A-LEVEL BIOLOGY OCR NOTES
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- 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
- N = total number of organisms of all species
- n = total number of organisms of each species
- 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
- 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