4.3B Biodiversity (Edexcel IGCSE Biology)

• Biodiversity is the range and variety of different species of organisms on Earth, or within an ecosystem
• It considers not only the species richness but the variation within each species, its distribution and population size
  • E.g. a high biodiversity would be found in an environment with lots of different species which show a lot of variation and are living in, all evenly distributed across the study area

• Many human activities are reducing biodiversity in individual ecosystems and on a global level
  • E.g. waste production, deforestation and global warming

The importance of biodiversity

• Different species depend on each other for:
  • Food
  • Shelter (eg. birds nesting in trees)
  • Maintenance of the physical environment (eg. 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 disease
• 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