For upper elementary-school students, research specific to the human body indicates that, in terms of internal bodily organs, upper elementary students are able to list a large number of organs. In terms of the nervous system, they know the brain helps the body parts but do not always realize the converse (that the body helps the brain). They do know, however, that nerves conduct messages, control activity, and stabilize the body. Upper elementary students do not understand the brain's role in controlling involuntary behavior. In terms of the digestive system, once students reach the fifth grade, they know that food undergoes a transformation process in the body. In terms of the respiratory system, they associate the lungs' activities with breathing. Further, they may have some knowledge about the exchange of gases in the lungs and understand that air goes to all parts of the body. In terms of the circulatory system, upper elementary-school students realize that the heart is a pump, but they do not realize that the blood returns to the heart. (Benchmarks for Science Literacy, pp. 344-345.)MOTIVATIONQuestions about familiar body systems can be useful in getting students to start thinking about systems ingeneral. This process can initiate the understanding that each organ affects and is affected by others. Hold up an apple (or some other healthy snack). Ask students:
What am I holding in my hand?If I were going to eat this apple, what parts of my body would I use?Have students discuss the body parts we use when biting, chewing, swallowing, and digesting an apple. You may want to create a chart on the blackboard or a large sheet of paper to record students' ideas. If so, you can use these categories to help you organize the information:Body Parts for BitingBody Parts for ChewingBody Parts for SwallowingBody Parts for DigestingNow ask students:How do the different parts work together? (Each part plays a special role, so once one task is accomplished, then the next part can perform it's role.)What happens if one of the parts is missing? (For example, if the teeth were missing, then it would be difficult if not impossible to chew some foods, and if one couldn't chew something large to get it small enough to pass through the esophagus, then they could choke.)Continue to guide student understanding of systems by asking:Who remembers what it's called when a number of different parts work together to make something happen or function? (Guide students so that they come up with system as an answer.)Can you think of an example of a system? (Some possible examples are a bicycle, a computer, a school, or a bus.)For the system you picked, write down any parts that belong to that system. (For example, some parts that are necessary for a bicycle are two wheels, gears, brakes, foot pedals, and handles.)DEVELOPMENTNow have students use the All Systems Go!student esheet to access the All Systems Go!interactive.