However, there are some germs that interfere with the body's defenses. There are some diseases that human beings can catch only once. After they've recovered, they don't get sick from them again. There are many diseases that can be prevented by vaccination, so that people don't catch them even once. Often human beings don't understand why others act the way they do, and sometimes they don't understand their own behavior and feelings.
Physical health can affect people's emotional well-being and vice versa.
One way to respond to a strong feeling, either pleasant or unpleasant, is to think about what caused it and then consider whether to seek out or avoid similar situations. Students work in collaborative groups listening to sounds that travel from a sound source to a receiver, their ears. In each of four mini-activities, the students encounter a new sound source and a new medium of sound travel. The students record their observations and discuss how sound travels. The proficiencies on this page were developed by the Indiana Department of Education from the Benchmarks for Science Literacy .