APES Unit Review Packet
Unit 1 - Ecosystems
Symbiotic Relationships
Symbiosis: Close relationships between organisms, not always mutualistic.
Competition: Organisms vying for the same resources.
Competitive Exclusion Principle: Two species can't occupy the same niche indefinitely if resources are limited.
Resource Partitioning: Species divide scarce resources by using them at different times, in different ways, or in different places.
Predator-Prey Interactions: One species feeds on another.
Introduction to Ecosystems
Mutualism: Both species benefit (e.g., bees and plants).
Commensalism: One species benefits, the other is unaffected.
Parasitism: One species benefits, the other is negatively affected.
Intraspecific Competition: Competition within the same species.
Interspecific Competition: Competition between different species.
Terrestrial Biomes
Tropical Rainforest
Location: Near the equator (South America, Central Africa, Southeast Asia).
Climate: High temperatures and rainfall year-round.
Soil: Nutrient-poor.
Biodiversity: High.
Savannas
Location: Tropical regions (Africa, South America, Australia).
Climate: Distinct wet and dry seasons.
Vegetation: Grasslands with scattered trees.
Fauna: Large herbivores and their predators.
Deserts
Location: Arid regions (Sahara, Arabian, Gobi, Sonoran).
Climate: Very low precipitation, extreme temperature fluctuations.
Vegetation: Sparse, adapted to water scarcity.
Scrubland
Location: Mediterranean climates (California, Mediterranean basin).
Climate: Hot, dry summers and mild, wet winters.
Vegetation: Adapted to fire, dominated by shrubs and small trees.
Temperate Grasslands
Location: Temperate regions (Great Plains, Pampas, Steppes).
Climate: Moderate rainfall and seasonal temperature changes.
Fauna: Large herbivores.
Soil: Fertile.
Temperate Deciduous Forests
Location: Eastern North America, Europe, East Asia.
Climate: Moderate temperature and precipitation.
Vegetation: Deciduous trees that shed leaves seasonally.
Taiga (Boreal Forests or Coniferous Forests)
Location: High latitudes (Canada, Russia).
Climate: Long, cold winters and short, cool summers.
Vegetation: Coniferous trees.
Significance: Important for carbon sequestration.
Tundra
Location: Arctic regions (Alaska, Siberia).
Climate: Cold, treeless areas with permafrost, short growing seasons.
Biodiversity: Low.
Adaptations: Plants and animals adapted to extreme conditions.
Aquatic Biomes
Freshwater Biomes
Lakes and Ponds
Characteristics: Standing bodies of water, stratification creates temperature layers, seasonal turnover promotes nutrient mixing.
Biodiversity: Supports diverse aquatic life.
Rivers and Streams
Characteristics: Flowing water bodies; shape and altitude influence oxygen, nutrients, and temperature.
Biodiversity: Diverse organisms adapted to flow.
Wetlands
Types: Marshes, swamps, and bogs.
Characteristics: High biodiversity and productivity; important for flood control and water filtration.
Threats: Human activities.
Marine Biomes
Oceans
Characteristics: Largest biome, covering most of Earth; zones include coastal, pelagic, benthic, and abyssal.
Role: Major role in climate regulation and carbon cycle.
Coral Reefs
Characteristics: Shallow, warm, coastal waters; high biodiversity.
Threats: Coral bleaching, overfishing, and pollution.
Estuaries
Characteristics: Where freshwater meets saltwater; high productivity and biodiversity.
Significance: Important for fish nurseries.
Vulnerability: Pollution and habitat loss.
Intertidal Zones
Characteristics: Area between high and low tide; organisms exposed to changing water levels and exposure.
Biodiversity: Diverse and productive.
Open Ocean (Pelagic Zone)
Characteristics: Vast area of deep water; supports large migratory species.
Productivity: Lower compared to coastal areas.
Deep Sea (Benthic Zone)
Characteristics: Cold, high-pressure environments; unique organisms adapted to darkness and cold; hydrothermal vents and chemosynthetic communities.
Main Zones of Lakes
Littoral Zone
Description: The top, near-shore layer of a lake.
Characteristics: Shallow with plentiful sunlight and nutrient inputs from the surrounding land.
Biodiversity: Supports a wide variety of plants and animals.
