Climate Change: Evolution (HL) (HL IB Biology)

• Natural selection is driven by selection pressures in the environment
  • Selection pressures are features of the environment that limit the survival chances of an individual, e.g. the presence of a predator, a lack of food, or antibiotics killing bacteria
• Climate change introduces new selection pressures, so can drive evolution by natural selection

Evolution in tawny owls

• Tawny owls show polymorphism, meaning that their alleles can give rise to different phenotypes, or morphs
  • E.g. some tawny owls are grey in colour, while some are brown
• A decades-long Finnish study has shown an increase in the frequency of brown owls in the population from around 30 % to around 50 %; this is thought the be due to natural selection
  • In a snowy environment, pale grey owls are less visible, so are more successful and have a better chance of surviving and reproducing
    • It is not known whether decreased visibility is relevant to increased success in catching prey or increased success in avoiding predators, or both
  • Global warming and milder winters mean that there is less snow, and owls that are brown in colour have increased success; these brown owls are more likely to survive, reproduce and pass on their alleles for brown feathers

CC BY-SA 2.0, via Geograph

CC BY-SA 2.0, via Wikimedia Commons

Tawny owls show colour variation; milder winters caused by global warming give a selective advantage to owls with brown feathers, which are increasing in frequency