Biodiversity - term used to describe variety in living world. Refers to number & variety of of living organisms in a particular area & has 3 components:
- 1. Species Diversity - number of different species & number of individuals of each species within any 1 community.
- 2. Genetic Diversity - variety of genes possessed by individuals that make up a species.
- 3. Ecosystem Diversity - range of different habitats within a particular area.
Species diversity is a measure of biodiversity and has 2 components: number of different species in a given area & proportion of the community that is made up of an individual species. 2 communities may have same number of species but the proportion is different.
Species diversity (d) = N(N-1)/sum of n(n-1)
where N = total number of orgs of all species & n = total number of orgs of each species.
Ecosystem - all the living and non-living components of a particular area.
- Biodiversity reflects how well an ecosystem functions.
- The higher the species diversity index, the more stable an ecosystem is and the less it is affected by climate change.
- In extreme conditions only a few species have the necessary adaptations to survive the harsh conditions so the species diversity index is usually low - communities are dominated by climatic factors, not the organisms.
- In less hostile environments the species diversity index is normally high resulting in a stable ecosystem dominated by living organisms.
Impact of Agriculture.
- As ecosystems develop they become complex communities with many individuals and species.
- Agricultural ecosystems are controlled by humans so are different.
- The number of species and the genetic variety of alleles is to reduced to the few that exhibit the desirable features.
- To be economic there need to be a large number with these features.
- Any particular area can only support a certain amount of biomass, if most of the area is taken up by species the farmer wants then there is a smaller area for other species.
- Species have to compete for the leftover space and resources.
- Pesticides exclude certain species that compete for light, mineral ions, water and food required by the farmer.
- Overall, reduction in species diversity so index is low.
Impact of Deforestation.
- Forests form many layers so there are lots of habitats available and so species diversity is high.
- Deforestation mostly due to deliberate human action.
- Deforestation - permanent clearing of forests and the conversion of land to other uses e.g. agriculture.
- Some forests are destroyed by man-made pollutants e.g. acid rain.
- Deforestation leads to loss of biodiversity.
- TRFs account for half of all the earth's species but cover only 7%.
- Replacement has reduced species diversity.