Limnetic Zone (Open-Water Zone)
Description: Sunlit surface layer where most photosynthesis takes place.
Location: Starts away from shore, just past the littoral zone, and extends to the depth penetrated by sunlight.
Biodiversity: Supports phytoplankton and zooplankton, along with freshwater fish.
Profundal Zone (Deep-Water Zone)
Description: Deep, open-water layer, which is too dark for photosynthesis.
Characteristics: Cooler water with less dissolved oxygen than shallower zones.
Biodiversity: Supports fish adapted to cooler waters.
Benthic Zone
Description: Soil and soil organisms that live at the bottom of a lake.
Biodiversity: Inhabited mostly by decomposers and other organisms that feed on dead and decaying material.
Characteristics: Low-oxygen environment.
Main Zones of a River
Source Zone (Headwaters)
Description: Where water at high elevations collects from precipitation and snowmelt.
Characteristics: Cold, fast-moving water with lots of dissolved oxygen and a low nutrient content.
Vegetation: Usually, only a few plant species grow near a river's source.
Transition Zone
Description: Where headwaters merge.
Characteristics: Wider, slower-moving river with less dissolved oxygen and more sediment than the source zone; warmer and more nutrient-rich water.
Biodiversity: Tends to support a larger variety of plants and animals.
Floodplain Zone
Description: Zone forms because the bulk of water in the river becomes greater than the river channel itself, and water spills out onto the land forming wetlands and temporary lakes.
Characteristics: Water usually contains more sediment and less dissolved oxygen than in the transition zone; warm, nutrient-rich waters.
Biodiversity: Supports the greatest variety of plants and animals.
Human Impact on Biomes
Terrestrial Biomes: Deforestation, agriculture, mining, and urbanization.
Aquatic Biomes: Pollution, overfishing, habitat destruction, and water withdrawal.
Both: Climate change and invasive species.
Carbon Cycle
Sources: Processes that release carbon into the atmosphere (respiration, decomposition, burning fossil fuels).
Sinks: Natural reservoirs that store carbon (forests, soils, and oceans).
Photosynthesis: Plants convert carbon dioxide into glucose using sunlight, releasing oxygen as a byproduct.
Respiration: Organisms consume oxygen to break down glucose for energy, releasing CO2 as a byproduct.
Decomposition: Decomposers break down dead organisms, releasing carbon as CO2 or methane back into the environment.
Sequestration: Carbon stored in natural reservoirs like forests, soils, and oceans, as well as geological formations such as oil and gas reserves.
Burning Fossil Fuels: Combustion of coal, oil, and natural gas releases stored carbon as CO2 into the atmosphere, contributing to climate change.
Carbon Storage and Release
Forests and soils store carbon as organic matter.
Oceans absorb atmospheric CO2.
Human activities disrupt this balance, leading to an increase in atmospheric CO2 levels and impacting climate and ecosystems.
Nitrogen Cycle
Atmospheric Nitrogen: Makes up 78% of the atmosphere; major nitrogen reservoir, but not directly usable by most organisms; DNA, RNA, and protein molecules all contain nitrogen atoms.
Nitrogen Fixation
Biological Fixation: Certain bacteria in soil and root nodules convert atmospheric nitrogen (N2) into ammonia (NH3) or ammonium (NH4+); usable by plants.
Abiotic Fixation: Lightning or industrial processes convert atmospheric nitrogen into nitrates (NO3-).
Nitrification
Ammonia Conversion: Soil bacteria convert ammonia (NH3) or ammonium (NH4+) into nitrites (NO2-).
Nitrite Conversion: Other bacteria convert nitrites (NO2-) into nitrates (NO3-) which plants can absorb.
Assimilation
Uptake by plants: Plants absorb nitrates (NO3-) or ammonium (NH4+) and incorporate them into proteins and nucleic acids.
Transfer to animals: Herbivores obtain nitrogen by consuming plants; carnivores obtain nitrogen by eating other animals.
Ammonification
Decomposition: Conversion back to N2: Decomposers break down dead organisms and waste, releasing ammonia (NH3) or ammonium (NH4+).
Human Impact
Fertilizers: Overuse of nitrogen-based fertilizers can lead to runoff, causing eutrophication in aquatic ecosystems.
Burning fossil fuels: Releases nitrogen oxides (NOx) into the atmosphere, contributing to air pollution and acid rain.
