Evolution

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Evolution

• Geology 103

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Fossil classification

• Body fossils actual representation of the
  organism preserved in the rock also includes
  molds and casts
• Trace fossils evidence of the passage of an
  organism includes burrows, borings and tracks

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Body fossil preservation

• Permineralization  Dissolved minerals
  precipitate in cavities within organism

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Body fossil preservation

• Replacement Dissolved minerals precipitate as
  organisms original materials dissolve

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Body fossil preservation

• Carbonization Organisms tissues are compressed
  and lose their volatile components, leaving
  behind a carbon film

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The key to good preservation

• Bury the organism quickly (anoxic conditions).
• Dont disturb it for a long time. This includes
  plate tectonics.

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Fossils

• Latin Dug up
• Represent any indication of past life
• Posed an issue for early geologists
• Some believed that fossils were rocks trying to
  become living organisms
• Aristotle to DaVinci agreed that they were
  remains of past life

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Neptunism

• School of thought about the origin of rocks that
  arose in the late 18th century
• Held that the world was inundated in a great
  flood (or floods) that deposited every single
  rock
• Abraham Werner (Freiburg School of Mining, 1750
   1817)

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Plutonism

• Werner believed that the heat source for
  volcanoes and other eruptive features were
  burning coal beds
• Others, notably James Hutton (University of
  Edinburgh, 1726  1797), argued for magma as the
  source for volcanoes
• Culminated in debate over the origin of granite
• Hutton also known for his quote that in the rock
  record we find no vestige of a beginning, no
  prospect of an end

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Catastrophism

• Baron Georges Cuvier (Museum of Natural History,
  Paris,1769-1832) was the main proponent
• Earth is immensely old but has recurring
  revolutions that result in extinctions of
  organisms

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Faunal succession
Faunal succession is not evolution because faunal
succession makes no claims as to the connections
between organisms found in different layers.
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How do organisms change over time?

• Jean-Baptiste Lamarck (Museum of Natural History,
  Paris, 1744  1829) suggested that changes in the
  environment caused changes in behavior of
  organisms that resulted in physical changes in
  those organisms that could be inherited by
  offspring

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First, we need to organize life

• Carl Linnaeus (University of Leiden, 1735)
  publishes Systema Naturae, which categorized much
  of what was being discovered of life on different
  continents

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Traditionally, the Linnean classification system
used anatomical differences to organize organisms
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Uniformitarianism

• Key to the past is the present
• Charles Lyell (1830) publishes Principles of
  Geology in which he advocates slow, gradual
  changes in Earth processes, implying an immense
  amount of time had already passed

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On the Origin of Species

• Charles Darwin (Geological Society of London,
  1859) publishes his theory of organic evolution
  based on observations he had made on the voyage
  of the Beagle and other work.
• Check out my colleage Rob Viens daily
  re-creation of the voyage http//beagleproject.wo
  rdpress.com/tag/voyage-of-the-beagle/

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The three tenets of Darwinian evolutionary theory

• There exists a group of organisms (population)
  that mate and reproduce fertile offspring
  (species)
• Natural selection favors one variation over
  another
• The favored variation survives to produce more
  offspring than unfavored variations

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One method of speciation

• Allopatric speciation suggests that
  geographically isolated populations may, through
  genetic drift, become distinct species over time
• Darwins finches

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Adaptive radiation

• Rapid speciation may occur when extinction
  vacates a lot of environmental niches.

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Punctuated equilibrium

• In fact, we have been modifying Darwins theory
• In 1972, Neals Eldrege and Stephen Jay Gould
  (Harvard) proposed that evolution of organism
  occurs relatively rapidly during periods of
  environmental stress, and that most species stay
  static otherwise

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Ideally, in the rock record...

• One would see a succession of evolved forms of
  the same type in successive layers

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But, in the real world,....

• Unconformities may remove the evidence of
  transitional species
• Also, sometimes hard to tell apart from rapid
  speciation.

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Cladistics the science of organizing organisms
by evolutionary history
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Cladistics the science of organizing organisms
by evolutionary history
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Cladistics are based on shared evolutionary
history

• This can be traced in many ways for instance,
  the traditional anatomical methods or (more
  recently) DNA analysis

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How to tell clades from non-clades

• Recall that a clade is a group of organisms that
  all share a common trait

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Now most clades dont change much over time

• This is because most organisms do not need to
  rapidly adapt or speciate during times of
  environmental stability

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Cladistics leads to some interesting results
No such clade as reptiles
Dinosaurs arent extinct
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And we arent that closely related to chimps
anyway

• Cladistics can reveal the evolutionary history of
  even closely-related organisms

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Clades over time

• Of course, you can add a numbers to the vertical
  time axis on a cladogram