Biodiversity (Edexcel GCSE Biology): Revision Note

Biodiversity

• Biodiversity is the range and variety of different species of organisms within a given area (e.g. on Earth or within an ecosystem)

• It considers not only the species richness, but also the variation within each species including the relative abundance (i.e. the population size) of each species present

  • For example, a high biodiversity would be found in an environment with lots of different species which show a lot of variation and are all evenly distributed across the study area

The importance of biodiversity

• Different species depend on each other for many things, including:

  • Food

  • Shelter (e.g. birds nesting in trees)

  • Maintenance of the physical environment (e.g. tree roots provide stability for soils, ensuring they do not get washed away. This, in turn, provides a stable habitat for other plant species)

• High biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for these three things

• Populations with high levels of diversity are also more likely to be resilient to sudden environmental impacts or diseases

• Consider the food web below:

  • If the mouse population was suddenly wiped out, the fox and the hawk populations might decrease but would not be wiped out as mice are not their only food source

  • This example ecosystem has sufficient biodiversity to support the fox and hawk populations

  • The fox population can still depend on the rabbit and frog populations for food

  • The hawk population can still depend on the frog and sparrow populations for food

A food web demonstrates the importance of biodiversity within an ecosystem