Student sample for assessment
Written by a Year 7 student in Bentleigh, Victoria, Australia.
Have you ever seen a firefly flashing in the dark on a summer night? Or seen the ocean glow blue when the waves crash? Both of these are examples of bioluminescence, which is light produced by living things through a chemical reaction. The word bioluminescence comes from 'bio' meaning life and 'luminescence' meaning light. Many creatures create their own light using special chemicals inside their bodies. Unlike the heat and light from a light bulb, which wastes a lot of energy as heat, bioluminescence is cold light. The chemical reaction inside the organism releases light but almost no heat at all. The chemistry of how bioluminescence works is based on two main chemicals: luciferin and luciferase. Luciferin is a chemical compound that reacts with oxygen in the organism's body. Luciferase is an enzyme that speeds up this chemical reaction. When luciferin reacts with oxygen in the presence of luciferase, light is produced. This light is what we see flashing from a firefly or glowing from ocean plankton. Different organisms have slightly different versions of these chemicals, which is why firefly light looks different from bioluminescent plankton or from the glowing lure of an anglerfish hunting in the dark deep sea. Scientists think bioluminescence has evolved independently in at least forty different groups of organisms. This means different creatures invented this ability separately, without copying each other. Why do organisms use bioluminescence? There are many reasons. Fireflies use light to attract mates; it is their way of saying 'I am here' in the dark. Anglerfish have a glowing lure hanging from a rod on their heads, which attracts prey into their mouths. Some bioluminescent plankton glow blue when they are disturbed, possibly to scare away predators or confuse them. Scientists estimate that more than seventy-six percent of deep-sea creatures produce bioluminescence. In the darkness of the deep ocean, light is a useful tool for finding food, attracting mates and avoiding danger. Understanding how different creatures use light in the dark helps us see that evolution has found many solutions to the same problems living things face.