CHAPTER INVESTIGATION Modeling Natural Selection OVERVIEW AND PURPOSE Organisms that are best adapted to their environment tend to survive and reproduce. In this lab you will • play a game that models the effect of natural selection in an environment • determine what happens to a group of organisms as a result of natural selection Write Question It Up As you read the steps to the game, think about what makes a population successful in an environment. How will the game model natural selection? MATERIALS • pair of number cubes • 16 red paper clips • 16 blue paper clips • 16 yellow paper clips Procedure Make a game board like the one shown below. In your Science Notebook make a table like the one on page 507 to record your data. 1 2 3 4 1 2 3 4 Count out 10 red paper clips, 4 blue paper clips, and 2 yellow paper clips. Randomly place the paper clips on the board. Keep the rest of the paper clips in a reserve pile. 506 Unit 4: Life Over Time Each color represents a different population of a single species. The board represents the environment. Roll the number cubes to determine which paper clips “live,” or remain on the board, and which paper clips “die,” or are removed from the board. Predict which color paper clip you think will be the last remaining color. Write down your prediction. Roll the number cubes to determine which square, or part of the environment, will be affected. For example, 2,3 indicates the paper clip in column 2, row 3. If the numbers 5 or 6 come up, roll again until you have a number between 1 and 4 for each cube. Now roll one cube to see what will happen to the paper clip or organism in that square. Use the chart below to determine if the paper clip “lives” or “dies.” If the paper clip lives, repeat steps 4 and 5 until one paper clip dies, or is removed from the board. In your table, record which colors live and die. Observe and Analyze Write It Up 1. OBSERVE Which color paper clip filled the board at the end of the game? 2. PREDICT Compare the results with your prediction. Do the results support your prediction? Conclude Write It Up 1. INFER What does the random selection by rolling both number cubes represent? Explain. 2. INFER If the individual paper clips represent different members of a single species, then what might the different colors represent? 3. LIMITATIONS What problems or sources of error exist in this model? Give examples. 4. APPLY How does this game model natural selection? Red Remove if you roll a 1, 2, 3, 4, or 5. INVESTIGATE Further Blue Remove if you roll a 1, 2, or 3. Yellow Remove if you roll a 1 or 2. CHALLENGE Occasionally mutations occur in a population that can either help or damage the population’s chance of survival. Add another step to the game that would account for mutations. Now that a paper clip has been removed, you need to see what population will reproduce to fill that space. Roll both cubes to choose another square. The color of the paper clip in that square represents the population that will “reproduce.” Pick the same color paper clip from your reserve pile and place it on the empty square. All squares on the board should always have a paper clip. al Selection Modeling Natur n s in a Populatio Table 1. Pattern Die Live Paper Clip Color Continue playing the game by repeating steps 4–6 until all the paper clips on the board are the same color. Chapter 14: The History of Life on Earth 507