Interest Grabber Section 15-1 A Trip Around the World While on his voyage around the world aboard the H.M.S. Beagle, Charles Darwin spent about one month observing life on the Galápagos Islands. There, he encountered some unique animals, such as finches and tortoises. 1. On a sheet of paper, list five animals that you have encountered in the past two days. 2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15 3 and 15 4 in your textbook.) 3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands.
Section Outline Section 15-1 15 1 The Puzzle of Life s Diversity A. Voyage of the Beagle B. Darwin s Observations 1. Patterns of Diversity 2. Living Organisms and Fossils 3. The Galápagos Islands C. The Journey Home
Voyage of the Beagle Charles Darwin was born in England on February 12, 1809. In 1831, Darwin set sail upon the H. M. S. Beagle on a voyage around the world. This voyage could be one of the most important explorations in the history of science. Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time. This hypothesis is now know as the Theory of Evolution.
Figure 15 1 Darwin s Voyage Section 15-1
Darwin s Observations On his journey, Darwin collected many different specimens of plants and animals from all over the world. Darwin was amazed with the amount of diversity that he discovered in his observations. For example, during a single day in the Brazilian forest, Darwin collected 68 different beetle species. Darwin also observed that these different organisms were extremely well suited for survival in their particular environment.
Living Organisms and Fossils Darwin soon realized that the living organisms were just a part of the puzzle. Darwin also collected preserved remains of ancient organisms called fossils. Some of these fossils resembled organisms that were still alive and other were like anything ever seen before.
The Galapagos Islands The most influential stop on Darwin s journey were the Galapagos Islands, 1000 km west of South America. Although the islands were close together, they had very different climates. Darwin was fascinated by the land tortoises and marine iguanas. The shape of the shell could be used to identify which island the turtle came from. He also collected small birds which had different shaped beaks.
Giant Tortoises of the Galápagos Islands Section 15-1
The Journey Home Darwin spent a great deal of time on his journey home studying his findings and going through his notes. He realized that the birds collected differed from island to island. The also realized that the turtles different from island to island. Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos.
Interest Grabber Section 15-2 My, How You ve Changed! Prior to the 1800s, life scientists knew that living things changed over generations. They just didn t know how these changes were brought about. 1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair. 2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument. 3. Which of the items in your lists do you think you might pass on to your children? Explain your answer.
Section Outline Section 15-2 15 2 Ideas That Shaped Darwin s Thinking A. An Ancient, Changing Earth 1. Hutton and Geological Change 2. Lyell s Principles of Geology B. Lamarck s Evolution Hypotheses 1. Tendency Toward Perfection 2. Use and Disuse 3. Inheritance of Acquired Traits 4. Evaluating Lamarck s Hypotheses C. Population Growth
An Ancient, Changing Earth Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.
James Hutton In 1975, geologist James Hutton published a hypothesis about geological forces that shaped the Earth. He proposed the rock layers formed very slowly. Some rocks are moved up by forces beneath Earth s surface, others buried, and still others are pushed up from under the ocean floor to form mountain. These are then shaped by a variety of natural forces: rain, wind, heat, and cold temperatures. Hutton proposed these processed occurred over millions of years and the Earth is a lot older than a couple thousands years old.
Charles Lyell Charles Lyell wrote a book called Principles of Geology. This book helped Darwin appreciate the significance of geological phenomena. This understanding influenced Darwin in two ways: 1. If the Earth could change over time, then life can change as well. 2. It must have taken many, many years for life to change in the way he suggested.
Movement of Earth s Crust Section 15-2 Sea level Sea level Sedimentary rocks form in horizontal layers. When part of Earth s crust is compressed, a bend in a rock forms, tilting the rock layers. As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed. New sediment is then deposited above the exposed older rock surface.
Jean-Baptiste Lamarck Lamarck believed all organisms are continually changing and acquiring features that help the live more successfully in the env t. He proposed that organisms can alter the size or shape of particular organs by using their bodies in new ways, Law of Use or Disuse. These new traits are then passed on to their offspring. Scientists have proven this ideas to be incorrect, but his work has paved the way for biologists down the road.
Figure 15 7 Lamarck s Theory of Evolution Section 15-2
Thomas Malthus In 1798, Malthus published a book that noted babies are being born faster than people dying. Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. Darwin believed this reasoning allied even more to plants and animals. An overwhelming majority of a species offspring die, and those that survive, only a few succeed in reproduction.
Interest Grabber Section 15-3 When Is a Flipper a Wing? All living things are related. Some relationships are easy to see your pet cat may not roar like a lion, but it clearly resembles one. Other relationships are less obvious.
