Pocket Genius Science: The living world – Food webs

Facts At Your Fingertips: The living world – Food webs

Energy passes from one living thing to another in the form of food. Food webs show how living things feed on one another.

At the bottom of a food web are plants, which make their own food using energy from the Sun.

At the top are predators, which feed on other animals.

Grasses are producers that make their own food by photosynthesis

Deer are primary consumers that feed on grass

Lions are secondary consumers that feed on deer

Decomposers, such as dung beetles, feed on droppings and the bodies of dead animals

Food chain

Food webs are made up of many different food chains that have different levels. In a food chain, plants are called producers because they make their own food. Animals that eat plants are called primary consumers.

Primary consumers are eaten by other animals called secondary consumers, or predators. When all living things die they become the food of organisms called decomposers.

Food pyramid

As we go up a food chain, the amount of food available decreases. This is because living things use most of the energy in the food they eat in respiration (see page 128). A food pyramid shows how energy is lost at each level.

Near the top, there are just a few predators, while at the bottom there are many more producers.

The number of living things decreases as we move up the food pyramid

Phytoplankton make their own food

Zooplankton feed on countless phytoplankton

Fish eat trillions of zooplankton

Seals eat thousands of fish

A polar bear eats dozens of seals in a year