In which of the following groups of vertebrates is parental care mostly exhibited ?

Analyze the question: The question asks which vertebrate group shows parental care most. Parental care means feeding, protecting, warming and teaching the young after birth or hatching.

Explain the concept: Parental care varies across vertebrate classes:

• Amphibia: Most just lay eggs in water and leave. Parental care is minimal.
• Reptilia: Most bury their eggs and leave. Care is limited, though crocodiles guard their nests.
• Aves (birds): They build nests, incubate eggs, and feed the chicks. Care is extensive, but it usually lasts only until the young can fly and feed themselves.
• Mammalia: Young develop inside the mother (in most species), are fed on milk from the mammary glands, and are protected, groomed and taught for a long time. Mammals show the most prolonged and intensive parental care.

Step-by-step solution:

1. Eliminate Amphibia (B) and Reptilia (A), since both show little or no care.
2. Compare Aves (C) and Mammalia (D). Both care for their young, but mammals nourish them with milk, carry them in the womb, and look after them for the longest time.
3. "Mostly exhibited" points to the group with the highest degree of care, which is Mammalia.

Answer: D. Mammalia

Exam tip: For "most parental care" questions, remember M for Milk and Mothering. Mammals feed their young with milk, which no other vertebrate group does, so Mammalia is the usual answer. If the question asks about nest building and incubation, think of Aves.