Download App

Human Health and Disease — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYHuman Health and Disease1 Mark
Question
For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion : Some diseases that attack in childhood do not attack again.
Reason: Memory cells plays an important role.
✓

Answer

  1. Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation:

This can be explained in terms of memory cells. After the infection disappears as a result of antigen-antibody interaction and killer T-cell-nonself cell interaction, some of the specific lymphocytes remain in lymphatic tissue as "memory or primed cells" which are ready to produce the antibodies and killer cells if the same antigens reappear. That is why the second attack of the infectious disease elicits quick and abundant antibody formation. The memory cells can give rise to more effector cells and memory cells in case of a second attack of antigens. Whereas the effector cells have a life of a few days only. and the memory cells live long, some even for whole life. The memory cells are stored in the spleen and lymph nodes.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Assertion (A) & Reason (B) MCQ" from Human Health and Disease→Human Health and Disease — all question types→BIOLOGY STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

Two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: Vitamins B2 is found in cereals, green vegetables, brewer's yeast, egg white, milk and liver.
Reason: Vitamins B2 can be commercially produced by some yeasts.
→
For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion : Haplodiploidy occurs in some insects.
Reason: Male insects develop parthenogenetically, while females grow from fertilised eggs.
→
For two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Epididymis is divided into three parts.
Reason: Epididymis is the organ that stores spermatozoa.
→
Assertion (A): Vertical distribution of different species occupying different levels in the ecosystem is called stratification.
Reason (R): Trees occupy top vertical strata or layer of a forest, herbs, grasses the second and shrubs occupy the bottom layers.
→
For two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Chasmogamous flowers require pollinating agents.
Reason: Cleistogamous flowers do not expose their sex organs.
→
For two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: In morula stage, the cells divide without any increase in size.
Reason: Zona pellucida remains undivided till cleavage is complete.
→
For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: Emigration is outward movement of some individuals from local population.
Reason: Emigration is caused by occurrence of deficiencies and calamities.
→
For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion : In birds, the chromosome composition of the egg determines the sex.
Reason: Female birds are heterogametic.
→
For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
Assertion: Cuscuta is an example of holoparasite.
Reason: Cuscuta does not depend on other plants for nutrition requirements.
→
For two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Placenta acts as a major endocrine organ.
Reason: In mammals, fetal components of the placenta derive initially from the chondroblast.
→