Evolution, biodiversity and classification

  • Created by: brad
  • Created on: 17-05-13 10:33


Evolution: The prcess by which organisms have developed over time from simple organsism.

Natural Selection: How well certain genes cope with the environment and the genes that cope the best will survive.

Natural selection and Evolution work hand in hand to create genetic variation within a species. It works like this 

  • A species that shows genetic variation is put under selection pressures such as straine resources.
  • The animals with the better adaptations are able to get the resources and will survive longer 
  • Becuase they can survive longer they are able to breed more and produce more offspring
  • These offspring have the better adaptations and over time these adaptations are normal and the animal have evovled. 
  • The adapations in the first place could have come from a mutation. 
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Evolution definitions

Species: An organism that can mate and reproduce fertile offspring with similar characteristics 

Species richness: The variety of different species within a population 

Genetic diversity: The variety of differnt alleles within a population 

Species density: The frequency of different species within a population 

Endemic: Where an organism is only found in one area. They are endemic 

Niche: A species role within a population. This is where it sleep, what it eats and what is does. Species' niche can overlap BUT two species cannot occupy the same niche of there will be fighting. 

Gene pool: The differnt alleles within a certain area

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Ways of natural selection

Natural selection can come about in three different ways: 

  • Directional selection where on set of genes is more favourable than other and this becomes the norm 
  • Diversifying selection: The areas environment is very diverse and leads to the development of subpopulation. This is where rarer alleles become more frequent 
  • Balencing selection: This is where rarer alleles are cut out becuase they aren't needed. 
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Decreasing genetic diversity

This is where certain alleles get cut out or one allele becomes much more frequent. This happens by: 

  • The founder effect: This is when a small popultion go off to start a colony. Then due to inbreeding a certain gene becomes amplified leading to a decrease in genetic diversity with other alleles. 
  • The bottle neck effect: This is where a popualtion size is cut drmamtically which reduces the amount of variation within the species and because of this the species can never recover leaving it very vulnerable 
  • Genetic drift: The change in frequency of different alleles with a population 
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The three domains

The three domains of molecular phylogeny are: 

  • Bacteria 
  • Archea 
  • Eukaryotes 

Archea and Euakyotes are most closely related and share the msot recent common ancestor. 

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