In which of the following ecosystems, the species diversity is relatively higher?

Coral reefs cover less than 1 percent of the ocean floor yet hold roughly a quarter of all known marine species, which is why they are called the rainforests of the sea. So C is the answer.

• Deep sea (A): Light and food are scarce, so absolute diversity is low, although endemism is high around hydrothermal vents.
• Deciduous rain forest (B): The term is loose. Tropical moist deciduous forests are less diverse than evergreen tropical rainforests because of seasonal leaf fall and dry months. Diversity is high here, but below coral reefs in this list.
• Desert (D): Water stress limits both plant and animal diversity, making it the lowest of the four.

The core concept is the latitudinal and habitat-wise pattern of biodiversity, linked to biodiversity hotspots and marine conservation under Environment and Ecology. Note that coral reefs face severe bleaching stress from rising sea temperatures, with mass bleaching events recorded on the Great Barrier Reef in 2016, 2017 and 2020.

Trap: Aspirants pick the tropical rainforest by reflex. Read the options carefully: the question asks about relative diversity across these ecosystem types, and coral reefs score highest here.