Darwin vs. Lamarck

People believed earth was only thousands of years old and organisms did not change. However, this did not explain the fossil record that showed very different organisms living in areas in the past.

Evolution Two scientists had theories as to how organisms changed over time.

Lamarck’s Ideas Proposed the idea of acquired traits to explain the changes. Changes in environment caused an organism behavior to change creating a new physical trait.

Traits used most often would be enhanced and passed to offspring and unused would diminish and disappear in offspring

Darwin’s Ideas Argued that descent with modification occurs Darwin’s idea that small changes accumulate over generations. Proposed that Natural selection is the mechanism for evolution.

Adaptation: a variation in a hereditary trait that helps an organism survive and reproduce in its environment. Ex. Giraffes with slightly longer necks survived and reproduced

Voyage on the H.M.S Beagle Went to Galapagos Islands and noticed variations of animals were well suited to animals environment

Darwin’s Finches 13 finch species that evidence suggests descended from one original species from Ecuador

Each island had different climates and food sources Each finch species beak was best suited for eating the available food source

Darwin observed fossil and geologic evidence supporting an ancient Earth. Suggested that modern organisms have relationship to fossil forms.

Darwin said, like the Earth, organisms must some how gradually change over time