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Evolution Lecture Notes - Paleontology - Lecture Notes, Study notes of Geology

Alliance UniversityGeology

Lecturer has discussed the following key points in these Lecture Notes : Evolution Lecture Notes, Fossil Record, Domains, Biology, Genetics, Comparative Anatomy, Paleontology, Paleobiology, Fossilized Organisms, Natural Selection

Typology: Study notes

2012/2013

Uploaded on 07/19/2013

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Evolution and the Fossil Record
The Study of Evolution
• Two domains: the present and the past
• The present: Biology
• Genetics
• Comparative Anatomy
• The past: Paleontology or Paleobiology
• Comparative Anatomy of Fossilized organisms
Natural Selection
• Natural selection, a creative force, is one of the prime mechanisms of
evolutionary change. (The other mechanism, a destructive force is mass
extinction.)
• Charles Darwin, 1859: The Origin of Species by Natural Selection.
Natural Selection: Key Points
• 3 facts lead to a conclusion:
• Fact 1. Overproduction of offspring
• Fact 2. Variation within populations
• Fact 3. Competition for resources
• Conclusion: Survival of the fittest
Sources of Variation
• Random mutations of DNA
• >>99.9% are harmful or neutral
• adaptive mutations are rare
• Sexual recombination
• new variants created by mixing of genes
• you have 4096 direct ancestors going back 12 generations (212)
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Evolution and the Fossil Record

The Study of Evolution

  • Two domains: the present and the past
  • The present: Biology
  • Genetics
  • Comparative Anatomy
  • The past: Paleontology or Paleobiology
  • Comparative Anatomy of Fossilized organisms

Natural Selection

  • Natural selection, a creative force, is one of the prime mechanisms of evolutionary change. (The other mechanism, a destructive force is mass extinction.)
  • Charles Darwin, 1859: The Origin of Species by Natural Selection.

Natural Selection: Key Points

  • 3 facts lead to a conclusion:
  • Fact 1. Overproduction of offspring
  • Fact 2. Variation within populations
  • Fact 3. Competition for resources
  • Conclusion: Survival of the fittest

Sources of Variation

  • Random mutations of DNA

  • 99.9% are harmful or neutral

  • adaptive mutations are rare
  • Sexual recombination
  • new variants created by mixing of genes
  • you have 4096 direct ancestors going back 12 generations (2^12 )

Evidence of Evolution

  • Homology
  • Analogous organs or Convergent Evolution
  • Vestigial organs
  • Adaptive radiation

Homology

  • The recognition of common ancestry of features. e.g. all primates have 5 fingers; apes and humans lack a tail; all tetrapods have similar limb bones.
  • Studied by comparative anatomy of living and fossil organisms.

Analogous Organs or Convergent Evolution

  • Produced by evolutionary convergence. Independent origin of similar features is called convergent evolution.
  • Shows natural selection in operation.
  • e.g., insects, birds, bats, and pterosaurs all evolved wings independently

Vestigial Organs

  • Organs no longer used show clear evidence of evolutionary change.
  • e.g., pelvic bones of whales, vestiges of former legs
  • e.g., human body hair, a vestige of former fur

Adaptive Radiation

  • Natural selection can fill a variety of niches starting with a single species.
  • e.g., Darwin’s finches in the Galapagos Islands, 14 species evolved from one ancestral species
  • e.g., all birds evolved from Archaeopteryx

Role of the Fossil Record

  • Provides the only actual record of evolutionary change over geologic time.
  • Provides data on the timing of evolutionary origins.
  • Shows mass extinctions to be a major cause of evolutionary change.
  • Rates of evolution.

Evolutionary Origins

  • Oldest life: 3.5 BY
  • Oldest nucleated cells: 2.1 BY
  • First animals: 600 MY
  • First tetrapods: 375 MY
  • First dinosaurs: 220 MY
  • First mammals: 220 MY
  • First hominids: 4 MY

Mass Extinctions

  • Survival of the luckiest?
  • Over geologic time, mass extinctions may subvert the notion of survival of the fittest.
  • Is evolutionary history predictable?

Rates of Evolution

  • Biologists cannot measure evolutionary rates. They have only the present. Darwin assumed gradual rates.
  • Paleontologists can measure evolutionary rates. They have found punctuated equilibria to be the major pattern in fossil species rather than gradual change.