Mechanisms of Evolution Chpt 6-1 Is evolution a Theory? Why is it Controversial?

Early Thoughts About Evolution Species- a group of organisms whose members successfully reproduce among themselves. Evolution- Change in the hereditary features of a species over time.

Evolution by Natural Selection Natural Selection- the organisms with traits best suited to their environments are more likely to survive.

Darwins Observations Darwin collected many plants, animals and fossils from all over the world. He was amazed at the unique plants and animals from the Galapagos Islands. Who Was Darwin

Darwins Observations Concentrated a lot of time to finches. Darwin and Finches

Darwins Observations 1.Organisms produce more offspring than can survive 2.Variations are found among individuals of a species 3.Some variations enable members of a population to survive and reproduce better than others

Darwins Observations 4. Over time, offspring of individuals with helpful variations make up more and more of a population. Darwin and Natural Selection

Variation Variation- the appearance of an inherited trait that makes an individual different from other members of the same species.

Adaptations Variations can be helpful. Adaptations are variations that are helpful Replacement of species

Sources of Variation Variations can include an organisms color, shape, behavior, or chemical makeup. Ex- camouflage

Gradualism The model that describes evolution as a slow change of one species to another new species. Ex- evolution of the horse

Punctuated Equilibrium The model of evolution that shows that rapid evolution of a species can come about by the mutation of just a few genes. Ex- mastodon evolution

Questions to Answer What is Natural Selection? Explain how the gradualism model of evolution differs from the punctuated equilibrium Model.