Chapter 52

  • Ecology is the study of interactions between organisms and the environment

    • Observations and experimentation are used in modern ecology

    • Rediscovery of the harlequin toad in Costa Rica raised questions about environmental factors and population size

  • Ecology can be studied at various levels

    • Global ecology: examines energy and material influence on organisms throughout the biosphere

    • Landscape ecology: focuses on connected ecosystems and the interchange of energy and materials

    • Ecosystem ecology: studies individual ecosystems, including biotic and abiotic components, energy flow, and chemical cycling

    • Community ecology: analyzes interactions between populations of different species in a specific area

    • Population ecology: studies factors affecting the size of a specific group of individuals of the same species over time

    • Organismal ecology: explores how an organism's physical structure, physiology, and behavior deal with environmental challenges

Climate and Global Patterns

  • Climate refers to long-term prevailing weather conditions

  • Four major abiotic components influence climate: temperature, precipitation, sunlight, and wind

  • Macroclimate: patterns on a larger scale (global, regional, landscape)

  • Microclimate: specific locations with fine-scale patterns

  • Solar energy and the planet's movement in space determine global climate patterns

  • Sun's warming effect causes temperature variations and influences evaporation, air, and water circulation

  • Sunlight hits at different angles, leading to latitudinal variations in climate

Circulation and Precipitation Patterns

  • Warm, wet air masses flow from the tropics to the poles, releasing water and causing precipitation

  • Descending dry air creates arid climates around 30 degrees north and south

  • Air flowing closer to the Earth's surface generates predictable wind patterns

    • Cooling trade winds blow from east to west in the tropics

    • Prevailing westerlies blow from west to east in temperate zones

Cycles and Regional Effects on Climate

  • Climate can be affected by seasons, large bodies of water, and mountains

  • Seasonality depends on light and temperature, increasing towards the poles

  • Belts of wet and dry air shift throughout the year based on the changing angle of the sun

  • Ocean currents and large lakes moderate the climate of nearby terrestrial environments

  • Mountains influence sunlight and create rain shadows and leeward sides

  • Every thousand-meter increase in elevation causes a temperature drop of approximately six degrees

Microclimate and Biomes

  • Microclimates are influenced by abiotic and biotic factors

  • Terrestrial biomes are identified by climate and disturbance

  • Biomes are recognized by vegetation type or environment

  • Climate plays a key role in determining biome distribution

  • Climatographs plot temperature versus precipitation in a region

  • Biomes are also affected by annual patterns

Global Climate Change

  • Global climate change has significant impacts on the biosphere

  • Past climate changes have affected species distribution and extinction

  • Predictions for future climate change scenarios show potential range shifts for species

Terrestrial Biomes

  • Terrestrial biomes can be identified by climate and disturbance

  • Various types of biomes exist, including tundra, taiga, temperate deciduous forest, tropical rainforest, grassland, desert, and chaparral

  • Temperature and precipitation patterns help distinguish between biomes

Terrestrial Biomes

Features of Terrestrial Biomes

  • Named for physical or climatic factors, as well as vegetation

  • Overlaps between biomes

  • Vertical layering with different layers providing habitats for animals

  • Biomes are dynamic and have ranges of patchiness

  • Similar characteristics in separated biomes arise through convergent evolution

Disturbance in Terrestrial Biomes

  • Storms, fire, human activity cause changes in the community

  • Fires can maintain savannah vegetation and create gaps in forests

  • Fire suppression has changed vegetation in the Great Plains

Tropical Forest

  • Found in equatorial and sub-equatorial regions

  • Constant rainfall

  • Vertically layered with intense competition for light

  • Home to millions of animal species

  • Human population growth is destroying tropical forests

Deserts

  • Occur in bands 30 degrees north and south of the equator, interior of continents

  • Low and highly variable precipitation

  • Plants adapted for heat and desiccation tolerance

  • Common desert animals include snakes, lizards, scorpions, ants, beetles, migratory resident birds, and seed-eating rodents

  • Urbanization and conversion to agriculture have reduced desert biodiversity

Grass Savannah

  • Found in equatorial and sub-equatorial regions

  • Seasonal precipitation

  • Grasses and forbs make up the majority of ground cover

  • Dominant plant species are fire-adapted and drought-tolerant

  • Common species include insects, wildebeests, zebras, lions, and hyenas

  • Human fires help maintain this biome by minimizing vertical layering

Chaparral

  • Found in mid-latitude coastal regions on several continents

  • Highly seasonal precipitation with rainy winters and dry, hot summers

  • Dominated by shrubs, small trees, grasses, and herbs

  • Plants adapted to fire and drought

  • Common species include amphibians, birds, reptiles, insects, mammals, and browsing mammals

