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Activity: Simulate Natural Selection

NGSS Science and Engineering Practices:

NGSS Crosscutting Concepts:

NGSS Disciplinary Core Ideas:

Materials

  • Shallow pan or bowl
  • Lid or piece of paper
  • Graph paper (or computer graphing program)

Materials for Part​ A

  • Table 1.5
  • Table 1.6
  • White rice
  • Wild rice (a mix of colored rice)
  • Black beans
  • White beans
  • Chopsticks for every member in the group
  • Small cup for every member in the group
  • Stopwatch or clock

Materials for Part B

  • Table 1.7
  • Table 1.8
  • White rice
  • 80 Black-eyed peas
  • Chopsticks for every member in the group
  • Forceps for every member in the group

Procedure

A. Model how variation in a phenotypic trait affects a prey population over time.

  1. Fill the shallow pan half way with white rice. This represents your environment. Count out 20 black beans and 20 white beans. These represent different phenotypes of the same organism living in the environment.
     
  2. Make sure the beans are mixed thoroughly into the environment. Mix by either by covering the pan with a lid and shaking for five seconds, or stirring for ten seconds. Keep the lid on the pan or cover the pan with piece of paper until you are ready to start.
     
  3. Read the following directions before you use your chopsticks to “hunt” prey for 60 seconds.
    1. Start with your chopsticks (your “predator mouth”) on the table.
    2. Simulate hunting by picking the prey (beans) out of the rice and putting them into a small paper cup (your “stomach”).
    3. Both black and white beans have the same nutritional value, therefore you should eat any beans you see, not hunt for or eat just one color bean.
    4. You can only pick up one bean at a time.
    5. You cannot scoop up the beans.
    6. After picking up a bean, put your chopsticks down on the table and touch your forehead before picking up your chopsticks and foraging for more prey. This simulates the time it takes you to digest your prey.
    7. All beans must be deposited in your cup. If you miss, you must collect your escaping prey and return it to your cup before continuing to hunt for new prey.
    8. As soon as time is up, put down your chopsticks. If a bean is not in your cup when time is called return it to the environment.
       
  4. After 60 seconds of predation, count the number of beans that have been eaten, and figure out how many remain in the population by subtracting the number eaten from the original 20. Record these numbers in Table 1.5.
     
  5. We will assume a simple model where there is no death and all individuals are able to produce one offspring that will survive to adulthood. Simulate a reproductive event by doubling the number of each color of bean remaining in the environment. Record that number in Table 1.5 as the start of the next generation.
     
  6. Add the new beans (the “offspring”) to the environment. Mix them thoroughly into the environment following step 2, and repeat the prey hunting process. Repeat predation for four generations of prey.
     
  7. Compare your results to those of your classmates.
     
  8. Graph the number of beans of each phenotype in the population at the beginning of each generation.
     
  9. Repeat the simulation, but this time place the beans into a new environment composed of wild rice.
    1. Before you begin, write down your prediction and reasoning about which color beans will do well in this new environment.
    2. Record your results in Table 1.6.
    3. Compare your results to those of your classmates.
    4. Graph your results.
       
  10. Answer questions 1–9.

 

B. Model how a variation in the phenotypic traits of a predator affects predation efficiency.

  1. Fill the shallow pan halfway with white rice. Count out 80 black-eyed peas. These represent prey living in the environment.
     
  2. Make sure the beans are mixed thoroughly into the environment. Mix the beans by either covering the pan with a lid and shaking for five seconds or by stirring for ten seconds. Keep the lid on the pan or cover the pan with piece of paper until you are ready to start.
     
  3. Using the chopsticks, each group member should hunt prey for 60 seconds following the same foraging criteria as in Part A Step 3.
    1. After 60 seconds of predation, count the number of beans that have been eaten by each team member. Record the number in Table 1.7.
    2. Add all the beans eaten by each team member to get the total number of beans eaten. Record the number in Table 1.7.
    3. Determine the proportion and percentage of beans eaten. Record the number in Table 1.7.
    4. Determine how many beans remain in population by subtracting the number eaten from the original 80 to determine how many remain in the environment. Record that number in Table 1.7.
       
  4. Repeat this experiment two more times. We are not simulating generations like in Part A of this activity, but rather our replications represent separate trials that each repeat the experiment.
    1. Start a new trial by returning all of the beans to the environment so there is a total of 80 black-eyed peas in the white rice.
    2. Mix the beans thoroughly.
    3. Follow step 3.
    4. At the end of your three trials, determine the average number of beans that remained in the population. Record the number in Table 1.7.
       
  5. Repeat steps 1–4, but this time each group member should use forceps. Record your results in Table 1.8.
     
  6. Compare your results to those of your classmates.
     
  7. Answer questions 10–16.

 

Activity Questions: 
  1. In Part A, did one bean phenotype survive better? Why? What features or qualities did it have that helped it survive in this environment?
     
  2. In Part A, how did the prey population change over the four generations? Did the percentage of each bean type eaten change over time?
     
  3. In Part A, were there any variations in predator efficiency (the number of prey eaten in 60 seconds) between group members? What were the causes for this variation?
     
  4. The simulation in Part A ended after four generations. What do you think would happen if the simulation continued for another four generations?
     
  5. In Part A, you were instructed not to preferentially select one color bean or another. However, did you ever find yourself looking for one color over another? Why?
     
  6. How did a different type of environment affect natural selection of the prey population? What happened when the prey were living in the environment made up of the darker wild rice compared to the white rice environment?
     
  7. What would happen if a non-visual predator moved in, such as one that hunts at night using smell? Would certain types of beans still have an advantage?
     
  8. In this simulation, white or black beans were different variations within the prey population. What would be necessary to consider them separate species?
     
  9. How realistic is the model for simulating predators and prey in Part A? Explain your reasoning.
     
  10. In Part B, what affected predator efficiency?
     
  11. Where are any variations in predator efficiency between group members when everyone was one predator type (all chopsticks or all forceps)? What were the causes for this variation?
     
  12. Do you think predator type affects prey selection? Why or why not?
     
  13. In Part B, why were you asked to replicate your predator trials? How is this different from the multiple trials in Part A?
     
  14. For both Parts A and B, how did other group’s number compare to your group’s number? Were the same patterns found?
     
  15. How realistic is the model for simulating predator efficiency in Part B? Explain your reasoning.
     
  16. Hypothesize factors that affect variations in prey and predators.
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.