Natural Selection and Evolution

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Natural Selection and Evolution
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Natural Selection A History

• Charles Darwin a British naturalist
• Journey aboard the HMS Beagle

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• Notes on flora and fauna
• Galapagos Islands point of interest

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Evolution by Natural Selection

• Requirements
• Variation in a trait within a
• population (giraffes necks)
• More individuals are born in
• a generation than can survive
• (Struggle for Existence)

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• Giraffes with longer necks get better food and
  have more babies (advantage in struggle for
  existence)
• Long necks ? Long necks (variation is heritable)

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• Results
• Over time, average neck length increases

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Evolution by natural selection a syllogism

• Socrates is a man.
• All men are mortal.
• Therefore,
• Socrates is mortal.

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Natural Selection

• If variation within a trait has a genetic basis,
• and some variants have greater survival and
  reproduction,
• then, over time, the favored trait will
  predominate in the population

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• Over long periods of time, new species can occur
  (like this Okapi zebra and giraffe descendant)

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Darwins Conclusions

• Variation exists within populations
• Certain organisms within the population have
  greater survival and reproduction
• Traits from these organisms will spread through
  the population (over time)

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But wait!!! Theres more to the story

• Darwin was very leery of divulging his findings
  (religious persecution)
• Charlie receives a manuscript from Alfred Russell
  Wallace

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Wallace has put forth the same ideas as Darwins

• Darwin Wallace fight it out!!!

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Evidence that evolution has occurred

• Comparative anatomy
• Geology and fossils
• Biogeography

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Life is constructed on a similar plan
Human and chimpanzee facial expressions
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Life is constructed on a similar plan
Homologous structures
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Vestigial organs

• Eye bulbs of blind, cave-dwelling creatures (like
  this salamander)
• Anthers and pollen of asexually reproductive
  Dandelion (Taraxicum officinale)

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Vestigial organs in humans

• Appendix
• Nictitating memb. in eye.

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Hind limbs in whales

• Whale embryo

Modern whale
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Natural Selection (contd.)

• Variance among all organisms (except identical
  twins!)
• The environment determines which traits are
  successful, not the individual! (trees
  giraffes)

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Geology and Fossils

• Major points
• Earth is 4.5 billion years old (decay half-life)
• Organisms have inhabited Earth for most of its
  history
• All organisms today share common ancestry with
  earlier, simpler life forms.

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Geology and Fossils

• Fossils of organisms bearing similar resemblance
  to living counterparts, but not exact features.
  Why?
• Principle of stratigraphy (Lyell)

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Fossils

• Transition fossils
• Archaeopteryx
• reptile ? bird transition

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Speciation
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Speciation

• Speciation formation of a new species
• New species arise from mutations
• Species are formed when members cannot interbreed
  and successfully produce offspring.

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Speciation

• Geographical isolation may lead to the formation
  of a new species.

Abert squirrel
Kaibab squirrel
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Barriers to Reproduction

• Geographic Isolation (G. canyon)
• Different reproduction times
• Physical differences (opossum)
• Hybrid offspring might not be fertile. (donkey)

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Taxonomy and Classification

• DOMAIN
• KINGDOM
• PHYLUM
• CLASS Create Mnemonic
• ORDER
• FAMILY
• GENUS
• SPECIES

Did King Phillip Come Over For Good Steak?