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