Evolution

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Evolution
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Evolution
Modern Humans

• Definition Change in a population of organisms
  over time.

• Human evolution illustrated on a cladogram

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Theories of Evolution

• Jean-Baptiste Lamarck 1809 published his theory
  of evolution
• Mechanism of Evolution Inheritance of Acquired
  Characteristics

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Theories of Evolution

• Charles Darwin 1859 published his theory of
  evolution in the major work, On the Origin of
  Species
• Mechanism of Evolution Natural Selection

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The Original Manuscript

• Most important book on biology ever published!

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Lamarcks Ideas

• Organisms change over time
• Organisms are adapted to their environment
• They are continually changing and acquiring
  features more suitable for their environment.
• Continued ?

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Larmarcks Ideas

• During an organism's lifetime, there is selective
  use or disuse of its organs and traits. If a
  trait isnt used?its lost.

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Larmarcks Ideas

• Traits that are used are passed on to their
  offspring. Over time, this process leads to the
  change in a species. (hence the term
  inheritance of acquired characteristics)

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Darwins Ideas on Evolution

• Variation organisms show variation in each of
  their traits height, colors of eyes/hair/skin,
  resistance to disease, etc.
• Natural selection Organisms better suited to
  their environment survive and reproduce (also
  known as survival of the fittest).
• Fitness ability to survive and leave offspring.
  No offspring No fitness.

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Worksheets

• Natural Selection and fur color

• Evolution comparison of Lamarck (acquired
  characteristics) and Darwins (natural selection)
  ideas on evolution.

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Darwins ideas on Evolution

• In the early 1800s, when Darwin was born, people
  thought the Earth was a few thousand years old.
• But by the 1820s, scientists hypothesized the
  Earth was millions of years old.
• 5000 years
• 5,000,000 years

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Darwins ideas on Evolution
17-11 MYA
5 MYA-present

• An ancient Earth was necessary to support
  Darwins ideas on evolutionpopulations change
  over (long, long periods of) time.

35,000,000YA
12-6 MYA
55,000,000YA
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Microevolution according to Darwins Ideas on
Natural Selection
Natural Variation in population of bacteria
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Macroevolution according to Darwins Ideas on
Natural SelectionSpeciation formation of new
species
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Genes and Variation

• Most phenotypes (traits) are polygenic.
• A graph of these traits often shows a bell curve.

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Stabilizing Selection

• If individuals near the center of the bell curve
  have higher fitness ( leave a greater amount of
  fertile offspring) then stabilizing selection
  occurs.

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Directional Selection

• If individuals at one end of the bell curve have
  higher fitness then directional selection occurs.

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Disruptive Selection

• If individuals at both ends of the curve have
  higher fitness than those in the middle then
  disruptive selection occurs.

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Genetic Drift

• If a small population is isolated from others of
  the same species, it is possible that just be
  chance one allele may become more common in a
  population.

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Genetic Drift

• For example The Bronx, NY, becomes built up and
  trees are cut down. Few squirrels are able to
  survive. However, one section of the Bronx is
  set aside for the development of the Bronx Zoo.
  Trees are NOT cut down in this area. By chance,
  several of the gray squirrels in the area of the
  zoo have black fur (a variation in fur color).
  Over time, the allele for black fur becomes
  common in this population.

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How do new species form?Example Galapagos
Finches

• A small group of a species of finch arrives on
  one of the Galapagos Islands
• These finches do not usually fly across open
  waterthey may have gotten lost or were blown
  there by the wind.

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Speciation continued!

• Over time these original finches may have ended
  up on other of the Galapagos Islands through some
  chance occurrence.
• USUALLY the finches do NOT fly from one island to
  another.

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Speciation continued!

• The Galapagos Islands had different environments.
  
• Some had a low elevation and were dry with little
  plant material.

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Speciation continued!

• Others had a higher elevation with greater
  rainfall and many plants.

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Speciation continued!

• Directional selection occurs
• One island may have seeds that are large and
  difficult to open.
• Birds with a larger, thicker beak will have the
  highest survival rate on this island

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Speciation continued!

• Directional selection occurs
• Another island may have seeds that are small and
  easy to open
• Birds with a small, thinner beak will have the
  highest survival rate on this island

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Speciation continued!

• Reproductive Isolation if the populations
  remain separate, and their gene pools continue to
  change, eventually they can no longer mate with
  each otherthey are then TWO NEW SPECIES!!!
• On the Galapagos Islands this processes resulted
  in the evolution of 13 different finch species.

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• Darwins Finches

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Evidence of Evolution

• Fossil Record

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Evidence of Evolution

• Comparative Anatomy
• Homologous structures structures that have
  different mature forms but develop from the same
  embryonic tissue

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Evidence of Evolution

• Vestigial organ organ that serves NO useful
  function in an organism.
• Wisdom teeth
• Appendix

HUMANS
Fingernails on Seals Fin
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Embryology
NOTE Similarity of embryos of all of these
animals
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Evidence of Evolution

• Similarities and dissimilarities in DNA code.
• Complete worksheet bar graph.