Wastewater and Sewage: Can introduce excess nitrogen into water bodies, leading to algal blooms and reduced water quality.
Phosphorus Cycle
Phosphorus cycles between terrestrial and aquatic sources and sinks, primarily moving through rock, soil, water, and organisms.
Critical nutrient for biological systems but naturally occurs in limited amounts, making it a limiting factor for plant growth; DNA, RNA, and cell membranes all contain phosphorus atoms.
Slow compared to other nutrient cycles because there is no atmospheric component to move phosphorus directly from the ocean to land.
Terrestrial Sources and Sinks
Rocks and Soil: Primary sources of phosphorus; weathering releases phosphate ions into the soil.
Plants: Absorb phosphate ions from soil, incorporating them into organic compounds.
Animals: Obtain phosphorus by consuming plants or other animals; excrete waste containing phosphorus back into the soil.
Decomposition: Dead organisms and waste decompose, releasing phosphorus back into the soil.
Aquatic Sources and Sinks
Runoff: Phosphorus can be transported from soil to aquatic ecosystems via runoff, especially when fertilizers when overused.
Water Bodies: Phosphorus enters lakes, rivers, and oceans, supporting aquatic life.
Sedimentation: Phosphorus can settle in sediments at the bottom of water bodies, storing it long-term.
Uplifting: Geological processes can uplift marine sediments, reintroducing stored phosphorus to terrestrial systems.
Human Impact
Fertilizers: Overuse can lead to runoff and eutrophication in aquatic ecosystems, causing harmful algal blooms and oxygen depletion.
Wastewater and Sewage: Can introduce excess phosphorus into water bodies, exacerbating eutrophication.
Mining: Phosphate rock mining for fertilizers can disturb ecosystems and contribute to pollution.
Water Cycle
The water cycle is the continuous movement of water through its solid, liquid, and gaseous states across the atmosphere, land, and oceans.
Key processes include evaporation, condensation, precipitation, infiltration, runoff, and transpiration.
Sources
Oceans: Largest source of water, primarily in liquid form; a major source of evaporation.
Surface Water: Lakes, rivers, and streams contain water in liquid form and provide water for various ecosystems.
Groundwater: Stored in aquifers, available in liquid form, accessed through wells.
Ice Caps and Glaciers: Contain water in solid form; store the majority of the world’s freshwater.
Sinks
Atmosphere: Holds water vapor and clouds as part of the water cycle.
Soils and Plants: Soil acts as a sink, absorbing water; plants transpire water back into the atmosphere.
Oceans: Act as a major sink for runoff and precipitation; regulate climate and store large amounts of water.
Transformation Processes
Evaporation: Water in liquid form turns into water vapor due to heat from the sun.
Condensation: Water vapor cools and turns into liquid, forming clouds.
Precipitation: Condensed water falls from the atmosphere as rain, snow, sleet, or hail.
Infiltration: Precipitated water seeps into the ground, recharging aquifers.
Runoff: Water flows over the land surface into rivers, lakes, and oceans.
Transpiration: Plants release water vapor through their leaves back into the atmosphere.
Sublimation: Solid ice turns directly into water vapor without passing through the liquid state.
Melting and Freezing: The transition between solid ice and liquid water depends on temperature.
Human Impact
Water Use: Overuse and pollution can disrupt the water cycle and impact sources and sinks.
Climate Change: Alters precipitation patterns and can lead to changes in the availability of water in various states.
Deforestation and Land Use Changes: Affect evaporation, transpiration, and runoff patterns.
Primary Productivity
The rate at which autotrophs convert sunlight into organic compounds (typically through photosynthesis)
Gross Primary Productivity (GPP): Total amount of energy captured by photosynthesis.
Net Primary Productivity (NPP): The energy left after the autotroph’s respiration available for growth and reproduction
High Primary Productivity
Tropical rainforests: High solar energy, consistent moisture, diverse and dense vegetation.
Estuaries and Wetlands: Rich nutrient availability and sunlight; support high productivity.
Coral Reefs: Warm, clear waters with abundant sunlight; high biodiversity.
Medium Primary Productivity
Temperate deciduous forests: Moderate temperatures and precipitation; diverse vegetation.
Savannas and Grasslands: Moderate NPP due to varying rainfall and temperature; grass-dominated biomes.