  • Agriculture and urbanization have reduced chaparral areas

Temperate Grasslands

  • Found on multiple continents

  • Highly seasonal precipitation with cold winters and hot, wet summers

  • Dominant plants are grasses and forbs adapted to drought and fire

  • Native mammals include bison, wild horses, and prairie dogs

  • Conversion to farmland has reduced grassland areas

Northern Coniferous Forest (Taiga)

  • Found in northern North America and Eurasia

  • Largest terrestrial biome

  • Variable precipitation with cold winters and hot summers

  • Dominated by conifers

  • Common species include migratory resident birds, moose, brown bears, and Siberian tigers

  • Logging is a significant threat to these forests

Temperate Broadleaf Forest

  • Found in mid-latitudes in the northern hemisphere, also in Chile, South Africa, Australia, and New Zealand

  • Lots of precipitation throughout the year

  • Cold winters and hot, humid summers

  • Vertical layers with deciduous trees in the northern hemisphere and evergreen eucalyptus in Australia

  • Mammals, birds, and insects utilize all vertical layers

  • Settlement and agriculture have impacted these forests, but some areas are showing recovery

Tundra

  • Found in expansive areas of the Arctic and alpine regions

  • Low precipitation in the Arctic, higher in alpine regions

  • Cold winters and cool summers

  • Permafrost prevents water absorption by soil

  • Vegetation includes herbaceous plants, mosses, grasses, forbs, shrubs, trees, and lichens

  • Mammals include musk oxen, caribou, reindeer, bears, wolves, and foxes

  • Sparse settlement, but oil and mineral extraction are threats

Aquatic Biomes

Overview of Aquatic Biomes

  • Largest part of the biosphere in terms of area

  • Salt concentrations of about 3% in marine biomes and less than 0.1% in freshwater biomes

  • Linked to surrounding terrestrial biomes

Zones in Aquatic Biomes

  • Stratified into zones based on light penetration, temperature, and depth

  • Upper photic zone has sufficient light for photosynthesis

  • Lower aphotic zone receives little light

  • Pelagic zone includes both photic and aphotic zones

  • Abyssal zone is deep in the aphotic zone with a depth of 2000 to 6000 meters

  • Benthic zone is the bottom sediment of all aquatic zones

  • Detritus from surface water provides food for organisms in the lower aphotic zone and benthic zone

Zonation in Aquatic Biomes

  • Aquatic biomes have zonation similar to terrestrial biomes

  • Lake zonation is different from ocean zonation

    • No abyssal zone in lakes

    • No significant depth variation in lake zonation compared to ocean zonation

  • Aquatic biomes vary based on depth, light penetration, distance from shore, and position in zones

  • Thermocline separates warm upper layer from cold deeper layer in aquatic biomes

  • Lakes undergo semi-annual mixing called turnover to distribute oxygenated and nutrient-rich water

  • Organisms primarily live in the shallow photic zone, while the aphotic zone has little life

Lakes

  • Lakes range from small ponds to large lakes

  • Temperate lakes have seasonal thermocline, while tropical lowland lakes have year-round thermocline

  • Oligotrophic lakes are nutrient-poor with high oxygen levels

  • Eutrophic lakes are nutrient-rich and often depleted of oxygen, especially when covered by ice in winter

  • Rooted floating aquatic plants live in shallow, well-lighted areas

  • Zooplankton graze on phytoplankton in lakes

  • Invertebrates live in the benthic zone, fishes live in zones with sufficient oxygen

  • Human nutrient input can lead to algae blooms, oxygen depletion, and fish kills

Wetlands

  • Wetlands are inundated by water and support water-adapted plants

  • High organic production and decomposition, low dissolved oxygen

  • Wetlands can develop in shallow basins, flooded river banks, or coastal areas

  • Wetlands are highly productive biomes

  • Plants found in wetlands include lilies, cattails, sedges, tamarack, and black spruce

  • Wetlands are home to diverse invertebrates, birds, otters, frogs, and alligators

