Human Health & Disease - 1 - NEET Biology Class 12 Free MCQ Test with solutions

• Common cold is caused by Rhinoviruses.
• Haemozoin is a toxic pigment released by Plasmodium during malaria infection.
• Widal test is used for the diagnosis of Typhoid caused by Salmonella typhi.
• Allergy is commonly caused by allergens like dust mites.

Hence, A-III, B-I, C-II, D-IV is correct.

• Cocaine is obtained from Erythroxylum coca.
• Heroin is derived from Papaver somniferum (opium poppy).
• Morphine acts as an effective sedative and pain reliever used in surgery.
• Marijuana is obtained from Cannabis sativa.

Thus, A-III, B-IV, C-I, D-II is correct.

• Typhoid is caused by Salmonella typhi (Bacterium).
• Leishmaniasis is caused by Leishmania (Protozoan parasite).
• Ringworm is caused by fungi such as Microsporum or Trichophyton.
• Filariasis is caused by a nematode (Wuchereria bancrofti).

Hence, A-IV, B-III, C-I, D-II is correct.

Statement I: Bone marrow is the main lymphoid organ where all blood cells, including lymphocytes, are produced.

This is correct because:

• Bone marrow is the primary lymphoid organ.

• All blood cells, including lymphocytes (B-cells and T-cell precursors), are formed in the bone marrow.

So, Statement I is correct.

Statement II: Both bone marrow and thymus provide microenvironments for the development and maturation of T-lymphocytes.

This is also considered correct at the Class 12 level because:

• In the bone marrow, the earliest T-cell precursors (pro-T cells) are formed.
  This is the first step in T-cell development.

• These immature cells then move to the thymus, where they develop and mature into fully functional T-lymphocytes.

So, both organs together help in the development pathway of T-cells:

• Bone marrow → formation of T-cell precursors

• Thymus → development and maturation of T-cells

Assertion (A): True
Sometimes organs such as the liver or kidney may fail due to disease or damage, and in severe cases organ transplantation becomes the only effective treatment to allow the patient to survive and live normally.

Reason (R): True
Before transplantation:

• Blood group and tissue matching are necessary to reduce the chances of rejection.

• After transplant, the patient must take immunosuppressant drugs to prevent the immune system from attacking the transplanted organ.

Why (R) is not the correct explanation of (A):
The reason only describes procedures and precautions involved in transplantation, not why transplantation becomes necessary when organs fail.

Therefore, both statements are correct, but the reason does not explain the assertion.

The image of above flowering plant shown is of Datura and it is well-known plant for its hallucinogenic properties.

Allergies are hypersensitivity reactions involving IgE antibodies bound to mast cells. Upon exposure to allergens, these cells release histamine and serotonin, producing symptoms like sneezing and difficulty in breathing.

Autoimmune diseases arise when the immune system attacks self-antigens, mistaking them for foreign molecules. This leads to tissue damage, as seen in rheumatoid arthritis.

Benign tumors remain localized and do not invade other tissues. Malignant tumors invade and destroy nearby tissues and can metastasize to distant organs through blood or lymph.

Oncogenic viruses contain viral oncogenes that can transform normal cells into cancerous ones. Examples include certain DNA and RNA viruses responsible for specific cancers.

MRI (Magnetic Resonance Imaging) uses non-ionising radiation and strong magnetic fields to detect structural and physiological changes within tissues, providing high-resolution internal images.

The thymus is the primary lymphoid organ where T-lymphocytes mature and become antigen-sensitive. The bone marrow produces all blood cells, including lymphocytes, but T-cell maturation occurs in the thymus.

HIV is transmitted via sexual contact, contaminated needles, blood transfusion, or from mother to child through placenta, not through food or water. ELISA is used for HIV detection.

Normal cells exhibit contact inhibition, stopping division upon contact with other cells. Cancer cells lose this property, leading to uncontrolled proliferation and tumor formation.