Biodiversity (AQA GCSE Biology): Revision Note

Importance of biodiversity

• Biodiversity is the variety of different species of organisms on Earth, or within an ecosystem

• Different species depend on each other for:

  • 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)

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

• For example, for 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 too, 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

Food web diagram

Use this image

• Many human activities, or consequences of human activities, are reducing biodiversity in individual ecosystems and on a global level. These include:

  • Producing waste (destruction of habitats to make space for landfill and toxic chemicals from landfill waste can leach into the soil)

  • Deforestation (destruction of forest habitats that contain high biodiversity)

  • Global warming (disruption of ecosystems and reduced biodiversity due to flooding of coastal habitats, coral bleaching, increased frequency of extreme weather events and many other factors caused by increasing global temperatures)

Maintaining biodiversity

• The future of the human species on Earth relies on the maintenance of biodiversity

• Just like any other species in an ecosystem, humans rely on many other species to survive. For example:

  • Photosynthetic organisms produce oxygen for respiration

  • Pollinator species, such as bees, pollinate food crops

  • Plant species are the source for many medicines

• Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction