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Chemical Reactions in Nature

Grades 9-12 | Analysis | Source-Based

Source Lexile®: 740L-1140L

Learning Standards




Prompt: Today you will read three passages about chemical reactions.


Write an essay analyzing how different organisms use chemical reactions for self-defense, and compare how each organism uses chemical reactions as presented in the articles. Remember to use evidence from all three articles to support your response.




Source 1

Battle of the Ants

Two invasive insects face off in a chemical showdown

By Jacqueline Adams


  1. Edward LeBrun arrived at the battlefield to watch two invading armies clash. But the ecologist from the University of Texas's Brackenridge Field Laboratory had to peer at the ground to see the action because the soldiers were ants. On one side, a species of fire ant called imported fire ants—named for their burning sting—tried to hold the Texas prairie where they'd settle. Their challengers, tawny crazy ants—named for their fast, erratic movements—were gaining ground.
  2. To draw the competitors together, LeBrun set out a dead cricket as bait. The fire ants, whose venom kills other ants, found the food first. "When you've got an item covered with fire ants," says LeBrun, "you don't expect to see other ant species coming up and challenging the fire ants for that bait." But this time, LeBrun witnessed something strange. Tawny crazy ants raced to the scene and attacked—and they weren't dying.
  3. By studying the insects in his lab, LeBrun discovered that tawny crazy ants have a chemical defense against fire ants that can shift the battle in their favor. As tawny crazy ants slowly make their way across the southern U.S., they're causing big problems not only for their ant rivals but for people and other creatures as well.


Insect Invaders

  1. Both of the dueling ant species originally came from South America. In the 1930's, imported fire ants may have hitched a ride to the U.S. in soil used for ships' ballast—and that meant trouble for native species. "Imported fire ants are very aggressive," says David Oi, an entomologist at the U.S. Department of Agriculture. "And they have big populations, so oftentimes they'll outcompete other ants for resources."
  2. One reason for the imported fire ants' success is a potent venom that's painful to humans and deadly to small animals. As the invasive species spread through the Southern states, it pushed out native fire ants, and its deadly venom reduced populations of ground-nesting birds and reptiles.
  3. But by 2002, a competing invader species was on the rise in the U.S. with its own chemical weapon. Tawny crazy ants don't sting, but they spray formic acid from an opening called an acidopore on the tip of their abdomen. "They use it like a nozzle from an aerosol can," says LeBrun. As the newcomers moved in, they used their deadly acid against other ant species—even imported fire ants.


Chemical Warfare

  1. As LeBrun watched the brawl over the cricket bait, a tawny crazy ant curled its abdomen under its body and sprayed formic acid at an imported fire ant. The fire ant arched its body, lifting its stinger into the air, and smeared venom on the crazy ant. "That is usually a fatal event for the victim," says LeBrun.
  2. But instead of dying, the tawny crazy ant ran off to the side, stood on its hind legs, and curled its abdomen. It took formic acid from its acidopore and wiped the acid all over itself, as it were using it as an antidote for the venom. Then the ant ran back into battle. "I was intrigued to see if they were able to counteract the fire ant venom somehow," says LeBrun. So he conducted an experiment to find out.
  3. In the lab, he sealed the acidopores of some tawny crazy ants with nail polish so they couldn't secrete formic acid but left the acidopores of others unsealed. Then he put the crazy tawny ants in vials with imported fire ants. After the crazy ants got smeared with fire ant venom, he separated the ants and watched. About half of the tawny crazy ants with sealed acidopores died, while 98 percent of those who secreted their antidote survived.
  4. Researchers aren't yet sure how the antidote works. It may prevent fire ant venom from entering the crazy ants' cells, so the poison can't deliver its toxic effects. Another possibility arises from the fact that chemical reactions occur easily between acids (like formic acids) and bases (like the fire ants' venom). Maybe a chemical reaction detoxifies the venom.





On the March


  1. However they're doing it, tawny crazy ants have the upper hand—and that doesn't seem to be a good thing. "In some areas, you have huge populations," say Oi. "It looks like the ground is moving."
  2. The invaders are decimating the native arthropods they prey on, such as insects and spiders. Since some of the arthropods control insect pests and provide food for birds and reptiles, their decline can trigger additional problems. All of the species in the ecosystem are interconnected.
  3. People in infested areas aren't happy either. Imported fire ants live in mounds outside, but tawny crazy ants invade houses, crawling over surfaces and short-circuiting electrical devices with their bodies. "Even though they don't sting, they're a lot more annoying," says LeBrun.
  4. No one knows if the tawny crazy ant boom will continue. LeBrun points out that imported fire ants used to swarm in greater numbers than they do now, so it's difficult to predict what may happen to the new invaders over time. Meanwhile, the fierce battle for the Southern states continues underfoot.


