General Knowledge · Class 5 · Nature and animals
Coral reefs and life under the sea
Coral looks like a colourful rock, or maybe a plant. It is neither. What is it?
Small test at the end: scroll down to the end of this page for five short questions that check what you have learnt. Tap an answer, then press Check answer. Go to the questions ↓
Jump to: Read first · Try it away from the screen · Check it yourself · Check yourself · For teachers
Read first
5 facts. The questions below make you use them, not just remember them.
- Coral is made of tiny animals called polyps. Each polyp builds a hard cup of limestone round itself, and over hundreds of years these cups build a reef.
- Coral reefs cover much less than one part in a hundred of the sea floor, but about a quarter of all sea creatures live on or near them.
- India has coral reefs in the Gulf of Mannar, the Gulf of Kutch, Lakshadweep, and the Andaman and Nicobar Islands.
- Tiny plant-like algae live inside coral and give it food and colour. When the sea gets too warm, the coral pushes them out and turns white. This is called coral bleaching.
- A clownfish lives among the stinging arms of a sea anemone. A coat of slime on its skin stops it from being stung.
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Try it away from the screen
Fill a bowl with water and float a few things on it, like a leaf, a bottle cap and a coin. Which float and which sink? Sea creatures float, sink or swim in different ways.
Make it on paper. Keep it with you. Nothing to upload.
Check it yourself
When you read "coral reefs are dying", look for who measured it, where and when. Reports from marine scientists name the reef, the year and how much coral was checked.
Check yourself
Five questions about what this page teaches. Choose an answer and press Check answer, or open "See the answer and why". Nothing is saved or sent: your choices stay on this screen and disappear when you leave or reload the page.
How do you want to answer? You choose, and you can change at any time.
See the answer and why
- A. A plant that grows on the sea floor Not this one. Coral looks like a plant, but it is an animal. Algae living inside it are plant-like.
- B. Tiny animals that build hard skeletons Correct. Yes. Coral polyps are animals related to jellyfish.
- C. A colourful rock shaped by the waves Not this one. A reef is hard like rock, but living animals build it.
- D. A kind of seaweed Not this one. Seaweed is algae. Coral is an animal.
See the answer and why
- A. Salt from the sea dries on it Not this one. Coral lives under water, so salt does not dry on it.
- B. The sea gets too warm and the algae inside it leave Correct. Yes. Without its algae, coral loses its colour and much of its food.
- C. Fish eat its colour Not this one. Some fish nibble coral, but bleaching comes from warm water.
- D. It gets old and its colour fades like old paint Not this one. Old coral can be bright. White coral is usually stressed by warm water.
See the answer and why
- A. Lakshadweep Correct. Yes. Lakshadweep's islands are built on coral.
- B. The Thar Desert Not this one. The Thar is dry land. Coral needs warm, clear sea water.
- C. The Sundarbans in West Bengal Not this one. The Sundarbans have mangrove forests, not coral reefs.
- D. Ladakh Not this one. Ladakh is high in the mountains, far from any sea.
See the answer and why
- A. 230 Not this one. That divides by 10, not 100.
- B. 2,200 Not this one. That takes away 100 instead of dividing by 100.
- C. 13 Not this one. Check: 13 days × 100 km is only 1,300 km.
- D. 23 Correct. Yes. 2,300 ÷ 100 = 23 days.
See the answer and why
- A. It moves so fast that the stings always miss it Not this one. It swims slowly among the arms. Its slime protects it.
- B. A slime coat on its skin stops the stings Correct. Yes. The slime keeps the anemone from stinging it.
- C. It has hard armour like a crab Not this one. A clownfish has soft scales, not armour.
- D. The anemone is asleep in the day Not this one. Anemones can sting at any time.
For teachers and grown-upsWhere the facts come from, and how to use this round.
Sources and notes
- Indian reef areas are listed by the Zoological Survey of India and the Ministry of Environment, Forest and Climate Change.
- The "about a quarter of sea species" figure is a widely used estimate from marine scientists; treat it as approximate.
- Safety: the floating task uses plain water only.