Evolution of species

• Biological definition of a species

  Members of a species can interbreed to produce fertile offspring
• What effects can mutations have on survival

  Can be neutral, confer an advantage or a disadvantage to survival
• Define the term mutation

  A random change to genetic material
• What are mutations

  Spontaneous and the only source of new alleles
• Two examples of environmental factors that cause mutations

  Radiation, some chemicals
• What is produced by mutation that can result in organisms being better adapted to their

  New alleles
• What allows populations to evolve over time

  Variation within a population
• Variation within a population makes it possible for a population to evolve over time in response to.

  Selection pressures
• Give the meaning of the term adaptation.


  An inherited characteristic that makes an organism well suited to survival in its environment/niche
• Species producing more off spring than the environment can sustain leads to

  Natural selection
• Natural selection occurs when there are

  Changing environmental conditions
• Explain natural selection

  As the best adapted individuals in a population survive to reproduce, passing on the favourable alleles that confer the selective advantage. These alleles increase in frequency within the population.
• Name three types of isolation barrier and give an example of each.

  Geographical – Oceans, mountain ranges

  Ecological – pH, salinity different habitats

  Behavioural – different mating rituals

  prevents breeding
• Describe the process of speciation.

  Single species living in an area

  ISOLATION

  Population becomes isolated by an isolation barrier.

  MUTATION

  Different mutations occur in each sub-population.

  NATURAL SELECTION selects

  for different mutations in each group, due to different selection

  pressures.

  -Each sub-population evolves until they become so genetically

  different that they are two different species.