Comparative Embryology

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Comparative Embryology

• The comparison of early stages of development in
  different species

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Comparative Embryology (cont.)
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Molecular Biology

• Scientists can use molecular biology to compare
  species at the molecular level
• DNA
• Protein
• The more similar two organisms are at the
  molecular level, the more closely related

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Molecular Biology (cont.)
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Natural Selection in Action

• Can we see evolution happening today?
• YES

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Three key points of natural selection

• It is an editing process (it does not create new
  individuals)
• It is contingent on time and place
• Significant changes can occur in a population in
  a short time

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Population Genetics

• Population group of individuals of the same
  species living in the same space at the same time
• Species - group of populations whose members are
  capable of interbreeding and producing fertile
  offspring

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Population Genetics

• Combination of ideas from Darwin and Mendel
• The study of genetic changes within a population
• Gene pool total of all genetic combinations in
  a population
• Do you remember what an allele is?
• When the allelic frequency changes over time, it
  is called microevolution.

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Hardy-Weinberg Equilibrium

• The genetic make-up of a population does not
  change with sexual reproduction
• An outside force is needed
• Hardy-Weinberg describes the allelic frequencies
  in a population
• If allelic frequencies change over time, this
  indicates that the population is evolving

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Hardy-Weinberg Equilibrium (cont)

• There are five basic conditions that must be met
  for a population to be at Hardy-Weinberg
  equilibrium (non-evolving)
• Very large population
• No gene flow
• No mutations
• Random mating
• No natural selection

• VERY IMPORTANT These conditions are never met
  in nature

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Three contributing factors to evolution

• Natural Selection
• Gene flow
• Genetic drift

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Genetic Drift

• Occurs when the gene pool of a population changes
  by chance
• Occurs when the size of a population shrinks so
  that the remaining members are not representative
  of the orginal
• Two situations which result in smaller population
• Bottleneck effect
• Founder effect

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Bottleneck Effect
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Founder Effect