Low Primary Productivity
Deserts: Low precipitation limits productivity; sparse vegetation.
Tundra: Cold temperatures and permafrost limit plant growth; low productivity.
Trophic Levels
Producers (autotrophs convert solar energy into chemical energy through photosynthesis)
Primary Consumers (Herbivores that eat producers)
Secondary Consumers (Carnivores that eat primary consumers)
Tertiary Consumers (Carnivores that eat secondary consumers)
Approximately 10% of energy is transferred from one trophic level to the next, with most energy lost as heat.
The Law of Conservation of Matter says that matter is neither created nor destroyed, it only changes forms.
Species richness is the number of different species in an area. An ecosystem with more species has a higher species richness.
Species evenness describes species' relative abundance in an area. An ecosystem that contains roughly equal numbers of individuals across multiple species has a higher species evenness than an ecosystem that is dominated by a single species.
Species diversity increases with both species richness and species evenness.
Ecosystem resilience is the ability of an ecosystem to absorb change and return to the same equilibrium state after a temporary disturbance Ecosystems with higher species diversity tend to be more resilient.
The effect of an ecological disturbance on a species depends on its role in the ecosystem or its ecological niche.
Food Chains and Food Webs
Trophic Cascades
Definition: Ecological phenomenon where changes in the population of a top predator cause changes throughout the food web, impacting multiple trophic levels.
Positive Impacts
Biodiversity Maintenance: Predators regulate prey populations, preventing overgrazing and maintaining plant diversity.
Ecosystem Balance: Trophic cascades can stabilize ecosystems by keeping populations in check and supporting the resilience of food webs.
Habitat Complexity: Top predators influence the structure of habitats, which can enhance ecosystem health.
Negative Impacts
Disruption of Food Webs: Removal or decline of top predators can lead to overpopulation of prey species, disrupting plant and animal populations.
Ecosystem Degradation: Overgrazing and overbrowsing by unchecked herbivores can degrade habitats and reduce biodiversity.
Economic Impact: Imbalances in food webs can impact fisheries, agriculture, and other human economic activities
Human Impact on Food Webs
Overfishing: Can deplete fish populations, causing imbalances in marine food webs.
Hunting and Poaching: Reduces populations of top predators, affecting entire ecosystems.
Habitat Destruction: Deforestation, urbanization, and agriculture can fragment habitats and disrupt food webs.
Pollution: Pesticides, herbicides, and industrial pollutants can accumulate in organisms, disrupting food web interactions.
Climate Change: Alters habitat and species distributions, affecting food web dynamics and interactions
Unit 2 - Biodiversity
Biodiversity
Biodiversity refers to the diversity of different life forms found in an ecosystem. There are three levels of biodiversity: genetic diversity, species diversity, and ecosystem diversity.
Genetic diversity allows for adaptation to environmental changes and disturbances.
Species diversity includes species richness and species evenness, impacting ecosystem resilience.
Ecosystem diversity refers to the variety of ecosystems in an area, affecting overall biodiversity.
Ecosystem Services
Ecosystem services are the benefits humans receive from natural ecosystems, categorized into four types:
Provisioning services: Direct benefits like wood, food, and water.
Supporting services: Processes that support human actions, like pollination.
Regulating services: Natural processes that stabilize climate and environment, like carbon sequestration
Cultural services: Recreational and intellectual benefits from nature, such as tourism and research.
Theory of Island Biogeography
Explains how island size and proximity to the mainland impact species richness.
Larger islands closer to the mainland have higher species richness due to more species migration.
Island ecosystems often host specialized species, making them vulnerable to invasive species.
Ecological Tolerance
Refers to the range of conditions a species can tolerate before experiencing stress or death.
Genetic diversity within a species helps buffer against environmental disturbances.
The optimal range is where a species functions best, while physiological stress and intolerance zones can lead to death.
Natural Ecosystem Disruptions
Periodic events: Regular occurrences like seasons.
Episodic events: Less regular but predictable events, like hurricanes.
Random events: Unpredictable occurrences, such as asteroids and volcano eruptions.
Gradual climate changes occur over thousands of years due to variations in Earth's orbit.
Ecological Succession
Primary succession: Starts from bare rock, with pioneer species like moss and lichen.
Secondary succession: Starts from the soil after a disturbance, with pioneer species like grass and wildflowers.
