Mechanisms of evolution

• Evolution


  The change of species overtime
• Artificial Selection


  • Intentional breeding of plants or animals
  • People get to select which organisms to reproduce
  • Selective breeding
• Natural Selection


  • Process through which populations of living organisms adapt and change
  • Heritable traits that help organisms survive and reproduce become more common in the population over a period of time
  • Traits that improve survival or reproduction accumulate in the population
  • Adaptive change (survival and reproduction)
• Principles of Natural Selection

  • Overproduction: an organism tends to produce more offspring that can survive and reproduce
  • Variation: within a population there are differences of variations in traits
  • Adaptation: organisms that have acquired more beneficial traits that are more likely to survive and reproduce
  • Selection: an organism with a beneficial trait is more likely to survive and reproduce
• Genetic Drift


  • Allelic drift/Sewall Wright Effect
  • Change in the frequency of a gene variant (allele) in a population due to random sampling of organisms
  • In contrast with Natural Selection
  • Frequency of traits changes in a population due to chance events
  • Random change
• Genetic Drift


  Survivors are just lucky because genetic drift is completely random
• Natural Selection


  Survivors are those with advantageous traits
• Mutation


  Change in DNA
• Recombination


  • Pieces of DNA are broken and recombined to produce new combinations of alleles
  • Crossing-over during Meiosis
• All of these mechanisms can cause changes in the frequencies of genes in populations, and so all of them are mechanisms of evolutionary change. However, natural selection and genetic drift cannot operate unless there is genetic variation, that is, unless some individuals are genetically different from others.