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

Darwin’s Observations

• Concentrated a lot of time to finches.

Darwin and Finches

Darwin’s 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

Darwin’s 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 organism’s 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.