the mine collapses.

      

      Environmental Damage from Mining

      • Acid mine drainage

      • Disruption of natural habitats

      • Chemicals from in situ leaching entering the water table

      • Disruption of soil microorganisms and, consequently, nutrient cycling processes

      • Dust released during the breakup of materials, causing lung problems and posing other health risks

      • Land subsidence

      • Large consumption and release of water

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      5.10: Impacts of Urbanization

      Urbanization

      • Urbanization: It refers to the movement of people from rural areas to cities and the changes that accompany it.

        • Areas that are experiencing the greatest growth in urbanization are countries in Asia and Africa.

      Pros	Cons
      Better educational delivery system.	Overcrowded schools.
      Better sanitation systems.	Sanitation systems have greater volumes of wastes to deal with.
      Large numbers of people generate high tax revenues.	Large numbers of poor people place strains on social services.
      Mass transit systems decrease reliance on fossil fuels—commuting distances are shorter.	Commuting times are longer because the infrastructure cannot keep with growth.
      Much of the pollution comes from point sources, enabling focused remediation techniques.	Since population densities are high, pollution levels are also high
      Recycling systems are more efficient.	Solid-waste buildup is more pronounced. Landfill space becomes scarce and costly.
      Urban areas attract industry due to the availability of raw materials, distribution networks, customers, and labor pool.	Higher population densities increase crime rates. Population increase may be higher than job growth.

      Urban Sprawl

      • Urban Sprawl: Also known as suburban, describes the expansion of human populations away from central urban areas into low-density and usually car-dependent communities.

      • Job sprawl: It has low-density, geographically spread-out employment patterns, with most jobs in a metropolitan area outside the central business district and increasingly in the suburbs.

      • Agricultural lands, which are/were frequently found immediately surrounding cities, are frequently taken from for urban sprawl.

      • Most housing is single-family homes on large lots with fewer stories than city homes, farther apart, and separated by lawns, landscaping, or roads.

      • Single-use development: Separate commercial, residential, institutional, and industrial areas. Thus, people live, work, shop, and play far apart and need a car.

      Smart Growth

      • Smart growth: It promotes compact, transit-oriented, walkable, bicycle-friendly land use, neighborhood schools, and mixed-use development with a variety of housing options to slow urban sprawl and concentrate growth in a compact, walkable "urban villages."

        • It values long-range, regional considerations of sustainability.

      • Sustainable development strategies include the following:

        • Adopting mixed-use planning: Combining residential, commercial, cultural, institutional, and/or industrial uses in a specific location

        • Creating greenbelts and another undeveloped, wild, or agricultural land around cities

        • Providing property tax incentives to companies that locate in urban centers

        • Providing subsidies for mass transit systems and riders

        • Replacing abandoned buildings with green spaces reduces urban blight.

      Urban or Planned Development?

      • Urban development: It is the process of designing and shaping the physical features of cities and towns with the goal of making urban areas more attractive, functional, and sustainable.

      • Some urban development strategies include the following:

        • Using recycled materials in waste-minimizing designs

        • Conserving energy through government and private industry rebates and tax incentives for solar and other clean energy

        • Improving indoor air quality

        • Locating buildings near multi-modal public transportation hubs like light rail, subways, and park and rides.

        • Preserving community history and culture while blending into its natural aesthetics

        • Using resource-efficient building techniques and materials

        • Conserving water through the use of xeriscaping

      Urban Runoff

      • Urban runoff: It is surface runoff of rainwater created by urbanization.

        • This runoff is a major source of urban flooding and water pollution in urban communities worldwide.

      • Urban runoff results in the following:

        • Erosion causes runoff sedimentation, which settles to the bottom of water bodies and reservoirs, affecting water quality and storage capacity.

        • As urban heat transfers to streams and waterways, fish and wildlife suffer.

        • Runoff with gasoline, motor oil, heavy metals, trash, fertilizers, and pesticides.

      • Runoff containing gasoline, motor oil, heavy metals, trash, fertilizers, and pesticides

        • Constructing wetlands to naturally filter water before it enters lakes, rivers, and oceans.

        • Water retention-infiltration basins—shallow artificial ponds—infiltrate storm water into the groundwater aquifer through permeable soils.

        • Frequently using street-sweeping vacuums that can reduce the trash and other debris and pollutants that end up in runoff

        • Expanding urban parks and green spaces to increase natural infiltration

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      5.11: Ecological Footprints

      • Ecological Footprint: A measure of human demand on Earth’s ecosystems and is a standardized measure of demand for natural capital that may be contrasted with the planet’s ecological capacity to regenerate.

        • It represent the amount of biologically productive land and sea area that is necessary to supply the resources a human population consumes, and to assimilate associated waste.

      

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      5.12: Sustainability

      • Sustainability: It refers to the capacity for the biosphere and human civilization to coexist through the balance of resources within their environment.

        • To ensure that available resources are never depleted faster than those resources can be replaced.

      • IPAT formula

        • I = P × A × T

      • Sustainable agricultural practices, reducing consumption and waste, universal fishing quotas, and collaborative water management is needed to solve environmental issues caused by unsustainable resource use and pollution.

      Threats to Sustainability

      Earth-System Processes	Control Variable	Boundary Value	Current Value	Boundary Crossed	Preindustrial Value
      Biodiversity Loss	Extinction rate	10	>100	yes	0.1–1
      Climate change	Atmospheric carbon dioxide concentration	350	400	yes	280
      Freshwater	Global human consumption of water	4000	2600	no	415
      Land use	% land surface converted to cropland	15	11.7	no	low
      Stratospheric ozone depletion	Dobson units	276	283	no	290

      Sustainable Agriculture

      • Sustainable agriculture: It emphasizes profitable, environmentally friendly, energy-efficient production and food systems that improve farmers' and the public's quality of life.

        • It prioritizes long-term solutions over short-term symptoms and land and rural community health.

      • Examples of sustainable agricultural practices include the following:

        • Developing ecologically-based pest management programs

        • Diversifying farms to reduce economic risks

        • Increasing energy efficiency in production and food distribution

        • Integrating crop and livestock production

        • Protecting the water quality

        • Reducing or eliminating tillage in a manner that is consistent with effective weed control

        • Rotating crops to enhance yields and facilitate pest management

        • Using cover crops, green manure, and animal manure to build soil quality and fertility

        • Using water and nutrients efficiently

      Soil Conversion Techniques

      • Contour plowing: Plowing along the contours of the land in order to minimize soil erosion

      • No-till agriculture: Soil is left undisturbed by tillage and the residue is left on the soil surface.

      • Planting perennial crops: Perennials live for several years; e.g., fruit trees.

      • Strip cropping: Cultivation in which different crops are sown in alternate strips

      • Terracing: Make or form (sloping land) into a number of level flat areas resembling a series of steps

      • Windbreaks: Rows of trees that provide shelter or protection from the wind

      6.1: Introduction to Energy

      • Energy: Defined as the fundamental entity of nature that is transferred between parts of a system in the production of physical change within the system and is usually regarded as the capacity for doing work.

      • Sun: The source of energy for most of life on Earth.

        • It is heated to high temperatures by the conversion of nuclear energy to heat in its core by the process of nuclear fusion.

      • Human civilization requires energy to function. Humans obtain energy from resources such as fossil fuels, nuclear fuel, or renewable energy.

      Forms of Energy

      • Chemical energy: It is stored in bonds between atoms in a molecule.

      • Electrical energy: It results from the motion of electrons.

      • Electromagnetic energy: This energy travels by waves.

      • Mechanical energy: Consists of potential and kinetic energies.

        • Potential Energy: Stored energy in any object.

        • Kinetic energy: Energy in motion.

      • Nuclear energy: It is stored in the nuclei of atoms, and it is released by either splitting or joining atoms.

      • Thermal Energy: the energy an object has because of the movement of its molecules.

      Units of Energy/Power

      • British thermal unit (Btu): It is the amount of heat required to raise the temperature of 1 pound of water by 1°F.

        • Btu/hr: A ton in many air conditioning applications.

      • Horsepower (HP): Used in automobile industries.

        • 1 HP = 746 watts

      • Kilowatt hour (kWh): A unit of power; a measure of energy used at a give moment.

        • A billing unit of energy delivered to consumers by electric utilities.

      Law of Thermodynamics

      • First Law of Thermodynamics: The law of conservation of energy; energy can't be created nor destroyed.

      • Second Law of Thermodynamics: The total system work is always less than the heat supplied into the system.

      • Zeroth Law of Thermodynamics: If a body A is in thermal equilibrium with another body B, and body A is also in thermal equilibrium with a body C, then this implies that the bodies B and C are also in equilibrium with each other.

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      6.2: Renewable and Nonrenewable Resources

      • Renewable energy: Defined as energy that is collected from resources that are naturally replenished on a human time scale.

        • Renewable energy resources exist over wide geographical areas, in contrast to other energy sources that are concentrated in a limited number of countries.

      • Nonrenewable Energy Sources: Their use is not sustainable because their formation takes billions of years like fossil fuels.

      • Arguments used to defend the continued use of fossil fuels include the following:

        • Abundant supply, resulting in relatively low prices for consumers

        • Concentrated fuel with a high net-energy yield

        • Infrastructure already in place for extraction, processing, and delivery

        • Politics

        • Technology already exists for their use.

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      6.3: Fuel Types

      • Fossil Fuels: Fuels formed from past geological remains of living organisms.

      • Burning wood fuel: It creates the following by-products: carbon dioxide, heat, steam, water vapor, and wood ash.

      • Peat: It is an accumulation of partially decayed vegetation or organic matter, mostly wetland vegetation like mosses, sedges, and shrubs, that forms in acidic and anaerobic conditions.

      • Coal: Formed when dead plant matter that covered much of Earth’s tropical land surface at one time decays into peat and is then converted into coal by the heat and pressure of deep burial over millions of years.

        • Lignite: Often called brown coal, is the type most harmful to human health and is used almost exclusively as the primary fuel for electric power generation around the world.

        • Bituminous: Used primarily as fuel in steam-electric power generation.

        • Anthracite: Used primarily for residential and commercial space heating.

      • Clean Coal: Technology that attempts to mitigate emissions of carbon dioxide and other greenhouse gases that arise from the burning of coal for electrical power.

        • Carbon capture and storage (CCS): Pumps and stores CO2 emissions underground.

      • Natural gas: A fossil fuel formed when layers of buried plants and gases are exposed to intense heat and pressure over thousands of years.

