Scott Collins, BHP Teacher
Illinois, USA

Look around you. Look at the faces you see. I mean REALLY LOOK. Study these faces. Study their features. What makes them similar? What makes them different? Take note of eye colors, hair colors, skin tones.  Look at bone structure, dimples, and birthmarks. Notice teeth, eyebrows, chins. Feeling uncomfortable yet? Good. Now, close your eyes. Compile your observations and try to answer this question: How different are we? Think beyond the surface of our skin. Think about our cells. Think about what’s in our cells–in their nuclei. Think about our DNA.

Lesson 5.0 includes an activity called How Closely Related Are We?   In it, students are asked to think about the genetic similarities between humans and a number of other organisms (fruit flies, chimpanzees, zebrafish, bacteria, mustard grass, and roundworms).

To introduce this activity, I like to lead students through the exercise above, and help them focus their thoughts on the anatomy of organisms and how DNA plays a vital role in creating it. Students are always amazed to learn that the genetic difference between individual humans across our globe is an average of only 0.1 percent. That 0.1 percent difference is enough to create all the iterations of facial features that we observed in that opening exercise. Imagine what an 80 percent difference would do! (Here’s a clue: We share 21 percent of our DNA with a roundworm).

With this in mind, students begin the task of completing the activity. I typically have them work individually and then compare answers after a few minutes. Students are usually quick to conclude that humans share 98 percent of our DNA with chimpanzees, Which is the highest percentage included among the choices. It’s finding the match for the 85 percent option that often brings the most debate. Students find it hard to believe that we share that much DNA—85 percent—with a zebrafish. It shows them the enormous anatomical differences that can result from a 15 percent difference in DNA.

This activity helps students gain an understanding of the relationship between different species, and see how we (humans) are related to other species. The evolution of life from bacteria to humans can be difficult for students to wrap their minds around, and showing connections among different species helps to increase their understanding. Speaking of these connections, chimpanzees share 98 to 99 percent of their DNA with us and 97 to 98 percent with gorillas. Ask students to think about what this means. Yes, chimps are more closely related to us than they are to gorillas! When you’re ready to begin Unit 5, be sure to give this activity a try.

About the author: Scott Collins is a high school science teacher in Lemont, IL. In addition to BHP, he teaches AP biology, honors biology, and integrated science. His school is on a semester system. Scott’s eleventh- and twelfth-grade BHP classes run about 85 minutes long and focus heavily on the science content. About 60 students per year join him on the 13.8-billion-year journey. 

Photo credits: Fruit fly by Martin Cooper, CC BY 2.0. Chimpanzee by Thomas Lersch, CC BY 2.5. Zebrafish by Oregon State University – Zebrafish, CC BY-SA 2.0. E. coli Bacteria by NIAID, CC BY 2.0. Mustard Plant by Skrissh2013, CC BY-SA 3.0. Round worm by Department of Pathology, Calicut Medical College – Government Medical College, Kozhikode, CC BY-SA 4.0.

 

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