Diversity and Natural Selection

• Genetic diversity is the degree of variation in the genes that exist in a certain population.
• What is genetic diversity?

  The degree of variation in the genes that exist in a certain variation
• There can be multiple versions of a specific gene, which are known as alleles.
• What are alleles?

  Multiple versions of a specific gene
• The greater the number of different alleles in a population, the greater the genetic diversity in that population
• The correlation between the number of different alleles in a population and genetic diversity is a positive correlation.
• What are two ways genetic diversity is increased in a population?

  Mutations and gene flow
• Genetic diversity in a population is increased in two ways:

  • Mutations (creation of new alleles)
  • Gene flow (introduction of new alleles by migration)
• What are mutations in relation to alleles?

  The creation of new alleles
• What are gene flow in relation to alleles?

  The introduction of new alleles by migration
• The presence of genetic variation in a population allows natural selection to take place.
• Advantageous traits increase an organism's chance of surviving long enough to reproduce, passing on its genes to offspring.
• Natural selection favours individuals with advantageous traits, which increases their chances of survival and reproduction.
• Disadvantageous traits decrease an organism's chance of surviving long enough to reproduce, reducing the frequency of those genes in future generations.
• Natural selection acts on a population to increase the frequency of advantageous alleles and decrease the frequency of disadvantageous alleles.
• What are advantageous alleles?


  Alleles that increase an individuals chances of survival, making them more likely to reproduce and pass on the alleles
• What are disadvantageous alleles?


  Alleles that decrease the chance of an individuals survival
• Natural selection is the process that leads to evolution in a population, thus meaning that they are better adapted to their environment.
• What does natural selection lead to?

  Evolution and adaptation of organisms to their environment
• Mutations are changes in the gene sequence of DNA, which can result in new alleles of a gene being formed.
• What are mutations?

  Changes in the gene sequence of DNA, which can result in new alleles of a gene being formed
• How can new alleles of a gene be formed?

  Through random mutations
• Changes in the gene sequence of DNA can result in new alleles of a gene being formed.
• Random mutations can arise spontaneously
• Many mutations are harmful, as they can alter the normal functioning of a gene, however, some mutations might provide an advantageous trait.
• An individual with a beneficial mutation will be more likely to survive and reproduce than an individual without the mutation.
• When an individual reproduces, their offspring will inherit half of their genes, and when an individual with an advantageous mutation reproduces, the allele is inherited by their offspring.
• How many genes will offspring inherit from an individual?

  Half
• Individuals in the next generation who have the advantageous mutation are more likely to reproduce and pass on the allele, and over many generations, the new allele will increase in frequency in the population.
• What is the change in allele frequency over time called?

  Evolution
• Over many generations, the new allele will increase in frequency in the population, and the change in allele frequency over time is called evolution
• Stabilising selection is the process where natural selection favours an average phenotype.
• What is stabilising selection?

  The process where natural selection favours an average phenotype
• Natural selection acts on an individual by imposing a selection pressure, which is an external factor that influences the reproductive success of an individual.
• What is a selection pressure?

  An external factor that influences the reproductive success of an individual
• What is an example of selection pressure?

  Diseases act as selection pressure that increases the reproductive success for individuals who are immune to the disease
• In stabilising selection, natural selection favours an average phenotype, and the selection pressure in stabilising selection selects against the extreme phenotypes.
• Stabilising selection selects against the extreme phenotypes
• Stabilising selection is where natural selection favours an average phenotype
• What is stabilising selection?

  A type of natural selection that favors the average phenotype and reduces variation in a population.