How do inherited adaptations impact on diversity?

Population modeling activity

Step 1) Divide the class into two teams, with roughly equal gender representation. One team will represent a group of asexual multi-cellular organisms, while the other team will represent a group of sexual multi-cellular organisms. Give each group an equal number of red, yellow, and blue slips of paper. These slips represent the simple trait ‘tail colour’ (assume these multi-cellular organisms have tails). Hand out white slips of paper to represent offspring and pencil crayons to colour the ‘offspring’ the correct colour according to it’s parent or parents.

Step 2) Read out the RULES OF THE GAME: 1) All asexual players can reproduce independently. 2) All sexual players require both a male and a female player to produce offspring. 3) Only single births allowed (no twins or triplets!) 4) Only the first generation can reproduce (these organisms take several years to mature and we will not carry out the scenario for that long).

Step 3) Read out the entire list of EVENTS (attached). Have students create a chart that shows their prediction of how many asexual and sexual organisms will exist in the environment after each event. Brainstorm sessions and active debriefing sessions help to ensure they get the points you are trying to get across. Have students use the events to fill in the following table:

Step 4) Play the Game! Read out the events and have students complete the tasks. At the end of the game have students decide, based on the events, whether it was better to be a sexual creature or an asexual creature in this environment. Remind the students that there are benefits to both, according to the environment. With students, create a table of disadvantages and advantages to asexual and sexual reproduction based on the scenario. Responses should include, but are not limited to, the information in the following table:

GAME EVENTS

Remind students that asexual reproduction will result in an offspring of the same tail colour every time, whereas sexual reproduction will result in a blending of the two parent tail colours – ex) red + blue = purple tailed offspring. Remember, only the first generation can mate! (The maturation of these organisms is slow)

NOTE – for the purposes of this scenario, I have assumed a class of 24 students: 12 asexual players (4 blue tailed, 4 red tailed, 4 yellow tailed), 12 sexual players (6 male, 6 female – 2 each of male and female red, yellow, and blue tailed organisms). You will have to adjust the numbers based on your class.

1. Reproduce one cycle.
   A) Why are there more asexual (24) than sexual (18)? B) What are the tail colours of the offspring?

2. Let both sides reproduce several cycles with no diseases or predation. Which side reproduces faster? Why?

3. The red-tailed organisms are easy for predators to spot. All red-tailed organisms are wiped out. A) How many asexual and sexual organisms are left?

4. Reproduce one cycle (parent organisms only!)

5. Blue tail rot kills all blue-tailed organisms. How may are left on each team?

6. Yellow-tailed organisms are more prone to sexual dysfunction. Only HALF of the yellow-tailed organisms are still able to reproduce. Reproduce one cycle. How many of each are left?

Continue to play, inventing scenarios with the class, until the students are able to come to conclusions about the disadvantages and advantages of sexual and asexual reproduction. Return to the lesson and complete the table

‘BIG PICTURE’ Questions

Relating Today’s Activity to Interactions Within Our World

1. Why are there an equal number of males and females in sexual organisms, if only "one" male is needed and they are such a waste of resources anyway?

2. If bacteria are asexual, why are they are so successful?

3. Wouldn't the ideal organism be one that could use either method depending on circumstances?

4. Should we allow only the "good" gene organisms to reproduce in a species, say, for example, in humans?