Evolution of species

• What is a species?

  a group of organisms that freely interbreed to produce fertile offspring
• What are mutations?

  random, spontaneous changes in genetic material and the only source of new alleles (different versions of a gene)
• What can speed up the rate of mutation?

  certain types of radiation (x-ray, gamma), higher temperatures, and some chemicals
• When are mutations harmful?

  Mutations can be harmful when they give the organism a disadvantage and so decrease its chances of survival
• When are mutations beneficial?

  Mutations can be beneficial if they give the organism an advantage and so increase its chances of survival
• What can new alleles produced by mutation result in?

  It can result in plants and animals becoming better adapted to their environment
• How can a population evolve over time?

  Variation within a population means a population can evolve over time in response to the changing environmental conditions
• Do species produce too many offpring?

  They often produce more offspring than the environment can support
• What is the intensity of a selective factor called?


  selection pressure
• What is natural selection?

  Natural selection selects different mutations in each sub population, leading to different adaptations. This is because each group will have different selection pressures
• What are types of selection pressures?


  Predation, disease, competition, climate and environmental conditions
• What happens to individuals with a selective advantage?

  They survive to reproduce, passing on the favourable alleles (genes) to give their offspring the selective advantage
• What is speciation?

  The evolution of two or more species from one original ancestor species
• When does speciation occur?

  It occurs after part of the population becomes isolated by an isolation barrier
• What can isolation barriers be?


  Geographical (eg. by river/mountain)

  Behavioural (eg. different mating rituals)

  Ecological (eg. living in different habitats)
• What happens in each sub-populations?

  Different mutations occur in each sub-population

  Natural selection selects different mutations in each sub-population, due to different selection pressures, leading to different adaptations

  Each population gradually becomes more different over time.

  Eventually they are so different that they become 2 different species.
• What is the term given to the formation of a new species?

  speciation
• Describe the process of speciation?

  Different mutations occur in each sub-population. Natural selection selects different mutations in each group, due to different selection pressures. Each sub-populations evolves until they become so genetically different that they are two different species.
• When can speciation occur?

  When part of a population becomes isolated by an isolation barrier
• Whats an example of a biological control?

  ladybirds eat aphids
• Example of a geographical barrier?

  Mountains, rivers
• Example of an ecological barrier?

  temperature, oxygen levels, salinity
• Example of a behavioural barrier?

  mating rituals
• Whats the role of variation in evolution?

  Variation within a population makes it possible for a population to evolve over time in response to changing environmental conditions