Darwin and Natural Selection Intro: Why does evolution matter now? http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html http://www.pbslearningmedia.org/resource/tdc02.sci.life.evo.whymatters/evolving-ideas-why-does-evolution-matter-now/ CHARLES DARWIN

Discuss with a Partner What do you think biological evolution is? Do you have any opinions about it? What do you think natural selection is? How do you think it works?

The voyage of the HMS Beagle 1831, when Darwin was 22 years old

The Galapagos Islands and Darwin’s Finches Short video about Darwin’s finches https://www.youtube.com/watch?v=l25MBq8T77w Intro (describes Darwin’s voyage) and 10:54 of “Unlocking the Mysteries of life” (shows finches feeding)

Natural Selection: Darwin’s idea In nature, organisms produce more offspring than can survive. This results in a struggle for survival Example: Fishes A single female cod can lay millions of eggs Atlantic cod

Variation exists in all populations Note: variation is heritable (genetic) Example: fish differ in color, size and speed

3. Individuals with useful variations survive and pass those traits (alleles) on to their offspring. Any useful variation that helps an organism to survive and reproduce is called an adaptation. Example: fast fish escape predators, survive and produce more fast fish.

4. Over time, organisms with certain variations become the majority and the population may look very different from the ancestral population

Natural Selection (summary) The environment acts on variations in a population, causing genetic change over time.

Watch the video and compare the concepts to your notes http://www.pbslearningmedia.org/resource/tdc02.sci.life.evo.howreally/evolving-ideas-how-does-evolution-really-work/

Quick Activity! Questions! Choose a number between 1 and 4 (show with fingers) Simulate natural selection by adding antibiotic to kill off those who are less resistant (by number) Allow survivors to reproduce (pick dead neighbor to be like them). Questions! Explain how the activity illustrates natural selection in your assignments notebook! Create your own example of natural selection and explain it! If you lift weights and get really strong, will your kids be really strong and therefore more likely to survive? Explain your answer.

There are three types of Natural Selection: Stabilizing Selection Directional Selection Disruptive Selection

Stabilizing Selection Type of selection in which… average individuals are favored (selected for) Extreme forms of a trait are selected against.

Example of Stabilizing Selection: Spiders Large spiders are easily seen and eaten by birds Small spiders can’t compete for food Medium size spiders are selected for

Directional Selection Type of selection in which… one extreme form of a trait is favored (selected for).

Example of Directional Selection: Woodpeckers A type of insect lives deep within the bark of trees Woodpeckers with short or average-size beaks can’t get to these insects Long-beaked woodpeckers are selected for

Disruptive Selection Type of selection in which… BOTH extreme forms of a trait are favored (selected for) Average individuals are selected against.

Example of Disruptive Selection: Limpets Limpets are snails that live attached to rocks in the tidepools Limpets range in color from white to tan to dark brown White colored limpets have the advantage on light-colored rocks Dark brown limpets dark-colored rocks

Which type of natural selection is shown in each graph? 1 2 3

How is Natural Selection related to Evolution? It is an important mechanism by which evolution occurs

Check your understanding For each of the following examples, tell me which type of selection it would be. Imagine a population of mice living at the beach where there is light-colored sand interspersed with patches of tall grass. Light-colored mice blend in with the sand and dark-colored can hide in the grass. Medium-colored mice would not blend in with either the grass or the sand and, thus, would more probably be eaten by predators. If thicker-shelled oysters are more resistant to breakage than thinner-shelled oysters, crabs will be less able to prey upon them, and thicker-shelled oysters will be more likely to survive to reproduce. Most robins lay 4 eggs. Larger clutch sizes result in malnourished chicks, while smaller clutch sizes may result in no viable offspring surviving.

For the following videos, determine which type of natural selection is occuring. Justify your conclusion. HIV and Natural Selection https://www.youtube.com/watch?v=34GeUa7RzvY skip first 35 seconds (Evolution and AIDS) Toxic Newts: http://www.pbslearningmedia.org/resource/tdc02.sci.life.evo.toxicnewts/toxic-newts/