UPSC Prelims 2008 Q136: Science & Technology – Biology
Among the following, which one lays eggs and does not produce young ones directly?
- (a) Echidna
- (b) Kangaroo
- (c) Porcupine
- (d) Whale
Answer: (a) Echidna
Explanation
Which animal lays eggs instead of giving live birth
Among these mammals, one is a rare exception — an egg-laying mammal (monotreme).
| Option | Verdict | Reason |
|---|---|---|
| (a) Echidna | Correct | The Echidna is a monotreme, one of the few mammals that lay eggs instead of giving live birth |
| (b) Kangaroo | Incorrect | Kangaroos are marsupials, giving live birth to underdeveloped young |
| (c) Porcupine | Incorrect | Porcupines are placental mammals, giving live birth |
| (d) Whale | Incorrect | Whales are placental mammals, giving live birth |
Echidna facts:
| Point | Detail |
|---|---|
| Classification | Monotreme (egg-laying mammal) |
| Other monotreme example | Platypus |
Answer: (a) Echidna.
Why each option is right or wrong
- (a) CORRECT. The Echidna is a monotreme, laying eggs instead of giving live birth.
- (b) Incorrect. Kangaroos are marsupials, giving live birth.
- (c) Incorrect. Porcupines are placental mammals, giving live birth.
- (d) Incorrect. Whales are also placental mammals, giving live birth.
Key point
The Echidna is a monotreme — a rare egg-laying mammal — unlike kangaroos (marsupials), porcupines, and whales (placental mammals), which all give live birth.
Remember
The Echidna lays eggs and does not produce young ones directly.
Common mistakes
- Not knowing the term 'monotreme' for the rare group of egg-laying mammals.
- Confusing marsupials (like kangaroos, which give live birth to underdeveloped young) with egg-laying mammals.
- Assuming all mammals give live birth, missing this rare evolutionary exception.
Exam tip
Echidna (and platypus) = monotremes, the only egg-laying mammals. A classic biology exception fact.
Sources
- NCERT Class XI Biology — Animal Kingdom (Mammalia)
- Encyclopaedia Britannica — echidna