09.29.07

Hands-on Microevolution activity (with M&Ms)

Posted in The nuts and bolts of it at 8:03 pm by Meg

Justyne over on Schoolless just had a neat activity on survival of the fittest using Legos. It looks like fun and I may have to remember it.

But reading over what they did reminded me of something similar that I did a few years ago for the biology labs that I taught. But instead of Legos, we used M&Ms.

Justyne asked me to send her the info and since I needed to type it up, I figured I’d post it here for anyone to use.

Now for anyone who isn’t familiar with the terms: macroevolution is the idea that we ‘came from apes,’ or at least share common ancestors with them; microevolution is the idea that creatures’ characteristics can change from one generation to another because of some kind of pressure on the population. Believe it of not, there are groups that will accept the idea of micro-, but still argue against macro-.

Anyway.

This activity uses the concept of Punnett squares to model the typical offspring produced for two individuals. For our hypothetical population:

• Red M&Ms have 2 dominate genes
• Pink M&Ms have a dominate gene and a recessive gene
• White M&Ms have 2 recessive genes

This activity also assumes that every pair of individuals produces 4 offspring that perfectly model their Punnet square probabilities. So, it helps to start this activity by developing the Punnett square for each pairing (Red-Red, Red-Pink, Red-White, Pink-White, Pink-Pink, and White-White) to have as a resource.

1. You start with putting 16 Red, 32 Pink, and 16 White M&Ms (you can use any set of colors, and any particular item for this. But the M&Ms work well, and as you’ll see, the kids love to model with them) in an opaque container.
2. Now individuals with 2 recessive genes have a potentially lethal phenotype that may kill them before they have a chance to reproduce. - Take out 8 of the White M&Ms and eat them.
3. Mix up the remaining M&Ms and then, without looking, remove them in pairs. As you remove them, log each pair in the correct column of the chart until all of the M&Ms have been pulled. These pairs are the parents of the next generation.
4. Now record the number of parent pairs for each combination in the second column of the data table Using the Punnett square predictions calculate the expected number of each type of offspring - columns 3, 4, and 5. Add up each of those columns for the composition of the next generation. (You can ignore the 4 spaces on the bottom, they were to be able to answer questions from the lab book.)
5. Begin generation 2. Take each of your totals and put that number of Red, Pink, and White M&Ms into your container.
6. Assume that half of the White M&Ms die without reproducing - take them out and eat them.
7. And so on…..

When we did it, you could see the population start to clearly shift by the 3rd generation, but we ran out of M&Ms to be able to model the next generation. (We would have needed - 176 Red, 160 Pink, and 44 White.)

And, of course, when we were done the kids got to eat all of the M&Ms.

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