This is an activity which demonstrates all of the parts of evolution. In fact, it is almost a model of evolution itself. Think about how it demonstrates the parts of evolution and the parts of Darwin's theory: how it is similar and how it is different.
You will need:
1. Each person runs a distance, a quarter way around a track or so. Everyone is timed, and holds a slip of paper with their time so they don't forget it. This obviously does not happen in nature, but we are going to demonstrate heredity, and since no one is really going to have offspring, we need some other way to make sure that traits are similar, or "passed on." It can be thought of as sort of like DNA.
2. Set up your notebook like this:
3. The four people with the slowest times start. They are the animals at the beginning of a long course of evolution, before they are fully adapted. In the chart, fill in the speed of each runner under Round 1.
4. Those four people race. The first two to finish are the ones who "survive." (Maybe there is only enough food for two so the two who get to it first survive, or maybe another animal is trying to eat them and the fastest ones can escape and survive.) In the chart under Round 1, fill in the original speeds of the people who won and the average of their speeds.
5. Now comes the heredity part. Each of the survivors picks two people. One of them has a slightly slower and one a slightly faster time. If anyone has the same time, pick them instead of either faster or slower. The people who won Round 1 now "die," but unlike the ones who lost, they die of old age and have lived to reproduce. There are now four people for the next race. Fill in their times under Round 2.
6. After they race, fill in the original speeds of those who won and their average.
7. Repeat steps 5 and 6 until everyone has raced. Keep filling in the chart. If you see by the last one or two rounds that someone has been skipped or left out and that their time is not near the winners', have him or her run as one of the four. His or her very different speed is the result of a mutation in the genes. See what happens.
8. Make a line graph of the average speeds in each round. What happened? What conclusions can you draw? How is this like or unlike real evolution?
If the number of people is not divisible by four, do a couple of rounds where someone has one more or one fewer offspring, or have someone be timer and someone fill in the chart the whole time, instead of having people trade off who keeps track.
You might want to have six people racing together instead of four. Then, either have three winners with two offspring each, or two winners with three offspring each. Five people racing together also works: two people survive, and one of them has two and the other three offspring. Who has two and who has three can be decided randomly, or the faster one can have three. This would work in nature if, for example, the animal that is better fed (faster, to be able to catch or get to more food) is able to have more offspring.