Chap. 15 : Darwin

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Chap. 15 Darwins Theory of Evolution

• Fossils
• - traces of dead organisms, collect in
  sediments (dust, mud, etc) to form sedimentary
  rock.

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A. Types

• 1. Mold imprint (living parts maybe left
  behind) common in limestone rock.
• 2. Cast when molds fill in with minerals
• 3. Amber fossilized sap or petrified rocks
• B. Law of Superposition states that layers of
  succession (called strata) build on top of each
  other.

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• 
  youngest
• 
  oldest
• all fossils found in same area are
  from the same time period.
• relative age comparison between
  fossils.
• absolute age - determined by
  radioisotopes.
• (carbon dating)

D
C
B
A
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C. Succession layers shows periods of boom of
certain organisms then periods of mass
extinctions. Caused by environmental changes.

• D. Biogeography the study of distribution of
  living (or once living) organisms.
• II. Evolution Theories
• A. Lamarck 1st to suggest that similar
  species arose from common ancestors.

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• Suggested the term acquired trait ( not passed by
  genes but changed by habitat or behavior and then
  passed to offspring). Ex. webbed feet resulted
  from repeated stretching.
• B. Darwin Origin of Species book about the
  idea of natural selection (nature selects for the
  most fit organisms to survive)
• - fitness how well an organism is adapted
  to its environment

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III. Evidence of Evolution

• A. Homologous/Analogous Structures
• - Homologous Structures features that
  originated from a shared ancestor. Ex. Different
  beaks, forelimbs of penguins, alligators, bats,
  and humans.
• indicates that different species
  shared a common ancestor
• - Analogous Structures features that
  look somewhat alike and serve similar functions
  but do not share the same embryo development. Ex.
  Birds and moths wings.

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B. Vestigial Structures structures that
presently serve no function.

• Ex. Appendix and tail bone in humans, 4-chambered
  stomach in whales, legs in boas and pythons.
• --- organisms with similar vestigial structures
  shared an ancestor
• C. Similar Embryo Development
• - in the early stages of development all
  vertebrates are the same. Ex. Fish,rabbits,birds,
  and humans

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D. Similar Macromolecules homologous structures
have similar amino acid sequences.The of
differences are related to how recent their
ancestor was.

• IV. Patterns of Evolution
• 1. Coevolution change of 2 or more species
  in close association with each other. Ex.
  Predator/prey , plants/animal pollinators
• -- bats and flowers bats long tongue and
  slender nose, flower light in color and smells
  fruity

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2. Convergent evolution environment selects
similar phenotypes even though the ancestors were
quite different. Ex. Sharks and porpoises

• 3. Divergent Evolution 2 or more related
  populations become more and more dissimilar.
  Caused by a change of habitat.
• --- usually results in new species
• a. Adaptive Radiation related species
  evolve from single ancestor. Ex. Darwin finches.
• b. Artificial selection speeding up of
  divergence by artificial means. Ex. Domestic
  dogs, horses
• -- doesnt result in new species but rather
  varieties of species.

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V. Events that lead to new species

• Barrier separating like organisms forms (flood,
  volcanic eruptions, earthquakes, forest fires,
  etc.)
• Time passes (thousands of yrs), environment
  changes
• Natural selection breeds changes
• Enough change occur overtime to change DNA
  significantly so no longer recognized.

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VI. Primates and Human Evolution

• 45 million years ago

Old World Monkeys (non- grasping tail, downward
nose)
New World Monkeys (tails that grasp, upward
noses)
Some evolved into apes and gorillas
monkeys
baboons
Evolved into humans