Structural Organisation in Animals — NEET UG practice

1. We need to check each statement one by one against the known anatomy of a frog.

2. Statement A: The hepatic portal system is indeed the special venous connection that carries blood between the liver and intestine, so this statement is correct.

3. Statement B: Frogs have only 10 pairs of cranial nerves, not twelve (twelve pairs is a mammalian feature), so this statement is incorrect.

4. Statement C: In female frogs, the ureters (carrying excretory waste) and the oviducts (carrying eggs) are separate ducts that open independently into the cloaca, so this statement is correct.

5. Statement D: The hind-brain actually consists of the cerebellum and medulla oblongata only; the optic lobes belong to the mid-brain, so this statement is incorrect.

6. Statement E: The sinus venosus is a thin-walled triangular sac that collects deoxygenated blood and opens into the right atrium of the heart, so this statement is correct.

7. Since A, C, and E are the correct statements, they match option D.

Hence, the answer is D (A, C and E only).

1. Cranial nerves are the nerves that arise directly from the brain (rather than from the spinal cord) and supply the head, sense organs, and some visceral structures.

2. The number of cranial nerve pairs is a fixed anatomical feature that differs across vertebrate groups — mammals (including humans) have 12 pairs, but amphibians like frogs have fewer.

3. In frogs specifically, only 10 pairs of cranial nerves arise from the brain, which is two pairs less than in mammals.

Hence, the answer is D (10).

1. To find features that distinguish male frogs from female frogs, we must separate structures that are common to both sexes from those that are sex-specific.

2. Features such as bulging eyes, webbed digits in feet, and olive green skin with dark irregular spots are body characteristics shared by both male and female frogs, so they cannot be used to tell the sexes apart.

3. Vocal sacs are membranous pouches found only in males, used to amplify their mating call — this is a true sex-distinguishing feature.

4. The copulatory pad (a rough, thickened cushion) on the first digit of the fore limb is also found only in males, helping them grip the female firmly during amplexus (mating clasp).

5. Since only vocal sacs (B) and the copulatory pad (D) are exclusive to males, these are the correct distinguishing features.

Hence, the answer is D (B and D only).