Classroom Explorations: Broken Hearts
Materials & Equipment
Group Size
  • whole class and individuals
  • Preview the Web pages Zebrafish: A model for heart development.
  • Download the student pages and provide them to the class. If you don’t have a tech center, print out the student pages.
  • Print out the PDF version of the Web pages and make one copy per student (optional). If you hand out the PDF version, it will be easier for students to read the text.
  • To learn why the zebrafish is a good model organism for studying heart abnormalities.
Display the live zebrafish if you have one. Then lead a discussion to introduce the class to the zebrafish, keeping the following points in mind:
  • The zebrafish is a model organism—an organism that scientists study to learn biological principles that can be applied to other organisms, particularly to humans in some cases.
  • Fish are like humans in the following ways: they’re eukaryotes, they’re vertebrates, they use oxygen, and they have some similar physiology. They’re unlike humans in that they are “cold-blooded,” breathe with gills, and extract oxygen from water.
  • Some human heart diseases develop because of genetic mutations, and scientists are studying the tiny zebrafish to learn more about genetic mutations that affect the heart.
  1. Project the Zebrafish: A model for heart development Web pages. Have students read the text on the screen, or from the PDF printout, section by section. Then play the accompanying videos for them.
  2. When you get to the Human heart–zebrafish heart video, click on "show structures." If your class has been studying the circulatory system, have students identify the four chambers of the human heart and describe their functions. (If your students haven’t studied the circulatory system, you might briefly explain the functions of the atria, ventricles, and valves.) Ask students to deduce what the two chambers in the zebrafish heart might be (atrium, ventricle) and how their functions might compare to the atria and ventricles in the human heart. Also ask whether or not the images of the hearts are to scale.
  3. Discuss any questions or comments students have about the Web pages. Then give students time to answer the questions on the student pages.
  • Remind students that scientists have learned a lot of biology from studying fruit flies. Ask students why they think the zebrafish and not the fruit fly is the model organism of choice for studying hearts, given that scientists hope to apply what they’ve learned to people. (Make sure students realize that because both humans and zebrafish are vertebrates, our hearts are more similar to theirs than to those of invertebrates.)
  • Explain that when blood leaves the zebrafish heart, it goes first to the gills to exchange carbon dioxide for oxygen. At that point, the blood pressure drops, so the oxygen-rich blood that then travels to the tissues does so rather slowly. But with our two-pump system—which we share with birds and other mammals—oxygen-rich blood travels quickly to our tissues. Ask students why they think a more efficient circulatory system evolved in birds and mammals. (Elicit, as necessary, that mammals and birds are “warm-blooded,” and have students consider the connection between being endothermic (warm-blooded) and needing a more powerful circulatory system.)
> Model Organism Resources
Thanks to Alisa Poppen, biology teacher at Menlo School in Menlo Park, California, who developed a prototype of this activity.