Structural Organisation in Animals

Explanation

Submerged frogs rely entirely on cutaneous respiration: dissolved oxygen diffuses across the moist, richly vascularised skin. The buccal cavity and lungs work only on land, and frogs have no trachea-based system of the kind insects use.

Explanation

Frogs have ten pairs of cranial nerves arising from the brain. Humans and other mammals have twelve pairs, which is the distractor this question is built around.

Explanation

Vessels carrying blood towards the heart are veins, which rules out the aorta and the pulmonary artery. The pulmonary vein does return to the heart but carries oxygenated blood from the lungs. Deoxygenated blood collected from the body reaches the frog’s sinus venosus through the vena cava, exactly as in other vertebrates.