Darwinian Evolution

• LaMarck
  • Organisms adapted to their environments by acquiring traits
  • Change in their lifetime
    • Disuse
    • Organisms lost parts because they did not use them

Like the missing eyes and digestive system of the tapeworm

• Perfection with use and need
  • The constant use of an organ leads that organ to increase in size

Like the muscles of a blacksmith or the large ears of a night-flying bat

• Transmit acquired characteristics to the next generation
• Charles Darwin
  • 1809-1882
  • British naturalist
  • Proposed the idea of evolution by natural selection
  • Collected clear evidence to support his ideas
• Voyage of the HMS Beagle
  • Invited to travel the world
  • 1831-1836
  • Makes many observations of nature
    • Main mission of the Beagle was to chart the South American coastline
  • Stopped in the Galápagos Islands
  • 500 miles off the coast of Ecuador
• Darwin’s Finches
  • Differences in beaks
  • Associated with eating different foods
  • Survival and reproduction of beneficial adaptations to foods available on islands
  • Darwin’s conclusions
  • Small populations of original South American finches landed on islands
    • Variation in beaks enabled individuals to gather food successfully in the different environments
  • Over many generations, the populations of finches change anatomically and behaviorally
    • Accumulation of advantageous traits in population
    • Emergence of different species
  • Differences in beaks allowed some finches to…
  • Successfully compete
  • Successfully feed
  • Successfully reproduce
    • Pass successful traits to their offspring
• Selective Breeding
  • Hidden variation can be exposed through selection
• A Reluctant Revolutionary
  • Returned to England in 1836
  • Wrote papers describing his collections and observations
  • Long treatise on barnacles
  • Draft his theory of species formation in 1844
    • Instructed his wife to publish this essay upon his death
    • Reluctant to publish, but didn’t want ideas to die with him
• Essence of Darwin’s Ideas
  • Natural selection
  • Variation exists in populations
  • Over-production of offspring
    • More offspring than the environment can support
  • Competition
    • Food
    • Mates
    • Nesting sites
    • Escape predators
  • Differential survival
    • Successful traits are adaptations
  • Differential reproduction
    • Adaptations become more common in population

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