Genetic Diversity and Adaptation

• What is genetic diversity?

  The number of different alleles of genes in a population
• What are alleles and how do they arise?

  • Variations of a particular gene (same locus) but different DNA base sequence
  • Arise by mutations
• What is a population?

  A group of interbreeding individuals of the same species
• What is intraspecific variation?

  Variation within a species
• What is interspecific variation?

  • Different species have different genes
  • This results in physical and physiological differences between organisms of different species
  • More similarities between genomes means a species is more closely related
• Explain the importance of genetic variation

  • Enables natural selection to occur
  • As in certain environments a new allele of a gene might benefit its possessor
  • By resulting in a change in the polypeptide coded for that positively changes its properties
  • Giving possessor a selective advantage - increased chances of survival and reproductive success
• What is evolution?

  • Change in allele frequency over many generations in a population
  • Occurring through the process of natural selection
• Explain the process of Natural Selection

  • Mutation - Random gene mutations can result in [named] new alleles of gene
  • Advantage - In certain environments the new allele might benefit its possessor [explain why] -> organism has a selective advantage
  • Reproductive success - possessors are more likely to survive and have reproductive success
  • Inheritance - Advantageous allele is inherited by members of the next generation
  • Allele frequency - Over many generations allele frequency increases in the population
• Describe three types of adaptations:

  • Anatomical - Structural / physical features that increase chance of survival
  • Physiological - Processes / chemical reactions that increases chance of survival
  • Behavioural - Ways in which an organism acts to increase chance of survival
• What is Directional Selection?

  • When an environmental change occurs the organisms that are best suited to the new conditions are most likely to survive (selective advantage)
  • Increased frequency of organisms with alleles for extreme trait
  • Normal distribution curve shifts towards extreme trait
• What is an example of directional selection?

  Antibiotic resistance in bacteria
• What is Stabilising selection?

  • Occurs when the environmental conditions remain stable
  • Organisms with an average variation of trait have selective advantage
  • Increased frequency of organisms with alleles for average trait
  • Decreases variation
• What is an example of stabilising selection?

  Human birth weight