7.2 Energy Flow & Food Webs (Ch. 47)

Producer (Autotroph)

Makes own food via photosynthesis (or chemosynthesis). Foundation of all food webs. Examples: plants, algae, phytoplankton.

Consumer (Heterotroph)

Cannot make own food; must eat other organisms.

Primary Consumer

Eats producers (herbivore). Examples: rabbits, deer, caterpillars.

Secondary Consumer

Eats primary consumers. Examples: frogs, small snakes.

Tertiary Consumer

Eats secondary consumers. Examples: hawks, wolves, orcas.

Decomposer

Breaks down dead organisms, returning nutrients to soil. Examples: fungi, bacteria, earthworms.

Energy Pyramid

Diagram showing energy transfer through trophic levels. Only ~10% of energy passes to the next level — the rest is lost as heat.

10% Rule

At each trophic level, only about 10% of the energy from the level below is transferred upward. This is why there are fewer top predators than herbivores.

Biomass

The total mass of living matter at each trophic level. Decreases as you move up the food chain.

Nutrient Cycle

Matter (like carbon and nitrogen) is RECYCLED through ecosystems, unlike energy which flows in ONE direction.