BY5.5 Population Genetics

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Population Genetics

Over production

  • all oragnisms reproduce to increase the population size
  • as the population increases various factors keep the number down
  • intra specific competition:
    • competition within a species
    • basis of natural selection
  • interspecific competiton
    • competition between different species
    • predator prey relationships

Selection pressures

  • selection pressures increase the chances of some alleles being passed on and decrease the chances of others being passed on
  • natural selection is the effect of such pressures on the frequency of alleles in a population
  • it is a process in which the organisms better adapted to the environment survive and reproduce
  • the better adapted the organism s, the more likely it is to pass o their characterisitcs to their offspring and future generations
  • the organisms environment  exerts a selection pressure and this determines the spread of any alleles in the gene pool

Population genetics:

  • organisms are members of a local population where mating occurs randomly
  • the study of inheritance factors in a population is concerned with the freqeuncy of phenotypes and genotypes in the whole population rather than the ratio of characteristics
  • population: a group of organisms that can freely interbreed
  • some populations are open and so immigration of genes from overlapping populations can occur
  • some populations are closed by being cut off from others by barriers


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