Key Facts

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13.3-13.4
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Key Facts

• Darwin devloped theory on evolotion by geographic
  distrubution, artificel selection, and fossil
  record.
• Organic substances of organism in most instances
  decay rapidly.
• In some instances hard parts of organism such as
  bones, teeth, shells of clams and snails become
  fossilized.
• Petrification occurs when minerals from ground
  water seep in to dead organsims and replace
  organic matter.

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Key Facts Contd

• Paleontologis are scientists that study fossils.
• Do not dig up actual remnants of organism but
  rocks that are replicas.
• Fossilization occurs when an organism decays and
  leaves a space in sediment and is filled by
  rocks.
• Use trace fossils which are remenants of
  organisms behavior such as footprints nd burrows

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Facts Contd

• Some can retain genetic material when buried in
  a medium that prevents bacteria and fungi from
  decomposing the organism
• Some prime exampels of this include The Ice Man

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Facts Contd

• Scientists can use the fossi record the orfered
  array of in which fossils appear in sedintary
  rock
• Sedinrary rocks form from layers of sand and mud
  at the bottem of seas, lakes, and marches.
• Aquatic organisms are covered by many layers of
  sediment and land organism can also be washed in
  the body of water or are covered when sea levels
  rise throughout the centuries.
• Because of constant changes of sea level strata
  or different layers of rock form
• Youinger layers are at the top and older layers
  are at the bottom

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Facts Contd

• We have been able to find linkage between modern
  and acient species
• For example modern whales have forlegs in the
  form of flippers but have back legs bones that do
  not extend from the body
• Palentologists Digging in Pakistan and Egypyt
  have whales with forelegs

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Facts Contd

• Biography is the geographic distrIbution of
  specie s
• Prime is example is the animals of the Galagos
  Islands off the coast of South America
• Darwin obserbed that the animals of the island
  were much like that of South Americas animals
• Obserbed that the animals on the isalnd evolved
  from early South American migrants
• Another example the marsupiels of Australia

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Fact Contd

• Comparitive anatomy is is the comparison of body
  structures of different species
• Can show a common ancestor
• Homology is the charecteristecs that result from
  a common ansestor
• For example skeletal elemnts of cat, human,
  whale, and bat are similar in structure but have
  different functions
• These organisms have homologous structures
  features that have different functions but
  similar structure because of common ansestory
• Shows descent with modification that states that
  as structues appear that take on new roles
• vestigal organisms that have no importance to an
  organism but still remain.
• Often these structures were phased out during
  evoloution
• Example of this is pelvbis that remain in many
  snake skeltons

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Facts Contd

• Comparison of early stages of devlopment is call
  comparitive embryology
• Can tell common ancestory by organs that form in
  devlopment
• Structue called pharyngeal that forms in the
  development of fishs, frogs, snakes, and mamels
• Organisms take on more devloped organisms as they
  mature

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Facts Contd

• Molecular biology gas allowed scientists to
  observe the seqiences of DNA of ancient organisms
• Can observe common organism by obserbing
  sequences of DNA bases
• The closer the sequences of DNA the closer the
  organisms are related
• Can obserbe the controls of master organ creation