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Area II: The Living World (10-15%)


Area IIA: Ecosystem Structure (Main ideas from Living in the Environment, 14th Edition, by G. Tyler Miller, Jr.)

4-1 The Nature of Ecology
  • Ecology is the study of connections in the natural world.
  • A population consists of a group of interacting individuals of the same species occupying a specific area. The habitat is the place where a population or an individual usually lives. Its distribution or range is the area over which a species may be found.
  • A community represents populations of different species living and interacting in a specific area.
  • An ecosystem is a community of different species interacting with each other and with their nonliving environment of matter and energy.

4-2 The Earth’s Life-Support Systems
  • The atmosphere is the thin membrane of air around the planet.
  • The hydrosphere consists of the earth’s water, found in liquid water, ice, and water vapor.
  • The lithosphere is the crust and upper mantle of the Earth.
  • The biosphere includes most of the hydrosphere, parts of the lower atmosphere, and upper lithosphere. All parts of the biosphere are interconnected.
  • Solar radiation warms the atmosphere, evaporates and recycles water, generates wind, and supports photosynthesis.

5-3 Ecological Niches and Adaptation
  • An ecological niche is a species’ way of life in an ecosystem, everything that affects its survival and reproduction.
  • Generalist species have broad ecological roles; specialist species have narrow ecological roles.
  • A population’s gene pool and its rate of reproduction limit the population’s ability to adapt to new environmental conditions.

8-1 Community Structure and Species Diversity
  • Ecologists use characterize biological communities by their physical appearance, species diversity, and niche structure.
  • The number of species on an island is determined by how fast new species arrive, how fast old species become extinct, the size of the island, and the distance from the mainland.

8-2 Types of Species
  • Types of species include native, nonnative, and indicator species.
  • Keystone species help ecological communities run smoothly; they determine the type and number of community species.
  • Foundation species shape communities by creating and enhancing habitat that benefits other species.

8-3 Species Interactions: Competition and Predation
  • Five basic species interactions are competition, predation, parasitism, mutualism, and commensalism.
  • Competition between species for food, sunlight, water, soil, space, nest sites, etc. is interspecific competition; this can result in resource partitioning and specialization.

8-4 Species Interactions: Parasitism, Mutualism, and Commensalism
  • Parasites live on or in another species. The host of this arrangement is obviously harmed by it, but the parasite can contribute to biodiversity by controlling the size of specific species populations.
  • Mutually beneficial interactions also exist in ecological environments.
  • Some species interaction helps one species but does nothing for the other; this is commensalism.
APES-Area2a-Ecosystems

Area IIA Animations: Community Interactions
Click the links to see the animations full size.
Species Interactions

Competitive Exclusion

Island Biogeography



4-3 Ecosystem Components
  • Terrestrial parts of the biosphere are classified as biomes, areas such as deserts, forests, and grasslands. Aquatic life zones describe the many different areas found in a water environment, such as freshwater or marine life zones (coral reefs, coastal estuaries, deep ocean).
  • The major components of ecosystems are abiotic (nonliving) water, air, nutrients, solar energy, and biotic (living) plants, animals, and microbes.
  • Biodiversity is the amazing variety of earth’s genes, species, ecosystems, and ecosystem processes.

6-3 Biomes: Climate and Life on Land
  • Different climates lead to different communities of organisms, especially vegetation.
  • Differences in average temperature and precipitation due to global air and water circulation lead to differences in climate.

6-4 Desert Biomes
  • Deserts have little precipitation and little vegetation. They are found in tropical, temperate, and polar regions.
  • Deserts take a long time to recover from disturbances.

6-5 Grassland, Tundra, and Chaparral Biomes
  • Grasslands, or prairies, have enough water to support grasses but few, if any, trees.
  • The three main types of grasslands are tropical, temperate, and polar (tundra).
  • Chaparral, or temperate shrubland, is found in coastal areas that border deserts.

6-6 Forest Biomes
  • Forests are found in areas with moderate to high average annual rainfall. Three main types of forests are tropical, temperate, and boreal (polar).

6-7 Mountain Biomes
  • Mountains are high-elevation forested islands of biodiversity, often with dramatic changes in altitude, climate, soil, and vegetation within very short distances.

7-1 Aquatic Environments
  • Saltwater and freshwater aquatic zones cover about 71% of the earth’s surface.
  • Salinity of the water determines the major types of organisms found in an aquatic environment.
  • There are four major types of organisms in aquatic systems: plankton, nekton, benthos, and decomposers.
  • Three layers of aquatic life zones can be used: surface, middle, and bottom.

7-2 Saltwater Life Zones
  • Oceans have two major life zones: the coastal zone and the open sea.
  • The coastal zone interacts with the land and is much affected by human activities.
  • Coral reefs in shallow coastal zones of tropical and subtropical oceans support a very diverse, complex ecosystem.
  • About 40% of the world population lives along coasts. Over half of the U.S. population lives within 62 miles of the coast.

7-3 Freshwater Life Zones
  • Freshwater life zones contain less than 1% by volume of salt. These zones include standing (lentic) bodies such as lakes, ponds, and wetlands and flowing (lotic) systems such as streams and rivers.
  • Stratification of water occurs in deep temperate lakes into temperature zones; no mixing occurs.
  • During fall and spring, lakes have turnover of water that brings up nutrients, reoxygenates bottom levels, and evens out water temperature.
  • Lakes are described with reference to their plant nutrients (eutrophic, mesotrophic, or oligotrophic).
  • Inland wetlands cover the land for a part of all of each year. Wetlands include swamps, marshes, prairie potholes, floodplains, and arctic tundra in summer.
APES-Area2a-Biomes

Area IIA Animations: Biomes and Aquatic Life Zones
Click the links to see the animations full size.
Biomes Map

Lake Zonation

Lake Turnover

Eutrophic vs. Oligotrophic Lakes

Ocean Zones