LAMARCK AND DARWIN Pages 297-299

HOW DO ORGANISMS CHANGE OVER TIME?

•Why do giraffes have long necks?

•How did giraffes get long necks?

EARLY EVOLUTION IDEAS

•People did not know the true age of the Earth and thought that organisms did not change over time

•This idea did not explain why fossils were being found that looked very different than current organisms

EARLY EVOLUTION IDEAS

•Buffon (1760s) started noticing that some animals had similar bone structure and this lead him to believe that all these animals came from an ancient common ancestor

•His student Lamarck came up with the first idea of how this change happened

EVOLUTION

•Development of new types of organisms from preexisting organisms over time.

LAMARCK

•Came up with the idea of acquired traits to explain changes seen over time

•Changes in environment caused an organism’s behavior to change, creating a new trait

LAMARCK

•Organisms strive to improve themselves, the organism was responsible for its own changes

•Unused body structures waste away and are not passed on

•Once a structure is modified, it would be inherited by its offspring

CHARLES DARWIN

•Went on a 5 year journey on the H.M.S. Beagle where he collected many artifacts

CHARLES DARWIN

•One stop was the Galapagos Islands

•He noticed that the variations in animals were well suited to the environment they lived in

•Variation: differences in physical traits

DARWIN’S IDEAS

•The trait that is more beneficial for survival became more common (the environment was determining which trait was best,

not the organism)

•Ex. Giraffes with slightly longer necks survived and reproduced

DARWIN’S IDEAS

•Said that organisms have adapted to their surroundings

Darwin’s Finches – 13 finch species that were each well adapted to their environment

-evidence suggests they descended from one original species from Ecuador

DARWIN’S IDEAS

•After his voyage and looking at fossils, he determined that organisms must change gradually over time

•He described this as descent with modification

•Proposed that natural selection is the mechanism for change over time