Module 9

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Module 9

• Evolution

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Abiogenesis

• Life first arose from non-living material in a
  primordial soup
• Experimentally tested by Miller and Urey
• Also called SPONTANEOUS GENERATION

H2S
CO2
N2
CO
CH4
Amino acids
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Heterotroph Hypothesis

• Explains evolution of prokaryotic cells
• Earliest cells had to take in nutrients
  (heterotrophic)
• Earliest cells had to live in oxygen free
  conditions (anerobic)

O2
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Heterotroph Hypothesis

• Photosynthetic prokaryotic cells evolved,
  allowing for release of free oxygen
• Led to ozone layer

O2
O2
O2
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Heterotroph Hypothesis

• Oxygen led to evolution of aerobic cells

O2
O2
O2
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Endosymbiont Hypothesis

• Explains the evolution of eukaryotic cells
• A symbiotic relationship formed between larger
  and smaller prokaryotic cells smaller cells
  became mitochondria and chloroplasts
• YouTube - The Evolution of Eukaryotic Organisms
  Endosymbiotic Theory

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Multicellular Life

• Multicellular organisms are made of eukaryotic
  cells
• The evolution of eukaryotic cells allowed
  multicellular life to evolve, and eventually
  colonize land

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Biogenesis Life comes from life

• Although life may have arisen spontaneously, life
  continues through other life!
• Spontaneous generation has been disproven by
  scientists

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Biogenesis Life comes from life

• Disproven by Francesco Redi

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Biogenesis Life comes from life

• Disproven by Louis Pasteur

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Evolution CHANGE over time

• Occurs through the process of NATURAL SELECTION
• Nature selects the best adapted organisms to
  survive and reproduce
• Natural Selection Stated Clearly
• (10 min)

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What is an Adaptation?

• A heritable trait
• Makes an organism better suited to its role in
  the ecosystem
• May be structural, behavioral, or physiological

Structural defensive structures, camouflage,
mimicry
Behavioral Herding, schooling, growling
Physiological enzymes, oxygen transport, sight
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Theory of Natural Selection

• Proposed by Charles Darwin
• 4 Requirements

Natural Selection Nature selects the best
adapted
Survival of the fittest Best adapted
individuals have greater reproductive success
Variation Different phenotypes in the population
Overproduction Leads to competition
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Individuals DONT EVOLVE!

• Individuals dont evolve populations do!
• This requires a change in the gene pool

MUTATION The raw material for change
Can be selected FOR
Can be selected AGAINST
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3 Selection Mechanisms
Stabilizing
Directional
Disruptive
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Speciation

• Speciation
• The development of a new species

Geographic Isolation
Natural Selection
Reproductive Isolation
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Timeframe for Evolution
GRADUALISM Occurs over a long period of time
with the accumulation of small changes PUNCTUATED
EQUILIBRIUM Occurs with speciation in rapid
bursts with 1000s of years of stability between
changes
Gradualism
Punctuated Equilibrium
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Evidence for Evolution
Fossil Record May give exact age or relative age
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Evidence for Evolution
Biochemical Evidence Comparing amino acid
sequences
REMEMBER If amino acids are similar, DNA is
similar because DNA is a code for making proteins!
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Evidence for Evolution
Homologous Structures Similar bone arrangement,
but different functions
REMEMBER Analogous structures do not give
evidence of evolution from a common ancestor!
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Evidence for Evolution
Vestigial Structures Not functional, but may have
been important in an ancestor
Vestigial Structures - SciShow
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Evidence for Evolution
Comparative Embryology Similar embryos give
evidence of a common ancestor
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Evolution Today

• Evolution is still happening!
• However, its usually too slow to observe
• EXCEPT
• 1) Pesticide Resistance

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Evolution Today

• Evolution is still happening!
• However, its usually too slow to observe
• EXCEPT
• Antibiotic
• Resistance