• Created by: portia
  • Created on: 05-08-17 16:32

Biodiversity can be defined as: the degree of variation of life forms in an ecosystem

This is usually taken to include diversity at three levels:

  • the variation in ecosystems or habitats
  • the number of different species in the ecosystem and their relative abundance
  • the genetic variation within each species

Areas in the world with very high biodiversity have many endemic species - that is, species that are only found in these areas and nowhere else

Species diversity

  • the number of species in a community is known as species richness
  • species diversity takes species richness into account, but also includes a measure of the eveness of the abundance of the different species
  • the more species there are, and the more evenly the number of organisms are distributed among the different species, the greater the species diversity

Coral reefs have very high biodiversity; such an ecosystem offers many different ecological niches, which are exploited by different species

Species diversity is considered important because ecosystems with high species diversity tend to be more stable than ones with limited diversity; they are more resistant to changes.

Some ecosystems are dominated by one or two species and other species may be rare

The tropics are important centres for biodiversity possibly because living conditions are not too extreme (no frost, snow or ice), there is light of high intensity all year round and birds and mammals do not need to expend energy keeping warm

Genetic diversity

Genetic diversity is the diversity of alleles within the genes in the genome of a single species.

  • all the individuals of a species have the same genes, but they do not all have the same alleles of those genes
  • genetic diversity within a species can be asessed by finding out what proportion of genes have different alleles and how many alleles there are per gene

Genetic diversity which may be obvious because we can see the differences (breeds of dogs) exists in natural populations

  • the genetic differences between populations of the same species exist because populations may be adapted slightly differently in different parts of their range
  • there is also genetic diversity within each population
    • this diversity is important in providing populations with the ability to adapt to changes in biotic and abiotic factors, such as competition with other species, evading new predators, resisting new strains of disease and changes in temperature, salinity, humidity and rainfall

Assessing species diversity

Collecting organisms and making species lists

  • The first task when assessing species diversity is to identify and catalogue the types of organism and build a species list
  • bilogists use identification keys, the most common is a dichotomous key
  • one can do a timed search throughout an area you are studying and see how many species you can collect then identify
  • if a particular species cannot be identified, they are named species A, B etc
  • some animals are hard to find and collect, especially small ones like tiny beetles
  • a pooter is a simple piece of apparatus that is used to these…


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