Explain the mechanism of evolution

Dear Student,
  • Evolution is the change in the characteristics of a species over several generations. 
  • Evolution can takes place by various mechanisms like mutation, genetic drift, gene flow, non-random mating, and natural selection.
  • 1 Mutation: Mutation is a sudden change that occurs in a DNA sequence. 
  • The ultimate source of all genetic variation is mutation. 
  • Hereditary mutations, which occur in egg or sperm cells, can be passed to future generations. 
  • These type of mutations contributes to evolution. 
  • 2 Genetic drift: It is a mechanism of evolution in which allele frequencies of a population change over generations due to chance.
  • Larger populations are unlikely to change as a result of genetic drift.
  • Genetic drift more effectively works on smaller populations. 
  • 3 Gene flow: Gene flow (gene migration / allele flow) is the transfer of genetic variation or genes from one population to another. 
  • This gene flow occurs when there is migration.
  • Evolution occur as a result of genes being transferred from one population to another.
  • 4 Non random mating: In this organisms prefer to mate with others of the same genotype or of different genotypes. 
  •  Non-random mating can alter genotype frequencies.
  •  Non-random mating can act as an ancillary process for natural selection to cause evolution to occur. 
  • 5 Natural selection: Natural selection is a mechanism of evolution. 
  • Organisms that are more adapted to their environment are more likely to survive and pass on the genes. 
  • This process causes species to change and diverge over time.


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Allele frequencies in a population may change due to four fundamental forces of evolution: Natural Selection, Genetic Drift, Mutations and Gene Flow. Mutations are the ultimate source of new alleles in a gene pool. Two of the most relevant mechanisms of evolutionary change are: Natural Selection and Genetic Drift.
One of the main controversial issues in population genetics is concerned with the relative importance of both mechanisms in determining evolutionary changes. Natural selection usually predominates in large populations whereas genetic drift does so in small ones.
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