      • Oil: A fossil fuel produced by the decomposition of deeply buried organic material (plants) under high temperatures and pressure for millions of years.

      • Cogeneration: Also known as combined heat and power (CHP), is an efficient technology to generate electricity and heat simultaneously at local facilities; otherwise, the heat produced from electricity generation is wasted.

      Technologies used to remove pollutants from flue gases

      • Baghouse filters: Fabric filters that can be used to reduce particulates.

      • Burning pulverized coal at lower temperatures: Coal is crushed into a very fine powder and injected into a firebox.

      • Coal gasification: A process that turns coal and other carbon-based fuels into gas known as “syngas.”

        • Impurities are removed from the syngas before it is combusted, which results in lower emissions of sulfur dioxide, particulates, and mercury.

      • Cyclone separator: A method of removing particulates through rotational (spinning) effects and gravity.

      • Electrostatic precipitator: A filtration device that removes fine particles, like dust and smoke, from a flowing gas using an electrostatic charge.

      • Fluidized-bed combustion: A method of burning coal in which the amount of air required for combustion far exceeds that found in conventional burners.

        • This process can be used to reduce the amount of NOx, SOx, and particulates.

      • Scrubbers: Systems that inject chemical(s) into a dirty exhaust stream to “wash out” acidic gases.

        • It can also be used to reduce SOx and particulates from burning coal.

      • Sorbents: Activated charcoal, calcium compounds, or silicates can convert gaseous pollutants in smokestacks into compounds that baghouse filters, electrostatic precipitation, or scrubbers can collect.

      

      

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      6.4: Fossil Fuels

      • Law of Supply: All other factors being equal, as the price of a good or service increases, the quantity of goods or services that suppliers offer will increase, and vice versa.

        • As the price of an item goes up, suppliers will attempt to maximize their profits by increasing the quantity offered for sale.

      • Law of Demand: All other factors being equal, the quantity of the item purchased is inversely related to the price of the item.

      

      • Fossil fuels are formed over time from deposits of once-living organisms and take thousands of years to form.

      • Coal originally comes from land vegetation, which over millions of years decays and becomes compacted.

      • Natural gas was formed from the remains of marine organisms and is relatively abundant and clean when compared to coal and oil.

      • Oil is a liquid fossil fuel that formed from the remains of marine organisms, these deposits became trapped in small spaces in rock and sediment, which now can be accessed by drilling.

      Other Fossil Fuel Nonrenewable Energy Resources

      • Methane Hydrates (Clathrates): These are recently discovered source of methane that form at low temperature and high pressure.

        • They are found:

          • On land in permafrost regions;

          • Beneath the ocean floor; and

          • On continental shelves.

      • Oil shale: An organic-rich, fine-grained sedimentary rock containing a solid mixture of organic chemical compounds (kerogen) from which liquid hydrocarbons (shale oil) can be produced.

      • Synfuels: Any fuel produced from coal, natural gas, or biomass through chemical conversion.

      • Tar sands: Contain bitumen—a semi-solid form of oil that does not flow. These are mined using strip mining techniques; in situ methods, using steam, can also be used to extract bitumen from tar sands.

      Combustion

      • The combustion of any fossil fuel follows the following reaction:

      

      • Carbon dioxide produced during fossil fuel combustion for heat and electricity generation is a major contributor to global CO2 emissions considered responsible for global warming due to its greenhouse gas effect.

      Steps Involved from Fuels to Electricity

      1. Extracting thermal energy from the fuel and using it to raise steam;

      2. Converting the thermal energy of the steam into kinetic energy in the turbine; and

      3. Using a rotary generator to convert the turbine’s mechanical energy into electrical energy.

      Hydraulic Fracturing

      • Hydraulic fracturing: Also known as “fracking,” is an oil and gas well development process that typically involves injecting water, sand, and chemicals under high pressure into a bedrock formation via a well.

        • This process is intended to create new fractures in the rock as well as increase the size, extent, and connectivity of existing fractures.

      • It is commonly used in low-permeability rocks like sandstone, shale, and some coal beds to increase oil and/or gas flow to a well from petroleum-bearing rock formations.

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      6.5: Nuclear Power

      Nuclear Fission

      • During nuclear fission, an atom splits into two or smaller nuclei along with by-product particles.

        • The reaction gives off heat.

      • If controlled, the heat that is produced is used to produce steam that turns generators that then produce electricity.

      • If the reaction is not controlled, a “meltdown” can result.

      • Nuclear Meltdown: A severe nuclear reactor accident that results in core damage from overheating.

      

      Nuclear Fuels

      • U-235: Less than 1% of all-natural uranium on Earth.

        • Critical Mass: The minimum amount of U-235 required for a chain reaction.

      • U-238: The most common isotope of uranium and has a half-life of 4.5 billion years.

        • When hit by neutron, it eventually decays into Pu-239.

      • Pu-239: It has a half-life of 24,000 years and is produced in breeder reactors from U-238.

        • Its fission provides about one-third of the total energy produced in a typical commercial nuclear power plant.

      Nuclear Components

      • Core: Contains up to 50,000 fuel rods.

        • Each fuel rod is stacked with many fuel pellets.

      • Fuel: Enriched (concentrated) U-235 is usually the fuel.

        • The fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.

      • Control rods: Move in and out of the core to absorb neutrons and slow down the reaction.

      • Moderator: It reduces the speed of fast neutrons, thereby allowing a sustainable chain reaction.

      • Coolant: Removes heat and produces steam to generate electricity.

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      6.6: Energy from Biomass

      • Biomass: It is biological material derived from living, or recently living, organisms that can be burned in large incinerators to create steam that is used for generating electricity.

        • It can be grown on marginal land that is not suitable for agriculture.

      • Anaerobic digestion: A collection of processes by which microorganisms break down biodegradable material, in the absence of oxygen, to produce methane gas, which is then burned to produce energy.

        • Reduces the reliance on coal and oil.

        • Reduces the impact of land disturbances required for coal mining.

        • Reduces the methane emissions from landfills that contribute to global warming.

      • Biofuel: A liquid fuel produced from living organisms.

        • These are biodegradable, can be converted into biodiesel or bioethanol to power vehicles.

        • It can be produced anywhere as opposed to fossil fuels.

        • It is a renewable energy source.

      

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      6.7: Solar Energy

      • Solar energy: It consists of collecting and harnessing radiant energy from the sun to provide heat and/or electricity.

        • Electrical power and heat is generated at home and at industrial sites through photovoltaic cells, solar collectors, or at a central solar-thermal plant.

      • Passive solar heating: It does not include any type of mechanical heating device and functions by incorporating building features that absorb heat and then release it slowly to maintain the temperature throughout the building.

      • Active solar heating: It generates more heat than passive systems, and relies on three components: a solar collector to absorb the solar energy, a solar storage system, and a heat transfer system.

      • Residential photovoltaic system: It consists of solar panels to absorb and convert sunlight into electricity, a solar inverter to change the electric current from DC to AC, and a battery storage and backup system.

      

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      6.8: Hydroelectric Power

      • Dams: These are built to trap water, which is then released and channeled through turbines that generate electricity.

        • Hydroelectric generation accounts for approximately 44% of renewable electricity generation, and 6.5% of total electricity generation in the United States.

        • There are about 75,000 dams in the United States that block ~600,000 miles (~1 million km) of what had once been free-flowing rivers.

      • Advantages

        • Dams result in habitat destruction.

        • Dams help control flooding

        • Long life spans

        • Low operating and maintenance costs, which result in affordable electricity

        • Moderate to high net-useful energy

        • No polluting waste products

        • Provide water storage for municipal and agricultural use

      • Disadvantages

        • Dams are expensive to build.

        • Dams create large flooded areas behind the dam from which people are displaced.

        • Dams destroy wild rivers.

        • Dams destroy wildlife habitats and keep fish from migrating.

        • Dams reduce the amount of land available for agriculture.

        • Sedimentation behind the dam requires dredging.

      • Floods can be caused by the following:

        • Failures of dams, levees, and pumps

        • Fast snowmelt

        • Increased amounts of impervious surfaces, e.g., asphalt or concrete

        • Natural hazards, such as wildfires, reduce the supply of vegetation that absorbs rainfall

        • Prolonged heavy rainfall

        • Severe winds over water

        • Tsunamis

        • Unusually high tides and storm surges

      

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      6.9: Geothermal Energy

      • Heat contained in underground rock and fluids from molten rock (magma), hot dry-rock zones, and warm-rock reservoirs produces pockets of underground steam and hot water that can be used to drive turbines, which can then generate electricity.

      

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      6.10: Hydrogen Fuel Cells

      • The hydrogen fuel cell operates similarly to a battery with two electrodes—oxygen passes over one and hydrogen passes over the other.

      • The hydrogen reacts with a catalyst to form negatively charged electrons and positively charged hydrogen ions (H+).

      • The electrons flow out of the cell to be used as electrical energy.

      • The hydrogen ions then move through a membrane, where they combine with oxygen and electrons to produce water.

      • Unlike batteries, fuel cells never run out.

      

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      6.11: Wind Energy

      • Wind turbines work very simply: instead of using electricity to make wind—like a fan—wind turbines use wind to make electricity.

      • Wind turns the giant turbine blades, and then that motion powers generators.

      • Wind Farms: Wind turbines clustered together.

      • Using wind power is by far the most efficient method of producing electricity

      • One megawatt of wind energy can offset approximately 2,600 tons of CO2.

      • About 6% of the electrical demand in the United States is now produced from wind energy.

      • The current capacity of wind power in the United States powers approximately 20 million homes.

      • Offshore wind represents a major opportunity to provide power to highly populated coastal cities.

      • The largest turbines can harness energy to power 600 American homes.

      • The country with the largest wind energy installed capacity is China, followed by the United States.

      • There has been a 25% increase in wind turbine use in the last decade, but wind energy only provides a small percentage of the world’s energy.

      

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      6.12: Energy Conservation

      • Add extra insulation and seal air leaks.

        • Improving attic insulation and sealing air leaks can save 10% or more on annual energy bills.

      • Change to a programmable HVAC thermostat.

        • A programmable thermostat can save as much as 15% on heating and cooling costs.

      • Change to more efficient LED lighting.

        • LED lights do not contain mercury and can be disposed of with the regular household trash.

      • Minimize phantom loads.

        • Phantom Load: Refers to the energy that an appliance or an electronic device consumes when it is not actually turned on.

