natural selection and evolution

• survival factors:

  Predation

  • Predation can decrease the probability of survival.
  • If an individual is exposed to high predation, they are more likely to be eaten by a predator.
  • If an individual is better at avoiding predators, they are more likely to survive and reproduce.
  • The genes that allow an individual to avoid predation are more likely to be passed onto offspring.
• survival factors:

  Disease

  • Disease can decrease the probability of survival.
  • If an individual is better at combatting disease or avoiding infection, they are more likely to survive and reproduce.
  • The genes that allow an individual to avoid disease are more likely to be passed onto offspring.
• survival factors:

  Competition

  • Competition can decrease the probability of survival.
  • Competition can exist between species (interspecific) or within species (intraspecific).
  • If an individual is better at outcompeting other individuals, they are more likely to survive and reproduce.
  • The genes that allow an individual to outcompete are more likely to be passed onto offspring.
• • Factors that influence survival
  • Competition
  • Interspecific competition
  • Intraspecific competition
  • Disease
  • Predation
• Natural selection is the process where the frequency of alleles in a population changes over time. Natural selection is a process that gives rise to evolution.
• Selective advantage

  • Genetic variation exists between individuals in a population.
  • Some individuals will be more likely to survive (e.g. by being better at fighting disease) than others.
  • Individuals that are better at surviving than others have a selective advantage.
• Producing offspring

  • Individuals with a selective advantage are more likely to survive to reproduce than others.
  • This means that the genes of an individual with a selective advantage are more likely to be passed onto offspring than the genes of an individual without a selective advantage.
• Increasing allele frequencies

  • Individuals with a selective advantage are more likely to pass on their beneficial alleles than other individuals.
  • The next generation is more likely to have alleles that provide a selective advantage than alleles that do not.
  • This generation is also more likely to survive to reproduce and pass on their genes.
  • This causes the alleles that provide a selective advantage to increase in frequency in the population.
• Natural selection

  • The process where the frequency of beneficial alleles increases over time is called natural selection.
  • Natural selection controls the frequency of alleles in a population.
  • If a harmful allele develops in an individual, this individual is less likely to survive and the harmful allele will decrease in frequency. This is also natural selection.
• Evolution

  • The process of natural selection gives rise to evolution.
  • Evolution is defined as a change in allele frequencies over time.
  • E.g. The evolution of humans is the change in allele frequencies that has taken place over millions of years. This change has been driven by natural selection.
• How do selective advantages contribute to natural selection?

  Individuals that are more likely to survive have a selective advantage.

  Individuals with a selective advantage are more likely to survive to reproduce.

  The genes of an individual with a selective advantage are more likely to be passed onto offspring than the genes of those without.

  Alleles that provide a selective advantage increase in frequency in the population.
• What principle predicts that allele frequencies will not change from generation to generation?

  The Hardy-Weinberg principle