Chapter 22 Darwinian evolution

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Chapter 22 Darwinian evolution

• Historical developments background
• Linnaeus
• Cuvier, Hutton, Lyell
• Lamarck
• Malthus
• Darwins insight

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Linnaeus classified organisms in 1700s

• Developed the binomial system still used.
• Every species has a unique two-word name
  consisting of a genus and species
• e.g. Homo sapiens (notice formatting)
• System grouped organisms by degree of similarity
• Several species collected into same genus
• Genera grouped into family
• What is a species?

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Understanding Earths history

• Earth was thought to be only 6,000 years old
• Fossils were found (e.g. by Georges Cuvier
  1700s)
• Deeper you dig the more different the fossils are
• Lower sediments represent older time periods
• Species seemed to have gone extinct! Why?
• Geologists suggested that landforms present today
  were created by same processes that occur now
• Gradualism (coined by James Hutton in 1795)
• Uniformitarianism (Charles Lyell in 1800s)

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Mutability of species

• Jean-Baptiste de Lamarck (in 1809) proposed that
  organisms change through time (evolve)
• Recognized Earth was very old
• Observed progression of fossils from older,
  different forms to newer, familiar forms
• Proposed a mechanism (inheritance of acquired
  traits)
• Features used developed in life passed on
• Giraffes stretching for higher leaves have
  longer-necked offspring

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Understanding population dynamics

• Thomas Malthus (in 1798) wrote about the coming
  catastrophe of human population explosion
• Populations were growing much faster than the
  increase in food supply
• Malthus expected to see a difficult future as
  people would have to fight for the limited
  resources

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Darwins own experience

• Exposed to variety of species while on voyage
  around the world on the Beagle
• Species seemed well designed for local habitat
• Species within a geographical area were similar
  to one another despite different adaptations
• E.g. Galapagos finches

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Geographic similarity

• Hawaiian honeycreepers
• Very similar in many ways
• Bill size shape reflects feeding behavior

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Darwins own experience

• Darwin fancied breeding his own pigeons
• By selecting certain traits, he could produce
  exaggerated features

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Another selective breeding example

• Wild mustard has been bred to produce many crops
  (cabbage, kale, cauliflower, broccoli, brussel
  sprouts)

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Evolution by natural selection

• Charles Darwin proposed the theory in The Origin
  of Species in 1859
• He had formulated his theory many years before
• Reluctant to publish until Alfred Russell Wallace
  sent him a letter describing his new theory in
  1858

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Evolution by natural selection

• Observations
• All species produce too many offspring
• Populations do not expand indefinitely
• Resources are limited
• Individuals vary within a population
• Traits are passed from parents to offspring

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Evolution by natural selection

• Inferences
• Individuals will compete for resources
• Individuals possessing certain traits will have
  an advantage (natural selection)
• Over time, the population will change as favored
  traits become more common in later generations
  (evolution)

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Evolution by natural selection

• Individuals do not evolve, populations do
• Individuals may adapt to conditions
• Populations (species) adapt by evolving
• Acquired traits are not passed on
• Evolution is not progressive
• Organisms are not always getting better
• more complex or smarter
• Sometimes simpler is selected for

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Some evidence of evolution

• Insecticide-resistant crop pests
• We lose about the same percentage of our crops to
  insects as we did before insecticides
• Antibiotic resistance in bacterial infections
• Drug resistance in HIV
• Fossil evidence documenting evolution of modern
  species from earlier ancestors
• Presence of vestigial organs in many species

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Common ancestry

• Homology
• Similarity of features due to shared ancestry
• Anatomical
• Molecular
• Embryological
• Analogy
• Similarity of form due to convergent evolution
• E.g. anatomical similarity of dolphins sharks

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Erosion of mans ( womans) prominence

• Earth was thought to be center of universe
• Nope, just another planet rotating around sun
• Sun is just one of billions billions of stars
• Humans thought to be created in present form at
  the time of creation
• Earth was around for billions of years before us
• Universe around for billions of years before
  Earth
• Current form is result of non-intelligent design