        • 75% of the electricity used to power home electronics is consumed while the products are turned off.

      • Use more energy-efficient appliances.

      7.1: Introduction to Air Pollution

      • Air pollution: It occurs when harmful or excessive quantities of substances are introduced into Earth’s atmosphere.

      • Parts per million (ppm): The most common form of expressing air pollutants.

      • Primary Pollutants: Emitted directly into the air.

      • Secondary Pollutants: Result from primary air pollutants’ reacting together and forming new pollutants.

      • Point source air pollution: It occurs when the contaminant comes from an obvious source.

      • Non-point source air pollution: It occurs when the contaminant comes from a source that is not easily identifiable or from a number of sources spread over a large, widespread area.

      • Criteria air pollutants: These are a set of eight air pollutants that cause smog, acid rain, and other health hazards and are typically emitted from many sources in the industry, mining, transportation, power generation, and agriculture.

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      7.2: Atmospheric CO2 and Particulates

      • Industrial smog: Trends to be sulfur-based and is also called gray smog.

      • Formation of Industrial Smog

        • Carbon in coal or oil is burned in oxygen gas to produce carbon dioxide and carbon monoxide gas.

        • Unburned carbon ends up as soot or particulate matter (PM).

        • Sulfur in oil and coal reacts with oxygen gas to produce sulfur dioxide.

        • Sulfur dioxide reacts with oxygen gas to produce sulfur trioxide.

        • Sulfur trioxide reacts with water vapor in the air to form sulfuric acid.

        • Sulfuric acid reacts with atmospheric ammonia to form brown, solid ammonium sulfate.

      Carbon Monoxide (CO)

      • Carbon monoxide: It is a colorless, odorless, and tasteless gas that is slightly less dense than air and is produced from the partial oxidation of carbon-containing compounds.

      • It forms when there is not enough oxygen to produce carbon dioxide.

      • Carbon monoxide is present in small amounts in the atmosphere, primarily as a product of the following:

        • Natural and man-made fires.

        • Photochemical reactions in the troposphere.

        • The burning of fossil fuels

        • Volcanic activity

      • Methods to reduce carbon monoxide pollution include the following:

        • Building more public transportation infrastructure

        • Requiring catalytic converters on all cars worldwide; however, this only converts carbon monoxide to carbon dioxide—a greenhouse gas

        • Switching to renewable energy sources

      Lead (Pb)

      • Lead: It is used in building construction, lead-acid batteries for vehicles, bullets and shot fishing weights, solder, and shields for radiation.

      • Exposure to lead can occur from inhalation of polluted air and dust and from the ingestion of lead in food and/or water.

      • Symptoms of lead poisoning include failure of the blood to make hemoglobin, which results in anemia disruptors, mental retardation and disabilities, hypertension, miscarriages and/or premature births, and even death at relatively low concentrations.

      Nitrogen Oxides

      • Nitrogen Oxide: A generic term for nitric oxide and nitrogen dioxide, which are produced from the reaction of nitrogen and oxygen gases in the air.

        • These gases are formed whenever nitrogen occurs in the presence of high-temperature combustion.

      • Nitrous oxide: It is a major air pollutant, with levels of N2O having increased by more than 15% since 1750.

        • It causes ozone depletion.

        • It is formed by denitrification and nitrification.

      Ozone

      • Ozone: It is an inorganic molecule with the chemical formula O3, and tropospheric (ground-level) ozone is a secondary air pollutant.

      • Tropospheric ozone: It does not have strong global effects, but instead is more influential in its effects on smaller, more localized areas.

      • Tropospheric ozone can have the following effects:

        • Cause asthma and bronchitis

        • Harm lung function and irritate the respiratory system

        • Result in heart attacks and other cardiopulmonary problems

        • Suppress the immune system.

      Peroxyacyl Nitrates (PANs)

      • Peroxyacyl Nitrates (PANs): These are secondary pollutants. Because they break apart quite slowly in the atmosphere into radicals nd NO2, PANs are able to move far away from their urban and industrial origin.

      • It causes:

        • Eye irritation

        • Impaired immune systems

        • Inhibited photosynthesis

        • Reduced crop yields by damaging plant tissues

        • Respiratory problems

      • Methods to reduce PANs include the following:

        • Limiting wood-burning fireplaces and stoves in new home construction

        • Reducing smokestack emissions through baghouse filters, cyclone precipitators, scrubbers, and/or electrostatic precipitators

        • Reducing the incineration of municipal and industrial wastes

        • Reducing the reliance on fossil fuels, especially oil and coal

      Sulfur Dioxides

      • Sulfuric Dioxide: A colorless gas with a penetrating, choking odor that readily dissolves in water to form an acidic solution.

      • Sulfur dioxide emissions come from power stations, oil refineries, and large industrial plants burning fossil fuels.

      • It is toxic to a variety of plants and reduces crop yields.

      • Sulfur dioxide, emitted in sufficient quantities at low or ground level, can combine with air moisture to form an acid solution that dissolves stonework.

      • It irritates the throat and lungs, and, if there are fine dust particles in the air, can damage the respiratory system.

      • Steps that can be taken to reduce the amount of SO2 in the atmosphere include the following:

        • Fluidized gas combustion

        • Using only low-sulfur coal

        • Using scrubbers in the smokestacks

        • Washing the coal

      Suspended Particulate Matter

      • Suspended particulate matter (PMx): It is microscopic solid or liquid matter suspended in Earth’s atmosphere.

        • The “x” refers to the size of the particle.

      • The smaller and lighter a particle is, the longer it will stay in the air.

      • Larger particles tend to settle to the ground by gravity in a matter of hours, whereas the smallest particles can stay in the atmosphere for weeks and are mostly removed by precipitation.

      • Particulate Matter

        • affects the diversity of ecosystems;

        • changes the nutrient balance in coastal waters and large river basins;

        • depletes the nutrients in the soil;

        • damages sensitive forests and farm crops;

        • increases health issues with humans and animals

        • makes lakes and streams more acidic.

      • Airborne particulate matter can be reduced by:

        • conserving energy to reduce demands on power plants;

        • increasing air-quality standards for emissions of particulate matter from smokestacks;

        • increasing automobile emission standards;

        • limiting the use of household and personal products that cause fumes;

        • not burning leaves and other yard waste;

        • not using wood in fireplaces

      Naturally Occurring PMx	Anthropogenic Occurring PMx
      Dust storms	Burning of fossil fuels—power plants
      Forest and grassland fires	Incineration of wastes
      Sea spray	Soil erosion—desertification, deforestation
      Volcanoes	Vehicle exhaust

      Volcanic Organic Compounds

      • Volcanic Organic Compounds (VOCs): These are organic chemicals that have a high vapor pressure (easily evaporate) at ordinary room temperature.

        • Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate and enter the surrounding air.

      • Health effects of “sick building” syndrome include

        • cancer;

        • damage to the liver, kidney, and central nervous system;

        • eye, nose, and throat irritation; and

        • headaches, loss of coordination, and nausea.

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      7.3: Photochemical Smog

      • Photochemical smog: It is catalyzed by ultraviolet (UV) radiation, tends to be nitrogen-based, and is referred to as brown smog.

      • Forming Photochemical Smog

        • 6 A.M.–9 A.M.: As people drive to work, concentrations of nitrogen oxides and VOCs increase.

        • 9 A.M.–11 A.M.: As traffic begins to decrease, nitrogen oxides and VOCs begin to react, forming nitrogen dioxide (NO2).

        • 11 P.M.–4 P.M.: As the sunlight becomes more intense, nitrogen dioxide is broken down and the concentration of ozone (O3) increases.

          • Nitrogen dioxide also reacts with water vapor to produce nitric acid (HNO3) and nitric oxide (NO).

          • Nitrogen dioxide can also react with VOCs released by vehicles, refineries, and gas stations to produce toxic PANs (peroxyacyl nitrates).

        • 4 P.M.–Sunset: As the sun goes down, the production of ozone is halted.

      

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      7.4: Thermal Inversion

      • Thermal inversions: These occur when air temperature rises with height instead of falling.

      • This effect traps pollution like smog close to the ground, which may harm human health.

      • This usually happens at night when solar heating stops and the surface cools, cooling the atmosphere above it.

      • A warm air mass moving over a colder one traps the cooler air below and stills the air, trapping dust and pollutants and increasing their concentrations.

      • Antarctica has a nearly constant temperature inversion.

      

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      7.5: Outdoor and Indoor Air Pollutants

      • “Sick building” syndrome (SBS): It is a term used to describe a combination of ailments associated with an individual’s place of work or residence.

      • Asbestos: It is inexpensive, durable, and flexible and naturally acts as an insulating and fireproofing agent.

      • Carbon monoxide poisoning: It is the most common type of fatal indoor air poisoning in many countries because it easily combines with hemoglobin to block the blood’s oxygen-carrying capacity.

      • Formaldehyde: It is an organic chemical that is prevalent in the indoor environment and is a carcinogen that is linked to lung cancer.

      • Radon: It is an invisible radioactive gas that results from the radioactive decay of radium, which can be found in rock formations beneath buildings.

      • Cigarette smoke: It contains almost 5,000 chemical compounds, including 60 known carcinogens (cancer-causing chemicals), one of which is dioxin.

      Remediation Steps to Reduce Indoor Air Pollutants

      • Add plants that absorb toxins.

      • Do not allow smoking indoors.

      • Install air purification systems and ensure adequate fresh air ventilation when temperatures permit.

      • Maintain all filters and vents.

      • Monitor humidity levels to reduce mold and mildew.

      • Test for radon gas and other dangerous indoor pollutants.

      • Use “green” cleaning products.

      • Use natural pest-control techniques.

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      7.6: Reduction of Air Pollutants

      Controlling Air Pollution/Pollution-Control Devices

      • Catalytic converter: It is an exhaust emission control device that converts toxic chemicals in the exhaust of an internal-combustion engine into less harmful substances.

      • Catalyst: It stimulates a chemical reaction in which by-products of combustion are converted to less toxic substances by way of catalyzed chemical reactions.

      • Most present-day vehicles that run on gasoline are fitted with a “three way” converter, since it converts the three main pollutants:

      • Oxidation of carbon monoxide to carbon dioxide:

      

      • Oxidation of unburned hydrocarbons to carbon dioxide and water:

      

      • Reduction of nitrogen oxides to nitrogen and oxygen:

        

      • Catalytic converters remove hydrocarbons and other harmful emissions, but they do not reduce fossil fuel-produced carbon dioxide.

