• 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