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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