Climax community: A stable community that forms at the end of succession.
Keystone Species
Vital to ecosystem function; their removal can lead to ecosystem collapse. Examples include wolves (predators) and ecosystem engineers like beavers and mangroves.
Unit 3 - Population
Generalist and Specialist Species
Specialist Species: Rely on a narrow niche with specific habitat and food requirements. Example: Pandas, which rely on bamboo.
Generalist Species: Have a broad range of food and habitat requirements, allowing them to adapt easily to changes. Example: Raccoons, which eat various foods and live in many habitats.
Reproductive Strategies
Replacement-level Fertility: about 2.1 children per woman
R-selected Species (Quantity over Quality): Produce many offspring, offer little parental care, and grow rapidly in population. Example: Invasive species.
K-selected Species (Quality over Quantity): Produce few offspring with high parental investment, slower population growth, and typically larger organisms. Example: Mammals.
Survivorship Curves
Type I: High survival rates in early life, common in K-selected species.
Type II: Constant mortality rate throughout the lifespan, common in some birds and rodents.
Type III: High mortality rates in early life, common in R-selected species.
Density-Dependent Factors:
Resources like food, water and disease, influence population size based on density.
Density-Independent Factors:
Events like natural disasters affect populations regardless of density.
Population Dynamics
Carrying Capacity: The maximum number of individuals an ecosystem can support.
Human Population Growth
Age Structure Diagrams: Show population composition by age, indicating growth rates and development levels.
Crude Birth Rate (CBR) and Crude Death Rate (CDR): Used to calculate growth rate and assess a country's development level.
Doubling Time: The time it takes for a population to double, calculated using the rule of 70.
Demographic Transition Model
Stage 1: Pre-industrial, high birth and death rates, low population growth.
Stage 2: Industrializing, decreasing death rates, still high birth rates, rapid population growth.
Stage 3: Industrialized, decreasing birth rates, slowing population growth.
Stage 4: Post-industrial, low birth and death rates, stable or declining population growth.
Factors Influencing Birth Rates
Economic and Social Factors: Access to education, economic opportunities, and healthcare affects birth rates.
Family Planning Resources: Availability of contraceptives and public education campaigns influence total fertility rate (TFR).
Impact of Invasive Species
R-Strategist as Invasive Species: Can rapidly populate and disrupt ecosystems due to their high biotic potential.
*Rapid growth - Stage 1: Pre Industrial / High birth rates and high death rates
*Slow growth - Stage 2: Transitional / High birth rates and declining death rates
*Stable growth - Stage 3: Industrial / Declining birth rates and low death rates
*Declining - Stage 4: Post-Industrial / Low birth rates and low death rates
Unit 4 - Earth Systems and Resources
Plate Tectonics
Tectonic plates are massive slabs of rock floating on the mantle, a sea of molten magma heated by the Earth's core.
Types of Plate Boundaries
Divergent Boundary: Plates move apart due to rising magma, causing seafloor spreading, trenches, and underwater ridges.
Convergent Boundary: Plates collide, causing subduction of the denser oceanic plate under the continental plate. This forms volcanic mountain ranges and trenches.
Transform Boundary: Plates slide past each other, often causing earthquakes when plates lock and then suddenly move.
Soil Formation
Soil is a mixture of weathered rock particles (sand, silt, and clay), organic material (microbes, decomposing leaves, and animal waste), and pore space (allowing oxygen and water for plant roots).
Soil has layers (horizons): O horizon (organic matter), A horizon (topsoil), B horizon (subsoil), and C horizon (parent material).
Weathering vs. Erosion
Weathering breaks down rocks, while erosion moves the rock pieces.
O Horizon (organic horizon)
made up mostly of organic matter such as leaf litter and decomposed plant material
can be thin, thick, or not present at all, depending on how the soil forms
A horizon (topsoil)
upper layer of soil in which plants have most of their roots
high concentration of organic matter and microorganisms
this layer and the O horizon are often the most nutrient-rich and productive layers in a soil
B Horizon (subsoil)
made up mostly of minerals from weathered parent material
usually lighter in color, ranging from yellow to reddish brown
less fertile than the A and O horizons, and is not capable of producing abundant plant growth
C horizon
a layer of poorly weathered or unweathered rock
high concentration of parent material and is generally infertile
Soil erosion is the removal of the fertile top layers of soil, which can be eroded naturally by wind and flowing water, and can be slowed by plants, whose roots help anchor the top layers of soil.
