NE

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