Speciation II

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There is no difference between fossil life forms
dating back hundreds of millions of years and
their counterparts living today. This fact
utterly disproves the evolutionary claim.

http//www.invitation2truth.com/evidences-of-creat
ion/tellme20.htm
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Punctuated Equilibrium Hypothesis

• Stasis is the retention of form through long
  segments of geological time
• Stasis is common following a brief event of
  innovation
• Speciation and innovation are coincident in time,
  and possibly linked as processes
• Periods of innovation are very brief,
  punctuating longer periods of stasis
• Credit to Niles Eldridge (with S. J. Gould)

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Who cares?

• Why did Darwin emphasize gradualism?
• Why are some scientists skeptical about
  punctuated equilibrium?
• How are these hypotheses related to
  microevolution?

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Case study 1 Bryozoa organisms
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Bryozoa fossils
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Bryozoa - lineages
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Foraminifera - living
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Foraminifera - fossils
microbewiki.kenyon.edu/index.php/Foraminifera
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Case study 2 foraminiferan Globoratalia
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Trilobites Stratiography and fossil characters
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Methods

• Geometric shape analysis
• define landmarks (51)
• quantify shifts in landmark relative positions

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Stasis, rapid change, gradual change Hypothesis
environmental tracking
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gradualism or punctuation?

• For some characters, gradual change is seen in
  the fossil record, but . . .
• For other characters, no systematic change
• MOSAIC EVOLUTION within a genetic lineage

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Interpreting pattern
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Resolution -- scales of time

• Geological vs. ecological perspectives
• Jumps are more likely to be perceived in coarse
  data sets
• What temporal resolution is needed before
  rejecting or accepting gradualism?

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Does conservative morphology mean no evolution?
Genetic vs. phenotypic change
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Historical evolution

• What were the major revolutions?
• When did they occur?
• What is the evidence?
• Why did they occur?

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Age of earths crust Evidence from
ZirconScientific American 2005 October Jack
Hills (Australia)
Zircon zirconium silicon oxygen
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Two isotope decay patterns
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Stable isotope ratios indicate cool environment
at 4.4 billion years BP
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Why would we care about the age of the crust?
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Major revolutions in evolution

• Pulses of unusually extensive adaptive radiation
  and increase in biodiversity
• Why is adaptive radiation punctuated?
• Why do groups undergo adaptive radiation?

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I. Life from non-life

• Multiple hypotheses
• Some potential mechanisms can be tested
  experimentally
• RNA world hypothesis
• Feasibility is testable we are a long way from a
  widely accepted hypothesis

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II. Biochemical diversification

• Began with the evolution of prokaryotes
• Proceeded for 1.5 billion years before the
  evolution of the first eukaryotes 3 billion
  years prior to multicellular diversification
• What are some examples of biochemical
  diversification for prokaryotes?

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Forms of biochemical adaptations
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III. Cellular diversification

• Eukaryotes at least 2 billion years bp
• Genomes with introns
• Organelles (endosymbiosis theory)

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IV. Body plan diversity

• Multicellularity
• Sexual reproduction developmental processes
• Alternative solutions to problems
• Surfacevolume issues
• Transport issues
• Nutrient acquisition issues
• Protection issues

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Evidence for multiple origins of multicellularity

• Plants and animals (clades with different trophic
  strategies)
• Within animals, creation of embryonic tissues
• diploblast vs triploblast
• symmetry none, radial, bilateral
• Strategy of blastula infolding
• gastrulation
• protostome vs. deuterostome (mouth first or
  second)

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When did multicellularity arise?

• Cambrian Explosion seen well after 1st forms
• 610 Ma radially symmetric form first seen
• 565 Ma to 525 Ma major phyla appear in fossils
• 0.8 of earths history accounted for almost all
  major diversity of multicellular strategies

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Why did body plans diversify?

• Changes in continents, oceans
• Changes in environment
• Rising oxygen concentrations in ocean
• Increasing complexity of biotic interactions

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V. Colonization of land

• Major adaptations to utilize a new environment
• Plant-animal coevolution
• Plant-herbivore coevolution
• Plant-pollinator coevolution
• Plant-disperser coevolution