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KEY CONCEPT 13.1 Ecology is the study of the relationships among organisms and their environment.

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Ecologists study environments at different levels of organization.

• Ecology is the study of the interactions among living things, and between living things and their surroundings.

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OrganismOrganism

• An organism is an individual living thing, such as an alligator.

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OrganismOrganism

Population

Population

• A population is a interbreeding group of the same species that lives in one area.

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OrganismOrganism

Population

Population

Community

Community

• A community is a group of populations that live together in one area.

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OrganismOrganism

Population

Population

Community

Community

Ecosystem

Ecosystem

• An ecosystem includes all of the organisms as well as the climate, soil, water, rocks and other nonliving things in a given area.

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OrganismOrganism

Population

Population

Community

Community

Ecosystem

Ecosystem

Biome• A biome is a major regional or global community of organisms characterized by the climate conditions and plant communities that thrive there.

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Ecological research methods include observation, experimentation, and modeling.

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• Experiments are performed in the lab or in the field.

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KEY CONCEPT 13.2 Every ecosystem includes both living and nonliving factors.

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An ecosystem includes both biotic and abiotic factors.

• Biotic factors are living things.– plants– animals– fungi– bacteria

plants

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• Abiotic factors are nonliving things. – moisture– temperature– wind– sunlight – soil

moisture

sunlight

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Changing one factor in an ecosystem can affect many other factors.

• Biodiversity is the assortment, or variety, of living things in an ecosystem.

• Rain forests have more biodiversity than other locations in the world, but are threatened by human activities.

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• A keystone species is a species that has an unusually large effect on its ecosystem.

keystone

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• Keystone species form and maintain a complex web of life.

creation ofwetlandecosystem

increased waterfowlPopulation

increased fishpopulation

nesting sites for birds

keystone species

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KEY CONCEPT 13.3 Life in an ecosystem requires a source of energy.

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Producers provide energy for other organisms in an ecosystem.

• Producers get their energy from non-living resources.• Producers are also called autotrophs because they make

their own food.

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Producers provide energy for other organisms in an ecosystem.

• Consumers are organisms that get their energy by eating other living or once-living resources.

• Consumers are also called heterotrophs because they feed off of different things.

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Almost all producers obtain energy from sunlight.

• Photosynthesis in most producers uses sunlight as an energy source.

• Chemosynthesis in prokaryote producers uses chemicals as an energy source.

carbon dioxide + water +hydrogen sulfide + oxygen

sugar + sulfuric acid

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KEY CONCEPT 13.4 Food chains and food webs model the flow of energy in an ecosystem.

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A food chain is a model that shows a sequence of feeding relationships.

• A food chain links species by their feeding relationships. • A food chain follows the connection between one producer

and a single chain of consumers within an ecosystem.

DESERT COTTONTAILGRAMA GRASS HARRIS’S HAWK

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• Consumers are not all alike.– Herbivores eat only plants.– Carnivores eat only animals.– Omnivores eat both plants and animals.– Detritivores eat dead organic matter.– Decomposers are detritivores that break down organic

matter into simpler compounds.

carnivore decomposer

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• Specialists are consumers that primarily eat one specific organism or a very small number of organisms.

• Generalists are consumers that have a varying diet.

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• Trophic levels are the nourishment levels in a food chain.– Primary consumers are herbivores that eat producers. – Secondary consumers are carnivores that eat

herbivores.– Tertiary consumers are carnivores that eat secondary

consumers.– Omnivores, such as humans that eat both plants and

animals, may be listed at different trophic levels in different food chains.

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A food web shows a complex network of feeding relationships. • An organism may have multiple feeding relationships in an

ecosystem.• A food web emphasizes complicated feeding relationships

and energy flow in an ecosystem.

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KEY CONCEPT 13.5 I can describe how matter cycles in and out of an ecosystem.

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• Matter cycles through ecosystems through

• Biogeochemical cycles• Bio-• Geo-• Chemical-

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• The 4 most common biogeochemical cycles are:

– Hydrologic cycle-(water cycle)– Carbon cycle– Nitrogen cycle– Phosphorus cycle

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• Hydrologic cycle-

precipitation condensation

transpiration

evaporation

water storagein ocean

surfacerunoff

lake

groundwater

seepage

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fossil fuels

photosynthesis

carbon dioxidedissolved in water

decompositionof organisms

respiration

carbondioxidein air

photosynthesis

combustionrespiration

• Carbon Cycle

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nitrogen inatmosphere

animals

denitrifyingbacteria

nitrifyingbacteria

nitrifyingbacteria

ammonium

ammonification

decomposers

plant

nitrogen-fixingbacteria in soil

nitrogen-fixingbacteria in

roots

nitrates

nitrites

• Nitrogen Cycle

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geologic upliftingrain

weathering ofphosphate from rocks

runoff

sedimentationforms new rocks

leaching

phosphate in solutionanimals

plants

decomposers

phosphatein soil

• Phosphorus Cycle-

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KEY CONCEPT 13.6 Pyramids model the distribution of energy and matter in an ecosystem.

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energy transferredenergy

lost

An energy pyramid shows the distribution of energy among trophic levels.

• Energy pyramids compare energy used by producers and other organisms on trophic levels.

• Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat.

• Only 10 percent of the energy at each tier is transferred from one trophic level to the next.

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Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms.

• Biomass is a measure of the total dry mass of organisms in a given area.

tertiaryconsumers

secondaryconsumers

primaryconsumers

producers

75 g/m2

150g/m2

675g/m2

2000g/m2producers 2000g/m2

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• A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem.

tertiaryconsumers

secondaryconsumers

primaryconsumers

producers

5

5000

500,000

5,000,0005,000,000producers

• A vast number of producers are required to support even a few top level consumers.