Chain, webs and pyramids

By the end of this page you will know:

• what a food chain is
• that many food chains link together to make a food web
• that pyramids can show the numbers , biomass or energy at different stages in a food chain.

The diagram show a food chain in the east African Serengeti. Food chain are examples of energy-transfer chains.The arrows show the flow of energy through the food chain. Because green plants use photosynthesis to make their own food they are called producers. Almost every food chain in the world begins with a green plant.

The Serengeti-Mara is the 26,000 km 2  home to more than 3 million large animals.After the rains, over 2 million grazers move into the area, feeding on grasses and acacia bushes.Large predators use the area as a hunting ground to find food.The savannah ecosystem has lots of different food chains. When food chains are linked together, they make a food web.The top carnivores have few predators.When top carnivores die, scavengers eat their bodies.

The Serengeti-Mara plains are not endless.Every lion needs about 350 grazers to feed it.Each grazer needs enough grass to survive. About 2000 lions live in the Serengeti-Mara.This gives each lion about 13 km of hunting ground.The same area contains about 350 grazers, mainly Thomson's gazelle,wildebeest and zebra.

Food chains tell you how energy is transferred from one organism to another but not much more.A food pyramid is a numerical (quantitative) way of showing the organism in a food chain.There are two kind of food pyramid:pyramids of number and pyramids of biomass.Biomass is the dry mass of living matter.Pyramids of number show how many of each organism are found at each level of a food chain.Pyramids of biomass show the amount of living matter at each level of  the pyramid.