Natural selection & adaptation

• What is genetic diversity?

  Genetic diversity is the number of different alleles of genes in a population.
• What is a gene pool?

  A gene pool is all the genes and alleles in a population at a particular time.
• What is meant by the allele frequency of a population?

  the proportion of organisms within the population carrying a particular allele.
• Define evolution.

  Evolution is the change in allele frequency over many generations in a population
• Natural selection results in species that are better adapted to their environment. Name three types of adaption.

  • Anatomical e.g. thick fur
  • Physiological e.g. enzymes that work at high temps
  • Behavioural e.g. migration, hibernation, courtship rituals
• Natural selection is the process that leads to evolution within a population. Describe the process of natural selection.

  • Random mutation occur within the population
  • This introduces genetic variation by producing a new allele in the population
  • Mutations can sometimes give rise to new alleles that provide an organism with an advantage to survive in its environment.
  • the new allele provides a reproductive selective advantage. therefore, the individual with the allele is more likely to reproduce & pass on the advantageous allele to their offspring.
  • Over many generations, there will be an increase in the frequency of allele within the population.
• Why is genetic diversity essential for natural selection?

  Genetic diversity is essential for natural selection, because it provides the variation needed for certain alleles to be favoured in a given environment.
• Name the two types of selection and give examples for each.

  • Directional selection: favours individuals at one extreme (e.g. antibiotic-resistant bacteria).
  • Stabilising selection: favours the average phenotype, reducing variation (e.g. human birth weights).