How can natural selection be modeled?
One example found in many textbooks is using colored dots on colored paper.
the dots are used to represent a population of organisms. The background paper is used to represent the environment.
The students become the predators. The students are given a pin or tweezers to "catch" the dots, and a limited time frame to catch the dots.
A set of dots ( 100 or so a paper punch can be used to produce the dots. ) of two different colors are placed on an 8 x 11 sheet of paper. One set of dots is the same color as the background sheet the other set of dots is of a contrasting color.
The students are told to 'catch" as many dots as possible in the limited time given. Then the number of dots of each color are counted. Natural selection predicts that the dots of the contrasting color will be "selected" by the student predators more frequently than the dots that are of the same color. This means that the dots that match the background will survive to reproduce.
(note use very thin pieces of paper as the thickness of the dot can be a means of locating the dot, as well as the color.
This experiment is easy to do not very expensive and integrates well with the textbook presentations of the peppered moths of England.