Theory of Evolution by Natural Selection

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Theory of Evolution by Natural Selection
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Theory of Evolution by Natural Selection

• 1 theory of Evolution present species are
  descended from species that lived in the past
  historical, genealogical connections exist
  between species.
• Evidence
• Homology
• Biogeography
• 2 theory of Selection frequencies of
  phenotypes change as a result of selection.
• Evidence
• Artificial selection
• Experiment

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1. Theory of EVOLUTION

• that all species originated from other species
  historical, genealogical connections exist
  between species.

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Biological Species Concept

• Biological Species A group of populations
  interfertile among each other and reproductively
  isolated from all other such groups (species).
• 2 essential points
• interfertility within species
• reproductive isolation between species

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Speciation (evolution of new species)

• Allopatric speciation
• Populations of a species become geographically
  isolated.
• Isolated populations evolve independently
• ? 2 or more species

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Allopatric speciation
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Allopatric speciation
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Allopatric speciation
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Speciation (evolution of new species)

• Sympatric speciation
• Populations of a species isolate themselves
• Behavior
• Ecology
• Isolated populations evolve independently
• ? 2 or more species

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Sympatric Speciation

• Polyploidy
• Habitat differentiation
• Adaptation to new habitat
• Apple maggot
• Sexual selection
• Differing female choice
• Lake Victoria cichlids

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Allopatric speciation

• One ancestral species (B) has evolved into two (E
  and D)
• E and D remain reproductively isolated from each
  other

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Maintaining Reproductive Isolation

• Prezygotic barriers
• Geographic (Habitat)
• Temporal (Seasonal)
• Behavioral
• Mechanical
• Gametic isolation
• sperm mortality, fertilization failure
• Postzygotic barriers
• Hybrid reduced viability (inviability)
• Hybrid reduced fertility (sterility)

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Biological Species Concept

• Practical problems in application
• Applies to living, sexually reproducing species,
  only.
• Individuals that are reproductively isolated in
  nature may hybridize in lab or zoo
• Individuals that are interfertile in nature may
  not breed in lab or zoo
• Reproductive biology of most species is
  unknown!
• Recognition/Naming of a species is a testable
  hypothesis!

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Biological Species Concept

• Practical problems in application
• Hybrid zones

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Speciation and Homology

• Speciation produces sister species descended
  from a common ancestor
• Descendant species retain characters of common
  ancestor possibly in modified form.
• descent with modification
• modified character HOMOLOGY