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Origins: Early Ideas

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Biogenesis: living organisms come from other living organisms. Cornerstone for biology ... In order for life to form, there must be: ... – PowerPoint PPT presentation

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Title: Origins: Early Ideas


1
Origins Early Ideas
  • Spontaneous Generation
  • Life is produced from non-living matter
  • Francesco Redi
  • Rotten meat experiment
  • Louis Pasteur
  • Broth experiment

2
New Ideas
  • Biogenesis living organisms come from other
    living organisms
  • Cornerstone for biology

3
But how did life begin?
  • Theoretical and experimental analysis
  • In order for life to form, there must be
  • Simple organic molecules important for life, ie.
    amino acids
  • Organization of these organic molecules into
    complex organic molecules, ie. proteins

4
How did organic molecules come about?
  • Early Earth had no free oxygen
  • Only thought to have water vapor, hydrogen,
    methane and ammonia
  • Life thought to have begun in oceans
  • Energy from sun and lightening triggered chemical
    reactions with existing compounds to form a
    primordial soup

5
Primordial Soup to the Test
  • In 1953, Miller and Urey put that hypothesis to
    the test
  • They simulated early earth environment in the lab
  • See figure 17.13 to see their experiment
  • They found that amino acids, sugars and other
    organic compounds formed!!!

6
NEXT
  • Complex organic compounds formed
  • These compounds are enclosure by some bounding
    membrane
  • But HOW?

7
The PROTOCELL
  • Sidney Fox produced protocells by heating
    solutions of amino acids
  • See figure 17.14 to see his experiment
  • Protocells are large, ordered structures that
    carry out some activities associated with life,
    ie. Growth, division and metabolism
  • What are the criteria for determining whether
    something is alive?

8
Evolution of Cells
  • Earliest forms of life were prokaryotes, having
    evolved from some sort of protocell
  • Anaerobic
  • Heterotrophs
  • Competition for nutrients led to the first
    autotroph
  • Like present day archaebacteria
  • Then photosynthesizing prokaryotes evolved

9
Then the Atmosphere Changed!
  • Photosynthesis releases oxygen, therefore the
    amount of oxygen in Earths atmosphere began to
    increase, allowing for
  • The evolution of aerobic respiration
  • The oxygen revolution

10
Oxygen also had another effect
  • Oxygen in the atmosphere was converted into ozone
    (O3) by lightening leading to our ozone layer
  • This shielded the emerging life forms from the
    damaging UV radiation from the sun, allowing for
    the evolution of even more complex organisms

11
Origin of Eukaryotes a theory
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