Biosphere to Ecosystems: Energy flow in ecosystems

Energy flow

The movement of energy through an ecosystem via food chains and food webs.

Main source of energy in ecosystems

The Sun.

Trophic levels

The different feeding levels occupied by organisms in a food chain or food web.

First trophic level

Producers, which manufacture their own food and have the greatest amount of energy.

Second trophic level

Primary consumers, which are herbivores that feed on producers.

Third trophic level

Secondary consumers, which are usually carnivores or omnivores that feed on primary consumers.

Fourth trophic level

Tertiary consumers, which are usually carnivores or omnivores that feed on secondary consumers.

Food chain

A sequence showing how energy is transferred from one organism to another through feeding.

Food web

A series of interconnected food chains in an ecosystem.

Arrows in a food chain or food web

They indicate the direction of energy flow, from the organism being eaten to the organism that eats it.

Energy loss in trophic levels

Energy is used for growth and other activities, lost as heat through respiration, or lost through urine and faeces. This energy is unavailable to the next trophic level.

Ecological pyramid

A diagram showing the relative amounts of energy or matter at each trophic level in a food chain or food web.

Energy pyramid

An ecological pyramid showing the relative amount of energy available at each trophic level.

Biomass pyramid

An ecological pyramid showing the total mass of organisms at each trophic level.

Pyramid of numbers

An ecological pyramid showing the total number of organisms at each trophic level.