      Remediation Steps to Reduce Air Pollution

      • Ban open burning of waste.

      • Buy smaller cars and energy-efficient appliances.

      • Decrease unnecessary travel.

      • Distribute solar cook stoves to developing countries to replace wood and coal.

      • Drive within the speed limit and keep tires inflated.

      • Institute flexible work shifts.

      • Maintain vehicle properly with regular tune-ups and oil changes.

      • Reduce idling and turn off engines while waiting.

      • Use mass transit systems or carpool when possible.

      • Toughen Corporate Average Fuel Economy (CAFE) standards.

      • Toughen legislation to reduce sulfur content in fuel.

      • Use fans instead of air conditioners.

      • Use fluorescent or LED lighting.

      • When buying a car, consider its fuel efficiency.

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      7.7: Acid Rain (Deposition)

      • Acid deposition: It occurs when atmospheric chemical processes transform sulfur and nitrogen compounds and other substances into wet or dry deposits on Earth.

      • Dry Deposition: In dry areas, acidic chemicals in the air may become dust or smoke and stick to the ground, buildings, homes, cars, and trees, which rainstorms wash away, increasing acidic runoff.

      • Wet Deposition: Acid rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals.

      • Acid rain: It causes acidification of lakes and streams.

        • It damages trees at high elevations and many sensitive forest soils by nitrogen saturation and acidification that harms decomposers and mycorrhizal fungi.

      • Acid shock: Caused by rapid melting of snow pack with dry acidic particles, raises lake and stream acid concentrations five to ten times higher than acidic rainfall.

      • Acid deposition due to sulfur dioxide begins with sulfur dioxide being introduced into the atmosphere by burning coal and oil, smelting metals, organic decay, and ocean spray.

        • It then combines with water vapor to form sulfurous acid which then reacts with oxygen to form sulfuric acid.

      • Acid deposition due to nitrogen oxides begins with nitrogen oxides formed by burning oil, coal, or natural gas.

        • They are also found in volcanic vent gases and are formed by forest fires, bacterial action in the soil, and lightning-induced atmospheric reactions.

      Effects of Acid Deposition

      • Acid shock

      • An increase in fish kills.

      • Changes in animal life due to changes in vegetation

      • Vegetation changes due to soil pH and ecosystem changes affect food webs.

      • Increased leaching of soil nutrients

      • Increased solubility of toxic metals, including methyl mercury, lead, and cadmium

      • Reduced buffering capacity of the soil

      Heat Islands and Air Pollution

      • Urban heat islands: These occur in metropolitan areas that are significantly warmer than their surroundings.

      • Since warmer air can hold more water vapor, rainfall can be as much as 30% greater downwind of cities when compared with areas upwind.

      • Reasons for higher urban temperatures are as follows:

        • Air conditioning, transportation, lighting, and other fuels generate heat.

        • Urban impervious materials reduce the cooling effect of soil and leaf evaporation and tree shading.

        • Buildings block Earth's thermal radiation.

        • There is a lack of vegetation and standing water.

        • More black asphalt and building surfaces absorb heat and reduce sunlight reflectivity.

      • Street Canyon: A place where the street is flanked by buildings on both sides, creating a canyon-like environment.

      • High levels of pollution in urban areas can also create a localized greenhouse effect.

      • Urban heat islands can directly influence the health and welfare of urban residents who cannot afford air conditioning

      ---

      7.8: Noise Pollution

      • Noise pollution: It is an unwanted human-created sound that disrupts the environment.

      • The dominant form of noise pollution is from transportation sources.

      Effects of Noise Pollution

      • Sensory hearing loss is caused by damage to the inner ear and is the most common form associated with noise pollution.

      • Excessive noise can cause:

        • a decrease in alertness and the ability to memorize;

        • anxiety and nervousness;

        • cardiovascular problems, which manifest as an accelerated heartbeat and high blood pressure; and

        • gastrointestinal problems.

      Techniques to Reduce Roadway Noise

      • Create computer-controlled traffic flow devices that reduce braking and acceleration, and implement changes in tire designs.

      • Create noise barriers.

      • Introduce newer roadway surface technologies.

      • Limit times for heavy-duty vehicles.

      • Place limitations on vehicle speeds.

      Techniques to Reduce Aircraft Noise

      • Develop quieter jet engines.

      • Reschedule takeoff and landing times.

      Techniques to Reduce Industrial Noise

      • Create new technologies in industrial equipment.

      • Install noise barriers in the workplace.

      • Control residential noise, such as power tools, garden equipment, and loud entertainment equipment, through local laws and enforcement.

      8: Aquatic and Terrestrial Pollution

      8.1 - Sources of Pollutants

      Point vs. Nonpoint Pollutant Sources

      • Point Source

        • Pollutant that enters the environment form an easily identified and confined place

        • You can “point” 👉 to it

      • Nonpoint Source

        • Pollutants entering the environment from many places at once. Difficult to “point” to one individual source

      Must-Know Pollution Examples

      • Point Source Examples

        • Animal waste runoff from a CAFO (ammonia (N), fecal coliform bacteria)

        • Emissions from smokestack of a coal power plant (CO2, NOx, SO2, PM)

        • BP Oil Spill (hydrocarbons, benzene)

      • Nonpoint Source Examples

        • Urban runoff (motor oil, nitrate fertilizer, road salt, sediment)

        • Pesticides sprayed on agricultural fields; carried by wind and washed off large agricultural regions ino bodies of water

        • Estuaries and bays are polluted by many nonpoint pollution sources from the large watersheds that empty into them

      Pollutants vs. Pollution

      • Pollutants

        • Specific chemicals or groups of chemicals from specific sources with specific env. & human health effects

        • Much more likely to earn you FRQ credit

      • Pollution

        • Vague, nondescript term for any substance that is harmful to the environment

        • Never acceptable on an APES FRQ

          • Exceptions:

            • Specific categories of pollution: thermal pollution, noise pollution, sediment pollution

      8.2 - Human Impacts on Ecosystems

      Range of Tolerance

      • Organisms have range of tolerance for abiotic conditions in their habitat

        • pH, temperature, salinity (saltiness), sunlight, nutrient levels (ammonia, phosphate)

      • Organisms also have range of tolerance for pollutants that human activities release into their habitats

        • Pollutants cause physiological stress such as

        • Limited growth

        • Limited reproductive function

        • Difficulty respiring (breathing), potentially asphyxiation (suffocation)

        • Hormonal disruption

        • Death (if concentration of pollutant is high enough)

      Environmental Effects of Acid Rain

      

      

      
      

      • pH Tolerance

        • As pH decreases (more acidic) outside optimal range for a species, pop. declines

          • When pH leaves range of tolerance, they cannot survive at all, due to:

            • Aluminum toxicity

            • Disrupted blood osmolarity (Na+/Cl- balance disrupted at low pH)

        • Indicator species can be surveyed and used to determine conditions of an ecosystem (soil, water, etc.)

          • Ex: high whitemoss/filamentous algae pop. indicates pH < 6.0

          • High crustacean pop. indicates pH > 6.0

      Temperature Tolerance of Reef Algae

      

      
      

      • Coral reef = mutualistic relationship between coral & photosynthetic algae called zooxanthellae; algae supply sugar & coral supply CO2 + detritus (nutrient containing org. matter.)

      • Algae have narrow temperature tolerance and leave the reef when temp. rises

        • Pollutants from runoff (sediment, pesticides, sunscreen) can also force algae from reef

      • Coral lose color & become stressed and vulnerable to disease without algae (main food source)

      Human Impacts on Coral Reef

      

      

      

      
      

      • Humans disrupt coral reef ecosystems via greenhouse gas emissions

        (warming ocean temp. & bleaching coral)

      • Overfishing decreases fish populations in coral reef ecosystems & bottom trawling can break reef structure and stir up sediment

      • Urban and agricultural runoff also damages coral reef ecosystems

        • Sediment pollution: sediment carried into the ocean by runoff makes coral reef waters more turbid, reducing sunlight (photosynthesis)

        • Toxicants: chemicals in sunscreen, oil from roadways, pesticides from ag. runoff

        • Nutrients (P/N): ammonia from animal waste, nitrates/phosphates from ag. or lawn fertilizers

      Oil Spill Effects

      

      
      

      • Hydrocarbons in crude oil (petroleum) are toxic to many marine organisms and can kill them, especially if they ingest (eat) the oil or absorb through gills/skin

      • Other physiological effects:

        • Decreased visibility and decreased photosynthesis due to less sunlight penetrating water surface

        • Oil sticking to bird feathers

        • Oil sinking to bottom and killing bottom-dwellers due to: direct toxicity or suffocation

      • Oil can wash ashore and decrease tourism revenue and kill fish, decreasing fishing industry revenue, hurt restaurants that serve fish

        • Oil can settle deep in root structures of estuary habitats like mangroves or salt marshes

          • Can be toxic to salt marsh grasses, killing them and loosening their root structure, leading to coastline erosion

            • Can remove habitats used by fish & shellfish for breeding grounds

      Oil Spill Clean Up

      

      

      
      

      • Oil spills can occur when an underwater oil well explodes/blows out (BP Gulf Spill) or when a tanker runs into a rock/iceberg and is punctured (Exxon Valdez)

        • Cleanup can involve booms on surface to contain spread and ships with vacuum tubes to siphon oil off of the surface or devices to skim it off

        • Physical removal of oil from beach sand and rocks with towels, soaps, shovels

        • Chemical dispersants sprayed on oil slicks to break up and sink to the bottom

          • Clears up surface, but can smother bottom-dwellers

          • Dispersant chemicals may be harmful

        • Burning oil off the surface

      8.8 - Biomagnification

      Bioaccumulation

      

      
      

      • Absorption and concentration of compounds (especially fat-soluble ones like POPs) in the cells & fat tissues of organisms

        • B/c fat-soluble compounds like POPs and methylmercury don’t dissolve easily in water, they don’t enter blood easily & don’t leave the body in urine easily

          • Instead they build up in fat tissue

          • This leads to them building up to reach higher and higher concentrations in the organism over time

      Biomagnification

      

      
      

      • Increasing concentrations of fat-soluble compounds like methylmercury and POPs in each level up the trophic pyramid or food web/chain

      • Biomagnification begins with POPs or methylmercury in sediments or plants in an ecosystem (phytoplankton, grass)

