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Gears used for the San Francisco Cable cars
San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

Concepts across the Sciences: Structure and Function

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This post is by Jacqueline Katz, the 2022-2023 Albert Einstein Distinguished Educator Fellow at the Library of Congress.

The relationship between structure and function is evident in all disciplines of science. By observing the structures of the world around us, we can determine much about possible functions. For example, the organelles present in a cell allow it to transport oxygen or send signals, and the angle between bonds in a molecule dictate the chemical reactions that molecule can engage in.

In a physics class, you might show students this image of the winding machinery of the San Francisco Cable Railway from the 1950s without telling them what they are looking at. Ask students to observe the image and identify some of the structures that are present. Students will likely recognize the wheels, chains, ropes, and pistons. Encourage them to ask questions about structures they don’t recognize. After students generate a list of structures, allow time for them to hypothesize the possible functions this system could carry out. To record their hypothesis and reasoning, students can fill in the sentence stem: “I think ___ because ____.”

Students could test their hypotheses by building small-scale models of this system. Provide student groups with materials such as yarn, pipe cleaners, craft sticks, wire thread, and toothpicks to recreate a small version of the winding machinery. Direct students to use the model to collect evidence to support or negate their previously written hypotheses. To document their updated thinking, students can fill in the sentence stem: “I used to think _____, but now I think _______ because ________.”

Once students have arrived at their conclusions with the collected evidence, show them an image of the San Francisco street car to reveal the actual function of this structure. Students can research more information about the mechanics of the streetcar to reveal interesting questions about the best materials for the rope core, the need for lubricants to reduce friction, as well as the force that needs to be exerted to move the cars up San Francisco’s infamous hills.

To further illuminate the connection between structure and function, present students with articles describing some of the initial streetcar accidents. For example in 1903 (the early years of the streetcar), “scores of lives are endangered and death averted by a miracle in accident on traction line.” Many similar articles can be found on Chronicling America, by searching for “streetcar” and limiting the location to California. After students read these articles, ask them which structures in the initial primary source might be involved in causing the accident described. Students can use their system model to test several of their predictions.

When presenting historical articles to students, it is important to discuss language choices made to describe some individuals in the article. Begin by asking what the students noticed while reading. They may make connections between the time of the articles’ publication and other events that were occurring in California at the time.

These primary sources related to the San Francisco streetcar provide the opportunity to discuss the relationship between structure and function, discipline-specific content, as well as interdisciplinary connections.

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