Biodiversity
Biology: Cambridge International A Level, topic 18.1.2
Biodiversity
Biodiversity is the complexity of a biological community. Biodiversity exists at many different levels and can be measured using species richness.
Habitats
- Biodiversity exists in habitats at a range of sizes.
- A habitat is an area where an organism lives.
- Biodiversity can be considered in a small, local habitat (e.g. a lake).
- Biodiversity varies between different habitats.
- E.g. Coral reefs are typically more biodiverse than meadows.
Global biodiversity
- Biodiversity can also be considered on the global scale.
- Biodiversity varies around the world.
- E.g. The equator is typically more biodiverse than the poles.
Species richness
- Species richness is the number of species in a habitat or community.
- Species richness can be measured by counting the number of different species in the habitat.
Factors Affecting Biodiversity
Biodiversity can be affected by changes to environmental conditions or the way a population affects its surroundings.
Human population growth
- The speed of growth of the human population means there is more forest cleared so that the land can be used for housing and food production.
- This land would otherwise support a more diverse range of species.
- Pollution and waste production also increases, putting further burden on fragile ecosystems.
- Human populations expanding outwards into animal habitats enables the zoonotic transmission of new diseases between species.
Agriculture (monoculture)
- It is more efficient to grow crops with the same requirements in terms of nutrition and ease of harvesting.
- Many farms now have fields set aside for growing only one crop species, such as wheat.
- Practising monoculture reduces biodiversity and can cause problems.
- Monocultures lacking genetic diversity may be less resistant to diseases.
Climate change
- Changes in global weather patterns, sea levels and temperatures can lead to habitat loss, driving animals to migrate.
- In other cases, some species and populations may be directly destroyed, decreasing the gene pool available for selection and evolution.
- The speed of climate change can sometimes be too fast for species to adapt to new conditions, leading to extinction.
Test yourself on Biodiversity
Which of the following statements about biodiversity are true?
What is the definition of species richness?
Which of these is NOT a direct cause of species extinction?