        • Primary consumers (zooplankton, bottom-feeding fish, insects) take in POPs by eating producers, causing bioaccumulation of POPs in their tissues

        • Secondary consumers eat primary consumers and take in the POPs in their tissues

          • Because of the 10% rule, organisms at each successive trophic level need to eat more and more biomass to receive enough energy, leading to higher and higher POP levels over their lifetimes

          • Large predators like salmon, dolphins, and whales have the highest POP/methylmercury levels

      DDT Biomagnification

      

      
      

      • DDT was banned in many developed nations, but still persists in sediments of many bodies of water

        • Taken in by bottom feeders/zooplankton & biomagnified at higher trophic levels

        • Reach highest levels in top predators, esp. predatory birds like eagles & osprey

          • Causes thinning of the eggshells in these birds

          • Linked to massive pop. decline of bald eagle in US, which prompted the passage of the Endangered Species Act (73’)

      Methylmercury Biomagnification

      

      

      
      

      • Mercury is emitted from burning coal & by volcanoes, carried by wind, and deposited in water where bacteria convert it into toxic methylmercury

        • Taken in by phytoplankton & biomagnified at higher trophic levels

        • Reach highest levels in top predators, tuna, sharks, whales

          • Neurotoxicant: damages the central nervous system of animals

        • Human exposure to methylmercury & POPs comes from eating large predatory fish like tuna & salmon (and other seafood)

          • Damage to human nervous system (esp. developing fetus) and disrupt the reproductive system

      8.3 - Endocrine Disruptors and Industrial Water Pollutants

      Endocrine Disruptors

      

      
      

      • Chemicals that interfere with the endocrine (hormonal) systems of animals

      • Bind to cellular receptors meant for hormones, blocking the hormone from being received, or amplifying its effects

        • Human medications that pass through urine & into sewage or are flushed down toilet are a common source (meant to influence human hormones, so they can also disrupt animals’)

      • Example:

        • atrazine (herbicide) binds to receptors of cells that should convert estrogen into testosterone in male frogs, leading to: high estrogen in males, low sperm count, even feminization (development of eggs in the testes or ovary formation)

      Endocrine Disruptors

      • Atrazine

        • broad-spectrum herbicide used to control weeds & prevent crop loss

          • Applied to ag. fields, runs off into local surface or groundwater or is carried by wind

          • Can contaminate human well-water, or enter body via unwashed produce

      • DDT

        • broad-spectrum insecticide that was phased out, but still persists in env.

          • Applied to ag. fields, runs off into local surface or groundwater or is carried by wind

      • Phthalates

        • compounds used in plastic and cosmetic manufacturing

          • Enter surface & groundwater via intentional dumping of trash, or chemical waste from plastic/cosmetic factories improperly disposing of waste, landfill leaching

          • Also found in some cosmetics & plastic food containers (#3 plastic & “fragrance”)

      • Lead, arsenic, mercury

        • heavy metals

      • Many human medications that enter sewage via human urine or flushed meds

      Mercury

      

      
      

      • mercury: naturally occurring in coal, released by anthropogenic activities:

        • Coal combustion, trash incineration, burning medical waste, heating limestone for cement

          • Attaches to PM released by burning & deposits in soil/water wherever PM settles

          • Can be released if coal ash stored in ponds overflow & runoff

        • Endocrine disruptor: inhibits estrogen & insulin (interferes with menstrual cycle & ovulation)

        • Teratogen: (chemical harmful to developing fetuses) can accumulate in fetus brain

          • Pregnant women can reduce risk by eating less seafood

      • Mercury itself isn’t toxic, but bacteria in water sources convert it to methylmercury which is highly toxic to animals (neurotoxicant that damages central nervous system)

      Arsenic and Lead

      • arsenic: naturally occurring element in rocks underground that can dissolve into drinking water; Natural release into groundwater can be worsened by mining

        • Anthropogenic sources: formerly in pesticides applied to ag. Fields (can still linger in soil, wood treatment chemicals to prevent rot, coal combustion & ash

          • Carcinogenic: (lungs, bladder, kidneys) & endocrine disrupting

          • Endocrine disruptor: (specifically glucocorticoid system)

            • Can be removed with water filters

      • lead: found in old paint (in homes), old water pipes, and soils contaminated by PM from vehicle exhaust before lead was phased out of gas in 70s

        • Also released in fly ash (PM) of coal combustion

          • Neurotoxicant (damages central nervous system, especially in children)

          • Endocrine disruptor

            • Can be removed with water filters

      Coal Ash

      

      
      

      • Coal ash can be a source of mercury, lead, and arsenic

        • Can attach to fly ash (PM) from smokestack and be carried by wind, deposited in ecosystems far away

        • Both fly and bottom coal ash are often stored on site in ponds, dug into soil & lined with plastic (sometimes)

          • Ponds can leach into groundwater, contaminating it with arsenic, lead, mercury

          • Ponds can overflow & runoff into nearby surface waters & agricultural fields

      8.4 - Human Impacts on Wetlands and Mangroves

      Wetlands

      

      
      

      • An area with soil submerged/saturated in water for at least part of the year, but shallow enough for emergent plants

      • Wetland plants have adapted to living with roots submerged in standing water (cattails, lily pads, reeds)

      • Ecosystem Services of Wetlands

        • Provisioning: habitat for animal & plant foods

        • Regulating: groundwater recharge, absorb. of floodwater, CO2 sequestration

        • Supporting: H2O filtration, pollinator habitats, nutrient cycling, pest control

        • Cultural: tourism revenue, fishing license, camping fees, ed/med research

      Threats to Wetlands

      

      
      

      • Pollutants: nutrients (N/P), sediment, motor oil, pesticides, endocrine disruptors

      • Development: wetlands can be filled in or drained to be developed into homes, parking lots, stores, or agricultural land

      • Water diversion upstream for flood control, agriculture, or drinking water can reduce water flow and dry up wetlands (ex: Everglades) ⬇

        • Dam construction for flood control/hydroelect. reduces water & sediment (N/P) flow to wetlands

      • Overfishing: disrupts food web of wetlands (decrease in fish predators, increase in prey)

      8.5 - Eutrophication

      Eutrophication Process

      

      
      

      • B/c they’re limiting nutrients in aq. ecosystems, extra input of N & P lead to eutrophication (excess nutrients) which fuels algae growth

        • Algae bloom covers surface of water, blocking sunlight & killing plants below surface

        • Algae eventually die-off; bacteria that break down dead algae use up O2 in the water (b/c decomp. = aerobic process)

        • Lower O2 levels (dissolved oxygen) in water kills aquatic animals, especially fish

        • Bacteria use up even more O2 to decompose dead aq. animals

        • Creates pos. feedback loop: less O2 → more dead org. → more bacterial decomposition → less O2

      Cultural Eutrophication

      

      
      

      • Anthropogenic nutrient pollution (N & P) that leads to eutrophication

        • Algae bloom due to increase of N/P → decreased sunlight → plants below surface die → bacteria use up O2 for decomp. → hypoxia (low O2) & dead zones

      • Major N/P sources:

        • Discharge from sewage treatment plants (N/P in human waste & phosphates in soaps/detergents)

        • Animal waste from CAFOS

        • Synthetic fertilizer from ag. fields & lawns

      Oligotrophic Waterways

      

      
      

      • Waterways with low nutrient (N/P) levels, stable algae pop, and high dissolved oxygen

        • Can be due to lack of nutrient pollution, or age of the body of water

        • Aquatic ecosystems naturally undergo succession

          • Sediment buildup on bottom (benthic zone) leads to higher nutrient levels

          • Overtime, ponds naturally shift from oligotrophic, to mesotrophic, to eutrophic

      Dissolved Oxygen and Dead Zones

      

      

      
      

      • Decrease in dissolved oxygen (hypoxia) is what causes a dead zone

        • All aq. life requires DO (dissolved oxygen) in water for respiration

        • As DO decreases, fewer species can be supported

          • Most fish require at least 3.0 ppm to survive, 6.0 ppm to reproduce

      8.6 - Thermal Pollution

      Solubility of Oxygen and Temperature

      

      
      

      • Solubility: the ability of a solid/liquid/gas to dissolve into a liquid (oxygen dissolving into water in this case)

      • Inverse relationship between water temp & oxygen solubility

        • As water temp. ⬆ DO (dissolved oxygen) ⬇

      • Thermal pollution: when heat released into water has negative effects on organisms living in the water

        • Heat increases respiration rate of aquatic organisms (thermal shock)

        • Hot water also has less O2

          • This can lead to suffocation without enough O2 to support respiration

      Sources of Thermal Pollution

      

      
      

      • Power plants use cool water from surface/ground water sources nearby to cool steam used to turn a turbine back into water to reuse

        • Steel mills, paper mills, and other manufacturing plants also use cool water to cool down machinery & return warmed water to local surface waters

        • Urban stormwater runoff can also cause thermal pollution due to heat from blacktop/asphalt

      • Nuclear power plants require especially large amounts of cool water to cool steam back into water & to cool the reactor core

      Cooling Towers

      

      
      

      • Cooling towers/ponds are used to cool steam back into water & to hold warmed water before returning to local surface water

        • Already standard in nuclear power plants, but can be optimized to cool water better or hold it longer before returning to nearby surface waters

      8.7- Persistent Organic Pollutants (POPs)

      POPs

      

      
      

      • Persistent (long-lasting) Organic (carbon-based) Pollutants

      • Synthetic (human-made) compounds that do not easily breakdown in the environment; accumulate and build-up in water & soil

        • Fat-soluble, meaning they also accumulate and persist in animals’ fat tissue instead of passing through the body (don’t easily dissolve into blood/urine)

          • Can slowly be released from fatty tissue into bloodstream and impact brain & other organs over time (esp. reproductive system)

      Examples and Sources of POPs

      • Examples

        • DDT (outdated insecticide)

        • PCBs (plastic/paint additive)

        • PBDEs (fire-proofing)

        • BPA (plastic additive)

        • Dioxins (fertilizer production & combustion of waste and biomass)

        • Phthalates (Plastics)

        • Perchlorates (rocket/missile fuel, fireworks)

      • Pesticides

        • DDT was widely used as an insecticide before phaseout in most dev. nations

        • Still persists in soils & sediments in aq. ecosystems and builds up in food webs

      • Medications (Pharmaceutical compounds)

        • Steroids, reproduct. hormones, antibiotics, that pass through human bodies & into sewage release from treatment plants

        • Persist in streams/rivers & disrupt aq. organisms’ endocrine function

      • Dioxins

        • Byproduct of fertilizer production & burning of medical waste, FFs, biomass

        • 90% of human dioxin exposure comes from animal fats (meat, dairy, fish) since dioxins buildup in animal fat tissue

      Examples and Transport of POPs

      

      
      

      • PCBS

        • Additives in paint and plastics, released into aquatic ecosystems by industrial wastewater

        • Toxic to fish, causing spawning failure and endocrine disruption

        • Reproductive failure & cancer in humans

          • Human exposure comes through animal products

      • Perchlorate

        • Given off by rockets, missiles, and fireworks

        • Especially common near military testing sites or rocket launch pads

        • Remain in soil and can leach into groundwater or runoff into surface waters

      • POPs travel long distances through wind & water, impacting ecosystems far away

        • Wastewater release from industrial processes, leachate from landfills or improperly buried industrial waste, fertilizer/pesticide production, emissions from burning waste/biomass

        • Enter soil/water, eaten by animals, stored in their fat, eaten by humans or taken in via drinking water

      8.9- Solid Waste Disposal

      Solid Waste Types and Sources

      

      
      

      • Municipal Solid Waste (MSW)

        • Solid waste from cities (households, businesses, schools, etc.

