Evolution/Origin of Life

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Evolution/Origin of Life

• What is life? Where does life come from?
• The Biogenesis/Abiogenesis Debate
• Abiogenesis also known as Spontaneous Generation
• Ancient Times (Aristotle) frogs from mud
  puddles
• 17th C (Jean Van Helmont) mouse recipe
• Presence of the active principle
• 17th C (Francisco Redi) maggots from decaying
  meat
• 1st scientist to use a control
• Gauze let air into the jar, and caught eggs on
  top

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• 18th C (John Needham) boiled meat broth in
  loosely sealed flasks
• Presence of vegetative force
• 18th C (Spallanzani) melted glass at top of
  flask
• 19th C (Pasteur) used swan-necked flasks to end
  the Biogenesis/Abiogenesis Controversy
• Pasteur-Pouchet Debate
• Virchow coined the term biogenesis

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Origin of Life

• Oparins Hypothesis (1936)
• 14.6 billion years ago (Big Bang)
• Sun formed from explosion of a small volume of
  matter and energy
• 4.6 billion years ago Earth, other planets
  formed
• Heavy elements in the center of the earth (Fe,
  Mg)
• Lighter elements form primitive atmosphere
  (CHON)
• Evaporation of H2O Clouds formed Rained for
  millions of years Lightning
• Formation of the oceans
• Polymer formation in the oceans (organic soup)
• Heterotrophs (1st cells) dependent on food source
  in the ocean (anaerobic)
• Autotrophs (2nd cells) independent able to
  produce their own food by photosynthesis
  (aerobic) release of O2 (formation of the Ozone
  Layer)

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• Stanley Miller (1953) proved Oparins Hypothesis
  in his lab
• Substituted electricity for lightning
• Filled a vat with H2O, CH3, NH3
• Result (2 weeks later) amino acids
• Amino acids are in all living things building
  blocks of proteins
• Life came from chemical changes in the ocean.
• Why is this explanation not considered to be
  spontaneous generation?
• It took millions of years
• If lightning occurredIf it rainedIf certain
  chemicals were present, then it is a possibility.

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Evolution

• Gradualism A gradual change in a species over
  millions of years (Charles Darwin)
• Punctuated Equilibrium periods of stability and
  periods of drastic changes within a species
  (Stephen Jay Gould)

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Proofs of Evolution

• Fossils in sedimentary rocks
• Homologous Organs same structure but different
  function examples birds wing, horses front
  leg, whales fin, humans arm, bats wing
• Common ancestor
• Divergent evolution (Adaptive radiation) adapt
  to different environments

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• Analogous Organs same function but different
  structure examples bats wing, butterfly wing
• No common ancestor
• Convergent evolution (organisms come together in
  the same environment)
• Vestigial Organs organs with no apparent
  function examples tone, wisdom teeth, ear
  muscles, appendix, 3rd eyelid, little toe,
  cave-dwelling fish with eyes
• DNA-RNA-ATP Similarities
• Similarities in Embryos

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Charles Darwin (1809-1882)

• Naturalist on the Beagle (5 year voyage)
• Galapagos Islands (100 km. west of Ecuador)
• Variety of finches (13), tortoises, iguanas
• Influences on Darwin
• Charles Lyell (Principles of Geology)
• Thomas Malthus (Essay on the Principle of
  Population)
• Work of Alfred Wallace
• 1859 On the Origin of Species

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• Darwins Theory of Evolution
• Overproduction of the species
• Observations of Thomas Malthus
• Constant struggle to survive
• Competition greatest among members of the same
  species
• Uniqueness (variety)
• Organisms produced sexually show a variety among
  offspring
• Natural Selection
• Nature/environment chooses which organisms will
  survive
• Survivors pass on genes
• Survival of the Fittest

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LaMarck (1744-1829)

• Theory of Need
• Organisms have an inner need to change
• Theory of Use and Disuse
• Organs not used weaken and eventually disappear
• Inheritance of Acquired Traits
• Acquired abilities/traits are passed on to
  offspring
• Giraffe Story
• How did giraffes get longer necks?
• Giraffes stretched their necks ---Led to longer
  necks---Organisms change to survive in their
  environment (L)
• Variety of giraffes with different neck
  sizes---Nature or environment determines which
  organisms will survive (D)

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Natural Selection and Adaptation

• A result of environmental change
• Story of English Peppered Moths
• 1800s 2 species of peppered moths in
• Northern England (light dark)
• Trees covered with light gray lichens
• What happened to the light-colored moths?
• What happened to the dark-colored moths?
• Industrial Revolution soot on blackened tree
  bark
• What happened to the light-colored moths?
• What happened to the dark-colored moths?

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Natural Selection Distribution Curves

• Stabilizing Selection
• Selection against the
• extremes
• When individuals near the
• center of the curve have
• higher fitness than
• individuals at either end
• of the curve
• Intermediate phenotype
• (average) favored

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• Directional Selection
• When individuals at one end of the curve have
  higher fitness than individuals in the middle or
  at the other end
• Evolution causes an increase in the number of
  individuals
• with the trait at one end of the
• curve

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• Disruptive Selection
• When individuals at the upper and lower ends of
  the curve have higher fitness than individuals
  near the middle of the curve
• Selection acts against individuals of an
  intermediate type (average)

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Adaptation

• The fitness of an organism for its environment
  (able to survive and reproduce)
• Structural involves body parts
• Camouflage hiding by blending in with background
• Mimicry copying body parts
• Monarch butterfly (bitter) and Viceroy butterfly
  (good tasting) Viceroy survives possible
  predators by copying Monarch

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• Physiological organism changes its metabolism to
  survive
• Bacteria adjusts to different doses of penicillin
• Behavioral organism changes its behavior to
  survive
• Courtship and mating behaviors

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Mechanisms of Evolution

• Gene Pool all the genes for a population
• Genetic Equilibrium all of the genes coming
  into a population equal all of the genes coming
  out of the population (inout)
• What causes changes in the genetic equilibrium?
• Mutations (DeVries), Genetic Drift (chance
  occurrence), Gene Flow (immigration and
  emigration), Natural Selection
• Hardy-Weinberg Law (1908) A constant
  population exists if there are no mutations, no
  genetic drift, no gene flow (immigration or
  emigration), random mating, and a large population

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Speciation

• Species a group of interbreeding organisms that
  share a gene pool
• Geographic Isolation members of the same species
  separated by a physical boundary (mountain,
  river) Darwins finches
• Reproductive Isolation formerly interbreeding
  organisms prevented from reproducing (seasonal
  different breeding seasons)
• Evolution vs. Creationism
• A belief in a scientific explanation for the
  creation of life vs. a literal interpretation of
  the Biblical story of Genesis
• 1925 Scopes Trial (Tenn.)
• John Scopes (a substitute biology teacher)
  violated Butler Act
• Wm. Jennings Bryant (Prosecutor) Clarence
  Darrow (Defense)
• Scopes found guilty (fined 100)

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Scopes Trial