A-Level Biology OCR Notes

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Biodiversity

Biodiversity is the variety of organisms in an area. It can be considered on different levels including habitat, species and genetic diversity of an area
Habitat diversity refers to the range of habitats present in a region
Species diversity is the number of species and the number of individuals within each species in a specified area. It takes into account species richness and species evenness.
Species richness is a measure of the number of different species in a community.
Species evenness is a measure of the relative abundances of different species in an area.

Genetic diversity is the variety of all the genes (number of different alleles of genes) possessed by the individuals in a population or whole species
Alleles are different forms of the same gene

The greater the genetic diversity, the greater the ability of the species to adapt to a changing environment.
Genetic diversity can be estimated by comparing physical characteristics or by analysing genomes.
Species with a greater number of polymorphic genes tend to have greater genetic diversity

Simpson’s diversity index (D) measure biodiversity taking into account species richness and evenness

Factors affecting biodiversity include:
- Human population growth increases the demand for resources from the environment
- Agriculture reduces biodiversity by monoculture, use of herbicide & pesticides, hedgerow removal and woodland clearance
- Climate change is causing animals to migrate or die

Reasons for maintaining biodiversity can be:
- Ecological- ecosystems are more stable when biodiversity is high. Keystone species are a species which has a disproportionate effect on its environment relative to its abundance, their removal will greatly reduce the ability of an ecosystem to function
- Economical- provides resources
- Aesthetic
- Ethical
Conservationists protect biodiversity with methods such as: giving endangered species legal protection, creating protected area & The Environmental Stewardship Scheme.
A balance between conservation and agriculture is needed

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