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Study a part of life cycle of… (Class 12 Biology 2025, Q23)

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BiologyCBSE Class 12 · Board exam 2025, set 57/1/1 · 3 marks · Short answer

CBSE Class 12 Biology 2025: question 23

Set in the CBSE Class 12 board exam of 2025, paper 57/1/1, section C, question 23, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q23 · 3 marks · Short answerCompetency-basedHuman Health and Disease

Study a part of life cycle of Plasmodium given below :

Answer the following questions :

  1. (a)

    Name the infective stage of Plasmodium that is stored in the female Anopheles mosquito.

    0 marks
  2. (b)

    Where does fertilization and development of parasite take place ?

    0 marks
  3. (c)

    Identify labels P and Q in the given diagram.

    0 marks
  4. (d)

    Asexual and sexual phase of the life cycle of the Plasmodium takes place in two different hosts. Write their names.

    0 marks

Figure in the paper: Part of Plasmodium life cycle: a mosquito biting a human; gametocytes (labelled Q) entering the mosquito; 'Fertilization and development' of a gamete/zygote; label P points to a large oocyst-like structure with sporozoites being released (arrows out). See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

The stage that enters a human through a mosquito bite is the infective stage.

Hint 2

Gametes form in the mosquito after it sucks blood. Think about where that blood goes first, and where the parasites wait before the next bite.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Sporozoites.

    ½ mark

  2. (b) Fertilisation and development take place in the gut (stomach) of the female Anopheles mosquito.

    ½ mark

  3. (c) P = the salivary glands of the female Anopheles mosquito, where sporozoites are stored.

    ½ mark

  4. Q = gametocytes.

    ½ mark

  5. (d) Asexual phase: in the human (liver cells and RBCs).

    ½ mark

  6. Sexual phase: in the female Anopheles mosquito.

    ½ mark

Answer: (a) Sporozoites; (b) gut of female Anopheles; (c) P = salivary glands, Q = gametocytes; (d) asexual in human, sexual in mosquito.

Where the marks are

  • Sporozoites (½ mark)
  • Gut of the female Anopheles mosquito (½ mark)
  • P = salivary glands (½ mark)
  • Q = gametocytes (½ mark)
  • Asexual phase in human (½ mark)
  • Sexual phase in mosquito (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Human Health and Disease, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 57/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.