Bioluminescence: a chemical reaction that lights up fireflies and jellyfish

Transcription

1 Bioluminescence: a chemical reaction that lights up fireflies and jellyfish By National Geographic, adapted by Newsela staff on Word Count 730 Level 820L This image shows a bioluminescent jellyfish in the Pacific Ocean. Photo from NOAA.gov/public domain Fireflies are not the only animals that can glow. There are actually many animals that can shine light from their bodies. This is called bioluminescence. Most bioluminescent animals and plants are found in the ocean, such as fish, bacteria and jellies. Others are on land, like fireflies and even some kinds of mushrooms. Animals' bodies are made up of many different chemicals, or kinds of matter. When two chemicals mix, they can react in different ways. This is called a chemical reaction. Chemical reactions can lead to new chemicals, make heat or shine light. This article is available at 5 reading levels at 1

2 The chemical reaction that causes bioluminescence needs two chemicals: luciferin and either luciferase or photoprotein. When luciferase and luciferin mix with oxygen, which is the part of the air we use to breathe, they make light. Photoprotein is another chemical that can mix with luciferin to make bioluminescence happen. Bioluminescent creatures come in many shapes, sizes and colors. Most bioluminescent sea creatures glow bluegreen, a color that is easy to see in the deep ocean. Yellow, red and purple light are rare since many marine animals cannot see these colors. Bioluminescence usually has a blue-green color on land too. But many creatures, like fireflies, give off yellow light. Not many creatures can glow in more than one color. One that can is the railroad worm. Its head glows red, while its body glows green. Some creatures glow constantly, but most give off light in short flashes. Sometimes their whole bodies light up. Other times, they only light up parts of their body, like the dots on a squid. Bioluminescence can be used in different ways. Many animals use it to defend themselves from hunters. Some animals, like many kinds of squid, light up when they are attacked. This can confuse their attackers long enough to let them escape. Some animals use counterillumination. Many predators, such as sharks, hunt prey by looking for their shadows. Counterillumination means hiding a fish's shadow. Hatchetfish, for example, can shine light downward and change it based on the sunlight. The glow gets rid of the fish's shadow, so predators can't find it anymore. Some animals are even more extreme. Brittle stars can take off a glowing part of their body to distract predators. The predators will follow the glowing arm, while the rest of the animal crawls away in the dark. Bioluminescence can also be used to look for prey. One famous predator that uses bioluminescence is the anglerfish. The anglerfish has a huge head, sharp teeth, and a long, thin growth called a filament on top of its head. At the end of the This article is available at 5 reading levels at 2

3 filament is a ball that the anglerfish can light up. Smaller fish, curious about the spot of light, swim in for a closer look. By the time they see the enormous, dark jaws of the anglerfish, it's too late. Other fish, like loosejaws, use bioluminescence to find prey in the dark. Loosejaws are able to shine red light, while most fish can only see blue light. This means that loosejaws can see their prey, but their prey can't see them. Adult fireflies, also called lightning bugs, are bioluminescent bugs. They light up to attract mates. Although both male and female fireflies can glow, most flashing fireflies in North America are male. The way in which they flash tells nearby females what type of firefly they are and that they're looking for a mate. Bioluminescence can also be found in certain plants, like algae. Bioluminescent algae live in water, and can sometimes cause parts of the ocean to glow. "Milky seas" are waters that glow thanks to bioluminescent bacteria on the surface. Bacteria are tiny creatures that are too small to see. But when they're together, their light can be bright and large enough to be seen from space. Scientists are studying bioluminescence to understand how people can use it to make life easier and safer. Bioluminescent trees, for example, could help brighten city streets and highways. Bioluminescent plants could glow when they need water, or when they are ready to be picked. These are just some examples of how bioluminescence might be used by humans. This article is available at 5 reading levels at 3

4 Quiz 1 Read the section "Offensive Adaptations." Choose the selection from the section that shows that some bioluminescent adaptations provide a hunting advantage to the fish. Bioluminescence can also be used to look for prey. One famous predator that uses bioluminescence is the anglerfish. The anglerfish has a huge head, sharp teeth, and a long, thin growth called a filament on top of its head. At the end of the filament is a ball that the anglerfish can light up. Smaller fish, curious about the spot of light, swim in for a closer look. By the time they see the enormous, dark jaws of the anglerfish, it's too late. Other fish, like loosejaws, use bioluminescence to find prey in the dark. Loosejaws are able to shine red light, while most fish can only see blue light. 2 Read the selection from the section "Bioluminescence And People." Scientists are studying bioluminescence to understand how people can use it to make life easier and safer. Bioluminescent trees, for example, could help brighten city streets and highways. Bioluminescent plants could glow when they need water, or when they are ready to be picked. Which of the following is the MOST accurate explanation of this paragraph? In the future, scientists will use bioluminescence to help farmers grow crops more efficiently. In the future, bioluminescent organisms may be used by humans in many different, creative ways. In the future, there may be fewer accidents because of bioluminescent cars and vehicles. In the future, scientists will be able to create bioluminescent plants that require less water. This article is available at 5 reading levels at 4

5 3 The word "bioluminescent" is a key term in the article. How does the author develop the meaning of this term? by describing which colors are most frequent, and explaining how bioluminescence is used to attract prey and for protection by providing examples of creatures that are bioluminescent, and showing how they are different from other animals by explaining how the glow is produced by chemical reactions, and providing examples of how animals use it by showing how different chemicals combine with oxygen to create light, and explaining the latest research 4 Read the following paragraph from the section "Adaptations." Then, fill in the blank. Some animals use counterillumination. Many predators, such as sharks, hunt prey by looking for their shadows. Counterillumination means hiding a fish's shadow. Hatchetfish, for example, can shine light downward and change it based on the sunlight. The glow gets rid of the fish's shadow, so predators can't find it anymore. The word "counterillumination" in the paragraph tells the reader that the animals are hidden by the shadows the animals are protected by the blue light the animals are illuminated by sunlight the animals are camouflaged by the light This article is available at 5 reading levels at 5