The number of generations varies with the class. More cooperative
classes may exceed 25 generations in a 55 minute period. Difficult
classes may only reach 10-12 generations. A student records the data
on the board. All students are responsible for copying the data and
graphing it for homework. The sample data graph would look like this:
Rules: All individuals begin eating simultaneously
Arm with cup cannot bend
One bean at a time
Stop when you reach 10
Classmates may not refuse to be offspring (cannot say no)
Offspring are always the same "type" as parent
Day 2: Begin the same as day one. When you reach
generation 3 with 8 individuals, select one (volunteer) to be a mutant.
Generation 3 then has 7 wild type and one mutant. The mutant types
include: No thumb (thumb is taped securely to palm), No fingers (4
fingers are taped together), Straight arm (neither arm can bend), Bent
arm (both arms can bend), 5 beans (individuals reproduce after collecting
only 5 beans instead of 10). I usually introduce mutants one at a
time, during a generation that ensures reproduction. Deleterious
mutations usually die out quickly. Eventually the 5 bean mutants
will replace the wild type. Rarely can all 5 mutants be used in a
55 min. period, 3 or 4 is more realistic.
Note: Always draw a new mutant type from the new generation of wild types. This reduces the wild type generation by one. The new mutant appears in its own column in the data table at the row for that particular generation.
If both beneficial mutants are used in a class, they may both replace the wild type. This demonstrates adaptive radiation as well as speciation.
Typical data for Day 2:
Generation Wild Type No Thumb No Fingers 5 Beans
3 7 1
4 14 2
5 10 2
6 7 0 1
7 14 2
8 5 0 1
9 10 2
10 8 4
11 16 8
12 4 16
13 0 20
The graph for the sample data for day 2 would look like this:
Students can be asked to speculate about what other real world variables would alter the outcomes or data. These might include double mutants, changes in available food, drought, disease, immigration, …
How would the model change as a result of these new variables?
Describe how to model or act out your variation.
Predict what the graph and data would look like if this new variable
The data tables and graphs produced by the students can be used to assess the activity.
Questions could be posed such as:
1. What makes a mutation harmful ? or beneficial?
2. Under what circumstances is having no thumb or no fingers not harmful?
3. Can you think of a mutation that would be harmful in one environment/condition yet beneficial in a different environment?