Food Chains and Food Web

Food Chain

A linear sequence showing how energy and nutrients pass from one organism to the next — from producer to consumers to decomposers.

Food Web

An interconnected network of multiple food chains in an ecosystem

Producer

An organism (usually a plant or algae) that makes its own food through photosynthesis. They are the base/start of every food chain. Also called autotrophs.

Consumer

An organism that must eat other organisms to get energy. Also called heterotrophs. They are divided into primary

Primary Consumer

An organism that eats producers (plants). These are herbivores. Examples: rabbits

Secondary Consumer

An organism that eats primary consumers. These are often carnivores or omnivores. Examples: frogs

Tertiary Consumer

An organism that eats secondary consumers. They are typically apex or near-apex predators. Examples: hawks

Apex Predator

The top predator in a food chain or web with no natural predators. Examples: great white sharks

Decomposer

An organism that breaks down dead organic matter and returns nutrients to the soil. Examples: fungi

Detritivore

A type of decomposer that physically breaks down dead material by eating it. Examples: earthworms

Autotroph

An organism that produces its own food using sunlight (photosynthesis) or chemicals (chemosynthesis). Synonymous with producer.

Heterotroph

An organism that cannot make its own food and must consume other organisms for energy. Synonymous with consumer.

Herbivore

An animal that only eats plants (producers). They are always primary consumers. Examples: cows

Carnivore

An animal that only eats other animals. They are secondary or tertiary consumers. Examples: lions

Omnivore

An animal that eats both plants and animals. They can occupy multiple levels in a food web. Examples: bears

Trophic Level

The position an organism occupies in a food chain based on its feeding role (e.g.

Energy Pyramid

A diagram showing the amount of energy at each trophic level. Only about 10% of energy is passed to the next level — 90% is lost as heat.

10% Rule

The principle that only 10% of the energy stored in one trophic level is transferred to the next. This is why food chains rarely exceed 4–5 levels.

Biomass

The total mass of living organisms at a given trophic level. Biomass decreases as you move up the food chain due to energy loss.

Keystone Species

A species that has a disproportionately large effect on its ecosystem. Removing it can cause the collapse of a food web. Example: sea otters.

Scavenger

An animal that feeds on dead organisms it did not kill itself. Helps clean ecosystems. Examples: vultures

Ecological Niche

The role and position a species occupies in its ecosystem

Predator

An organism that hunts and kills other organisms (prey) for food.

Prey

An organism that is hunted and eaten by a predator.

Symbiosis

A close