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Biology

Class 12 · Science & Environment

Ch 11 · Organisms and Populations

Real UPSC Prelims questions from 2016–2026, linked to this book. Try each one first, then open the answer. 2026 answers follow UPSC's provisional answer key.

Prelims 2021 · Q22

Consider the following kinds of organisms:

  1. 1.Copepods
  2. 2.Cyanobacteria
  3. 3.Diatoms
  4. 4.Foraminifera

Which of the above are primary producers in the food chains of oceans?

  1. (a)1 and 2
  2. (b)2 and 3
  3. (c)3 and 4
  4. (d)1 and 4
Show answer

UPSC's answer: (b)

NCERT answers it: Class 12 Biology, Ch 11 (Organisms and Populations); Class 8 Curiosity, Ch 2 (The Invisible Living World: Beyond Our Naked Eye).

How to solve it with NCERT: Class 12 Biology, ch 11: cyanobacteria photosynthesise, and copepods live as parasites on fish, so they are consumers. Class 8 Curiosity, ch 2: diatoms are microalgae that make their own food using sunlight. So 2 and 3 are producers. Answer (b).

Hindi version: UPSC's official question paper (2021), question 22 ↗

Prelims 2024 · Q28

Which one of the following shows a unique relationship with an insect that has coevolved with it and that is the only insect that can pollinate this tree?

  1. (a)Fig
  2. (b)Mahua
  3. (c)Sandalwood
  4. (d)Silk cotton
Show answer

UPSC's answer: (a)

NCERT answers it: Class 12 Biology, Ch 11 (Organisms and Populations).

Class 12 Biology, ch 11: many fig species have a one-to-one relationship with a wasp species — a fig can be pollinated only by its 'partner' wasp. The wasp, in turn, lays its eggs in the fig fruit. Answer (a).

Hindi version: UPSC's official question paper (2024), question 28 ↗

Prelims 2024 · Q29

Consider the following:

  1. 1.Butterflies
  2. 2.Fish
  3. 3.Frogs

How many of the above have poisonous species among them?

  1. (a)Only one
  2. (b)Only two
  3. (c)All three
  4. (d)None
Show answer

UPSC's answer: (c)

NCERT answers it: Class 12 Biology, Ch 11 (Organisms and Populations).

The one fact NCERT doesn't give: Some fish, such as pufferfish, are poisonous.

Class 12 Biology, ch 11: some frogs are poisonous, and the Monarch butterfly carries a chemical from a poisonous weed that makes it distasteful to birds. With the fact, all three. Answer (c).

Beyond NCERT: pufferfish carry tetrodotoxin, mainly in the liver and sex organs, and tetrodotoxin poisoning can be fatal. Source: CDC NIOSH, Tetrodotoxin: Biotoxin (emergency response card, cdc.gov)

Hindi version: UPSC's official question paper (2024), question 29 ↗

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