Ecosystems and biodiversity - AQA SynergyPredator-prey cycles

An ecosystem is the living organisms in a particular area together with the non-living components of the environment, such as soil, air and water. An ecosystem is biodiverse if it contains many different species.

Part ofCombined ScienceExplaining change

Predator-prey cycles

In a healthy, balanced the numbers of and remain fairly constant. They can go up and down during each year, but generally over the years, these increases and decreases remain fairly constant.

If numbers of either predators or prey increase or decrease, it could be due to a change in the factors, like water or sunlight, or factors, like a new predator or . This would result in a less balanced ecosystem.

An example is shown in the graph below and shows characteristic repeating patterns called predator-prey cycles.

Predator prey graph. As the number of predators increases the number of prey descreases. As the number of predators decrease the number of prey increase.

The graph shows that there is almost always more prey than predators. It also shows the following patterns:

  1. The number of predators increases because there is more prey.
  2. The number of prey then reduces because there are more predators.
  3. The number of predators then reduces because there is now less prey.