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General Knowledge · Class 6 · Nature and animals

Mammals of land and sea

A dolphin lives in water all its life, but it would drown if it could not reach the surface. Why?

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

6 facts. The questions below make you use them, not just remember them.

  1. Mammals have hair or fur, breathe air with lungs, and feed their babies on milk. Most give birth to live babies.
  2. Whales and dolphins are mammals. They must come up to breathe through a blowhole. The blue whale is the biggest animal that has ever lived, about 30 metres long.
  3. The Ganges river dolphin is India's national aquatic animal. It is almost blind and finds food in muddy water by sending out clicks and listening for the echoes.
  4. Bats are the only mammals that can truly fly. Their wings are skin stretched over long finger bones.
  5. A few mammals lay eggs: the platypus and the echidna of Australia.
  6. More than half of the world's wild Asian elephants live in India.

Offline

Try it away from the screen

Watch a pet, a cow, a squirrel or a dog for five minutes from a safe distance. Write down what shows it is a mammal: fur, breathing, how it cares for its young.

Make it on paper. Keep it with you. Nothing to upload.

Check it yourself

Videos of "talking" or "crying" animals are often edited. Look for the same story in a wildlife organisation or a newspaper that names the place and the scientist.

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.

  1. Question 1 of 5Which of these sea animals is a mammal?

    See the answer and why
    • A. An octopus, with its eight long arms Not this one. An octopus is a mollusc, related to snails.
    • B. A dolphin Correct. Yes. It breathes air and feeds its baby on milk.
    • C. A shark Not this one. A shark is a fish. It breathes through gills.
    • D. A sea turtle Not this one. A sea turtle is a reptile. It lays eggs on beaches.
  2. Question 2 of 5What is India's national aquatic animal?

    See the answer and why
    • A. The blue whale Not this one. Blue whales swim in the seas around India, but they are not the national aquatic animal.
    • B. The Ganges river dolphin Correct. Yes. It was named the national aquatic animal in 2009.
    • C. The dugong Not this one. The dugong is a rare sea mammal near Tamil Nadu and the Andamans, but not the national aquatic animal.
    • D. The olive ridley turtle Not this one. Olive ridleys nest in Odisha, but they are reptiles and not the national aquatic animal.
  3. Question 3 of 5The Ganges river dolphin is almost blind. How does it find fish in muddy water?

    See the answer and why
    • A. Its skin glows and lights up the water Not this one. It does not glow. It uses sound, not light.
    • B. It waits for fish to swim into its mouth Not this one. It hunts actively, using sound.
    • C. It smells the fish from far away Not this one. Dolphins have almost no sense of smell.
    • D. It sends out clicks and listens for the echoes Correct. Yes. This is called echolocation.
  4. Question 4 of 5A blue whale can be about 30 metres long. A school bus is about 10 metres long. About how many buses would make one blue whale?

    See the answer and why
    • A. 3 Correct. Yes. 30 ÷ 10 = 3 buses.
    • B. 300 Not this one. That multiplies instead of dividing.
    • C. 40 Not this one. That adds instead of dividing.
    • D. 20 Not this one. That takes away instead of dividing.
  5. Question 5 of 5Which of these mammals lays eggs?

    See the answer and why
    • A. The kangaroo Not this one. A kangaroo gives birth to a tiny baby that grows in its pouch.
    • B. The platypus Correct. Yes. The platypus and the echidna lay eggs.
    • C. The bat Not this one. Bats give birth to live babies and feed them milk.
    • D. The whale Not this one. A whale gives birth to a live calf in the water.

For teachers and grown-upsWhere the facts come from, and how to use this round.

Sources and notes
  • Ganges river dolphin declared National Aquatic Animal in 2009 (notified 2010). Bihar has the Vikramshila Gangetic Dolphin Sanctuary near Bhagalpur.
  • Asian elephant figures: Project Elephant / MoEFCC estimates (about 27,000 to 30,000 in India).
  • Safety: watch animals from a distance; do not touch stray animals.
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