Genetic Diversity & Adaptation

• Genetic Diversity

  The total d=number of alleles in a population.
• Allele

  an alternative form of a gene that occupies a specific position on a chromosome.
• Allele Frequency

  The number of individuals with a particular allele in a given population.
• Gene Pool

  All alleles present in a population.
• Population

  A group of individuals of the same species that live in the same area.
• Normal Distribution Curve

  Curve is considered that most common probability distribution in statistics.
• Organisms in a population may not have equal reproductive success if those with one particular genotype are:

  • more likely to die before reproducing
  • unable to grow sufficiently well to reproduce successfully
  • unable to attract a mate.
• Some characteristics are controlled by a single allele and tend to produce discontinuous variation. The are said to be monogenic. Many characteristics that we might observe are not just under control of one gene though- they are under the control of several genes and this can give a wider variety of phenotypes in the population. This is known as polygenic inheritance and results in continuous variation.
• Types of Selection

  • Directional Selection
  • Stabilising Selection
  • Diversifying Selection
  • Disrupting Selection
• Directional selection acts against one of the extremes in a range of phenotypes. As a result, one phenotype becomes rare and an alternative becomes common.
• Stabilising selection acts against two extremes in a range of phenotypes. This time, the mode is in the same position: this is the most advantageous phenotype. Stabilising selection has decreased the standard diviasion about this modal value.