Natural Selection Enviro 2 Go 6.2.4.2 6.2.4.3 6.2.4.4

Natural Selection Objective- You should be able to: Explain how species change overtime Define natural selection Describe Charles Darwin’s observations Describe the peppered moth case study

Natural Selection Important Vocabulary Variation Adaptation Traits Survival of the Fittest Evolution Natural Selection

Natural Selection An important process in explaining how species change overtime. Helps maintain healthy populations.

Charles Darwin’s Observations 1. Organisms have the ability to produce more offspring than can usually survive.

Charles Darwin’s Observations 2. Members of the same species normally have slight differences called variations. (They are not all identical!)

Charles Darwin’s Observations 3. Members of a species must compete with each other and with other species to survive. Some organisms cannot successfully compete for limited resources.

Charles Darwin’s Observations 4. Some members of a species have traits that are helpful for survival, called adaptations. Other traits are not helpful for survival.

Charles Darwin’s Observations 5. Those organisms with traits that are helpful for survival are more likely to survive and reproduce than those without these traits.

Charles Darwin’s Observations 6. The ability to successfully reproduce establishes the population for the next generation.

Survival of the Fittest Natural selection is sometimes referred to as “survival of the fittest.” Being “fit” means that an organism has adaptations, traits that help it to survive. More importantly, being “fit” means that the organisms are able to pass their genes onto the next generation.

Survival of the Fittest Examples: A faster cheetah might be more fit than a slower cheetah Better camouflage Certain behaviors Other traits to aid in survival

Remember This!!! Natural Selection explains how a species may change over time. The change is created because of successful reproduction. The organism most “fit” for an environment is most likely to be the one to successfully reproduce and have offspring that mature into adults and reproduce.

Natural Selection Animation Watch the following animations about natural selection. Evolution: How Does Evolution Really Work?

Interesting Science Fact After talking to local farmers, Charles Darwin discovered that the farmers had been using artificial selection for centuries. The farmers and ranchers never allowed their stock to reproduce on their own. Instead the farmers and ranchers always allowed their best plants and animals to reproduce, but did not allow the weak ones to reproduce. This type of reproduction creates stronger, better produce and livestock.

The Process of Natural Selection Traits are passed from parents to offspring Those organisms that survive pass on the genes for those traits that helped them survive. Organisms without those traits helpful for survival are less likely to reproduce, so their genes are not likely to be passed on to the next generation. Organisms that can survive long enough to reproduce are able to determine the characteristics of the next generation.

??? Questions ??? How does the successful reproduction of an organism affect the next generation? How does the unsuccessful reproduction of an organism affect the next generation?

Remember This!!! Only those organisms able to reproduce affect the next generation. Organisms that reproduce pass their unique traits in the form of genes on to the next generation; therefore the next generation inherits genes that helped the previous generation to survive.

Natural Selection and the Environment If the environment stays the same, then natural selection favors organisms with certain adaptations. Organisms with these adaptations (traits) survive and reproduce. Organisms that do not possess these traits may not survive long enough to reproduce. The population adjusts to the environment over time through reproduction or the failure to reproduce.

Natural Selection and the Environment What happens if the environment changes? When the environment changes (which it almost always is), then other adaptations might be favored. The traits that helped an organism survive in one environment may not help in another situation.

Natural Selection and the Environment Example: Peppered Moth Study There are two types of peppered moths: White Dark Normally, they are found in equal amounts in forested areas of England. During the Industrial Age, the white variety almost became extinct in areas around the factories because the factories produced large amounts of black soot that covered everything for miles.

Natural Selection and the Environment Peppered Moth Continues… The dark moths were able to hide on trees and it became hard for their predators to find them. The white variety was very easy to see and the predators had no trouble finding and eating them. Therefore, only the dark moths survived long enough to reproduce.

Natural Selection and the Environment And the Pepper Moth Story continues… As the environment changed, it favored the dark color over the white color. In areas where the environment had not changed, both moth variations were found with the same population numbers. The environment determined which variation would survive long enough to reproduce. The next generations were almost exclusively dark colored peppered moths.

??? Questions ??? 3. Predict what might happen to the population of the white and dark moths if the factories covered the landscape with a white soot instead of a black soot. 4. Explain how a changing environment affects the population of the organisms living in that area. 5. Compare how a changing population and a non-changing population affect the organisms that live in the area.

Evolution There is much evidence that the Earth has changed greatly over the last 4.6 billion years. Natural selection has continually favored the survival of organisms with adaptations that make them suited to their environment. However, since the environment has changed, the species have changed. This is referred to as evolution.

Test Yourself: Matching Test Yourself: Matching ________ 1. natural selection ________ 2. variation ________ 3. adaptations ________ 4. fit ________ 5. survival of the fittest Traits that help an organism survive An organism that has adaptations A phrase to describe natural selection The process that explains how species change over time Differences among individuals of the same species

Test Yourself: True or False _____ 1. In order to understand natural selection, several observations must be understood together. _____ 2. Organisms have the ability to produce very few offspring. _____ 3. Organisms have the ability to produce more offspring than can usually survive. _____ 4. Variations are traits that help an organism survive. _____ 5. Variations are traits that do not help an organism survive. _____ 6. Variations are differences among members of the same species. _____ 7. All members of the same species are identical. _____ 8. Members of a species must compete only with organisms of other species. _____ 9. Members of a species must compete with members of their own species and members of other species.

Test Yourself: True or False Cont. ______ 9. Members of a species must compete with members of their own species and members of other species. ______ 10. Adaptations are traits that do not help an organism survive. ______ 11. Adaptations are differences among members of the same species. ______ 12. Adaptations are traits that help an organism survive. ______ 13. Organisms have an equal chance of surviving and reproducing. ______ 14. Organisms with adaptations have a better chance of surviving and reproducing than organisms without adaptations. ______ 15. A fit organism is more likely to survive and reproduce than a less fit organism. ______ 16. Evolution is the changing of species over time. ______ 17. Natural selection has little to do with evolution. ______ 18. Natural selection explains how species can change over time.

Test Yourself: Fill in the Blank Natural selection evolution fit Adaptation variation survive Reproduction compete ______________ is the process often describe as “survival of the fittest.” _____________ is the changing of species over time. Organisms must _______________ to survive. Those organisms that are more ________ have more traits that help them survive. A trait that helps an organism survive is called an __________________. Since there is ______________ in a population, not all organisms are identical. Some organisms are more likely to ________ because of their adaptations. Organisms that survive long enough to _______________ can pass on the genes for their adaptations to their offspring.

Test Yourself: Short Answer What is a variation? 2. What is an adaptation? Give an example. 3. What are the five observations that explain natural selection? 4. How does natural selection change a population?

The End!!!