Genetic diversity

• genetic diversity


  number of different alleles of genes in a population
• selection pressure


  an environmental factor that increases the chance of individuals with a specific phenotype surviving and reproducing over others
• fitness of an organism

  its ability to survive pass on its alleles to offspring
• Higher fitness


  organisms with higher fitness posses adaptations that make them better suited to their environment
• disadvantage/advantage of a large or small gene pool in a population

  -populations with a large gene pool have a strong ability to adapt to change

  -populations with a small gene pool are less able to adapt to changes in the environment and so can become vulnerable to extinction
• principals of natural selection

  -random mutations produce new alleles of a gene

  -new alleles may benefit the organism and give it an increased chance of survival and increased reproductive success

  -advantageous allele passed onto the next generation

  -frequency of new alleles will increase in frequency in the population over several generations
• The founder effect

  changes in allele frequencies occur in a different direction for the newly isolated small population in comparison to the larger parent population due to chance
• genetic drift


  gradual change in allele frequencies in a small population due to chance and not natural selection
• The bottleneck effect

  reduction in the gene pool of a population due to a dramatic decrease in population size
• natural selection


  selection pressures produce a gradual change in allele frequencies over several generations
• selection pressures


  environmental factors that effect the chance of survival of an organism
• types of selection

  stabilising and directional
• stabilising selection


  a type of natural selection that keeps allele frequencies constant over generations, stay as they are unless there is a change in environment
• Directional selection


  a type of natural selection that produces a gradual change in allele frequencies over several generations, it favours one extreme phenotype and causes the mean trait value in the population to change over time
• evolution


  the change in adaptive features of a population over time as a result of natural selection
• courtship

  is a behaviour in animals that eventually results in mating and reproduction, it plays a major role in species recognition as organisms can only belong to the same species is they can produce fertile offspring