Genetic diversity and adaptation

• Define population


  All the organisms of a particular species that live in the same place
• What is an allele

  ~Different forms of a particular gene, found at the same locus on a chromosome

  ~A single gene could have many alleles
• Define genetic diversity


  The total number of different alleles in a population
• What advantage does a high genetic diversity provide

  Ability to adapt to a change in environment and allows natural selection to occur
• Explain how natural selection results in development of new characteristics

  ~Random mutations result in new alleles

  ~Some alleles provide an advantage, making an individual more likely to survive and reproduce

  ~Their offspring receive the new allele, and frequency continues to increase over many generations
• What is directional selection


  ~Occurs when environmental conditions change

  ~Individuals with phenotypes suited to the new conditions will survive and pass on their genes

  ~Over time the mean of the population will move towards these characteristics
• Give an example of directional selection

  ~Antibiotic resistance

  ~Bacteria with a mutation allowing them to survive in the presence of antibiotics will reproduce

  ~Therefore frequency of this allele will increase and the population will shift to have greater antibiotic resistance
• What is stabilising selection


  ~Occurs when environmental conditions stay the same

  ~Individuals closest to the mean are favoured, and any new characteristics are selected against

  ~Results in low diversity
• Give an example of stabilising selection

  ~Birth weight

  ~Babies that weigh around 3kg are more likely to survive than those at lower or higher weights
• Define a niche


  ~The role of a species within its environment

  ~Species sharing the same niche will compete with each other
• What are the three types of adaptation

  ~Anatomical

  ~Physiological

  ~Behavioural