Food webs

When all the food chains in an ecosystem are joined up together, they form a food web. Here is an example of a food web:

Food web: the producer is grass, which is eaten by rabbits, insects and slugs. Rabbits are eaten by the foxes. Slugs are eaten by thrushes. Insects are eaten by frogs, voles and thrushes. Frogs, voles and thrushes are eaten by a hawk. Frogs and voles are also eaten by foxes

Although it looks complex, it is just several food chains joined together. Here are some of the food chains in this food web:

grass → insect → vole → hawk

grass → insect → frog → fox

grass → insect → vole → fox

Notice that:

  • the rabbits and slugs have just one predator
  • the frogs and voles have two predators (the foxes and hawks)
  • the insects have three predators (frogs, voles and thrushes)

This leads to some interesting effects if the population of a particular organism in the food web decreases. Some animals can just eat more of another organism if food is in short supply, while others may starve and die. This in turn can affect the populations of other organisms in the food web.