        • Waste “stream” refers to flow of solid waste to recycling centers, landfills, or trash incineration (burning) facilities

        • Aka - trash, litter, garbage, refuse

        • ~ ⅓ paper

        • ~ ⅔ organics (compostable)

      • E-Waste

        • Old computers, TVs, phones, tablets

        • Only ~2% of MSW; is considered hazardous waste due to metals like cadmium, lead, mercury, and PBDEs (fireproof chemicals)

        • Can leach endocrine-disrupting chemicals out of landfills if thrown away with regular MSW (should be disposed of at special facilities that recycle parts)

      Sanitary Landfills

      

      
      

      • APES lingo for “landfills” or where developed nations dispose of trash; different than “dumps” which are just areas where trash is dumped, without the features below

      • Clay/plastic bottom liner: layer of clay/plastic on the bottom of a hole in the ground; prevents* pollutants from leaking out into soil/groundwater

      • Leachate Collection System: System of tubes/pipes at bottom to collect leachate (water draining through waste & carrying pollutants) for treatment & disposal

      • Methane Recovery System: System of tubes/pipes to collect that methane produced by anaerobic decomposition in the landfill

        • Methane can be used to generate electricity or heat buildings

      • Clay Cap: Clay-soil mixture used to cover the landfill once it’s full; keeps out animals, keeps in smell, and allows vegetation to regrow

      Landfill Contents and Decomposition

      

      
      

      • Landfills generally have very low rates of decomposition due to low O2, moisture, and organic material combination

        • Since these 3 factors are rarely present together in landfills, little decomp. occurs and landfills typically remain about the same size as when they were filled

      • Things that should NOT be landfilled:

        • Hazardous waste (antifreeze, motor oil, cleaners, electronics, car batteries)

        • Metals like copper & aluminum (should be recycled)

        • Old tires; often left in large piles that hold standing water ideal for mosquito breeding

      • Things that SHOULD be landfilled:

        • Cardboard/food wrappers that have too much food residue & can’t be recycled

        • Rubber, plastic films/wraps

        • Styrofoam

          • Food, yard waste, and paper can and do go in landfills, but should be recycled or composted

      Landfill Issues

      

      
      

      • Landfills have environmental impacts like groundwater contamination and release of GHGs

        • Groundwater can be contaminated with heavy metals (lead, mercury), acids, medications, and bacteria if leachate leaks through lining into soil/groundwater beneath

        • Greenhouse gases (CO2 and CH4 - methane) are released from landfills due to decomposition; both contribute to global warming & climate change

      • NIMBY (Not In My Back Yard): idea that communities don’t want landfills near them for several reasons

        • Smell & sight

        • Landfills can attract animals (rats, crows)

        • Groundwater contamination concerns

          • Landfills should be located far from rivers & streams and neighborhoods to avoid H2O cont.

      • Landfills are often placed near low-income or minority communities that don’t have the resources or political power to fight against these decisions

      Waste Incineration and Ocean Dumping

      • Waste can be incinerated (burned) to reduce the volume that needs to be landfilled; since most waste (paper, plastic, food) = hydrogen, carbon, and oxygen, it easily combusts at high temp.

        • Can reduce volume by 90%, but also releases CO2 and air pollutants (PM, SOx, NOx)

          • Bottom ash may contain toxic metals (lead, mercury, cadmium) & is stored in ash ponds, then taken to special landfills

          • Toxic metals can leach out of storage ponds or be released into atmosphere

      • Can be burned to generate electricity

      • Illegal ocean dumping occurs in some countries with few environmental regulations or lack of enforcement

        • Plastic especially collects into large floating garbage patches in the ocean

        • Can suffocate animals if they ingest (eat) it or entangle them so they can’t fly or swim and may starve

      8.10- Waste Reduction

      Reduce, Reuse, Recycle

      • The Three Rs

        • Reducing consumption is the most sustainable because it decreases natural resources harvesting and the energy inputs to creating, packaging, and shipping goods

          • Ex: Metal/reusable water bottle to reduce plastic use Riding bike or walking to reduce gasoline use

            • Reusing: the next most sustainable b/c it doesn’t require additional energy to create a product

          • Ex: Buying second hand clothes, using old wood pallets for furniture, washing plastic takeout food containers and reusing

      • Recycling: processing and converting solid waste material into new products

        • Ex: Glass being turned into glass again (closed-loop), plastic water bottles being turned into fabric for clothes/jackets (open loop)

          • Least sustainable of the three Rs due to the amount of energy it requires to process and convert waste materials

      Recycling Pros and Cons

      • Pros of Recycling

        • Reduces demand for new materials, especially metals and wood which cause habitat destruction & soil erosion when harvested

          • Reduces energy required to ship raw materials and produce new products (fewer FF comb, less CC)

          • Reduces landfill volume, conserving landfill space & reducing need for more landfills

      • Cons of Recycling

        • Recycling is costly and still requires significant energy

          • Cities that offer recycling services need to process, sort, and sell collected materials; prices change rapidly, leading to “recycled” materials often being thrown away

            • When citizens recycle items that shouldn’t be recycled (wrappers with food, styrofoam, etc.) it increases the cost for cities to sort & process

      Composting

      

      
      

      • Org. matter (food scraps, paper, yard waste) being decomposed under controlled conditions

        • Reduces landfill volume and produces rich organic matter that can enhance water holding capacity, nutrient levels of agricultural or garden soil

          • Produces valuable product to sell (compost)

        • Reduces the amount of methane released by anaerobic decomposition of organic matter in landfills

        • Should be done w/proper mix of “browns” (Carbon) to “greens” (N) ~ 30:1

          • Should also be aerated and mixed to optimize decomposition (bacteria need O2 for decomp.)

      • Potential drawbacks include the foul smell that can be produced if not properly rotated & aerated and rodents or other pests that may be attracted

      E-Waste

      • Waste from electronics (phones, computers, etc.) that often contain heavy metals (lead, merc, cadmium)

        • Can leach these toxic metals into soil & groundwater if disposed of in landfills or open dump

      • Can be recycled and reused to create new electronics, but often sent to developing nations for recycling due to health hazards, more strict env. & worker protection laws in developing nations

        • Can be dismantled and sold to countries that extract valuable metals (gold, silver, platinum) from motherboards

        • Often burned or dumped due to less strict env. regulations or lack of enforcement in developing nations

      Waste to Energy

      

      

      
      

      • Waste can be incinerated (burned) to reduce the volume & also generate electricity; most waste (paper, plastic, food) = hydrogen, carbon, and oxygen so it easily combusts at high temp.

        • Same process as burning coal, NG, biomass

        • Heat → water → steam → turbine → generator → ⚡

      • Methane gas produced by decomposition in landfill can be collected with pipes & burned to generate electricity

        • Heat → water → steam → turbine → generator → ⚡

        • Reduces landfill volume

        • Produces electricity without fracking or mining for FFs

      8.11- Sewage Treatment

      Water Treatment Process

      • Primary Treatment

        • Physical removal of large debris (TP, leaves, plastic, sediment) with a screen or grate

      • Secondary Treatment

        • Biological breakdown of organic matter (feces) by bacteria; aerobic process that requires O2

      • Tertiary Treatment

        • Ecological or chemical treatments to reduce pollutants left after primary & secondary (N, P, bacteria)

      • Disinfectant

        • UV light, ozone, or chlorine is used to kill bacteria or other pathogens, such as e. Coli (considered part of 3)

      • Effluent: liquid waste (sewage) discharged into a surface body of water, typically from a wastewater treatment plant

      Primary and Secondary Treatment

      

      
      

      • Primary

        • Screens or grates filter out large solids (paper, plastic)

        • Grit chamber allows sediment (sand, gravel)

          to settle out & be removed

      • Secondary

        • O2 is bubbled into aeration tank filled with bacteria that break down org. matter into CO2 and nutrients like N & P

        • Secondary treatment removes 70% of P and 50% of N DOES NOT remove POPs such as medications or pesticides

      • Sludge: inorganic, solid waste that collects at the bottom of tanks in primary and secondary treatment

        • Water is spun/pumped off to concentrate it further

        • Dry, remaining physical waste is collected to be put in landfill, burned, or turned into fertilizer pellets

      • After primary & secondary treatment, some plants go directly to disinfectant (UV, ozone, chlorine) & discharge into surface water, while some will use tertiary treatment to remove more nutrients before discharge

      Tertiary Treatment

      

      
      

      • Tertiary treatment uses chemical filters to remove more of the nitrates & phosphates from secondary treatment discharge

      • Critical step because effluent that is discharged into surface waters with elevated nitrate/phosphate levels leads to eutrophication

      • Expensive and not always used

      Sewage Treatment Issues

      

      
      

      • Combined sewage and stormwater runoff systems can cause wastewater treatment plants to flood during heavy rains, releasing raw sewage into surface waters

      • Beneficial b/c it treats stormwater runoff normally, but causes overflow during heavy rains

      • Raw sewage release contaminates surface waters with:

        • E. coli

        • Ammonia

        • Nitrates

        • Phosphates

        • Endocrine disruptors (medications)

      • Even treated wastewater effluent released into surface water often has elevated N/P levels and endocrine disruptors (medications passed through the body)

