Natural Selection in Action-Dennis Y

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Title: Natural Selection in Action

Principle(s) Investigated: Natural Selection, Survival of the Fittest

Standards :

7^th Grade:

Evolution

a. Students know both genetic variation and environmental factors are causes of evolution and diversity of organisms.

b. Students know the reasoning used by Charles Darwin in reaching his conclusion that natural selection is the mechanism of evolution.

12^th grade:

a. Students know how natural selection determines the differential survival of groups of organisms.

b. Students know a great diversity of species increases the chance that at least some organisms survive major changes in the environment.

Materials: forks, knives, spoons, forceps, paper clips, beans, paper plates, plastic cups

Procedure:

1) Prepare all the materials for each station. Provide one type of tool per group-fork, knife, spoon, forceps, paper clip plus one plastic cup and paper plate with beans. Fill each paper plate with beans (pinto beans work great)

2) Divide students into groups of 5(or depending on how many tools you use) and ask them to pick one tool (fork, knife, spoon, forceps, and paper clip). That tool will represent the beak of a finch in the Galapagos. Explain that the finches that Darwin found had different traits depending on their location. The beans will represent food that each bird feed on.

3) One person will use their tool at a time. For 20 seconds, the student will pick the beans from the plate and place them into the cup. They will do it as fast as they can. The instructor will use a stopwatch to keep time. After each 20 second period, the student will count the number of beans transferred to the cup.

4) The students will log into their worksheet the number of beans for each tool.

5) Repeat for all 5 different tools. Compare the data for all 5 groups.

Student prior knowledge: Individuals in a certain population have variations.

Explanation:

Each tool represents different type of beaks of finches found in the Galapagos Islands. The action of picking up beans from the cup is analogous to the finches feeding. Certain tools perform better in picking up beans from the plate. The same thing is true with the beaks of the finches. Some are better adapted to feeding a certain type of plants. The most successful tool represents the most adaptive beak for that environment. As a result, more of the finches with the most advantageous beaks will live on and reproduce and there will be more of such traits in the population. In contrast, the least successful beaks will decline in number due to unsuccessful feeding. Eventually, the finches with the most adaptive beak will continue to survive and reproduce. This is "survival of the fittest". The most adapted finch is the "fittest" one to survive. In the demonstration, we see in action that certain tools are better at picking up beans just as certain beaks are better at feeding certain plants on the island.

Questions & Answers:

1) Are evolution and "survival of the fittest" the same thing?

They are related but not the same thing. Evolution is a process that results in changes in a population. It is a change in gene frequencies over time. Survival of the fittest, on the other hand, refers to the mechanism (natural selection) that brings about change.

2) How would you describe the principles of Natural Selection?

1-Traits vary in a population.

2-These traits are then inherited from one generation to the next

3-There are more offspring than resources in the environment

4-Due to limited natural resources, only some offspring will survive.

Therefore, the individuals with the most adaptive trait will survive and reproduce and thus accumulating more favorable traits in the population.

3) Can Natural Selection work against the survival of an individual?

This can indeed happen. The elaborate plumage of the male peacock makes them less likely to survive due to predation. However, Natural Selection still selects for traits that will enhance the likelihood of perpetuating your genes. In this case, the female peacock instinctively sees that the male peacock is still alive and has such a beautiful tail, he must possess "great" survival genes to avoid being eaten. It would be ideal to mate with him so that our young can also be strong and more likely to survive. Natural Selection "selects" for beautiful tail genes. The peacocks with beautiful tails are more likely to reproduce and pass down their genes while at the same time are more likely to be attacked by predators.

Applications to Everyday Life:

-One example of Natural Selection and Evolution is resistance to antibiotics. The frequent use of antibiotics could create resistance to bacteria as most of them die off except for a strong resistant few. These few survived the antibiotics and produce offspringe that are also resistant to antibiotics. This is also why we need to take a new flu shot every year as new flu virus strains evolve each year.

-Another example we've seen is the use of pesticides that left the agricultural world with even more resistant insects rendering DDT nearly useless to the "target species." Pesticides kill off most of the individuals in the insect population except those resistant few. Eventually, the whole insect population is repopulated by only pesticide-resistant individuals. The insect populations have evolved to become more resistant.

Photographs:

Materials Required