UNESCO’s International Year of Light offers many hooks for physical science lessons about the nature and behavior of light. (See part 1, “Waves, Particles, and More: The Science of Light.”) Another way to bring light into science classrooms is to examine the many ways in which light affects the growth and behavior of living organisms.
Start with photosynthesis, the process through which plants harness light energy from the sun and turn it into chemical energy. Life Science, session 7, “Photosynthesis,” explains this process in simple terms. Science in Focus: Energy, workshop 5, “Energy in Food,” shows how photosynthesis forms the base for food chains and provides the energy that we need to survive. To extend this idea further, see the overview of energy transfer in ecosystems in The Habitable Planet, unit 4, “Ecosystems.” This unit can set up a discussion about eating at different trophic levels and the energy impacts of various human diets.
Light also drives human and animal behavior in fundamental ways. Journey North’s mini-unit, “Reasons for Seasons,” includes five activities in which students in grades 4-8 can explore how the amount and intensity of daylight create what we know as distinct seasons. Next, see Journey North’s discussion of “Sunlight and the Seasons” for examples of the link between seasonal light levels and the behavior of living creatures. Daylight hours are increasing now in the Northern hemisphere. What kind of seasonal events are occurring in response? How do they vary from lower to higher latitudes?
Some parts of Earth are always dark – for example, areas of the oceans more than 200 meters deep (for details, see The Habitable Planet, unit 3, “Oceans”), and the insides of caves. But many life forms exist in dark zones. How do they adapt? What are their food sources? The Smithsonian Museum of Natural History’s “Ocean Portal” offers some examples of deep ocean life forms, and a photo gallery of bioluminescent marine organisms that produce light through chemical reactions in their body tissues. High school students in chemistry or ecology can tackle “Hot Food,” a lesson from the National Oceanographic and Atmospheric Administration (NOAA) about chemosynthesis – the process that deep-water coral communities use to obtain energy from light hydrocarbons in nearby sediments.
Finally, students may notice their own moods changing as daylight hours increase this spring. Our bodies move according to circadian rhythms that are regulated by the presence or absence of light. The Brain: Teaching Modules, unit 13, “Sleep and Circadian Rhythms,” looks at our natural rhythms and the stages of sleep. And when the sun becomes brighter and more direct in spring, we seek the outdoors. Some experts believe this behavior may have a biological function (perhaps restoring depleted levels of vitamin D), while others are skeptical. What can be said, though, is that these approaches to teaching the science of light will illuminate classrooms.