Speciation and Patterns of Evolution

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Speciation and Patterns of Evolution
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SpeciesLatin for kind

• Group of natural pops whose members can
  interbreed with one another but cannot (or do
  not) interbreed with members of other such groups
• Species can stay separate when have GENETIC
  ISOLATION in place (otherwise, would lose unique
  characteristics that set them apart.)

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Speciation

• Definition
• When splinter groups, reproductively isolated
  from the population as a whole, undergo
  sufficient change that can become new species.
• Changes in allele frequencies that are
  significant enough to mark the formation of a new
  species (a daughter species from a parent
  species.)
• Speciation is NOT the same thing as Natural
  Selection speciation could be a potential
  consequence of natural selection or any other
  processes working with N.S.

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Species Concepts.

• Biological Species Concept
• defines a species as a pop or group of pops
  whose members have the potential to interbreed
  with one another in nature to produce fertile
  offspring but who cannot produce fertile
  offspring with members of other species
• hinges on reproductive isolation
• each species isolated by barriers that prevent
  interbreeding

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Prezygotic and Postzygotic barriers pages 466-467

• Pre -habitat isolation
• -behavioral isolation
• -temporal isolation
• -mechanical isolation
• -gametic isolation
• Post -reduced hybrid viability
• -reduced hybrid fertility
• -hybrid breakdown

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Figure 24.5 A summary of reproductive barriers
between closely related species
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• Ecological Species Concept
• defines a species in terms of its ecological
  niche, the set of environmental resources a
  species uses.
• Pluralistic Species Concept
• here, the factors that are most important for
  the cohesion of individuals as a species varies
  (takes into account more possibilities)

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• Morphological Species Concept
• characterizes species in terms of unique
  structural species
• Genealogical Species Concept
• defines a species as a set of organisms with a
  unique genetic history

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Modes of Speciation

• Allopatric takes place in a pop with
  geographically separate ranges
• Sympatric new species arise within the range of
  parent populations rather than in geographically
  separate pops

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Patterns of Evolution

• Mass Extinctions
• Adaptive Radiation small group of species
  evolved into several different forms
• Convergent evolution unrelated orgs look
  similar because of similarity in environments
• Coevolution process by which two species evolve
  in response to each other over time
• Ex. Flowers and insects that pollinate
• Punctuated Equilibrium long stable periods of
  no changes followed by brief periods of rapid
  change
• Gradualism slow, minute changes that build up
  over time

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