Genetic diversity and adaptation

• Genetic diversity 


  Number of different alleles of genes in a population
• random mutation can result n new alleles of a gene
• many mutations are harmful but in certain environments the new allele of a gene might benefit its possessor leading to increased reproductive success
• advantageous allele is inherited by member of next generation
• as a result over many generations he new allele increase in frequency in the population
• directional selection 


  favours one extreme

  antibiotic resistance in bacteria
• stabilising selection 


  favours average

  human birth weights
• natural selection 


  species better adapted into their environment

  anatomical - structural features (whale fat to stay warm)

  physiological - processes (bears lower metabolism to conserve energy during hibernation)

  behavioural - acts (possums play dead to escape attack)
• bottleneck effect 


  event causing reduction (large number dying before reproduction)

  reduces different alleles in gene pool

  reduces genetic diversity

  survivors reproduce
• founders effect 


  type of genetic bottleneck

  small number of different alleles in initial gene pool

  rare allele may become more popular

  higher chance of genetic disease