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Evolution
How do organisms change?
Some basic ideas
• Evolution is the change in characteristics
of a species over time
• Remember a species is a group of
organisms that share similar
characteristics and can reproduce
• An adaptation is anything that makes an
organism better suited to its environment
2 Theories of Evolution
• Lamarck
• Aquired
characteristics is the
idea that you will
inherit the exact traits
that your parents
have
• His theory was NOT
accepted
• Darwin
• Natural selection is
his idea
• He studied finches
and other species of
plants and animals on
the Galapagos
Islands
• His theory is accepted
Natural Selection
• This was Darwin’s hypothesis
• It is the idea that organisms with the traits
best suited to their environment will
survive and reproduce
• Variations are any adaptations that make
an individual different from others of the
same species
• Darwin's Finches & Natural Selection Biology Online
Speed of Evolution vs. Speed of
Adaptation
• Evolution
• Happens slowly
• 2 models to explain
this:
– Gradualism a slow
ongoing process
– Punctuated equilibrium
a mutation can make a
new species in a short
amount of time
• Adaptation
• Happens more
quickly
• “instant” changes
– Ex. Cold room and you
get a sweatshirt or
leaving for lunch on
the first bell
Evidence for Evolution
•
Vestigial structures: structures in the body that no longer serve a purpose
– Appendix in humans, pelvic bones in whales
•
Embryology: study of embryos and their development
•
Homologous structures: body parts that are similar in structure
– Human hand, dolphin flipper, bat wing…bones same in function too
•
DNA: similar hereditary material suggest common ancestry
•
•
Fossils: most evidence for evolution comes from these
One Species, Living Worldwide | Smithsonian Human Origins Program