Biodiversity (Edexcel IGCSE Biology (Modular): Unit 2): Revision Note

Biodiversity

• Biodiversity is defined as

the range and variety of different species of organisms on Earth, or within an ecosystem

• Biodiversity 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