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 Progr

am