Evolution and Ecology

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Evolution and Ecology

• Chapter 2

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What is evolution?

• Variation
• Excess of offspring
• Not all individuals survive and reproduce
• Only best fit individuals survive and reproduce
• Characteristics found in best fit individuals
  become more frequent from generation to generation

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Types of Selection

• Directional
• Darwins Finches
• Evolution of resistance to pesticides
• Stabilizing Selection
• Human Birth weight

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Directional selection
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Stabilizing Selection
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Stabilizing Selection
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Analyzing Selection

• Proximate factors-how is something regulated at
  the organismal level?
• Nutrients, hormones, gametes
• Ultimate factors-what is the long-term
  evolutionary adaptation?

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Studies of clutch size in birds

• Clutch size is the number of eggs laid by a bird
• What is the most adapted clutch size?
• Use a cost-benefit model, optimal clutch size is
  the maximum difference between benefits and costs
• Experimentally test by removing and adding eggs
  to a nest, examining survival
• Lack proposed that there is an optimal clutch
  size
• Some field studies support this idea, some do not

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Field data with Blue Tits supports Lacks
hypothesis
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Field data with House Wrens does not support Lack
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Coevolution

• Reciprocal evolution between groups of species,
  usually applied to plants and their herbivores
• Plants evolve defensive chemicals to avoid
  herbivory, some insects evolve mechanisms to
  avoid, utilize, or detoxify chemicals
• Specialized plant-pollinator interactions, ie,
  figs and fig wasps

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Units of Selection

• Generally applied to individuals
• Can also apply to gametes
• Think of individual pollen grains on a stigma
  racing to get to the ovary first
• Family groups (kin)
• Individuals can gain fitness by helping
  genetically related individuals (kin)
• A brother is worth two cousins
• Group selection (controversial)
• Unrelated individuals can gain fitness, alarm
  calls, language acquisition in humans