Observations and results
How did the population of paper dots change? Did dots of a certain color become more common than dots of other colors? Which dot colors died out? What do you notice about the dots who survived and reproduced? Why were they able to avoid you, their predator? If their "habitat," (the surface) was a different color, would the same dots have survived and reproduced?
Natural selection is the process by which certain traits in a population become more common because individuals with those traits survive and reproduce. They pass on their traits to their offspring, making them more common in the population. There is a species of moth in England called the peppered moth, whose story helps to illustrate the idea of evolution by natural selection.
Peppered moths lived among birch trees. There are both white peppered moths and black peppered moths. Before the Industrial Revolution, white peppered moths were much more common. They blended in well on the white bark of the birch trees. They remained hard for their predators, birds, to detect. As a result, they survived longer and reproduced more than the black moths, so the light-color traits were much more common in the peppered moth population. However, when the Industrial Revolution occurred, soot from factories covered the birch trees' white bark, turning them black. When this happened, the white peppered moths were no longer camouflaged against the bark. Now they were easily spotted—and eaten–by the birds while the black peppered moths were better camouflaged. After several generations, black peppered moths became much more common.
When England passed its version of the clean air act, decreasing the amount of soot that factories were allowed to emit, the birch trees eventually returned to having white bark again. With your knowledge from this activity, can you hypothesize which colored moth eventually became more common?
Share your color changing dots observations and results! Leave a comment below or share your photos and feedback on Scientific American's Facebook page.
Recycle the paper dots and clear off the surface.
More to explore
"Animal Mimics: More than just camouflage" from Scientific American
"Ugly Animals Need Love, Too" from Scientific American
"Animal Mimicry" overview from Alleghany County Public Schools
If You Can't Run, You've Got to Hide! activity from the University of Richmond
Claws, Coats and Camouflage: The ways animals fit into their world by Susan E. Goodman, ages 4–8
Living Color by Steve Jenkins, ages 9–12
Find the DNA in a Banana
What you'll need
• Ripe banana
• Half cup of water
• Teaspoon of salt
• Resealable zip-top bag
• Dishwashing soap or detergent
• Rubbing alcohol
• Coffee filter
• Narrow glass
• Narrow wooden stirrer