Unit 5 Lesson 1 Theory of Evolution by Natural Selection Copyright © Houghton Mifflin Harcourt Publishing Company 1

Unit 5 Lesson 1 Theory of Evolution by Natural Selection Florida Benchmarks SC.7.L.15.1 Recognize that fossil evidence is consistent with the scientific theory of evolution that living things evolved from earlier species. SC.7.L.15.2 Explore the scientific theory of evolution by recognizing and explaining ways in which genetic variation and environmental factors contribute to evolution by natural selection and diversity of organisms. Copyright © Houghton Mifflin Harcourt Publishing Company 2

Unit 5 Lesson 1 Theory of Evolution by Natural Selection Florida Benchmarks SC.7.L.15.3 Explore the scientific theory of evolution by relating how the inability of a species to adapt within a changing environment may contribute to the extinction of that species. LA.6.4.2.2 The student will record information (e.g., observations, notes, lists, charts, legends) related to a topic, including visual aids to organize and record information and include a list of sources used. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Darwin’s Voyage What did Darwin observe? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Darwin’s Voyage What did Darwin observe? Evolution is the process in which populations gradually change over time. A scientist named Charles Darwin developed a theory of how evolution takes place. Darwin formed the theory with the observations that he had made on an almost five-year journey. Copyright © Houghton Mifflin Harcourt Publishing Company 4

What did Darwin observe? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What did Darwin observe? On his journey, Darwin observed and collected many living and fossil specimens. Darwin made his most influential observations on the Galápagos Islands of South America. Copyright © Houghton Mifflin Harcourt Publishing Company 5

What did Darwin observe? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What did Darwin observe? Darwin collected birds from the Galápagos Islands and nearby islands. The birds on each island were different from the birds on the other islands, and all were different from the birds on the mainland. Darwin wondered if the birds had evolved from one species of finch. Copyright © Houghton Mifflin Harcourt Publishing Company 6

Darwin’s Homework What other ideas influenced Darwin? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Darwin’s Homework What other ideas influenced Darwin? Darwin was influenced by the ideas of many scientists. These helped him develop his theory about how populations change over time. Farmers and breeders select plants or animals for breeding based on desired traits. This is called artificial selection. A trait is a form of an inherited characteristic. Copyright © Houghton Mifflin Harcourt Publishing Company 7

What other ideas influenced Darwin? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What other ideas influenced Darwin? Scientist Jean-Baptiste Lamarck thought that organisms could bring about the changes they needed to survive in the environment. He did not know that acquired traits do not become part of an organism’s DNA and the traits cannot be passed to the offspring. His idea that organisms’ traits help them survive influenced Darwin’s theory. Copyright © Houghton Mifflin Harcourt Publishing Company 8

What other ideas influenced Darwin? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What other ideas influenced Darwin? Geologist Charles Lyell theorized that small changes in rock have collected over hundreds of millions of years. Darwin reasoned that if Earth were very old, then there would be enough time for very small changes in life forms to collect over a very long period of time as well. Copyright © Houghton Mifflin Harcourt Publishing Company 9

What other ideas influenced Darwin? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What other ideas influenced Darwin? Darwin read an essay by Thomas Malthus that suggested populations are limited by food resources, disease, competition, and predation. Copyright © Houghton Mifflin Harcourt Publishing Company 10

What other ideas influenced Darwin? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What other ideas influenced Darwin? Darwin reasoned that survivors probably had traits that helped them survive in their environment. Darwin thought that some of these traits would be inherited by the offspring of the survivors. Copyright © Houghton Mifflin Harcourt Publishing Company 11

Natural Selection What are the four parts of natural selection? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Natural Selection What are the four parts of natural selection? Natural selection is the process by which organisms that inherit advantageous traits tend to reproduce more successfully. Plants and animals can overproduce, meaning that they make more offspring than the environment can support. Only some of them will successfully reproduce. Copyright © Houghton Mifflin Harcourt Publishing Company 12

What are the four parts of natural selection? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What are the four parts of natural selection? Within a species there are natural differences, or variations, in traits. Variations come from differences in genetic material and can make an individual better able to survive. Genetic variation is important for the survival of a species. Copyright © Houghton Mifflin Harcourt Publishing Company 13

What are the four parts of natural selection? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What are the four parts of natural selection? Individuals of a species try to get the resources they need to survive. Darwin reasoned that individuals with a certain trait might be more likely to survive long enough to reproduce. As a result, the trait is “selected,” or is more common in the next generation of offspring. Copyright © Houghton Mifflin Harcourt Publishing Company 14

What are the four parts of natural selection? Unit 5 Lesson 1 Theory of Evolution by Natural Selection What are the four parts of natural selection? An adaptation is an inherited characteristic that helps an organism survive and reproduce in its environment. As natural selection repeats from generation to generation, these adaptations become more common. Over time, a population becomes better adapted to the environment. Copyright © Houghton Mifflin Harcourt Publishing Company 15

Well-adapted How do species change over time? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Well-adapted How do species change over time? An incredible diversity of life exists because species have changed over time, or evolved. Populations evolve by becoming better adapted to their environment by the process of natural selection. Copyright © Houghton Mifflin Harcourt Publishing Company 16

How do species change over time? Unit 5 Lesson 1 Theory of Evolution by Natural Selection How do species change over time? Sometimes a population changes so much that the population becomes a new species. Some of the adaptations that help species survive are behaviors that help them to find food, protect themselves, or reproduce. Copyright © Houghton Mifflin Harcourt Publishing Company 17

Why is adaptation important for survival? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Why is adaptation important for survival? The traits that help an organism survive depend on both the needs of the species and environmental factors. Different environments have different factors. A green snake has a better chance of surviving to reproduce in green grass than on a brown forest floor. Copyright © Houghton Mifflin Harcourt Publishing Company 18

Why is adaptation important for survival? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Why is adaptation important for survival? Changes in environmental conditions can affect the survival of individuals with a particular trait. If no individuals are born with traits that help them to survive and reproduce in the changed environment, the species will become extinct. Copyright © Houghton Mifflin Harcourt Publishing Company 19

Why is adaptation important for survival? Unit 5 Lesson 1 Theory of Evolution by Natural Selection Why is adaptation important for survival? Extinction is when all of the members of a species have died. The fossil record shows that many species have become extinct in the course of the history of life on Earth. Copyright © Houghton Mifflin Harcourt Publishing Company 20