Ecology and the Biosphere
Ecology is the study of interactions between organisms and the environment. These interactions can happen on a variety of levels, from the single organism up to a global scale. A main purpose of ecology is to understand the distribution of animals and how the abiotic factors affect a population's abundance and dispersion.
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Chapter Summary

52.1 Ecology integrates all areas of biological research and informs environmental decision making

The Scope of Ecological Research

Gathering information for ecology is primarily done through discovery science: through observing the natural world. Ecology is studied at different levels of organization
Here are the varying levels of organization of ecology.

These levels from smallest to largest are as follows:
  • Organismal
  • Population
  • Community
  • Ecosystem
  • Landscape
  • Biosphere

Organismal Ecology

This deals with the physiological, behavorial, and morphological ways and individual interacts within an environment.

Population Ecology

A population is a group of organisms of the same species. Population Ecology refers to the factors that affect population size, density, and compostion.

Community Ecology

Community is all of the different species of organisms living in an area. This deals with the interactions between species and tries to understand how predation, competition, and disease affect a community.

Ecosystem Ecology

An ecosystem includes the community and ALL of the abiotic factors of the environment like rocks, water, and the sun. This study of ecology deals with the energy flow of an ecosystem between the abiotic and biotic factors.

Landscape Ecology

Landscapes and seascapes deal with all of the connections of ecosystem. This deals with the arrangement of ecosystems and how they relate.

Linking Ecology and Evolutionary Biology

Through evolution, natural selection causes populations to adapt to their environment over generations - the time of evolutionary time. Ecology is studied in a minute-to-minute time frame of interactions between organisms and environment. The differential survival and reproduction of individuals over this time frame is ecological time. An example of the link could be described with a farmer and fungus. To remove a fungus population, a farmer would apply a fungicide, decreasing the population. This would be the ecological effect. Over time, the fungus will slowly grow immune to the fungicide, an evolutionary effect.

Ecology and Environmental Issues

Evironmentalism is a movement for the protection of nature. In turn, this practice has becomed linked to ecology. However, there is a distinction between ecology and advocacy. Ecologist educate educators about environmental issues. Rachel Carson is an important individual who published a book called Silent Spring. Doing so allowed the public to be warned of the harmful effects of DDT.

52.2 Interactions between organisms and the environment limit the distribution of species

Biogegraphy is the study of past and presnt distributions of species in evolutionary time. Ecologists focus on two factors of an ecosystem to dertemine how and why species occur where they do: biotic, the living factors, and abiotic, the nonliving factors.

Dispersal and Distribution

The movement of individuals away from their area of origin or from centers of high population density is dispersal. This provides to the global distribution of organisms. This concept is important to understand both geographic isolation in evolution and the current patterns of the geographic location of species.

Natural Range Expansions

Dispersion is important when organisms inhabit an area where they did not exist before. To determine if dispersal is the limiting factor to population success, humans have transplanted species into an area where they did not exist. If the species is successful and reproduces, the potential range is larger than the actual range.

Behavior and habitat selection contribute to the distribution of organisms

Organisms occasionally select only paticular habitats. Habitat selection is not completely understood, but it does limit distribution.

Biotic factors affect the distribution of organisms

Influences such as predation, parasitism, or competition may limit an organism's ablity to survive. Also, a species may be dependent on a different species, like pollinators to flowers. Predators, herbivores, food resources, parasites, diseases, and competition are all examples of living limiting factors.

Abiotic factors that affect the distribution of organisms

Nonliving factors can also affect the distribution of organisms. Temperature, water, and sunlight all affect where organisms survive and reproduce. Spatial heterogeneity is the idea that more organisms live where there are more abundance of resources. Organisms can also avoid certain conditions such as dormancy or hibernation.
  • Temperature - Species can only maintain homeostasis at specific temperatures. At temperatures too high or too low, organism's active metabolism may begin to fail. Some organisms can adapt to temperatures unnatural for most organisms but most must remain in a certain range.
  • Water availability - Organisms that live on the shore line may face destruction as the tide recedes. Terrestrial organisms have adaptations that allow them to retain and conserve water.
  • Salt concentration - Affects the water balance of organisms through osmosis. Most aquatic organisms have limited ability for osmoregulation, or the balance of water content, which separates marine and freshwater organisms. Only some organisms can survive in salty waters.
  • Sunlight - Provides energy for almost all ecosystems. Intensity of light doesn't necessarily affect an ecosystem, however shading increases competition for sunlight.
  • Sunlight in aquatic environments - Water limits the absorption of red light, and reflects blue light the deeper it is. Most photosynthesis in aquatic environments occurs at the surface.
  • Too much light also limits survival - The atmosphere is thinner at higher elevations, absorbing less UV rays. The sun rays then will likely damage DNA and proteins at higher elevations
  • Soil composition - Physical structure, pH, and minerals of soils and rocks limit the distribution of plants, which in turn affects other organisms. Extremely acidic and basic soils are not good fro most plants
  • Water composition - Solutes can affect the chemical stability of waters, affecting organisms


