Natural Selection

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24 Terms

1
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State what natural selection is

  • Process where better-adapted individuals survive & reproduce more
  • Over time, advantageous traits increase in the population
2
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Explain why Darwin’s theory was a paradigm shift

  • Replaced Lamarckism with evidence-based mechanism
  • Showed evolution happens by natural selection
3
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State two sources of variation for natural selection

  • Mutations create new alleles
  • Sexual reproduction mixes alleles into new combinations
4
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Explain why variation is needed for evolution

  • Without differences, no one has advantage → no selection
5
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Describe overproduction of offspring

  • More young are born than environment can support
  • Leads to competition for food, space, mates
6
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Give two examples of limited resources that drive competition

  • Food supply
  • Nesting sites
7
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Define abiotic selection pressure

  • Non-living factor (e.g. temperature) affecting survival chances
8
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Give one abiotic factor that could act as a pressure

  • Extreme heat or cold
9
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State what fitness means in evolution

  • Ability to survive & reproduce (pass on genes)
10
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Explain why heritable traits are required

  • Only genetic traits can be passed to offspring & change population
11
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Why are acquired characteristics not part of evolution?

  • They aren’t encoded in DNA → not inherited
12
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Define sexual selection

  • Traits are favoured because they increase mating success
13
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Give one example of a sexually selected trait

  • Bright plumage in birds of paradise
14
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Explain Endler’s guppy experiment findings

  • High predation → dull colours (natural selection)
  • Low predation → bright colours for attracting mates (sexual selection)
15
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Define gene pool

  • All alleles of all genes in a breeding population
16
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Explain why allele frequencies differ in isolated populations

  • Little gene flow → evolve separately over time
17
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State what causes a change in allele frequencies

  • Natural selection acting on heritable variation
18
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Distinguish directional vs stabilising vs disruptive selection

  • Directional
19
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State Hardy–Weinberg allele equation

  • p + q = 1
20
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State Hardy–Weinberg genotype equation

  • p² + 2pq + q² = 1
21
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List two conditions needed for Hardy-Weinberg equilibrium

  • Large population, random mating (no selection, mutation or migration)
22
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Define artificial selection

  • Humans choose parents with desired traits to breed
23
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Give an intended result of artificial selection

  • Cows producing more milk
24
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Give an unintended consequence of artificial selection

  • Breeding dogs → health problems in some bre