AIPMT 2012 Prelims question paper with solutions

1. Erythrocytes (red blood cells) differ structurally between frogs and humans, so we compare their key features.

2. In frogs, erythrocytes are large, oval, and biconvex, and importantly, they retain their nucleus, unlike mature human red blood cells, which lose their nucleus during development.

3. Despite being nucleated, frog erythrocytes still contain the respiratory pigment haemoglobin in their cytoplasm, which is essential for carrying oxygen.

4. This rules out options suggesting the cells lack a nucleus or lack haemoglobin, since frog RBCs have both a nucleus and haemoglobin.

5. Since option C correctly describes frog erythrocytes as nucleated and containing haemoglobin, it is the correct answer.

Hence, the answer is C (Nucleated and with haemoglobin).

1. We check each statement about Periplaneta americana (the cockroach) against known anatomical facts.

2. Statement A is correct: male cockroaches bear a pair of short, thread-like accessory appendages called anal styles, which are absent in females and assist during copulation — this is a true distinguishing feature.

3. Statement B is incorrect in detail because although Malpighian tubules are numerous (around 100-150 thin filaments, not exactly 16 long ones as stated), the actual number and description given here do not match cockroach anatomy accurately.

4. Statement C is incorrect because the cockroach's nervous system is located ventrally (on the underside of the body), not dorsally.

5. Statement D is incorrect because grinding of food is carried out not just by the mouthparts (mandibles) but also by the gizzard, which has hard chitinous plates for mechanical grinding.

6. Since only statement A is accurate, it is the correct answer.

Hence, the answer is A (Males bear a pair of short thread like anal styles).

1. Autogamy requires a flower to pollinate itself, and geitonogamy requires pollen transfer between two different flowers on the same plant — both scenarios require that a single plant carries both male and female reproductive structures.

2. Papaya is a dioecious plant, meaning individual plants bear either only male flowers or only female flowers, never both.

3. Since no single papaya plant has both types of flowers, pollen from a male flower can never reach a female flower on the same plant — this rules out both autogamy and geitonogamy simultaneously.

4. Cucumber and maize are monoecious (having both flower types on the same plant), so geitonogamy remains possible in them.

5. Hence, the answer is Option A: Papaya.