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First teaching 2023

First exams 2025

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

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Naomi H

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Naomi H

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Climate Change: Evolution

  • 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
tawny-owl-brown

CC BY-SA 2.0, via Geograph

tawny-owl-grey

 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

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Naomi H

Author: Naomi H

Expertise: Biology

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.