The History of Life

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The History of Life

• Chapter 14

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Where did life come from?

• Many theories, ideas, and opinions exist
• NO ONE knows exactly
• Early idea
• Spontaneous Generation nonliving material can
  produce life
• First disproved in 1668 by Francesco Redi
  (Italian Physician) used decaying meat in jars
  to show that flies produce flies
• See page 388 in textbook

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• though Redi had disproved spontaneous generation
  of large organisms, many scientists thought that
  microorganisms were so numerous that they arise
  spontaneously from a vital force in the air
• In mid-1800s, Louis Pasteur designed an
  experiment that disproved the spontaneous
  generation of microorganims

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Figure 26.9 Pasteur and biogenesis of
microorganisms (Layer 1)
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Figure 26.9 Pasteur and biogenesis of
microorganisms (Layer 2)
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Figure 26.9 Pasteur and biogenesis of
microorganisms (Layer 3)
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Biogenesis

• life comes from life
• Result of Pasteurs experiment
• Cornerstone of Biology

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Biogenesis does NOT answer origin of life

• Again, no one knows for sure, but there are
  several theories that have developed for HOW life
  on Earth originated
• 2 developments must have preceded life on Earth
• 1. simple organic molecules must have formed
• 2. These simple organic molecules organized
  into complex organic molecules carbs, lipids,
  proteins, nucleic acids

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Alexander Oparin

• 1930s
• Russian scientist
• Hypothesized that life began in the oceans on the
  early Earth
• Suggested that energy from sun, lightning, and
  Earths heat triggered chemical reactions that
  formed organic molecules
• Rain washed these into the oceans primordial
  soup

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Stanley Miller and Harold Urey

• 1953
• American scientists
• Tested Oparins hypothesis
• Simulated conditions of early Earth in lab
• Mixed water vapor with ammonia, methane, and
  hydrogen gases
• Sent in an electrical current (lightning)
• Cooled the mixture, collected liquids
• Found amino acids, sugars, and other small
  organic molecules

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Figure 26.10 The Miller-Urey experiment
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Taking it further

• 1950s experiments showed that if amino acids
  are heated without oxygen present, they link and
  form proteins
• Can also form ATP and nucleic acids in a similar
  manner
• HOW FORMED FIRST CELLS?
• Stanley Fox American biochemist
• demonstrated formation of protocells large,
  ordered structures enclosed by membranes that
  carry out some life activities (growth and
  division)
• See page 391 in textbook

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Endosymbiosis

• 1960s
• Proposed by American biologist, Lynn Margulis
• Possible explanation for eukaryotic cell
  formation
• See page 393