Evolution

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Evolution

• Darwin

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• Hence, both in space and time, we seem to be
  brought somewhat near to the great fact-mystery
  of mysteries-the first appearance of new beings
  on Earth

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The voyage

• Recommended at age 22, to be the naturalist
  aboard a vessel heading to S. America
• In December of 1831, he set sail on the HMS
  Beagle, on what can be considered one of the most
  influential voyages in human history.
• Initially slated to take years, instead it took
  5.
• Captained by Robert FitzRoy, with the primary
  objective to map the S. American coast for the
  British navy.
• Darwins role?
• Find evidence for the creation story.

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The voyage

• Supplies jars, a microscope, binoculars, a
  compass, notebooks, pistols, a rifle, and a book
  authored by Lyell
• In regular intervals, he sent his findings back
  to England.
• Found fossils of giant Glyptodon and Megatherium
• Significance?
• Found a resemblance to the modern armadillo and
  sloth respectively.
• Also noted that this set of animals along with
  the extinct shared the same patterns of
  distribution

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The Galapagos

• Sailed west from S. America to reach the
  Galapagos
• Darwin immediately noticed that the flora and
  fauna was very similar to that he just observed
  in S. America, yet they also had unique traits
• Furthermore the species differed from island to
  island
• Similarly he found the same phenomena with
  respect to the Cape Verde Islands and Africa
• Thus he went in search of the creation story and
  left with the exact oppositehis conclusions and
  those of others, make him one of the foremost
  scientist of all time!

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Darwin's issue

• Why would continents separated by
• large distances have entirely different
• species occupying similar niches?
• This is now known as biogeography which is the
  observation and analysis of the geographic
  distribution of organisms.
• It was later confirmed that the fossils he found
  were in fact larger versions of the current
  species.
• How?
• ...maybe they were ancestral forms

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Further observations

• It was found that 25 of 26 bird species found
  were different species
• How?
• maybe a single ancestral species was brought
  there, and diverged based on what island they
  were occupying
• Darwin dedicated the rest of his life to this
  investigation

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Homologous/analogous features

• Homologous feature structures that share a
  common origin but serve different functions in
  different species. (i.e. dolphins flipper vs
  human hand)
• Note homologous features need not be not be
  physically visiblecan also be embryonic
• Analogous feature structures that share a
  similar function but do not share a common source
  nor are they anatomically similar. (i.e. bird
  wings vs fly wings)
• Darwin guessed that species with similar
  homologous features shared a common ancestor
  while those with analogous features did not.

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Vestigial features

• Structures that serve no useful function in
  living species.
• Examples digits in dogs, pigs and horses humans
  have the same muscles present that dogs do to
  move their ears some snakes and whales have hip
  bones appendix in humans.
• Further evidence for evolution.

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Artificial selection

• Darwin became sure that there must exist some
  mechanism of inheritance.
• Shifted focus from looking at fossils and single
  specimens, to observing populations of
  reproducing species.
• He started to breed his own pigeonsmodel
  evolution
• Examples of artificial (Human) selection today
  domesticated plant and animal species.
• Darwin guessed that if humans could alter the
  morphology of certain species, then perhaps the
  environment could be exhibiting the same kind of
  process in the wild.

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Final piece to the puzzle

• At this point, Darwins observations/research and
  that of others led him to be fully convinced
  about the evolution of life forms.
• But how does nature choose who to breed?
• 1798, Thomas Malthus essay on the principle of
  populationin nature both plants and animals
  produce more offspring then can survive
• VOILA!!favourable traits would be preserved and
  less favourable ones would be eliminated due to
  intense competition within the species

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References

• Text pgs 519-528
• Quiz Tuesday covering everything up to and
  including Fridays notes.