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 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.

Evolution by Natural Selection 1. Every species produce more offspring than will survive to maturity. 2. Natural variation Differences among individuals 3. Struggle for existence Compete 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

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