Evolutionary Theory: Tracing the History of Life and Biodiversity

1. Chapter 15: Evolution Georgia Performance Standards: Trace the history of evolution Explain the history of life in terms of biodiversity, ancestry, and the rates of evolution Explain how fossil and biochemical evidence support the theory Relate natural selection to changes in organisms • Essential Questions: • Why are there species alive now that were not found in the past fossil record? • Why is important to understand evolutionary theory? • How does fossil and biochemical evidence support the evolutionary theory? • What is the role of natural selection in speciation? • Do individuals evolve?

2. 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.

3. 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.

4. 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

5. 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

6. 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.

7. 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.

8. 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:

9. 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.

10. 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?

11. 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.

12. 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.

13. 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 to their environment and thus better able to survive and reproduce

14. 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

15. 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.

16. Descent With Modification • Natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. • As a result, species today look different from their ancestors. • Each living species has descended, with changes, from other species over time. • If we look far enough back, the logic concludes, we could find the common ancestors of all living things. This is the principle known as commondescent.

17. Fossil record - by examining fossils from sequential layers of rock, one could view how a species had changed and produced different species over time, as shown in the figure at right. Geographical distribution of living species Biochemistry Similarities in Embryonic Development Homologous structures of living organisms structures that have different mature forms in different organisms but develop from the same embryonic tissues Not all homologous structures serve important functions. Vestigial organs (the organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. 15.2: Evidence of Evolution:

18.  Homologous Body Structures Section 15-3 Turtle Alligator Mammals Bird Typical primitive fish

19. The fossil record Geographic distribution of living species Homologous body structures Similaritiesin early development Physical remains of organisms Common ancestral species Similar genes Similar genes Concept Map Section 15-3 Evidence of Evolution includes which is composed of which indicates which implies which implies

20. Summary of Darwin’s Theory • Individual organisms in nature differ from one another. Some of this variation is inherited. • Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce. • Because more organisms are produced than can survive, members of each species must compete for limited resources. • Because each organism is unique, each has different advantages and disadvantages in the struggle for existence.

21. Summary of Darwin’s Theory • Individuals best suited to their environment survive and reproduce most successfully. The characteristics that make them best suited to their environment are passed on to offspring. Individuals whose characteristics are not as well suited to their environment die or leave fewer offspring. • Species change over time. Over long periods, natural selection causes changes in the characteristics of a species, such as in size and form. New species arise, and other species disappear. • 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.

22. Checkpoint Questions: • How is artificial selection dependent on variation in nature? • The theory of evolution by natural selection explains, in scientific terms, how living things evolve over time. What is being selected in this process? • What types of evidence did Darwin use to support his theory of change over time? • What is the “struggle for existence”? How was this idea based on Malthus’s work? • Compare and contrast Darwin’s theory of evolution with that of Lamarck. How are they similar? How are they different?

23. Checkpoint Questions: • What is macroevolution? Describe two patterns of macroevolution. • What role have mass extinctions played in the history of life? • Use an example to explain the concept of coevolution. • How might hox genes contribute to variation? • Compare and contrast the theories of gradualism and punctuated equilibrium.