Interest Grabber continued Section 15-3 1. On a sheet of paper, construct a table that has five columns and six rows. In the columns, write the following heads: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect. 2. Give one example for each group, and then fill in the information for that example. For Legs, write in the number of legs that each animal has. Do animals with fins have legs? Do animals with wings have legs? If so, how many? 3. Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer.
Section Outline Section 15-3 15 3 Darwin Presents His Case A. Publication of On the Origin of Species B. Inherited Variation and Artificial Selection C. Evolution by Natural Selection 1. The Struggle for Existence 2. Survival of the Fittest 3. Descent With Modification D. Evidence of Evolution 1. The Fossil Record 2. Geographic Distribution of Living Species 3. Homologous Body Structures 4. Similarities in Embryology E. Summary of Darwin s Theory F. Evolutionary Theory Since Darwin
Publication Even though Charles Darwin had notebook upon notebook filled with information that he had collected from all over the world, he was hesitant in publishing his findings. His ideas of evolution over millions of years goes against the mainstream of society at that time. Finally, in 1859, Darwin published On the Origin of Species. Darwin explanation of evolution was based on his idea of natural selection.
Inherited Variation and Artificial Selection Darwin noticed that members of each species vary from one another. He argued that these variations matter. Farmers agreed with him. They would select for breeding only the largest hogs, fastest horses, or cows that produce the most milk. Darwin called this process artificial section. In artificial selection, nature provided the variation, and humans selected those variations that they found useful.
Evolution by Natural Selection 1. The Struggle for Existence - Members of each species compete regularly to obtain food, living space, and other necessities of life. 2. Survival of the Fittest - Individuals that are better suited to their environment, have adaptations that enable fitness, survive and reproduce most successfully. - Darwin referred survival of the fittest as natural selections. 3. Decent With Modification - Each living species has descended, with changes, from other species over time.
Evidence of Evolution 1. The Fossil Record - evidence of living creatures throughout the history of Earth 2. Geographic Distribution of Living Species - Organisms exposed to similar environmental pressures evolved similar characteristics. 3. Homologous Body Structures - Structures that develop from the same embryonic tissues, but develop into very different appearance and function. 4. Similarities in Embryology - Different organism start off life as embryos that look very similar.
Concept Map Section 15-3 Evidence of Evolution includes The fossil record Geographic distribution of living species Homologous body structures Similarities in early development which is composed of which indicates which implies which implies Physical remains of organisms Common ancestral species Similar genes Similar genes
Section 15-3 Figure 15 14 Geographic Distribution of Living Species Beaver NORTH AMERICA Capybara Muskrat SOUTH AMERICA Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara Coypu
Section 15-3 Figure 15 15 Homologous Body Structures Turtle Alligator Bird Mammal Ancient lobe-finned fish
Go Online The latest discoveries in evolution Interactive test Articles on evolution For links on evolution, go to www.scilinks.org and enter the Web Code as follows: cbn-5151. For links on Darwin, go to www.scilinks.org and enter the Web Code as follows: cbn-5152. For links on natural selection, go to www.scilinks.org and enter the Web Code as follows: cbn-5153.
Interest Grabber Answers 1. On a sheet of paper, list five animals that you have encountered in the past two days. Sample answers: dogs, cats, insects, snakes, birds, and so on. 2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15 3 and 15 4 in your textbook.) Students may not see a noticeable difference between birds in their area and finches. However, the land tortoises, which are very large, would be very different from any turtles that students may have on their lists. 3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands. Sample hypothesis: Animals become well suited to their surroundings.
Interest Grabber Answers 1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair. Students should list traits that are genetically influenced. 2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument. Remind students that many features, including skills, appearance, and athletic ability, can be changed to some degree by effort. 3. Which of the items in your lists do you think you might pass on to your children? Explain your answer. Genetically influenced traits are passed on. Some items, such as musical or athletic talent, may have both inherited and learned components.
Interest Grabber Answers 1. On a sheet of paper, construct a table that has five columns and six rows. In the columns, write the following heads: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect. 2. Give one example for each group, and then fill in the information for that example. For Legs, write in the number of legs that each animal has. Do animals with fins have legs? Do animals with wings have legs? If so, how many? Fish do not have legs. Birds have two legs, while insects have six legs (three pairs). 3. Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer. It is difficult to tell from the table that a fish is more closely related to an amphibian than to a bird. Accept all reasonable explanations. Students may say that the fish is more closely related to the amphibian than to the bird because an amphibian and a fish spend time in the water.
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