      8.12 and 8.13- LD50 and Dose-Response Curve

      Dose-Response Studies and LD50

      • Studies that expose an organism to different doses of concentrations of a chemical to measure the response (effect) of the organism

      • Independent variable = concentration of the chemical (added to food, water, or air)

      • Dependent variable = response measured in org. (usually death or impairment)

      • LD50 refers to the dose or concentration of the chemical that kills 50% of the population being studied (ex: arsenic LD50 in mice = 13 mg/kg)

        • LD50 data are usually expressed as:

          • mass (g, mg)/body unit mass (kg)

          • ppm - parts per million (in air)

          • mass/volume (in water of blood)

      Dose-Response Curve

      

      
      

      • The data from a dose-response study, graphed with percent mortality or other effect on the y-axis and dose concentration of chemical on x-axis

      • Lowest dose where an effect (death, paralysis, cancer) starts to occur is called the threshold or toxicity threshold

      • Dose-response curves are usually “S-shaped” - low mortality at low doses, rapid increase in mortality as dose increases, level off near 100% mortality at high dosage

      ED50 and Other Dose Responses

      

      
      

      • ED50 refers to the dose concentration of a toxin or chemical that causes a non-lethal effect (infertility, paralysis, cancer, etc.) in 50% of the population being tested

        • Ex: the concentration of atrazine in water that causes 50% of frogs to become infertile

        • Same general “s-shape” as LD50 dose-response curve, but at lower dose concentrations

      Dose-Response Data and Human Health

      • Dose-response studies for toxic chemicals are not done on humans; data from other mammals (mice, rats) are used to simulate human toxicity

      • To determine maximum allowable levels for humans, we generally divide LD50 or ED50 dose concentration by 1,000 for extreme caution

      • Acute vs. Chronic studies: Most dose-response studies are considered acute, since they usually only measure effects over a short period of time; they’re also isolated to a lab, so they don’t measure ecological effects of organisms dying (trophic cascades)

        • Chronic studies are longer-term and follow developmental impacts

          • Ex: study of fish from hatchlings to adults to study sexual maturation

      8.14 Pollution and Human Health

      Routes of Exposure & Synergism

      • It’s difficult to establish exactly how toxic different pollutants are to humans because we have so many routes of exposure to so many different pollutants, that studying the effects of just one pollutant is difficult.

      • Routes of Exposure

        • Ways that a pollutant enters the human body

          • Lead → water pipes & paint chips

          • Mercury → seafood (tuna)

          • CO → indoor biomass comb.

          • PM → pollen, dust, etc.

          • Arsenic → rice, groundwater

      • Synergism

        • The interaction of two or more substances to cause an effect greater than each of them individually

          • Ex: Asthma caused by PM from coal PPs and COVID-19 damaging lungs

          • Carcinogenic effect of asbestos combined with lung damage from smoking

        • Synergisms make it especially hard to pinpoint the exact effects of one specific pollutant on humans

      Dysentery

      • ⛰Bacterial infection caused by food or water being contaminated with feces (often from sewage release into rivers & streams used for drinking water)

      • Causes intestinal swelling and can result in blood in feces

        • Results in severe dehydration due to diarrhea (fluid loss)

        • Kills 1.1 million people annually, mostly in developing countries with poor sanitation and limited access to water filtration

      • Can be treated with antibiotics that kill the bacteria causing the infection and access to treated/filtered water that can rehydrate

      Mesothelioma (asbestos)

      

      
      

      • A type of cancerous tumor caused by exposure to asbestos, primarily affecting the lining (epithelium) of the respiratory tract, heart, or abdominal cavity

      • Asbestos exposure comes primarily from old insulation materials used in attics, ceiling and flooring boards; when the insulation becomes physically disturbed, asbestos particles are released into the air & inhaled

      • Removal of asbestos-containing insulation material should be done by professionals with proper training and equipment that protects them from inhaling the asbestos

        • The area where asbestos is removed from should be sealed off from other areas in the building and well-ventilated during the removal process

        • Insulation without asbestos should be used to replace it

      Tropospheric Ozone (O3)

      

      

      
      

      • Worsens respiratory conditions like asthma, emphysema, bronchitis, COPD

      • Limits overall lung function

        • Irritates muscles or resp. tract causing constriction of airways & shortness of breath

        • Irritates eyes

        • Sources: photochemical breakdown of NO2 (car exhaust, coal & NG combustion)

      • ONLY HARMFUL IN TROPOSPHERE (beneficial in the stratosphere)

      8.15 Pathogens and Infectious Diseases

      Pathogens and Vectors

      • Pathogen

        • A living organism (virus, bacteria, fungus, protist, worm) that causes an infectious disease

          • Infectious diseases are capable of being spread or transmitted (HIV, ebola, Covid-19); noninfectious diseases are not transmissible (heart disease, asthma, cancer, diabetes)

          • Pathogens adapt and evolve to take advantage of humans as hosts for their reproduction and spread (Covid-19 is a SARS-associated coronavirus that evolved to become especially effective at surviving and reproducing in humans)

        • Vectors

          • A living organism (rat, mosquito) that carry and transmit infectious pathogens to other organisms

            • Climate change is shifting equatorial climate zones north and south away from the equator; this brings warmer temperatures to subtropical and temperate regions

            • Warmer temperatures allow pathogens and their vectors (mosquitos) to spread north & south to parts of the world previously too cold

              • Many pathogenic bacteria and viruses survive and replicate better in warmer weather

      Infectious Disease and Development

      • Less developed, poorer countries typically have higher rates of infectious disease

      • Less sanitary waste disposal; pathogens can reproduce in open waste areas where children may play or animals may scavenge & pass to humans

      • Less access to healthcare facilities and antibiotic medications to treat infectious diseases cause by bacteria & other pathogens

      • Lack of treatment/filtration for drinking water & sewage treatment exposes people to bacterial and viral pathogens in water, often from human waste

      • Tropical climates & more open-air living can expose people to vectors like mosquitoes; less money for vector eradication (spraying mosquito breeding grounds)

      Plague

      

      
      

      • Bacterial (pathogen) infection transmitted by fleas (vector) that attach to mice & rats (vectors as well)

        • Transmitted by flea bite, rodent contact or contaminated human fluids

        • Aka “bubonic” or “black” plague; modern antibiotics are highly effective against it, but some isolated instances still occur

      Tuberculosis (TB)

      

      
      

      • Bacterial (pathogen) infection that targets the lungs

        • Transmitted by breathing bacteria from body fluids (resp. droplets) of an infected person, which can linger in air for hours

        • Causes night sweats, fever, coughing blood; treatable in developed nations with access to powerful antibiotics

        • Leading cause of death by disease in the developing world ~ 9 million cases per year and 2 million deaths (for comparison ~ 2.8 million global deaths from Covid-19)

      Malaria

      • parasitic protist (pathogen) infection caused by bite from infected mosquitoes (vector)

        • Most common in sub-Saharan Africa (& other tropical regions of Middle East, Asia, South & Central America; recurring flu-like symptoms; kills mostly children under 5

        • Can be combated with insecticide spraying that kills mosquitoes; US eradicated in 1951

      West Nile

      • Virus (pathogen) infection caused by bite from infected mosquitoes (vector)

        • Birds are the main host, but the virus can be transmitted to humans by mosquitoes that bite infected birds and then bite humans

        • Causes brain inflammation, which can be fatal

      Zika Virus

      • Virus (pathogen) infection caused by bite from infected mosquitoes (vector) & sexual contact

        • Causes babies to be born with abnormally small heads and damaged brains; can be passed from mother to infant

        • No known treatment currently, so prevention is focused on eliminating mosquito populations

      Severe Acute Respiratory Syndrome (SARS)

      • Coronavirus (pathogen) infection caused by respiratory droplets from infected person

        • Primarily transmitted by touching or inhaling fluids from an infected person

        • Causes a form of pneumonia

        • Initial outbreak was in Southeast Asia

        • SARS-CoV-2 is the virus that causes the disease COVID-19

      Middle East Respiratory Syndrome (MERS)

      • Virus (pathogen) respiratory infection transmitted from animals to humans

        • Originated on Arabian peninsula

      Cholera

      • Bacterial (pathogen) infection caused by drinking infected water

        • Vomiting, muscle cramps and diarrhea; can cause severe dehydration

        • Can be introduced by water contaminated with human feces or undercooked seafood

      Chapter 9: Global Change

      9.1: Stratospheric Ozone Depletion

      • Stratosphere: Contains approximately 97% of the ozone in the atmosphere, and most of it lies between 9 and 25 miles (15–40 km) above Earth’s surface.

      • Formation of Stratospheric Ozone

        • Ultraviolet radiation (uv) strikes an oxygen molecule, creating atomic oxygen.

        • Atomic oxygen can combine with oxygen molecules to form ozone.

      • Ultraviolet radiation is subdivided into three forms:

        • UVA: It is closest to blue light in the visible spectrum and is the form of ultraviolet radiation that usually causes skin tanning.

        • UVB: It causes blistering sunburns and is associated with skin cancer.

        • UVC: It is found only in the stratosphere and is largely responsible for the formation of ozone.

      • Ozone Layer: A belt of naturally occurring ozone gas that sits between 9 and 19 miles (15–30 km) above Earth and serves as a shield from the harmful ultraviolet B radiation emitted by the sun.

      • Ozone: A highly reactive molecule and is constantly being formed and broken down in the stratosphere.

        • There are no natural reservoirs of chlorofluorocarbons (CFCs) or halocarbons (halons), but their chemical stability allows them to reach the stratosphere and degrade the ozone layer.

        • Chlorofluorocarbons: These are nonflammable chemicals that contain atoms of carbon, chlorine, and fluorine.

        • Halocarbons (halons): These are organic chemical molecules that are composed of at least one carbon atom with one or more halogen atoms; the most common halogens are fluorine, chlorine, bromine, and iodine.

      Effects of Ozone Depletion

      • A reduction in crop production

      • A reduction in the effectiveness of the human body’s immune system

      • A reduction in the growth of phytoplankton and the cumulative effect on food webs

      • Climatic changes

      • Cooling of the stratosphere

      • Deleterious effects on animals

      • Increases in cataracts

      • Increases in mutations, since UV radiation causes changes in the DNA structure

      • Increases in skin cancer

      • Increases in sunburns and damage to the skin

      Reducing Ozone Depletion

      • Support legislation that reduces ozone-destroying chemicals in medical inhalers, fire extinguishers, aerosol hairsprays, wasp and hornet sprays, refrigerator and air conditioner foam insulation, and pipe insulation.

