Darwin’s Theory

Rate Yourself• 4 Apply concepts of natural selection and

evolution by creating a scenario that demonstrates the ideas

• 3 Explain ways in which genetic variation and environmental factors contribute to evolution.

• 2 Explore the cause and effect of natural selection and evolution.

• 1 Identify ways genetic variation and environmental factors contribute to evolution.

Who was Charles Darwin?

• His observations of plants and animals led him to develop the theory of evolution by natural selection.

What is a species?

• A group of similar organisms that can mate with each other and produce fertile offspring.

What did Darwin notice on the Galapagos Islands?

• Many of the plants and animals on the Galapagos were similar to organisms on mainland South America.

• However, there were also important differences between the organisms on the islands and those on the mainland.

What did Darwin conclude led to the differences between species?

• After studying the different finches on the Galapagos Islands Darwin concluded that their different beak shape was due to an adaptation.• Adaptation – A trait

that helps an organism survive and reproduce.

What did Darwin start to believe was occurring amongst the different species?

• Darwin thought the species gradually changed over many generations and became better adapted to the new conditions.• Evolution – the gradual

change in a species over time.

Why was Darwin’s idea considered a scientific theory?

• It was a well-tested concept that explains a wide range of observations.

Pair-Share

•What do you already know about evolution?

•What evidence supports the theory of evolution?

What is Natural Selection?

• The process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

What are the factors that affect the process of natural selection?

• Overproduction• Competition• Variations

How does overproduction affect natural selection?

• So many species are produced that there are not enough resources (food, water, and living space).

How does competition affect natural selection?

• Since food and other resources are limited, the offspring must compete in order to survive.

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How do Variations affect natural selection?

• Any difference between individuals of the same species is called a variation.• Some variations of a

species may provide an advantage over the other members of the species without the variation.

Pair-Share

• What factors affect natural selection?

• Pick one factor and explain to your partner why your factor affects natural selection?

How is natural selection related to evolution?

• Over a long period of time, natural selection can lead to evolution.• Helpful variations gradually

accumulate in a species, while unfavorable ones disappear.

What role do genes “play” in evolution?

• Darwin did not know anything about genes or mutations so he could not explain what caused the variations or how they were passed on.• Only traits that are

inherited, or controlled by genes, can be acted upon by natural selection.

Rate Yourself• 4 Apply concepts of natural selection and

evolution by creating a scenario that demonstrates the ideas

• 3 Explain ways in which genetic variation and environmental factors contribute to evolution.

• 2 Explore the cause and effect of natural selection and evolution.

• 1 Identify ways genetic variation and environmental factors contribute to evolution.