Human Health and Disease, on the exam screen.

Infection begins when a female Anopheles mosquito injects sporozoites into the human during a bite (Statement V).
Sporozoites travel through the blood to the liver (Statement IV).
multiply asexually in liver cells and burst out into the blood (Statement II).
then invade and multiply asexually in red blood cells (RBCs), rupturing them (Statement I).
Finally gametocytes develop in the RBCs (Statement III) to be taken up by the mosquito.

Correct order: V, IV, II, I, III.

Nicotine stimulates the adrenal gland to secrete catecholamines (P-II), morphine is an effective sedative and painkiller (Q-III), heroin is a depressant that slows body functions (R-IV), and cocaine produces a sense of euphoria and increased energy (S-I). This gives P-II, Q-III, R-IV, S-I, which is option (3).

Primary lymphoid organs are where lymphocytes are produced and mature - the bone marrow and the thymus. Secondary lymphoid organs are where mature lymphocytes go to meet antigen and mount a response: the spleen, lymph nodes, tonsils, Peyer's patches of the small intestine and the appendix. Tonsils and spleen therefore belong to the secondary group. NCERT Class 12, Human Health and Disease.

Colostrum, the yellowish fluid produced in the first few days after birth, is rich in immunoglobulin A (IgA) antibodies. Because these are ready-made antibodies handed directly to the infant rather than produced by the infant itself, this is a form of NATURAL PASSIVE IMMUNITY, protecting the newborn until its own immune system matures. NCERT Class 12, Human Health and Disease.

Morphine is an opioid extracted from the latex of Papaver somniferum. It binds to receptors in the central nervous system and is a very effective sedative and painkiller, which is exactly why it is used for patients recovering from surgery - and also why it carries a high risk of abuse and dependence. NCERT Class 12, Human Health and Disease.

The division of labour between the two hosts is the key to this life cycle. In the human, Plasmodium multiplies ASEXUALLY - first in liver cells, then in red blood cells, where gametocytes also form. Those gametocytes are taken up when a female Anopheles bites; only inside the mosquito's gut do the gametes fuse, so fertilisation and subsequent development happen there. The mosquito is therefore the definitive host. NCERT Class 12, Human Health and Disease.

Typhoid-Salmonella, pneumonia-Haemophilus, filariasis-Wuchereria and malaria-Plasmodium give P-III, Q-IV, R-I, S-II. Chapter: Human Health and Disease.

The infectious stage of Plasmodium that enters the human body is the sporozoite stage. Sporozoites are transmitted through the saliva of an infected female Anopheles mosquito. Chapter: Human Health and Disease.

Active immunity involves the production of antibodies by the host's immune system, which takes time to develop a full response, not immediately. Chapter: Human Health and Disease.