1.6 Evolution of Species

• What is a mutation?

  A random change to genetic material.
• What are the three types of mutation that can arise?

  - neutral

  - advantageous to survival

  - disadvantageous to survival
• Why are mutations important in evolution?

  They are the only source of new alleles.
• Name a factor that can increase the rate of mutation.

  - radiation (e.g. X-rays and UV light)

  - some chemicals (e.g. mustard gas).
• What is an adaptation?

  An inherited characteristic that makes an organism well suited to survival in its environment/niche.

  (e.g. a polar bear is adapted to live in a cold environment by having black skin to absorb heat and thick fur)
• Describe the process of natural selection

  
  

  - species produce more offspring than the

  environment can sustain.

  - Survival of the fittest (natural selection) occurs when there are

  selection pressures.

  - The best adapted individuals in a population survive to reproduce passing on their favourable alleles

  - the organisms that are less adapted will die out

  -these alleles increase in frequency within the population
• What is speciation?

  The formation of two different species from one.
• Give an example of an isolation barrier in speciation.

  - geographical (e.g. a mountain range)

  - ecological (e.g. pH)

  - behavioural (e.g reproductive)
• Describe the process of speciation in four main points.

  -part of the population is seperated due to an isolation barrier

  - different mutations occur in each sub-population.

  - natural selection selects for different mutations in each group due to different selection pressures.

  - each population evolves until they become so genetically different they are two different species.