Climate is the long-term, dominant weather conditions in an area. Abiotic factors that affect climate are:
  • Temperature
  • Water
  • Sunlight
  • Wind
Climate patterns can be described on two levels. Macroclimate patterns are on a global, regional, or local levels. Microclimate patterns are very fine patterns, such as the conditions experienced by a community of organisms under a fallen log.

Global Climate Patterns

These patterns are determined by sunlight and Earth's movement. Sunlight intensity plays a major part in Earth's climate patterns: it establishes temperature variation, cycles of air movement, and evaporation of water. More heat and light per unit of surface are reach the tropics than the high latitudes.

Regional, Local, and Seasonal Effects on Climate

Bodies of water and mountains can affect regional climate, while smaller variations affect local climates. Seasonal variation is a factor too.
  • Bodies of Water - Ocean currents affect climate by cooling or heating air along the coast. Oceans and large lakes usually keep the temperature consistent due to water's high specific heat.
  • Mountains - Limit the amount of sunlight on an area, as well as temperature and rainfall.
  • Seasonality - Angle of sun leads to seasonal changes in local environments


Microclimate are minute factors that affect sunlight and wind. Forest trees moderate climate beneath them by shading. Every environment has abiotic factors that affect species on a small scale.

Long-term Climate Change

To predict future climate change, scientists study previous climate changes. Researches can determine current climate limitations for organisms, they can determine the effects of global warming.

52.3 Aquatic biomes are diverse and dynamic systems that cover most of Earth

Biomes are the major ecological associations that occupy broad geographic regions of land or water. Combinations of biotic and abiotic factors determine certain biomes. Aquatic biomes are the most diverse and widespread. Ecologist differentiat freshwater and marine biomes on physical and chemical differences. Marine biomes are more concentrated in salt than freshwater, and cover approximately three-fourths of Earth's surface. (Evaporation creates rainfall, and moderates temperature). Also, photosynthesis from marine biomes account for a large portion of oxygen on Earth. These are often linked to terrestrial biomes

Stratification of Aquatic Biomes

Many aquatic biomes are separated into zones by light penetration, temperature and depth. Light intensity decreases with depth.
These are the zones of an ocean

  • The photic zone receives a significant amount of sunlight
  • The aphotic zone receives little light
  • The bottom of the aquatic biome is the benthic zone. It is made up of sand and sediment and is occupied by communities of organisms called benthos. The major food source is dead organic material, or detritus.
  • The most extensive part of the open ocean is the abyssal zone, which is extremely deep.
In bodies of water, a boundry called the thermocline separates a warmer upper layer from a colder deep layer. Turnover is the semiannual mixing of this water, which allows oxygenated water to mix with nutrient rich water.

Winter. Spring. Summer. Autumn.


Organism distribution is determined by depth of water, degree of light penetration, distance from shore, and open water versus bottom. Major aquatic biomes are lakes, wetlands, streams, rivers, estuaries, intertidal biomes, oceanic pelagic biomes, coral reefs, and marine benthic biomes.


Oligotrophic lakes are nutrient-poor and generally oxygen rich. Eutrophic lakes are nutrient-rich and often depleted of oxygen if ice covered in winter. Rooted and floating aquatic plants live in the shallow and well-lighted littoral zone. Water is too deep in the limnetic zone to support rooted plants. Zooplankton graze on phytoplankton.

Oligotrophic Lake in Grand Teton National Park, Wyoming
Eutrophic Lake in Okavango Delta, Botswana


Wetlands are covered with sufficient water to support water plants. They include marshes bogs and swamps. They are usually home to many invertebrates and bird. There is not a lot of oxygen in the soil and water, but have high nutrients
Okefenokee National Wetland Reserve in Georgia.

Streams and Rivers

These are bodies of waters that move in one direction. They are low with many mineral nutrients, but has high oxygen. It's nutrients are determined by the terrain and plants.

Stream in the Great Smoky Mountains
Mississippi River


These are areas of transition between river and sea. The salt concentration of these are very high. They have complex flow patterns with a variety of environments. They support many fish and invertebrates.

Intertidal Zone

Is submerged and revealed by the tide. Organisms in these biomes are faced with the challenge of wave action. Many animals are able to stick onto a hard substrate. The upper zone experiences more air exposure and greater variety of temperature and chemicals.

