Are Corals Animals, Plants, or Rocks?

When you think of paradise, what comes to mind? Although the answer is sure to be different for everyone, many people likely share a vision of paradise that includes warm, sunny days spent on pristine tropical beaches.

If your idea of paradise includes sandy beaches and crystal-clear waters, then you would probably spend a lot of time swimming and diving in your lush aquatic surroundings. Besides swimming with colorful fishes, you would also enjoy the sight of long stretches of coral reefs.

While swimming past and closely examining the corals, you may start to QUESTION what exactly they are. They seem to be alive, yet they also resemble rocks. The way they are attached to the ocean floor also makes them look like plants. So, are they animals, plants, or rocks?

According to scientists, corals are indeed animals without backbones. They belong to the vibrant group of animals called Cnidaria, which also includes jellyfish and sea anemones. These fascinating creatures consist of a simple stomach and a single mouth surrounded by stinging tentacles.

Corals cannot produce their own food like plants. Instead, they have small arms that resemble tentacles to capture food in the water around them.

Unlike most other animals, corals cannot be identified by their faces or any distinct body parts. In reality, a structure that we refer to as a piece of coral is usually composed of hundreds or even thousands of small coral creatures known as polyps.

Each polyp has a soft body. To survive in their watery environment, each polyp extracts calcium from seawater and converts it into a solution of calcium carbonate that it secretes around itself. The solution hardens and forms a limestone outer skeleton. As the skeletons of thousands of polyps attach to each other, they create coral reefs and acquire a unique, rock-like appearance.

Corals are sessile, meaning they permanently attach themselves to the ocean floor. However, being rooted to the ocean floor is not the only characteristic that makes them appear like plants.

Corals have a special symbiotic relationship with algae that resemble plants and live within their tissues. The algae, called zooxanthellae, process the metabolic waste of corals and use it for photosynthesis. In return, the algae remove waste and produce oxygen and food that corals need to survive.

Scientists estimate that this relationship between corals and zooxanthellae has existed for over 25 million years. In fact, it is believed to be the reason why coral reefs are the largest living structures on Earth, comparable to old-growth forests in terms of longevity.

Try It Out

Isn’t coral fascinating? Learn even more when you explore the following activities with a friend or family member:

  • Have you ever seen what corals look like? Go online and have a look at the Photo Gallery: Corals online. Which corals do you like the most? Why? If you had the opportunity to go diving and explore a coral reef, where would you choose to go?
  • If you are searching for a wide range of the most stunning corals in the world, where would you go? Australia, undoubtedly! The Great Barrier Reef is renowned worldwide for its breathtaking and vast coral reefs. If you want to take a virtual tour of the Great Barrier Reef, you should definitely check out these Great Barrier Reef Aerial Panoramas online.
  • Can you recognize the creatures that frequently inhabit coral reefs? Take a look at the Coral Critters Collage and then read more about the depicted animals once you have identified them. You can also ask a friend or a family member to assist you!

Additional Resources

  • http://oceanservice.noaa.gov/facts/coral.html
  • http://www.icriforum.org/about-coral-reefs/what-are-corals
  • http://www.teachoceanscience.net/teaching_resources/education_modules/coral_reefs_and_climate_change/what_is_a_coral/

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