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Transcript of Unit 5 Lesson 1 Theory of Evolution by Natural Selection Copyright © Houghton Mifflin Harcourt...
Unit 5 Lesson 1 Theory of Evolution by Natural Selection
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 5 Lesson 1 Theory of Evolution by Natural Selection
Florida Benchmarks
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• 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.
Unit 5 Lesson 1 Theory of Evolution by Natural Selection
Florida Benchmarks
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• 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.
Darwin’s Voyage
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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.
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.
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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.
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Unit 5 Lesson 1 Theory of Evolution by Natural Selection
Darwin’s Homework
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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.
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.
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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.
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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.
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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.
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Unit 5 Lesson 1 Theory of Evolution by Natural Selection
Natural Selection
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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.
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.
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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.
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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.
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Unit 5 Lesson 1 Theory of Evolution by Natural Selection
Well-adapted
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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.
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.
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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.
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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.
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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.
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Unit 5 Lesson 1 Theory of Evolution by Natural Selection