Soil Properties
Texture: The proportion of sand, silt, and clay determines permeability and water-holding capacity.
Soil pH: Acidic soil can lower nutrient levels and damage plant roots.
Fertility: High nutrients and balanced pH contribute to soil fertility.
Atmosphere and Global Wind Patterns
Atmosphere Composition: Mostly nitrogen (78%) and oxygen (21%), with trace gasses including greenhouse gasses like methane and carbon dioxide.
Atmosphere Layers: Troposphere (weather occurs), stratosphere (ozone layer), mesosphere, thermosphere (hottest layer), and exosphere (outermost layer).
Global Wind Patterns: Influenced by warm air rising at the equator (Hadley cell), trade winds, and the Coriolis effect.
Watersheds
A watershed is an area that drains into one central body of water, influenced by slope, vegetation, and soil type. Land use impacts water movement and quality in the watershed.
Seasons
Caused by Earth's tilt, not proximity to the sun. Insolation varies based on the angle of the sun's rays and Earth's curvature. Summer and winter occur in opposite hemispheres due to Earth's tilt.
El Nino
El Nino is a climate pattern in the Pacific Ocean that occurs every two to seven years, impacting weather across the globe. The phenomenon is named after a warm period in the Pacific that South American fishermen noticed around December, which coincided with Christmas.
During El Nino, weakened trade winds lead to warm water accumulating near Central and South America, while the western Pacific experiences cooler water. This shift disrupts typical weather patterns, causing heavy rainfall and flooding in some regions, such as California and Ecuador, while leading to drought and fires in others, such as Indonesia. There is weakened upwelling during El Nino, when there is less nutrient dense waters, resulting in less fishery.
The 1997-1998 El Nino was particularly devastating, causing an estimated $$36 billion in damage worldwide.La Nina is the opposite climate pattern, featuring stronger-than-normal trade winds and cold water accumulating in the eastern Pacific, which leads to different weather effects.There is increased upwelling during La Nina, resulting in nutrient rich waters rising to the surface, leads to more fishery.
Waste Production:
Overburden (soil removal), spoils (waste from mining), and tailings (mining residue) contribute to pollution.
Unit 5 - Land and Water Use
Tragedy of the Commons:
Overuse and exploitation of common resources like oceans, atmosphere, and public lands. Leads to unsustainable practices, profit-driven depletion of resources, overfishing, and dead zones. Example: Overfishing in the Gulf of Mexico causing oxygen-depleted dead zones.
Water Resources:
Ogallala Aquifer: Largest aquifer in the U.S., spanning from Texas to the Midwest, nearing depletion due to human use. Only a small percentage of Earth's water is accessible as freshwater, leading to concerns of pollution, misuse, and depletion. Groundwater overdrafts can lead to subsidence and saltwater intrusion in coastal areas. Water is heavily used for irrigation, causing high evaporation rates in methods like furrow and flood irrigation.
Agricultural Practices:
Soil Erosion: Caused by tillage, deforestation, and overgrazing, leading to loss of nutrients and difficulty in growing plants.
Salinization: Accumulation of salts in soil due to irrigation, hindering plant growth.
Integrated Pest Management: Utilizes crop rotation, natural predators, GMOs, and mulch to reduce pesticide use.
Mining Impacts:
Environmental Disruption: Strip mining and open pit mining damage land, habitats, and water quality due to erosion and washout.
Fishing Impacts:
Bycatch: Unintended catch of other marine life, leading to potential loss of species.
Fishery Collapse: Decline in fish populations by over 90%, affecting recovery and genetic diversity.
Ocean Pollution: Fishing gear can damage seafloor and coral reefs, posing environmental hazards.
Solutions include regulations, marine reserves, and consumer choice to reduce overfishing.
Forestry and Deforestation:
Benefits of Forests: Stabilize soil, slow runoff, purify water, act as carbon sinks.
Deforestation Drawbacks: Soil erosion, loss of carbon sinks, and increased runoff and sedimentation.
Fire Suppression: This can lead to the accumulation of woody material, causing uncontrolled wildfires.
Selective Cutting: Leaves some trees behind to maintain forest health.
