Endosymbiotic Theory

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Endosymbiotic Theory

• Endosymbiotic Theory states that eukaryotic cells
  were formed when some prokaryotic cells started
  living inside other prokaryotic cells
• Eventually these other cells became organelles
  like mitochondria or chloroplasts
• Margulis proposed this to explain why
  mitochondria and chloroplasts contain their own
  DNA

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Jean Baptiste Lamarck

• Theory of evolution in 1809
• Mechanism
• use and disuse - the idea that the parts used the
  most grow stronger the parts that dont get used
  deteriorate
• inheritance of acquired characteristics - the
  modifications that an organism acquires during
  its lifetime can be passed along to its offspring
• recognized adaptation to environment as a primary
  product of evolution

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Charles Darwin (1809-1882)

• Father of modern
• evolutionary theory
• English biologist who traveled on board the HMS
  Beagle
• His job was to collect biological and geological
  samples during the voyage

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Darwins Observations

• Darwin noticed that several birds on the
  Galapagos Islands were modified finches.
• The only differences in the birds were their
  beaks and what they ate.
• These finches looked very similar to one type on
  South American continent, but none of these were
  found in S.A.
• How did one species change into a different
  species?

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Darwins Theory of Natural Selection

• Individuals within a population vary in their
  traits.
• Some of these traits are heritable.
• More offspring are produced than can survive
  because of limited resources.
• Individuals with advantageous traits will survive
  and reproduce.

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What is natural selection?

• Natural selection - a population of organisms can
  change over generations if individuals having
  certain heritable traits leave more offspring
  than others
• Darwin inferred that if people could change
  species through artificial selection, nature
  could work the same way
• Artificial Selection often seen in breeding
  (dogs, horses, crops
• The process where traits are selected for by
  crossing certain organisms

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The Origin of Species

• After 20 years of study, Darwin published On the
  Origin of Species by Means of Natural Selection
  in 1859
• His book served as a means to explain HOW
  evolution works

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Evidence for Evolution

• The Fossil Record
• Fossils provide a record of species that lived
  long ago
• They show that ancient species share similarities
  with species that now live

Glyptodont
Armadillo
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Evidence for Evolution

• Homologous Structures
• Anatomically similar features inherited from a
  common ancestor

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Evidence for Evolution

• Vestigial Structures
• Structures that are reduced forms of structures
  in other organisms
• Examples include
• Pelvic bones and legs in snakes and whales
• Appendix in humans

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Evidence for Evolution

• Analogous Structures
• Features that have the same function, and appear
  similar, but are NOT inherited from a common
  ancestor
• Form follows Function

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Evidence for Evolution

• Comparative Embryology
• Vertebrate embryos appear similar and have
  homologous structures during certain phases of
  development, but become totally different
  structures in the adult form
• Comparative Biochemistry
• Organisms with more closely related physical
  appearance have more closely related metabolic
  chemistry