Coral Quiz

Coral reefs are hosts to thousands of species of fish, countless invertebrates, and lots of scuba divers. Ok, the scuba divers don't live there. But what exactly is coral? Find out in this quiz!

What is coral?

animal

plant

metal

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Coral is an animal. Many species of coral have really close relationships with algae, though – they get most of their energy from algae that live inside them and carry out photosynthesis, making food with energy from sunlight.

Which of these is coral most closely related to?

Shark

Jellyfish

Oak tree

Sea cucumber

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Jellyfish, sea anemones, and coral are all cnidarians, which is a funny word. (The "C" is silent.) Cnidarians have two body plans: the polyp, like coral, which sticks to something, and the medusa, like jellyfish, which floats around.

Where does all that hard stuff in a coral reef come from?

Coral scavenge tiny rocks and deposit them in a pile

Coral build hard skeletons of calcium carbonate

The hard stuff is lava, which coral prefer to live on

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Some coral species make their own external skeletons; when they die, the skeleton is left behind and another coral grows on top of it. These build up over generations and generations to make a reef.

True or false: Coral reefs live mostly in shallow water.

True

False

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True. Because the algae that live with reef-building corals depend on the sun for energy, coral reefs are only in shallow, clear water. Soft corals don't necessarily have those algae, and they're found in both shallow and deep water.

True or false: Coral can cope with wide ranges of temperature, salinity (saltiness), and acidity.

True

False

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False. Coral are sensitive little critters, and they don't do well if the water changes. If you're saying, "uh-oh, global climate change," you're right. Rising temperature is bad for coral, and so is the water getting more acidic – which happens when there's more carbon dioxide in the atmosphere.

What do coral do when they're stressed?

Drink too much

Turn white

Release sperm and eggs

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They turn white. It's called coral bleaching – the coral expel the little algae that live with them, so the white calcium carbonate underneath shows through the clear coral polyps. Coral usually revive after bleaching, but it can take a while.

Where does coral, the gemstone, come from?

Tibetan mines

Meteorites

It's actually coral

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It's actually a species of coral that grows mainly in the Mediterranean and has a hard pink or red skeleton. People have harvested these coral for jewelry for thousands of years – coral beads have been found in ancient Egyptian graves.