Preying on Beans
Author: Jolene Routson
Overview: Students act as predators searching for prey (beans) in two different settings to demonstrate the processes of adaptation and selection.
Grade Span: 35
At the market, select four colors of beans of about the same size.
Mix the four types of beans together and distribute them in the designated search areas. It is best to have areas cordoned off prior to the distribution.
Data table for each student to record number and color of prey caught.
Time: 5060 minutes
Grouping: Solo or pairs
Natural selection is one of the basic mechanisms of evolution. Darwin's grand idea of evolution by natural selection is relatively simple, but often misunderstood. For example, imagine a population of beetles. Some are greenish and some are brownish, and these different colors are the result of inherited traits. Since the environment cannot support unlimited population growth, not all beetles get to reproduce to their full potential. Let us suppose that in this example the greenish beetles tend to get eaten by birds and therefore have less chance to reproduce. (This is called differential reproduction.) The surviving brownish beetles have an advantageous trait, which allows them to produce more offspring. The brownish color will become more common, and if the trend continues, all beetles in that population will eventually be brown.
Explore these links for additional information on the topics covered in this lesson:
The concept of natural selection may be difficult for younger students to grasp in its entirety. However, the main objective should be to understand that those individuals that blend with their environments will be less likely to be caught by predators. More of the "blenders" tend to survive and therefore have an opportunity to reproduce.
Thirty seconds search time is suggested, however you may choose to vary the amount of time to accommodate your students. Predators should not have enough time to catch all of the prey.
It is helpful to create a data table for students to record how many of each color of prey (bean) was collected. Students can make graphs from their own data tables.
Vocabulary: predator, prey, survival, reproduction, and natural selection
There are many variations of this activity. For example, colored toothpicks can be used instead of beans or colored hole punches on patterned fabric. Note: colored toothpicks in a lawn are an excellent way to do this activity, but leftover toothpicks in the lawn may present a hazard. Colored pasta is another potential option.
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