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

Lára Marie McIvor

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Biodiversity

  • Biodiversity is defined as

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

Food web, IGCSE & GCSE Biology revision notes

A food web demonstrates the importance of biodiversity within an ecosystem

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Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology, Psychology & Sociology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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