Speciation Notes

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Speciation Notes
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Speciation

• Speciation - a process of producing two
  individual species from one
• Species - members of the population that
  interbreed to produce fertile offspring

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Three Causes of Speciation

• Geographic isolation

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• b. Reproductive isolation

• Organisms may appear to be alike and be different
  species. These meadowlarks look almost identical,
  yet do not interbreed with each otherthus, they
  are separate species.

• Organisms may look different and yet be the same
  species. These two ants are sisterstwo ants of
  the species Pheidole barbata, fulfilling
  different roles in the same colony.

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• c. Change in chromosome number
• Polyploid species result from nondisjunction
  (chromosomes fail to separate properly) during
  meiosis or mitosis.

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Prezygotic and Postzygotic barriers

• Prezygotic Barriers
• 1)Temporal isolation (2 species reproduce at
  different times of day, year or season.
• 2) Habitat Isolation
• 3) Behavioral Isolation (different courtship
  behaviors)
• Postzygotic Barriers
• Hybrid inviability and sterility (ie. Mules)

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So, how long does it take for a new species to
evolve?
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Rates in Speciation

• a. Polyploid speciation only takes one generation
• b. Gradualism- the idea that species evolve at a
  slow, steady rate, with small, adaptive changes
  gradually accumulating over time.

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• c. Punctuated Equilibrium - argues that
  speciation occurs quickly, in rapid bursts, with
  long periods of genetic equilibrium in between.
• Caused by changes in the environment, which
  rapidly change a populations gene pool
• i.e. Raise in temperatures, introduction of
  competitive species, reproductive isolation

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Types of evolution

• Gradualism
• Punctuated Equilibirum

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Do patterns of evolution always look the same?

• Why might they be different? What causes the
  evolution of new species?

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Patterns of Evolution

• a. Divergent Evolution- when species that were
  once similar diverge (become more and more
  different)
• b. Adaptive Radiation- When one species evolves
  into an array of different species to fit
  environmental habitats

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• c. Convergent Evolution - when species that were
  unrelated evolve similar characteristics
• Occurs when unrelated species occupy similar
  environmental habitats in different areas of the
  world. Similar environmental pressures and
  similar natural selection pressures allows
  different species to look alike.

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Where did the first living thing come from?

• Stanley Miller (Exobiology)
• Student at the University of Chicago (now
  professor at UCSD)
• Designed experiment showing formation of organic
  compounds (amino acids)
• http//www.ucsd.tv/miller-urey/
• Check out the Stanley Miller interview here

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What is Exobiology?

• http//www.chem.duke.edu/jds/cruise_chem/Exobiolo
  gy/index.html

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