May 23, 2013

Natural Selection Activities

This week we took a kid friendly look at natural selection.  We started out with some talks by Sal, over at Khan Academy, and then we got down to business with some fun, hands-on activities to help us experience natural selection for ourselves.

Activity 1: Birds on a Bug Hunt

green and red construction paper
dried red kidney beans
dried split peas
small bowl or cup for each child


I told the kids that they were birds and that they love, love, love to eat bugs!  The little bowls were their bellies and their job was to fill their bellies with bugs.  

On a green piece of construction paper, I spread out the red and green beans.  This represented the bugs in the grass.  The directions were to close their eyes and then open them and put the very first bug they saw in their bellies.  We did many rounds of this little bug-eating exercise, and as you would guess, they grabbed mostly red beans because they are easier to see on green paper than split peas are.  After a few rounds, I announced that the remaining bugs had reached reproductive age.  The kids paired off the remaining bugs into like pairs and then we added a bug for each pair.  We did more rounds of bug-eating.  Soon enough, there were only a few red bugs left and green bugs seemed to be taking over.  

This seemed to adequately get the point across that the varieties of a critter that happen to have some little characteristic that help them survive to reproductive age are going to increase in population, while those that lack that characteristic will dwindle and maybe eventually vanish altogether.  

We took that a step farther and declared that the environment changed and the grass died off in large quantities, leaving the red dirt grassless.  I slipped the red paper under the remaining bugs and we went through all of the steps again, and by the end, the red bugs had almost made a comeback!  The point of this second part of the activity is simply to demonstrate how changes in the environment lead to changes in which critters are naturally selected for.  

Activity 2: Peppered Moth Flash Activity

The Peppered Moth is one of the most common critters that teachers use to demonstrate natural selection because they changed and changed again over a very short and observable period of time, during a time of great pollution in England.  

This website offers a very cool and interactive set of flash activities that cover the history of the peppered moth and how scientists observed its changes over time.  The best part is a cool activity at the end where you get to be the bird and you have to eat moths in both a light forest and a dark forest. The kids love it and it gets right to the point without being too wordy or dry.  

Activity 3: Blending Butterflies

White paper
colored pencils
tablet of patterned scrap book paper


After toying around with the peppered moth, I cut out 3 paper butterflies and told the kids to color them any way they wanted.  I gave them about 10 minutes to design their own cool variety of butterfly.  Then I pulled out my tablet of mixed patterned scrap book paper.  We spread the butterflies out across different patterns of paper and decided which ones were best suited to each "environment."  

To take it a step farther, we chose one piece of paper and picked the 2 butterflies that might last the longest in that "environment" and actually did a round 2, designing their offspring, which had to have some combination of the parental patterns and color scheme, and then we carried this out over several generations.  

Next stop?  DNA!


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