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