How a living thing grows and eventually dies are excellent questions for students investigating biophysics. The life cycle of fish, their behavior under different stressors, and how they adapt to a changing environment show environmental relationships and the transfer of energy. Slight temperature changes in the water, for example, may alter a fish's behavior. The biophysics principle of energy transfer is at play, as the energy used to heat the water is transferred to the fish. For instance, some fish swim faster in warmer water because they require less energy to stay warm and the excess energy is used to increase their physical power. Constantly moving, rather than still, water also will have visible effects on the fish and algae in the tank.
An experiment that can be done by a whole classroom is to test the functions of the anatomy of the human ear and how the shape relates to function. In a quiet room, students are instructed to write down every sound they hear, including breath, footsteps, rustling trees and small ringing sounds. Then, holding their hands behind the ears like cups, students observe what they hear.
Consider the structure of the ear and how it funnels sound, and how the funneling changes when using the hands to "catch" more sound. By examining the shapes of the human ear and making slight modifications to them, students learn how the ear functions. Principles of human anatomy, the physics of sound waves, and genetic diversity all factor into this easy experiment.
To test the sensitivity of nerves in different parts of the body, bend a pipe cleaner in half so the two ends are about 1 inch apart. Working in pairs, have one student press the two ends into her partner's palm. Ask whether her partner feels one point of pressure or two. If she feels only one point, widen the angle of the ends and press again. Test different parts of the body to see which area has more sensitivity and can feel the two points of pressure when they are very close together. Using geometry and distance measurements, students can see which areas of the body have higher sensitivity, and where denser collections of nerves are found.
One of the earliest applications of biophysics was the study of osmosis, or how liquid moves into and through a semipermeable cell membrane. A simple potato experiment illustrates the process of osmosis. Place one half of a potato, cut side down, in a dish of fresh water. Place the other half in a dish of saltwater. After a few days, the fresh-water potato will not look much different, but the saltwater potato will be wilted and discolored. If the water outside the potato, and the cells it is made of, is saltier than the water inside the potato, thermodynamics dictates that the water will move into the potato's cells until a balance is met between them. Try different concentrations of salt and chart the results.
A biophysics experiment growing the same types of plants at different angles tests how a plant adapts to environmental stressors. Using a metal gardening display rack, tilt some pots slightly, and observe how the plants respond and adapt to the change. Place some at greater angles than others, and observe the different results when keeping other factors, such as sun and watering schedules, the same. Students learn how environmental factors, such as a plant's angle to the sun, drainage and the slope of its soil bed, affects growth.