Homeostasis is one of several characteristics all living things share. The term refers to the body's ability to maintain a consistent internal environment. This internal environment includes factors such as fluid levels, temperature and pH levels. Because homeostasis occurs in all living things, the concept appears in biology classrooms frequently and can be illustrated through several different experiments.

## Flashlight Experiment

Small groups of students can see homeostasis in action by observing one of their classmates. A volunteer from each group will have a flashlight shown into her eyes by another student while the lights in the classroom are turned off. Before beginning the experiment, students should hypothesize what effects they think they will see when the light is shined in their peer's eyes. Students should write down what happens to the pupil and iris of the volunteer's eyes then the class can discuss the cause of the reaction. This type of activity can be used to introduce the homeostasis concept.

## Jumping Jack Test

Students can learn how homeostasis occurs in their bodies by participating in a class experiment. All students count their respiration for 15 seconds to get a baseline reading on themselves. They should write down the data. Have the class do jumping jacks for one minute. Then have the whole class count their respiration for another 15 seconds and write down the data. Ask students what they think will happen to their respiration rate after five minutes. After five minutes passes, have students count their respiration again. Students can offer explanations for what caused their respiration to return to or near to baseline levels within five minutes.

## Math Anxiety

Students can see how stress disrupts homeostasis by conducting an experiment on math anxiety levels. The day before the experiment, half of the students should be connected to a pulse monitor for two minutes. The other half of the students monitors the pulse rates and write down those rates every five seconds. The next day the same students will wear pulse monitors, but they will also be given an arithmetic test including up to 50 problems. As they take the test, the other student monitors and records their pulse levels. The instructor should warn the class about the time left to complete the test at specific intervals: 1 minute, 40 seconds, 30 seconds, 20 seconds, 15 seconds, 10 seconds, 5 seconds and then each second until time concludes. Students' resting pulse rates can be compared to their testing rates to see how anxiety affects their heart rate.

## Ants and Homeostasis

This experiment demonstrates homeostasis in non-human living things. Small groups of students should place a small amount of sugar in a jar then place it outside. After the group captures at least six ants in their jar, they can put on the lid. The students should watch the ants and record their behavior. Students then place part of their jar in warm water and watch the ants for fifteen minutes. Again, the group should record what they see. Finally, students place the bottom of the jar in cold water while at least one student wraps her warm hands around the upper portion of the jar. The rest of the students should observe and record how the ants move upwards to get to the warmer part of the jar.