Intertidal zone on the Oregon Coast

Oceanic Pelagic Zone

This biome is the ocean blue water with oceanic currents. The surface of the water faces turnover in spring. It has high oxygen levels but low nutrients. This biome covers 70 percent of Earth's surface

Open ocean off the island of Hawaii

Coral Reefs

Coral reefs are limited to the photic zone of tropic marine environments. They are formed by the calcium carbonate skeletons of coral animals. Home to a diverse number of vertebrates and invertebrates. Pollution is currently destroying the Coral Reefs.
A coral reef in the Red Sea

Marine Benthic Zone

This zone consits of the seafloor below the surface waters of coastal, or neritic, zone and the offshore pelagic zone. Organisms in the abyssal zone are adapted to continuous could and high water pressure. Unique organisms are associated with deep-sea hytrothermal vents of volcanic origin on mid-oceanic ridges.

A deep-sea hydrothermal vent community

52.4 The structure and distribution of terrestrial biomes are contolled by climate and disturbance

Patterns of climate correlate with patterns of biomes. A climograph is used to determinen the annual mean temperature and precipitation of an area. Factors other than temperature and rainfall affect a biome, such as minerals, soils, and vegetation. Each biome is characterized mostly by what plants live there, or major physical features. Terrestrial biomes usually cross over, creating the ecotone. Some terrestrial biomes layer vertically. The canopy of a forest is the top layer, covering the lower tree layer, shrubs, ground layer of plants, forest floor (litter layer), and roots. Same biomes might have different species. Biomes are affected by natural disturbance rather than remain stable. That is why biomes exhibit patchiness. This is also due to Human disturbances.

Terrestrial Biomes

Tropical Rain Forests

Found close to the equator. Consist of high rain fall. Competition for light is intense. Most diverse biome.
Tropical rain forest in Borneo


Have varying levels of rainfall. Vegetation is sparse, and contains cacti and shrubs. Most desert animals are nocturnal as to avoid the heat. Many organisms display adaptations to survive in the heat. Plants can retain water well and have reduced surface area for leaves.
Desert in the United States


Rainfall is seasonal and it is usually warm all year round. The vegetation is grassland with scattered trees. Most animals are herbivores, mainly insects. Fire plays a key role in maintaining these biomes.


Characterized by wet winters and dry, hot summers. Dominated by shrubs and small trees, with some grasses and herbs. Plant and animals are diverse. Adaptations to fire and droughts are common.
Chaparral in California

Temperate Grasslands

Characterized by seasonal droughts, fires, and variation in temperature. Grazers and burrowing mammals are the main animals. Ideal for agriculture, and has been converted to farm land.
Sheyenne National Grassland in North Dakota

Coniferous forest (Taiga)

Largest terrestrial biome on earth. Has long, cold winters, and short, wet summers. The trees are adapted to snow and drought. They are home to many birds and mammals
Rocky Mountain National Park in Colorado

Temperate Broadleaf Forests

Characterized by cold winters, hot summers, and lots of precipitation. Has very distinct layers, including a canopy, understory trees, shrubs, and herbs. Deciduous trees drop their leaves in the winter and become dormant. Home to many hibernating mammals.
Great Smoky Mountains National Park in North Carolina


This biome covers a large portion of the Arctic. It is found on high mountaintops. Winter is long and cold while summer is short and mild. Vegetation is primarily lichens, mosses, grasses, and small shrubs and trees. A frozen layer known as permafrost prevents water infiltration and root growth. Migratory birds use the Tundra as nesting grounds in the summmer.
Denali National Park, Alaska in Autumn

Vocabulary (See above for definition)

  • Ecology
  • Organismal ecology
  • Population ecology
  • Community ecology
  • Ecosystem ecology
  • Landscape ecology
  • Biosphere
  • biotic
  • abiotic
  • dispersal
  • macroclimate
  • microclimate
  • biome
  • photic zone
  • aphotic zone
  • benthic zone
  • benthos
  • detritus
  • abyssal zone
  • thermocline
  • turnover
  • oligotrophic
  • eutrophic
  • littoral zone
  • limnetic zone
  • wetlands
  • streams
  • rivers
  • estuaries
  • intertidal zone
  • oceanic pelagic biome
  • coral reefs
  • marine benthic zone
  • neritic zone
  • pelagic zone
  • climate
  • climograph
  • ecotone
  • canopy
  • tropical forests
  • deserts
  • savanna
  • chaparrals
  • temperate grasslands
  • coniferous forest (taiga)
  • temperate broadleaf forests
  • tundra


This guy's videos serve as great comprehensive reviews, which are also easy to understand.

This link also has several videos on biomes

Study Material

These sites I found helpful while studying

Quiz Yourself

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