BIOLOGY 1500 OUTLINE FOR CHAPTER 3
Ecosystems
1. Define ecology.
a. Ecology is the study of how organisms interact with each other and their
environment.
2. Name the levels of biological organization and identify those that are important in
ecology.
a. See PowerPoint figure
b. Levels important to ecology are organisms, populations, communities,
ecosystems, and the biosphere.
i. Organism are individual animals, plants , fungi, algae, protozoa, and bacteria;
the smallest unit capable of independent life.
ii. Populations consist of all of the members of a species in an area; in sexual
organisms, those organisms that are actually capable in interbreeding on a
regular basis.
iii. Communities consist of all of the populations of all the organisms in a given
area; the living environment.
iv. Ecosystem consists of the community of organisms and also all of the
nonliving environment that supports them: air, soil, water, sunlight,
weather, but also the processes, such as nutrient cycles.
v. The biosphere consists of all the parts of the earth’s environment that
support life; contains all the ecosystems on earth.
c. A cell is the basic unit of life.
d. All of the processes that make living things alive happen in cells: reproduction,
growth, development, metabolism, energy use, etc.
3. Define species
a. Species is a group of organisms that resemble each other in terms of appearance,
lifestyle, behavior, chemistry, and genetics.
b. Sexual species consist of those organisms that are potentially able to interbreed
and produce viable, fertile offspring.
c. All species consist of populations, and populations are the units of sexually
reproducing species in which all members actually do interbreed.
4. Name the four spheres of the earth’s “life-support system” and describe their
structures (see PowerPoint figure)
a. Atmosphere: all the grasses around earth.
i. Lowermost level the troposphere, which holds most of the atmosphere
gasses, has almost all the weather, and in which the greenhouse effect
occurs.
ii. Next layer up the stratosphere, which contains the ozone layer: screens out
ultraviolet.
iii. Far above the surface are the Van Allen radiation belts, which trap most
cosmic rays.
b. Geosphere/lithosphere consists of the rigid surface of the earth and all the rocks
down to ~20 or 30 miles.
c. Hydrosphere consists of all the water in, on and above the earth’s surface.
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d. The biosphere consists of all the parts of the earth’s environment in which there
is life.
e. Atmosphere, hydrosphere, geosphere all form the physical environment; the
biosphere forms the biological environment.
Describe the processes that sustain life on earth.
a. There is constant one-way flow of energy through the biosphere.
b. There is also constant cycling of matter inside the biosphere.
c. Another definition of an ecosystem is a system through which energy flows and
matter cycles.
d. See PowerPoint figure for major cycles and energy flow in the biosphere.
e. Gravity, which holds things on earth.
f. Solar energy is eventually lost as heat, whether it is reflected by the atmosphere
and hydrosphere, turned into heat by absorption, or turned into chemical
energy by living things.
Explain why the earth is so favorable for life.
a. See PowerPoint figure.
b. Oxygen atmosphere.
c. Liquid water
d. Atmospheric pressure.
e. Greenhouse effect.
f. Ozone layer
g. Atmosphere protecting surface from meteorites.
h. Also right size of planet and distance from the sun.
Define biome, aquatic life zone, abiotic, and biotic.
a. Biome is a region described by a particular type of vegetation and caused by a
particular climate (average temperature and precipitation).
i. Temperate deciduous forest
ii. Northern coniferous forest
iii. Prairie
iv. Desert
v. Chaparral (Mediterranean scrub)
vi. Tundra
vii. Tropical rain forest
b. An aquatic life zone is the equivalent of a biome underwater, but is determined
by the type of water (fresh or salt), depth, and presence of a bottom or of
sunlight.
c. Abiotic refers to all of the factors in the environment that are nonliving: the
physical environment.
d. Biotic refers to all the factors in the environment caused by living things: the
biological environment.
e. Some biotic and abiotic factors can be tolerated by a species; some cannot.
f. There is also a range of factors: at extreme high and low ends, these factors
cannot be tolerated, but moderate values promote the growth of the
organism.
Describe the factors that limit population growth.
a. Limited resources
b. The most limiting resource, the one that if increased could allow population to
grow, is called the limited factor.
c. An example if a limiting factor is dissolved oxygen (DO)
d. Limiting factors are usually abiotic.
9. List the biological components of an ecosystem.
a. “Links in the food chain”: producers, consumers, and decomposers
b. Producers are organisms that produce or synthesize their own food from nonliving materials and energy in the environment.
i. Usually use water, carbon dioxide, and sunlight
ii. Includes organism like plants and algae.
iii. Also called autotrophs
c. Consumers are organisms that need to feed on other organisms
i. Can be herbivores (eat plants) or carnivores (eat other consumers).
ii. Includes all animals and most protozoa
iii. Also called heterotrophs
d. Decomposers break down once living material
i. Includes fungi, most bacteria, some protozoa and some animals.
ii. Larger decomposers are called detritivores (“trash eaters”)
10. Explain how biodiversity is natural capital and can be either a renewable or
nonrenewable resource
a. Biodiversity reflects the variety of natural resources available
i. The greater the variety, the more possible “solutions” there are.
ii. The greater the variety, the more redundancy there is in the system.
11. Define food chain and food web and use these concepts to describe energy flow in
an ecosystem.
a. A food chain is a simple straight-line diagram showing who eats who in an
ecosystem.
i. Producer  primary consumer  secondary consumer tertiary consumer.
ii. All send material back to decomposers, which then send it back to producers.
iii. See PowerPoint figure
b. A food web consists of all the food chain in an ecosystem, showing the
interconnectedness of the ecosystem.
i. Multiple organisms at each trophic level.
ii. Multiple connections between trophic levels
iii. A more realistic depiction of how nature works
iv. See PowerPoint figure
c. A trophic level represents the number of steps on organism is away from the sun
as a source of energy.
i. Producers first trophic level
ii. Primary consumers second trophic level
iii. Secondary consumers third trophic level, and so on.
12. Define soil, horizon, soil profile, and leaching
a. Soil is a thin covering over most land that consists of a mixture of weathered
rock, organic matter, water, air, and organisms.
b. Soil arranged in horizons: layers of soil characterized by composition and depth.
i. O horizon: leaf litter
ii. A horizon: topsoil
iii. B horizon: subsoil
iv. C horizon: bedrock
v. See PowerPoint figure
c. Soil profile consists of the horizons present and their thicknesses
d. Leaching is the removal of nutrients from soil by the action of water.
13. Compare and contrast the soil profiles of a humid temperate area and of the tropics
a. Humid temperate areas have the classic O A B C profile, with thick topsoil.
b. Tropical areas have very thin topsoils and thick subsoils.
14. Name the major nutrient cycles and be able to diagram them and identify the
reservoirs in each cycle.
a. Water cycle also called the hydrologic cycle
i. See PowerPoint figure
ii. Reservoirs include atmospheric moisture, groundwater, ice caps, and oceans.
b. Carbon cycle
i. See PowerPoint figure
ii. Reservoirs in soil, oceans, rocks, living things, and atmosphere.
iii. Critically important in food webs, atmospheric temperature (global warming
and the greenhouse effect), and ocean chemistry.
c. Nitrogen cycle
i. See PowerPoint figure
ii. Reservoirs in atmosphere and soil (minor in food webs)
iii. Absolutely necessary for synthesizing proteins.
d. Phosphorus cycle
i. See PowerPoint figure
ii. Reservoirs in rocks, soils, and food webs.
iii. Used for DNA and ATP: heredity and energy transfer.
e. Sulfur cycle
i. See PowerPoint figure
ii. Reservoirs in atmosphere, oceans, and food webs.