Skip to content

How does a human body… (Class 12 Biology 2025, Q20a)

questionbuddy.in/q/cbse-12-biology-2025-57-7-1-q20a-how-does-human-body-respond

BiologyCBSE Class 12 · Board exam 2025, set 57/7/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2025: question 20(a)

Set in the CBSE Class 12 board exam of 2025, paper 57/7/1, section B, question 20(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q20(a) · 2 marks · Very short answerHuman Health and Disease

How does a human body respond when vaccine is introduced into it ? It is said that vaccinations are a must for a healthy society. Justify.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/7/1.

Hints

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

Hint 1

Think of what the immune system makes when it meets an antigen for the first time.

Hint 2

Vaccination is based on immunological memory. Then think about what happens to disease spread when most people are protected.

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 vaccine contains inactivated or weakened pathogens or their antigens. The body responds by producing antibodies against these antigens, and the antibodies neutralise the pathogen during a real infection.

    ½ mark

  2. Vaccination also produces memory B and T cells. These recognise the pathogen quickly on later exposure and give a fast, strong response.

    ½ mark

  3. Why vaccination is a must for society: vaccinated people are protected from the disease and do not pass it on. When most people are vaccinated, the spread of the disease stops, so the society stays largely disease-free; for example, smallpox was eradicated and polio was controlled in this way.

    1 mark

Answer: The body makes antibodies and memory B and T cells against the vaccine antigens; this gives quick protection and stops disease spreading, keeping society healthy.

Where the marks are

  • Production of antibodies that neutralise the pathogen (½ mark)
  • Generation of memory B and T cells (½ mark)
  • Justification: prevents disease and its spread, making society disease-free (1 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 57/7/1: 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.