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  • Early Theories of EvolutionEVOLUTION: change in a population

    (DNA) over time

    no scientific explanations of evolution were given until the 18th


    1. Lamarcks Hypothesis of Evolution (Theory of Use and Disuse):

    1809 was one of the first to develop

    a theory of evolutionJ.B. Lamarck

  • Three Main Ideas:i. organisms strive to improve themselves,

    to become more advanced

    ii. the most used structures develop, while the less used ones waste away. Known as the principle of Use and Disuse

    iii. once a modification has occurred it is passed on to the offspring

    - disproved by Weisemann cut off the tails of mice, allowed them to

    reproduce and then cut off the offsprings tails

    he continued this for 20 generations and they continued to produce offspring with tails

  • 2. Charles Darwins Theory of Natural Selection(aka: Survival of the Fittest) 1844(but took him 20 years to publish

    his ideas) 5 main points:

    i) there is variation within populationsii) Some variations are favourable. A favourable variation is one that improves the organisms ability to function and reproduceiii) More young are produced in each generation than can surviveiv) Those with the favourablevariations, survive, reproduce and pass on the favourable trait to their offspring.v) Over enormous spans of time, small changes accumulate and populations change.

  • Darwins Finches

  • Requirements:

    2. those with longer necks

    get better/more food, have

    more babies

    (have an advantage in

    the struggle for existence)

    1. Variation in a trait

    within a population.

    (some had longer necks

    than rest of population)

  • 3. More individuals are born each

    generation than can survive

    struggle for existence

    4. those with longer necks are

    more likely to survive, and pass

    this trait on to their offspring

    (variation is heritable)

    5. gradually, over many generations, necks

    became longer and longer

  • Results:

    Over time,

    average neck

    length increases

  • Homework

    Compare how Lamarck and Darwin would explain the frogs tongue for capturing food

    Use one paragraph to explain Lamarcks theory and another paragraph to explain Darwins theory.