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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
