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What is natural selection? It’s the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory.

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Presentation on theme: "What is natural selection? It’s the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory."— Presentation transcript:

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2 What is natural selection? It’s the process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully explained by Charles Darwin and is now believed to be the main process that brings about evolution.

3 Darwin: Process of Natural Selection: 1.Living things face a constant struggle for survival. 2.Only strong individuals survive to reproduce. 3.Causes genetic changes gradually over many generations. 4.Species adapt or become better suited to their environment.

4 What is an adaptation? Is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats

5 What is evolution? A gradual process in which something changes into a different and usually more complex or better form.

6 What evidence do we have of evolution? The fossil record provides evidence to support the theory of evolution. A scientific theory is a well-tested concept that explains a wide range of observations. The fossil record shows that millions of types of organisms have evolved. But many others have become extinct. We can look at fossils and see changes in the features of animals over time.

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9 Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

10 Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

11 Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

12 Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

13 Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

14 Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

15 Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

16 Natural Selection Rests on 4 Premises: 3) Traits have a genetic basis, or are inherited from parents

17 Natural Selection Rests on 4 Premises: 3) Traits have a genetic basis, or are inherited from parents

18 Natural Selection Rests on 4 Premises: 4) Advantageous traits, which allows organisms to have more offspring, will become more common in the population over time.

19 Examples of Natural Selection: The Evolution of The Polar Bear Our story begins with the Polar Bear’s closest living relative – the Brown Bear

20 The Evolution of The Polar Bear Around 300,000 years ago a small group of Brown Bears became reproductively isolated from the rest of the population

21 The Evolution of The Polar Bear This small founding population of Brown Bears were able to survive and reproduce living in the Arctic Tundra. After MANY generations, a random genetic mutation occurred...

22 The Evolution of The Polar Bear Because of the genetic mutation, a litter of Brown Bears exhibited WHITE coloration

23 The Evolution of The Polar Bear How do you think the white fur color affected these bears chances of surviving long enough to have cubs of their own?

24 Answer this question on a blank sheet of lined paper. Then, you must write a 4-5 sentence summary about today’s notes IN YOUR NOTEBOOK!!! Explain in 4-5 sentences why a characteristic that helps an animal to live longer tends to become more popularin the population over time. Be sure to explain what evolution by natural selection has to do with it.


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