Evolution of species

• Mutation


  Is a random change to the genetic material of an organism
• Mutagen


  Is a name given to anything which can increase the rate of mutation
• What are examples of mutagens?

  Radiation and chemicals
• Mutations can either be:

  Neutral, advantageous or disadvantageous
• Variation

  • Allowing new alleles to be produced by mutations can result in animals and plants adapt to their environment
  • Variation within a population makes it possible for a population to evolve overtime
• Adaptation


  Is an inherited characteristic that makes an organism well suited to survival in it's environment/ niche
• Species produce more offspring than the environment can sustain. Natural selection or survival of the fittest occurs when there are selection pressures.

  The best adapted individuals in a population survive to reproduce, passing on the favourable alleles that confer the selective advantage
• Selection pressures


  Are any factors which can affect the survival or reproduction of an organism
• Speciation


  Is the formation of new species in the cause of evolution
• Isolation barrier


  A barrier which separates a group of species
• What are the three types of isolation barriers?

  Geological, ecological and behavioural
• Process of speciation:

  • A group of one species is isolated by a barrier creating two sub populations
  • Different mutations occur at random in each of the sub population causing new variation
  • Natural selection selects for different mutations in each group due to different selection pressures
  • Each sub population evolves until they become genetically different that they are now two different species
  • The isolation barrier breaks now resulting in two different species that are not able to interbreed to produce fertile offspring