The Ants Weapon

  1. The pH scale measures how acidic or basic a substance is. An acid is a substance that gives up positively charged particles called hydrogen ions. A base is a substance that gives up negatively charged particles called hydroxide ions. The more acidic or basic a substance is, the more easily it reacts.
  2. On the scale, a 7 is neutral. Lower numbers are more acidic and higher numbers are more basic. Tawny crazy ants secrete formic acid, which has a low pH. Imported fire ant venom is basic, so it has a high pH.




Adams, Jacqueline. "Battle of the Ants." Science World (2014): n. pag. Web.



Source 2

Toxic Blast

By Jennifer Cutraro





  1. Predators beware! This sea slug squirts out a purple cloud of toxic chemicals as self-defense. How does Aplysia californica (ap-LEE-zha cal-ih-FOR-nika) store this nasty brew without harming itself?
  2. Charles Derby, a biology at Georgia State University, found that the slug holds different toxin-making molecules, or two or more atoms joined together, in separate body compartments. These molecules are harmless until they are mixed together.
  3. When threatened, the slug shoots the molecules into another compartment. There, an enzyme starts a chemical reaction, producing harmful substances such as ammonia. When a slug spurts out the nasty mix, most predators back away.

Cutaro, Jennifer. "Toxic Blast." Science World (2006): n. pag. Web.




Source 3

All Lit Up

How four glow-in-the dark organisms make their own light

By Ferris Jabr


  1. On a summer evening, you may have seen fireflies flashing in the grass. These insects make light using a chemical reaction. It's similar to what happens in a glow stick, says biologist Edith Widder.
  2. "When you bend and snap a glow stick, you let different chemicals flow together. That creates light," she explains. "Some animals do the same thing inside their bodies."
  3. Fireflies may be the most familiar glowing creatures. But many different organisms are capable of bioluminescence (byeoh-loom-in-ESS-ens). Here are four living things that sparkle, shine, and shimmer on land and in the sea. Some species are trying to communicate or disguise themselves. Others want to find a mate or something to eat. Each is brilliant in its own way.


Looking for Love


  1. There are thousands of different species of fireflies. They live in fields and forests around the world. When they light up, they're usually telling each other that they want to find a mate.
  2. To make light, chemicals mix together in a part of a firefly's body called the lantern. Different species produce different colors of visible light. Some fireflies glow yellow. Others are green, red, or orange.
  3. Many firefly species sit still and glow. Others zoom around and blink. Each species has its own particular pattern. When one firefly recognizes another one's flashes, it knows they'll be a match.


Invisibility Cloak

  1. To stay safe from predators, the Hawaiian bobtail squid hides in the sand during the day. At night, it swims into the open water to eat. But that's a risky move. From below, the squid's dark silhouette stands out against the moonlit surface of the water. That could make it an easy target for a big, hungry fish.
  2. Luckily for the squid, it knows a trick called counter-illumination When the squid is out in the water at night, its body lights up. The glow helps it blend in with the moonlight above it. This makes it practically invisible from below.


On the Hunt


  1. The odd-looking anglerfish lives deep in the ocean. Its home is too deep for sunlight to reach. To attract prey in the dark, the anglerfish uses a light-up lure.
  2. The flexible "fishing rod" on an anglerfish's head is filled with tiny bioluminescent bacteria. "Most animals that glow make light themselves," says Widder. "But some creatures get bacteria to do it for them."
  3. To catch its meals, an anglerfish wiggles the rod around. Smaller fish can't resist the glow. When prey gets close enough, SNAP! The anglerfish gobbles it up with its needle-like teeth.
  4. Anglerfish and their glowing bacteria are symbiotic. The bacteria provide the fish with the light they need to hunt. In return, the anglerfish share their food with the bacteria. That's teamwork!


Night Lights


  1. Have you ever seen a mushroom this spooky? It's called a foxfire fungus. Lighting up helps it spread its spores, which are like a plant's seeds.
  2. There are more than 70 different species of bioluminescent fungus in forests around the world. At night, chemicals mix inside the fungus, causing it to light up. Insects like flies, beetles, and ants are attracted to the colorful display.
  3. When an insect lands on the fungus, spores stick to its body. Later, the spores drop off the bug, helping mushrooms sprout in a new place.

Jebr, Ferris. "All Lit Up: How Four Glow-in-the Dark Organisms Make Their Own Light." Science World (2016): n. pag. Web.









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