Darwin and Evolution

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Darwin and Evolution
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Charles Darwin

• Son of Robert Darwin, a physician and grandson of
  Erasmus Darwin, also a physician
• Was to study medicine, stomach not strong enough
• Studied Theology, loved natural science

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Darwins Voyage

• 1831 - 1836
• Naturalist on the HMS Beagle
• Looking for a biblical account of creation
• Many specimens collected (hares, tortoise,
  finches) and observations made that contradicted
  creationism
• Put his ideas into an essay, but sat on it for 20
  years for fear of being discredited as a scientist

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Pre - Post Darwinian Views

• Earth is young
• Fixity of species
• Adaptation due to creator variation-
  imperfections
• Observations should confirm view

• Earth is old
• Species related by descent
• Adaptation random variations in environmental
  conditions
• Observations used to test hypothesis

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Evolution versus Creationism

• Descent with modification- as descent occurs
  through time so does diversity
• Explains the unity and diversity of life
• Living things share common characteristics
  because they are descended from a common ancestor

• Higher being created the species
• Fixity of species
• Each species has ideal structure and function

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Mid-18th century contributions

• Carolus Linnaeus taxonomy, scala naturae
  ladder of life simple to complex (humans)
• Count Buffon French naturalist, work support
  DWM
• Erasmus Darwin grandfather physician,
  naturalist, work eluded to DWM
• All these mens work opened the door to the
  thought of evolution but still supported fixity
  of species

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Late 18th century contributions

• Georges Cuvier
• comparative anatomy for classification, founded
  paleontology
• Fixity of species supporter
• Tried to explain strata of earth was due to
  catastrophes/mass extinction

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Cont.

• Jean Baptist LaMarck
• First to believe evolution occurs
• Inheritance of Acquired traits use it or lose
  it environment brings about change
• Phenotype does not result in genetic changes
• Giraffe neck length
• Suntan, muscles

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Darwins Theory of Evolution

• Influenced by Charles Lyells Principle of
  Geology
• James Hutton geological changes occur slowly
  over time, natural process EARTH IS OLD
• Contradicts Cuvier due to catastrophes

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Natural Selection Charles Darwin and Alfred
Wallace

• Idea that those organisms that are best suited to
  their environment will reproduce and pass on
  their traits
• Alfred Russell Wallace sent Darwin essay on
  Natural selection before he published his own
• Variations (mutations) are essential to natural
  selection process ex. Independent assortment

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Natural Selection

• Thomas Malthus socio-economist
• human population increase faster than food
  supply struggle for existence
• Each generation of organisms have same
  reproductive potential, but not all will survive
  to reproduce

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Natural selection

• Fitness ability to survive and reproduce in its
  environment relative to others
• Usually has most resources
• Survival of the fittest
• Artificial selection characteristics are
  selected for and select organisms to reproduce.

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Natural Selection

• Adaptation trait that helps organism be better
  suited for its environment
• Flippers water, wont help on land
• Natural selection occurs because certain members
  of a population happen to have a variation
  (mutation) that allows them to survive and
  reproduce.

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Darwins Theory of Evolution - Evidence

• Biogeography study of range and geographic
  distribution of life forms on earth
• Darwin reasoned related species could be modified
  based on their environment (ex. Tortoises)
• Observed geographical changes 1st hand and
  collected fossils to support his theory that
  species are not fixed, but change over time.

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Evidence of Evolution

• Biochemical evidence
• Darwin was not aware of biochemical evidence
• Amino acids- cytochrome c (used in electron
  transport)
• DNA/RNA/enzymes similarities
• Introns (junk DNA)
• Fossils

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Evidence of Evolution

• Anatomical structures
• Homologous structures - similar in structure but
  have different function
• Vestigial structures features that are fully
  developed in one group of organisms but are
  reduced and may have no function in similar
  groups
• Embryological development look at dorsal rod
  (notochord), pharyngeal slits (gills)

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Theory of Evolution

• Unifying theory in biology
• Large number of observations
• have not yet been found lacking or disproven