Rangeland Management:
Overgrazing by cattle leads to soil erosion and nutrient loss. Solutions include fencing streams, supplementing feed, and rotating cattle grazing areas.
Urbanization and Impervious Surfaces:
Runoff Issues: Impervious surfaces like concrete and asphalt prevent water infiltration, leading to erosion and flooding.
Eutrophication: Runoff carries nutrients and pollutants into waterways, causing excessive algae growth and dead zones.
Meat Production:
Concentrated Animal Feeding Operations (CAFOs): High-density growth of animals like cows, pigs, and chickens for food.
Challenges: Antibiotic resistance, concentrated waste, and ethical concerns about dense animal housing.
Sustainable Agricultural Practices
Soil Conservation to prevent erosion.
Contour plowing
planting crops in rows that run parallel to a slope’s topographic contour lines
help slow runoff and hold topsoil in place
Windbreaks
lines of trees and shrubs planted at the edges of agricultural fields
break the force of the wind, preventing soil from blowing away
Perennial crops
crops that live for multiple years
results in less soil disturbance than planting annual crops, which die after one year
Terracing
used to farm hilly or mountainous areas
growing crops on terraces, which are flat strips of land built into a hillside
Water flows gradually from terrace to terrace, reducing overall water loss and soil erosion
No-till agriculture
planting seeds without first turning over top soils
Crop residues are left in the field from season to season and the top layer of soil is left undisturbed
helps maintain soil structure and promotes water infiltration
Strip cropping
crop rotation system in which strips of erosion-susceptible and erosion-resistant plants are grown in an alternating pattern
helps stabilize the soil and maintain soil fertility
Soil fertility to sustain plant growth
Crop rotation
changing the type of crop grown in a field, usually season-by-season
rotated to balance out nutrient demands on the soil, reducing the need for added fertilizer
Green manure
crop grown specifically to be mixed into topsoil while still green
nutrients are released into the soil when the plant decomposes
Limestone
type of rock composed primarily of calcium carbonate
can be mixed into acidic soils to increase the soils' pH
Making soils less acidic can help increase the nutrient availability of the soil
Aquaculture is the practice of raising fish, shellfish, and seaweed in controlled aquatic environments. Unlike wild-caught seafood, aquacultured seafood is bred, raised, and harvested in enclosed pens and tanks.
Advantages
help alleviate pressure on overfished wild populations while still meeting the demand for seafood
efficient, producing a large amount of food in a small area of water, and requiring a relatively small amount of fuel
help lower seafood prices and create job opportunities
Disadvantages
Wastewater released from aquaculture facilities may contain feces, uneaten food, and antibiotics, which can contaminate the environment
often dense, which means disease-causing bacteria, viruses, and parasites spread easily, pathogens can then spread to nearby wild populations
Fish that escape from aquaculture facilities may compete or breed with wild fish populations, potentially disrupting the local ecosystem
Unit 6 - Energy Resources and Consumption
Renewable vs. Nonrenewable Resources
Nonrenewable resources: Have a set amount and can't be replenished once consumed. Examples include coal, oil, and natural gas, which take millions of years to form. Found in specific countries such as the US, Russia, China (coal), Saudi Arabia, Venezuela, and Canada (oil).
Renewable resources: Easily replenished energy sources like solar, wind, geothermal, and hydropower. Biomass can be renewable if used sustainably; otherwise, it can become nonrenewable. Availability and effectiveness vary by region (e.g., hydropower in Brazil, and solar in the Southeast US).
Energy Trends
As countries industrialize, they shift from biomass to fossil fuels and advanced resources like nuclear power. Over time, the use of different energy sources changes (e.g., increase in natural gas after the 1950s).
Coal
Acquired through mining, causing environmental impacts (e.g., land disturbance, erosion). Three types: lignite (low heat, low sulfur), bituminous (high heat, high sulfur), and anthracite (high heat, low sulfur). Releases particulate matter and carbon dioxide, contributing to pollution and climate change.
Crude Oil
Drilled and pumped from the ground, often converted into other fuel types. Releases carbon dioxide and particulate matter when burned. The second law of thermodynamics applies (energy loss as heat during conversion).
Natural Gas
Extracted through hydraulic fracturing (fracking), which can cause earthquakes and groundwater contamination