Natural Selection a Simulation

Name: Period: Natural Selection – A Simulation Color is a trait, or physical characteristic, that many animals have. Imagine a bug of a species that occurs in ten different colors in a small population. In this activity we will examine what happens to such a bug when birds prey upon it.

Procedure 1) Setup: A) Obtain five paper “bugs” of each of the ten colors listed in the table below. Each of these “bugs” represents a bug of that color. B) Spread out the fabric habitat on your tabletop. Your tabletop has become an island habitat with a specific appearance and foliage. 2) Predation/Selection: A) Appoint 1 team member as the keeper of the bugs. The keeper then should spread the bugs uniformly over the fabric. B) Imagine yourself as a predator, the paper bugs are your prey, and the fabric background the habitat. C) When your keeper says, “Pounce!” open your eyes and grab the first paper bug you see. Do this 12 times quickly. D) If you have three instead of four people in your group the keeper must also act as a predator to insure that three bugs are taken on each “pounce”. E) The keeper MUST keep a tally of how many times predators have pounced. F) MAKE SURE you stop “pouncing” after EXACTLY 12 pounces. This will “kill” 36 bugs (3 predators x 12 pounces). 3) Results, or Who Survived? A) Now remove the survivors from the cloth and group them according to color. B) While the keeper is sorting the survivors, sort the prey you have eaten back into groups of the same color, being careful not to mix them with the survivors. C) Record the number of each color that survived in the table below. 4) Reproduction: A) Each of the 14 survivors produces 2 offspring of the same color. Place these below each bug that survived. Use your prey pile and the instructor’s reserve supply. B) Return the rest of the prey paper bugs that have been eaten to the instructor’s reserve supply. C) Appoint a new keeper. 5) Repeat entire process of selection 2 more times starting at #2 above. 6) Separate out the bugs into piles of the same color and return to the instructor’s supply.

Table 1: Color Distribution in a Bug Population Over Time Original Survivors after Selection Round Color # 1 2 3 Red 5 Yellow 5 Pink 5 White/Off White 5 Grey 5 Black 5 Brown 5 Blue 5 Purple 5 Green 5 Discussion:

1. Did 1 color of bug survive better than others after the 1st round of “pouncing”? If so, which one? Why?

2. What, if any, changes in occurrence (numbers) of certain colors happened between the 1st and 2nd, and between the 2nd and 3rd rounds of “pouncing”? Why?

3. Compare the original and survivor populations after the activity is over. Are there any colors from the original population that are not represented in the survivor population? If so, which ones? Why do you think this happened?

4. If you took this experiment further and did more rounds of “pouncing” what do you think would happen to the occurrence of colors in your population?

5. What do we call this process of change of frequency (occurrence) of a trait in a population?

6. Did an individual organism change (adapt) or did some just die and some live to reproduce?

7. What might happen to two populations of animals of the same species that were separated onto two remote islands? Might enough change take place eventually that they no longer looked much alike? Did this happen with your “bugs” and another group’s that were on a different background/island?

8. Is it possible that this process could also act on reproductive traits such as color for mate selection, or on penis shape or size, so that the two populations could at some point lose the ability to interbreed?

9. If they lost of the ability interbreed would the two populations still be members of the same species?