EVOLUTION Chapter 15

Question for Thought Earth has millions of other kinds of organisms of every Earth has millions of other kinds of organisms of every imaginable shape, size, and habitat. imaginable shape, size, and habitat. This variety of living things is called biological diversity. How did all these different organisms arise? How are they related? How are they related?

I. Darwin’s Theory of Evolution A. EvolutionA. Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. A. Evolution 1. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world. 1. A scientific theory is a well-supported testable explanation of phenomena that have occurred in the natural world.theory

B. Voyage of Beagle 1. Dates: February 12th, Captain: Charles Darwin 3. Ship: H.M.S. Beagle 4.Destination: Voyage around the world. 5. Findings: evidence to propose a revolutionary hypothesis about how life changes over time

C. Patterns of Diversity 1.Darwin visited Argentina and Australia which had similar grassland ecosystems. a. those grasslands were inhabited by very different animals. b. neither Argentina nor Australia was home to the sorts of animals that lived in European grasslands.

D. Living Organisms and Fossils 1. Darwin collected the preserved remains of ancient organisms, called fossils. fossils 2. Some of those fossils resembled organisms that were still alive today.

Living Organisms and Fossils 3. Others looked completely unlike any creature he had ever seen. 3. Others looked completely unlike any creature he had ever seen. 4. As Darwin studied fossils, new questions arose. a. Why had so many of these species disappeared? b. How were they related to living species?

Fossils

E. The Galapagos Island 1. The smallest, lowest islands were hot, dry, and nearly barren-Hood Island-sparse vegetation 2. The higher islands had greater rainfall and a different assortment of plants and animals-Isabela- Island had rich vegetation.

3. Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galápagos. a. Giant tortoises varied in predictable ways from one island to another. b. The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited.

4.Animals found in the Galapagos a. Land Tortoises b. Darwin Finches c. Blue-Footed Booby d. Marine Iguanas

Animals

F. The Journey Home 1. Darwin Observed that characteristics of many plants and animals vary greatly among the islands a. Hypothesis: Separate species may have arose from an original ancestor

G. Lamarck’s Theory of Evolution 1Tendency toward Perfection(Giraffe necks) a. Use and Disuse (bird’s using forearms) b. Inheritance of Acquired Traits

II. Natural Selection & Artificial Selection *Natural variation--differences among individuals of a species *Artificial selection- nature provides the variation among different organisms, and humans select those variations they find useful.

A. Evolution by Natural Selection 1. The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities 2. Survival of the Fittest-Some individuals better suited for the environment

Struggle For Existence & Survival of The Fittest

3. Over time, natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment

B. Descent 1. Descent with Modification-Each living organism has descended, with changes from other species over time 2. Common Descent- were derived from common ancestors

C. Evidence for Evolution 1. The Fossil Record- Layers show change

2. Geographic Distribution of Living Things-similar environments have similar types of organisms

3. Homologous Structures -structures that have different mature forms in different organisms, but develop from the same embryonic tissue

4. Vestigial organs-organs that serve no useful function in an organism i.e.) appendix, miniature legs, arms

5. Similarities in Early Development

D. Summary of Darwin’s Theory 1. Individuals in nature differ from one another (variation) 2. Organisms in nature produce more offspring than can survive, and many of those who do not survive do not reproduce.

Summary of Darwin’s Theory 3. Because more organisms are produced than can survive, each species must struggle for resources 4. Each organism has advantages and disadvantages in the struggle for existence

Summary (cont.) 5. Individuals best suited for the environment survive and reproduce most successful 6. Species change over time

Summary (cont.) 7. Species alive today descended with modification from species that lived in the past 8. All organisms on earth are united into a single family tree of life by common descent