  • Wetlands are important for water purification and flood reduction

  • Human activities have destroyed up to 90% of wetlands

Streams and Rivers

  • Current is the prominent physical characteristic of streams and rivers

  • Headwaters are cold, clear, turbulent, and oxygen-rich

  • Rivers are warmer, more turbid, and more oxygenated

  • Unpolluted rivers can support diverse fish and invertebrate populations

  • Pollution can degrade water quality and harm organisms

  • Damming for flood control disrupts stream and river ecosystems

Estuaries

  • Estuaries are transition areas between rivers and the sea

  • Salinity varies with tides, nutrient-rich and productive

  • Estuaries have tidal channels, islands, natural levees, and mud flats

  • Salt marsh grasses and algae are major producers in estuaries

  • Estuaries attract marine invertebrates, fish, waterfowl, and marine mammals

  • Humans consume oysters, crabs, and fish from estuaries

  • Human interference upstream has disrupted estuaries worldwide

Intertidal Zones

  • Intertidal zones are periodically submerged and exposed by tides

  • Organisms in intertidal zones face temperature and salinity variations and wave forces

  • Oxygen and nutrient levels are high

  • Sandy zones support seagrass and algae, rocky zones support attached marine algae

  • Animals in rocky zones have structural adaptations to attach, while sandy zones bury organisms

  • Animals in intertidal zones include sponges, sea anemones, echinoderms, and small fishes

  • Oil pollution has disrupted many intertidal zones

Oceanic Pelagic Zones

  • Oceanic pelagic zones are constantly mixed by oceanic currents

  • High oxygen levels, turnover in temperate oceans renews nutrients in the photic zone

  • Phytoplankton and zooplankton are dominant organisms

  • Free-swimming animals and marine mammals also inhabit pelagic zones

  • Overfishing has reduced fish populations, pollution has harmed the zone

Coral Reefs

  • Coral reefs are formed from coral skeletons in the photic zone

  • Shallow reef-building corals live in warm, clear water

  • Deep-sea corals live at greater depths with less light availability

  • Corals require high oxygen concentrations and a solid substrate to attach

  • Coral reefs can progress from fringing reefs to barrier reefs to coral atolls

Marine Benthic Zone

  • Marine benthic zone is below the surface waters of coastal and offshore zones

  • Deep benthic abyssal zone has cold temperatures and high water pressures

  • Soft sediments and occasional rocky areas in the benthic zone

  • Seaweeds and filamentous algae are found in the benthic zone

  • Deep-sea hydrothermal vents have unique prokaryotes, echinoderms, and arthropods

  • Neritic benthic communities include invertebrates and some fishes

  • Overfishing and pollution have depleted populations in the benthic zone

Interactions between Organisms and Environment

  • Species distribution is influenced by interactions between organisms and their environment

  • Evolution and ecological interactions both play a role in species distribution

  • Ecological events can lead to evolutionary changes, such as beak size in Galapagos finches

Factors Influencing Species Distribution

  • Biotic and abiotic factors can influence species distribution

  • Climate, interspecific interactions, and other factors impact kangaroos

Ecologists' Approach

  • Ecologists study species distribution and the factors that allow them to exist in certain areas

  • Dispersal allows for global distribution of organisms

  • Natural range expansions and adaptive radiation demonstrate the role of dispersion in species distribution

  • Cattle egrets expanded their distribution in the Americas since the late 1800s

  • Greater distances of dispersal can lead to adaptive radiation

  • Hawaiian silver swords descended from a North American tarweed species

Transplants and Invasive Species

  • Transplants involve intentional or accidental relocation of organisms

  • Invasive species can disrupt communities and ecosystems

  • Successful transplants may indicate a larger potential range for a species

Factors Affecting Species Distribution

  • Organisms do not occupy all potential range habitats

  • Predation, herbivory, and competition can affect species distribution

  • Abiotic factors such as temperature, water, sunlight, wind, rocks, and soil also influence species distribution

  • Factors vary depending on location and time

Influence of Abiotic Factors

Environmental Temperature

  • Temperature impacts biological processes

  • Cells can freeze and rupture below zero degrees Celsius

  • Proteins can become denatured above certain temperatures

  • Mammals and birds maintain internal temperature for survival

Water

  • Water is crucial for survival

  • Desert organisms have adaptations to conserve water

  • Oxygen diffusion is slow in water, leading to low oxygen concentrations in deeper oceans and lakes

  • Salinity affects water and impacts excretory system and water balance in aquatic organisms

  • Freshwater and saltwater environments are inhabited by different organisms

Sunlight

  • Intensity and quality of sunlight impact photosynthesis

  • Water absorbs light in aquatic environments, leading to more photosynthesis near the surface

  • Available light in deserts provides energy but can also cause stresses on plants and animals

Soil Characteristics

  • Soil characteristics limit plant growth and