RAS question
Biodiversity is richest in:
Correct answer: (A) Tropical regions.
Biodiversity is richest in tropical regions because species diversity generally increases towards the equator.
Explanation
Biodiversity is richest in tropical regions. NCERT explains this as part of the latitudinal gradient in biodiversity: species diversity generally decreases as one moves away from the equator towards the poles, and the tropics harbour more species than temperate or polar areas. The main ecological reasons are warm temperatures, high rainfall, lower seasonal variation and greater solar energy through the year. Together, these conditions make tropical environments relatively constant and productive, which supports niche specialisation and higher species richness. For RAS, the core point is not just that tropical forests are species-rich, but that biodiversity follows a broad equator-to-pole pattern.
Why the other options are wrong
- (B) Desert regions are not the richest because their harsh conditions limit biodiversity compared with the warm, wet and more productive tropics.
- (C) Temperate regions have only moderate biodiversity, and NCERT notes that tropical areas harbour more species than temperate areas.
- (D) Polar regions are wrong because species diversity generally falls as we move from the equator towards the poles.
Concept
This tests the biodiversity pattern called the latitudinal gradient. It recurs in RAS Environment and Ecology because it links climate, productivity and species richness in a single, exam-friendly principle.