Unit 8 Ecology Key Terms

Apex Predator

a predator at the top of a food chain, with no natural predators of its own. Unlike other predators, they are not hunted by other animals.

Atmosphere

The layer of gases that surrounds Earth; part of Earth's system, including nitrogen, oxygen, carbon dioxide, and more.

Autotrophs / Producers

Organisms that create their own food, usually through photosynthesis (converting sunlight into chemical energy).

biome

A large region with a specific climate and particular types of plants and animals (e.g., desert, rainforest, tundra).

Biosphere

The part of Earth where life exists; includes all ecosystems and living organisms on land, water, and in the air.

Carnivore

An organism that eats only other animals.

Community

All the different populations (species) living and interacting in the same area.

Consumers / Heterotrophs

Organisms that cannot make their own food; they get energy by eating other organisms.

Primary consumers

Eat producers (herbivores).

Secondary consumers

Eat primary consumers (carnivores or omnivores)

Tertiary consumers

Eat secondary consumers and primary consumers

Quaternary consumers

• Eat tertiary consumers, tertiary consumers, secondary consumenrs, and primary consumers (often apex predators).

Decomposer / Detritivore

Organisms (like fungi, bacteria, or some insects) that break down dead organisms, returning nutrients to the soil.

Ecosystem

A system of interacting organisms (living) and their physical (non-living) environment.

Ecosystem Engineer

An organism that changes its environment in a significant way (e.g., beavers building dams).

Equilibrium

A stable balance in an ecosystem where populations and resources remain relatively constant over time.

Exotic / Non-native / Introduced Species

Species that are brought to an ecosystem where they didn’t evolve. They can spread rapidly and outcompete native species due to lack of natural predators.

Food Chain

A single, linear path of energy flow (who eats whom).

Food web

A complex network of interconnected food chains where arrows point from the food to the organism that eats it, showing energy flow.

Geosphere

The solid part of Earth, including rocks, minerals, mountains, and the Earth's interior.

Herbivores

Definition: Organisms that eat only plants. (Primary consumers)

Hydrosphere

All water on Earth—oceans, lakes, rivers, glaciers, and even water vapor in the air.

Invasive Species

Non-native species that spread rapidly and disrupt the balance of an ecosystem. They can outcompete native species, destroy habitats, and reduce biodiversity.

Keystone Species

A species that has a disproportionately large effect on its ecosystem. Removing it would cause major changes.

Limiting Factors

Conditions that control population size or growth. (Biotic or Abiotic)

Omnivore

An organism that eats both plants and animals.

Population

A group of individuals of the same species living in the same area that can interbreed (share a gene pool).

Scavengers

Animals that eat dead animals (not killed by the scavenger itself) to gain energy

Trophic Levels

The steps in a food chain or food web, representing the flow of energy. Producers (autotrophs)

• Primary consumers (herbivores)

• Secondary consumers

• Tertiary consumers

• Quaternary consumers

Energy Flow

Only about 10% of energy is passed from one level to the next.