Evolution

1. Evolution Georgia Performance Standards: SB5b: Explain the history of life in terms of biodiversity, ancestry, and the rates of evolution. SB5d: Relate natural selection to changes in organisms. Essential Questions: Why is it important to understand evolutionary theory? What is the role of natural selection in speciation? Why are there species alive now that were not found in the past fossil record? How do fossil and biochemical evidence support the evolutionary theory?

2. Bell Work: • What would you say is the most noticeable feature on this bird? • 2. What are some possible advantages this feature gives the bird? What are some disadvantages? • 3. What changes might increase this bird’s ability to survive and • reproduce? Explain your answer.

3. What scientific explanation can account for the diversity of life? • Answer: The evolutionary theory • Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. • A theory is a well-supported testable explanation of phenomena that have occurred in the natural world.

4. Charles Darwin • During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time. • That hypothesis, now supported by a huge body of evidence, has become the theory of evolution.

5. Darwin’s Observations: • Patterns of Diversity - the many ways in which organisms survived and produced offspring. • Living Organisms and Fossils- Why had so many of these species disappeared? How were they related to living species? • The Galápagos Islands - The higher islands had greater rainfall and a different assortment of plants and animals

6. Giant Tortoises of the Galápagos Islands Section 15-1 Pinta Tower Marchena Pinta IslandIntermediate shell James Fernandina Santa Cruz Isabela Santa Fe Hood Island Saddle-backed shell Floreana Hood Isabela Island Dome-shaped shell

7. Understanding Evolution: Problem-based discussion Natural selection in Darwin’s finches 1) What characteristics of the graphs show that there was variation in the population? How much variation was in the population in 1976? How much variation was in the population in 1978? 2) What happened to the population size between 1976 and 1978? What other changes occurred in the population? 3) Based on the data, what is the approximate average beak depth of the population in each year? Ribozyme structure comes from Scott, W.G., Finch, J.T., Klug, A. (1995) The crystal structure of an all-RNA hammerhead ribozyme: a proposed mechanism for RNA catalytic cleavage. Cell 81: 991-1002

8. Understanding Evolution: Problem-based discussion Natural selection in Darwin’s finches 4) Based on these limited data, which mode of selection seems to have operated on the finches? What evidence supports this idea? 5) What do you hypothesize could have caused this change between 1976 and 1978? Describe a possible ecological relationship between drought and beak size. 6) Assume the drought continues for another 2 years,. If natural selection is occurring, what would you expect to see in future generations? If the changes in beak size are not due to natural selection, but to drift, then what would you expect to see in future generations? Ribozyme structure comes from Scott, W.G., Finch, J.T., Klug, A. (1995) The crystal structure of an all-RNA hammerhead ribozyme: a proposed mechanism for RNA catalytic cleavage. Cell 81: 991-1002

9. Ideas That Shaped Darwin's Thinking • Hutton’s Theory of Geological Change • proposed that Earth had to be much more than a few thousand years old. • Lyell’sPrinciples of Geology • Lyell’s work explained how awesome geological features could be built up or torn down over long periods of time. • Lyell helped Darwin appreciate the significance of geological phenomena that he had observed.

10. Ideas That Shaped Darwin's Thinking • This understanding of geology influenced Darwin in two ways. 1. If Earth could change over time, might life change as well? 2. Darwin realized that it would have taken many, many years for life to change in the way he suggested.

11. Lamarckproposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species. Lamarck’s ideas were incorrect in several ways (he did not know how traits are inherited) He did not know that an organism’s behavior has no effect on its inheritable characteristics. Lamarck was one of the first to develop a scientific theory of evolution and realize that organisms are adapted to their environments. He paved the way for the work of later biologists. Ideas that shaped Darwin’s Thinking:

12. Ideas that Shaped Darwin’s Thinking • Malthus& Population Growth - reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

13. Checkpoint Questions: • What two ideas from geology were important to Darwin’s thinking? • According to Lamarck, how did organisms acquire traits? • According to Malthus, what factors limited population growth? • Why has Lamarck’s theory of evolution been rejected? 5. Malthus formed his theory by studying factors that control the population growth of humans. How might factors operating on organisms in nature differ from those of Malthus’s theory?

14. Darwin’s Conclusions: • On the Origin of Species. • In his book, he proposed a mechanism for evolution that he called natural selection. • He then presented evidence demonstrating that the process of evolution has been taking place for millions of years—and continues in all living things.

15. Darwin’s Conclusions: • Natural variation, defined as differences among individuals of a species, is found in all types of organisms. Variation is present in species in nature • Artificial selection, nature provided the variation among different organisms, and humans selected those variations that they found useful.

16. Darwin’s Conclusions: • Evolution by Natural Selection • struggle for existencemeans that members of each species compete regularly to obtain food, living space, and other necessities of life. • The ability of an individual to survive and reproduce in its specific environment fitness, which is the result of adaptations. • An adaptation is any inherited characteristic that increases an organism’s chance of survival. • Successful adaptations enable organisms to become better suited “Fit” to their environment and thus better able to survive and reproduce .

17. Darwin’s Conclusions: • Individuals that are better suited to their environment—that is, with high levels of fitness—survive and reproduce most successfully. • This was a process that Darwin called survival of the fittest. • Because of its similarities to artificial selection, Darwin referred to the survival of the fittest as natural selection. • In both artificial selection and natural variation, only certain individuals of a population produce new individuals

18. Darwin’s Conclusions: • Over time, natural selection results in changes in the inherited characteristics of a population. • These changes increase a species’ fitness in its environment. • Natural selection cannot be seen directly; it can only be observed as changes in a population over many successive generations.

19. Summary of Darwin’s Theory • Natural Selection is always taking place: Because more organisms are produced than can survive, members of each species must compete for limited resources. • Struggle to survive: Because each organism is unique, each has different advantages and disadvantages in the struggle for existence. • Variation among offspring: Individual organisms in nature differ from one another. Some of this variation is inherited. • Living things overproduce: Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce.

20. Summary of Darwin’s Theory • Individuals best suited to their environment survive and reproduce most successfully. • Species change over time. • Species alive today have descended with modifications from species that lived in the past. • All organisms on Earth are united into a single tree of life by common descent.