Chapter 15

Evolution: Evidence and Theory

“The mechanisms of evolution are debated, not the fact that it has occurred and is occurring”

Charles Darwin

Proposed the theory that organisms evolve, or change over time by natural selection.

Darwin’s voyage was on the H.M.S Beagle. He was only 22 years old.

                                                                                                                                                                                                    

Darwin made many of his observations on the Galapagos Islands.

Darwin found similar birds with different shaped beaks.

Darwin noted that tortoises from different island had different shell shapes.

Darwin began to wonder if the animals living on different islands had once belonged to the same species.

These different species would have evolved from a common ancestor.

For Darwin’s theory of evolution by natural selection to work, Earth would have to be very old and change slowly over time.

Hutton and Lyell proposed that geological forces shaped the Earth over Millions of years.

The Origin of Species

Darwin publishes

his theory 25 years

after his voyage on

the Beagle.

1. Every species produce more offspring than will survive to maturity.

2. Natural variationDifferences among individuals

3. Struggle for existenceCompete for food, shelter, etc

4. Survival of the fittest Fitness = The ability to Survive & reproduce Adaptation = anything that increase the

chance an organism will survive

Evolution by Natural Selection

Evidence of Evolution

1. Homologous structures 2. Vestigial structures

appendix “tail bone” muscles that move the ears

3. Similarities in early development

4. Similarities in macromolecules