      • Introduce tariffs on products produced in countries that allow the use of chlorofluorocarbons (CFCs).

      • Offer tax credits or rebates for turning in old refrigerators and air conditioners.

      • Use helium, ammonia, propane, or butane as a coolant alternative to HCFCs (hydrochlorofluorocarbons) and CFCs.

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      9.2: The Greenhouse Effect

      • When sunlight strikes Earth’s surface, some of it is reflected back toward space as infrared radiation (heat).

      • Greenhouse gases absorb this infrared radiation and trap the heat in the atmosphere.

      

      
      

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      9.3: Increases in Greenhouse Gases

      Greenhouse Gases by Source

      • Agriculture: Mostly comes from the management of agricultural soils.

      • Commercial and residential buildings: On-site energy generation and burning fuels for heat in buildings or cooking in homes

      • Energy supply: The burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions.

      • Industry: Primarily involves fossil fuels burned on-site at facilities for energy; cement manufacturing also contributes significant amounts of CO2 gas

      • Land use and forestry: It includes deforestation of old-growth forests (carbon sinks), land clearing for agriculture, strip-mining, fires, and the decay of peat soils

      • Transportation: It involves fossil fuels that are burned for road, rail, air, and marine transportation.

      • Waste and wastewater: Landfill and wastewater methane (CH4), and incineration as a method of waste management.

      Greenhouse Gas Emissions by Gas

      • Carbon dioxide (CO2): It is an important heat-trapping (greenhouse) gas, and is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions.

      • Agricultural activities, waste management, and energy use all contribute to methane emissions.

      • Fertilizer use is the primary source of nitrous oxide emissions.

      • Fluorinated gases: Industrial processes, refrigeration, and the use of a variety of consumer products all contribute to this gases, which include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

      • Black carbon (soot): It is a solid particle or aerosol, not a gas, but it also contributes to the warming of the atmosphere.

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      9.4: Global Climate Change

      • The world’s oceans contain more carbon dioxide than the atmosphere.

      • Atmospheric temperatures, cloud cover, surface albedo, and water vapor cause pole-wide warming.

        • The north and south poles are warming faster because of energy in the atmosphere that is carried to the poles through large weather systems.

      • Ocean currents carry heat around the Earth.

        • As the oceans absorb more heat from the atmosphere, sea surface temperatures rise and ocean circulation patterns change.

        • As the oceans store a large amount of heat, even small changes in these currents can have a large and lasting effect on the global climate.

      • Air temperatures today average 5°F to 9°F (3°C to 5°C) warmer than they were before the Industrial Revolution.

        • Higher average air temperatures may increase the frequency or severity of storms, surface water/groundwater inputs, sedimentation in bodies of water, flooding and associated water runoff, and aquifer recharge.

      • Global warming could completely change estuaries and coastal wetlands.

        • Sea-level rise threatens to inundate many coastal wetlands, threatening biota that cannot move inland due to coastal development.

      • The UN estimates that 150 million people will need to be relocated worldwide by 2050 due to coastal flooding, shoreline erosion, and agricultural disruption.

      • The total surface area of glaciers worldwide has decreased 50% since the end of the 19th century.

      • The main ice-covered landmass is Antarctica at the South Pole, with about 90% of the world’s ice and 70% of its freshwater.

        • If all of the Antarctic ice melted, sea levels around the world would rise about 200 feet (60 m).

      • Greenhouse gases trap solar radiation in the Earth’s atmosphere, making the climate warmer.

      • Due to global warming, mosquitoes have more places to breed, which increases malaria, dengue fever, Zika virus, and yellow fever rates.

        • Warmer water may spread amoebic dysentery, cholera, and giardia because it increases bacterial activity.

      • Higher air temperatures have been proven to result in higher incidences of heat-related deaths caused by cardiovascular disease, heat exhaustion, heat stroke, hyperthermia, and diabetes.

      • Arctic fauna will be the most affected. The food webs of polar bears that depend on ice floes, birds, and marine mammals will be drastically affected.

      • The movement of tectonic plates causes volcanoes and mountains to form, which can also contribute to changes in the climate

      • Volcanic gases that reach the stratosphere have a long-term effect on climate.

      • The fluctuations in the solar cycle impact Earth’s global temperature by ~0.1°, slightly hotter during solar maximums and slightly cooler during solar minimums.

      • As rivers and streams warm, warm-water fish are expanding into areas previously inhabited by cold-water species.

      • The Arctic region is a large natural source of methane.

        • Arctic methane release, caused by melting glaciers, creates a positive feedback loop because methane is a greenhouse gas.

      • Sea levels have risen 400 feet (120 m) since the peak of the last ice age approximately 18,000 years ago.

        • From about 13,000 years ago to the start of the Industrial Revolution, sea levels rose 0.1 to 0.2 mm per year. Since 1900, sea levels have risen about 3 mm per year.

      • The amount of energy absorbed and stored by the oceans has an important role in the rise of sea levels due to thermal expansion.

      • Ocean acidification: It occurs when atmospheric carbon dioxide reacts with seawater to form carbonic acid,

      • Kyoto Protocol (2005): A plan created by the United Nations to reduce the effects of climate change, which results in a reduction in the pH of ocean water over an extended period of time.

      • Montreal Protocol (1987): An international treaty designed to phase out the production of substances that are responsible for ozone depletion.

      • Paris Agreement (2016): It deals with greenhouse gas emissions and mitigation.

        • The goal is to keep global temperature rise below 2°C above pre-industrial levels while each country determines its own plans to mitigate global warming.

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      9.5: Biodiversity and Invasive Species

      • Plants are initially more susceptible to habitat loss than animals. This occurs for several reasons, as follows:

        • Plants cannot migrate.

        • Plants cannot seek nutrients or water.

        • Seedlings must survive, and they are grown in degraded conditions.

        • The dispersal rates of seeds are slow events

      • Animals can cope with habitat destruction by migration, adaptation, and/or acclimatization. Migration depends upon:

        • access routes or corridors;

        • the magnitude and rate of degradation;

        • the organism’s ability to migrate; and

        • the proximity and availability of suitable new habitats.

      • Adaptation: The ability to survive in changing environmental conditions.

        • Adaptation depends upon:

          • birth rate;

          • gene flow between populations as a function of variation;

          • genetic variability;

          • population size;

          • the length of generation; and

          • the magnitude and rate of degradation.

      • Acclimatization: The process by which an individual organism adjusts to a gradual change in its environment allowing it to maintain performance across a range of environmental conditions.

        • Acclimatization depends upon:

          • physiological and behavioral limitations of the species; and

          • the magnitude and rate of degradation.

      Invasive Species

      • Invasive species: These are animals and plants that are transported to any area where they do not naturally live.

      • Characteristics of Invasive Species

        • Abundant in native range

        • Broad diet

        • High dispersal rates

        • High genetic variability

        • High rates of reproduction

        • Living in close association with humans

        • Long-lived

        • Pioneer species

        • Short generation times

        • Tolerant of a wide range of environmental conditions

        • Vegetative or clonal reproduction

      • Examples of Invasive Species

        • Dutch elm disease is transmitted to elm trees by elm bark beetles — killing over half of them elm trees in the northern US.

        • European green crabs found their way into the San Francisco Bay area in 1989 threatening commercial fisheries.

        • Water hyacinth is an aquatic plant, introduced to the United States from South America.

          • It forms dense mats, reducing sunlight for submerged plants and aquatic organisms, crowding out native aquatic plants, and clogging waterways and intake pipes.

        • Zebra mussels can attach to almost any hard surface—clogging water intake and discharge pipes, attaching themselves to boat hulls and docks, and even attaching to native mussels and crayfish.

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      9.5: Endangered Species

      • Endangered Species: A species considered to be facing a very high risk of extinction in the wild.

      • Factors are taken into account for being labeled “endangered:”

        • Breeding success rate

        • Known threats

        • The net increase/decrease in the population over time

        • The number of animals remaining in the species

      • Arguments for protecting endangered species

        • Maintaining genetic diversity

        • Maintaining keystone species

        • Maintaining indicator species

        • Preserving the endangered species’ aesthetic, ecological, educational, historical, recreational, and scientific value

        • Preserving the yet-to-be-discovered value of certain endangered species

      • Characteristics That Have Contributed to Endangerment

        • Compete for food with humans

          • African penguins

        • High infant mortality

          • Leatherback turtles

        • Highly sensitive to changes in environmental conditions

          • Cotton-top tamarins

        • Hunting for sport

          • Passenger pigeons, blue whales, Bengal tigers

        • Introduction of nonnative invasive species

          • Bandicoots threatened by cats that were introduced by Europeans

        • Limited environmental tolerance ranges

          • Frogs, whose eggs are sensitive to water pollution, temperature changes, and the destruction of wetlands

        • Limited geographic range

          • Pandas

        • Long or fixed migration routes

          • Salmon in the Pacific Northwest that have been driven to extinction because of dam construction, logging, and water diversion

        • Loss of habitat

          • Red wolves. Whooping cranes

        • Low reproductive rates

          • Whales, elephants, and orangutans.

        • Move slowly

          • Desert tortoises

        • No natural predators, which makes them vulnerable as they lack natural defensive behaviors and mechanisms

          • Dodo birds, Steller’s sea cows, sea otters

        • Not able to adapt quickly

          • Polar bears

        • Possess characteristics sought after for commercial purposes

          • Sharks, elephants, rhinoceros’ horns. gorillas

        • Require large amounts of territory

          • Tigers

        • Small numbers of the species, which limits genetic diversity

          • Tigers

        • Specialized feeding behaviors and/or diet

          • Pandas (Bamboo)

        • Spread of disease by humans or livestock

          • African wild dogs

        • Superstitions

          • Aye ayes—some people native to Madagascar believe that aye ayes bring bad luck, and therefore kill them.

      Maintaining Biodiversity

      • Creating and expanding wildlife sanctuaries

      • Establishing breeding programs for endangered or threatened species

      • Managing habitats and monitoring land use

      • Properly designing and updating laws that legally protect endangered and threatened species.

      • Protecting the habitats of endangered species through private and/or governmental land trusts

      • Reintroducing species into suitable habitats

      • Restoring compromised ecosystems

      • Reducing non-native and invasive species