evolution

• A mutation is a random change to genetic material and is the source of new alleles in a population.

  Mutations can:

  • be neutral
  • confer an advantage to survival
  • confer a disadvantage to the chance of survival

  mutations are spontaneous
• Environmental factors such as radiation and some chemicals can increase the rate of mutation
• natural selection is when the best adapted individuals in a population survive and reproduce, passing on favourable alleles that confer a selection advantage.
• Natural selection or survival of the fittest occurs when there are selection pressures.
• Variation within a population make it possible for the population to evolve over time, in response to changing environmental conditions.
• A new allele can result in the plant or animal being better adapted to their environment.
• After a population becomes isolated, different mutations occur in each sub-population. Natural selection selects for different

  mutations in each group due to selection pressures.

  
  

  Each sub-population evolves, until they become so genetically different, that they are two different species.

  
  

  this means that when the 2 sub-populations breed they do not produce fertile offspring

  
  

  this is called speciation
• • geographical isolation occurs when they are separated by a geological feature
• • ecological isolation occurs when the species adapts to different living conditions
• • behavioural isolation occurs when there are differences in behaviour, such as mating rituals