NCERT Class 12 Biology: Chapter – 8 Human Health and Diseases Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 10:

If a regular dose of drug or alcohol is not provided to an addicted person, he shows some withdrawal symptoms. List any four such withdrawal symptoms.

Answer: If a regular dose of drug or alcohol is not provided to an addicted person, he shows some withdrawal symptoms which are as follows:

1. It leads to anxiety.

2. Trouble concentrating on things and thinking clearly.

3. Headache and nausea.

4. Mood swings are also seen.

Question 11:

Why is it that during changing weather, one is advised to avoid closed, crowded and air-conditioned places like cinema halls etc. ?

Answer: During changing weather, one is advised to avoid closed, crowded and air conditioned places like cinema halls etc. because at this time the microbes are active and prevalent. This makes an individual more susceptible to viral infections.

Question 12:

The harmful allele of sickle cell anemia has not been eliminated from human population. Such afflicted people derive some other benefit. Discuss.

Answer: Sickle cell Anaemia is a genetic disorder in which Valine is substituted instead of Glutamic Acid in the beta Hemoglobin chain. This mutation leads to the change of RBC՚s shape from disc shape to sickle like shape leading to decreased oxygen in the body and the sickle cell trait developed, also makes people less prone to Malaria.

Question 13:

Lymph nodes are secondary lymphoid organs. Explain the role of lymph nodes in our immune response.

Answer: Sites where lymphocytes interact with the antigens and then proliferate to become effector cells are called as secondary lymphoid organs.

Functions of lymph nodes:

1. Main function of lymph node is to clear the lymph (it is a clear liquid which comes from plasma) which carries pathogens and other foreign substances (like cancer cells) that are brought by the lymph, through lymphatic cells.

2. It is also responsible for providing immunity as it is the place were B and T lymphocytes interact.

Question 14:

Why is an antibody molecule represented as ?

Answer: Antibody is also known as Immunoglobulin. It is a large Y-shaped protein, produced by the plasma. It has two light chains () and two heavy chains () hence the representation . Antibodies are produced in response to various antigens (bacteria, virus, fungi etc.) as an immune response.

Question 15:

What does the term ‘memory’ of the Immune system mean?

Answer: Memory of the immune system means the body remembers the antigen, recognise it from previous encounter and initiate the immune response against it.

During this response the body produces B & T memory cells which are clones of the B and T lymphocyte cells already present in the body.

Question 16:

If a patient is advised Anti-Retroviral Therapy, which infection is he suffering from? Name the causative organism.

Answer: If a patient is advised Anti-Retroviral Therapy the patient is suffering from Acquired Immune Deficiency Syndrome (AIDS) . The causative organism is a virus called HIV or Human Immuno Deficiency Virus . This virus spreads through contaminated blood, reuse of HIV infected needles etc.

Short Answer Type Questions

Question 1:

Differentiate between active immunity and passive immunity.


Active Immunity & Passive Immunity
Active ImmunityPassive Immunity
i. Body prepares antibodies in response to a pathogen or foreign materiali. Antibodies are deliberately put into the body by artificial means.
ii. It is slow and takes time to show response.ii. It is fast and responds quickly.

Question 2:

Differentiate between benign tumor and malignant tumor.


Benign Tumor and Malignant Tumor
Benign tumorMalignant tumor
i. Usually, they remain confined to their original location and do not spread to other parts of the bodyi. they spread to other parts of the body as well.
ii. They cause little damage.ii. They cause severe damage.
iii. They cannot start a new tumor at a new placeiii. They may start a new tumor when they reach a new place.

Question 3:

Do you consider passive smoking is more dangerous than active smoking? Why?


The term Passive smoking means indirectly inhaling the smoke produced by someone else, also known as second-hand smoke. It is equally dangerous as active smoking because an individual inhales nicotine and other harmful substances which may lead to emphysema, lung cancer, coronary heart disease and many more.

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