Which of the following statement is NOT true ?

Question

UnlockIAS · Accepted Answer

Correct — A, 'Species diversity increases from equator towards poles.' The stem asks which statement is NOT true, and this one states the latitudinal gradient of species diversity backwards. For almost every group of organisms, species richness is at its maximum near the equator and falls steadily as you move towards either pole. The standard NCERT illustration is birds: Colombia, sitting on the equator, has roughly 1,400 species; New York at about 41°N has around 105; Greenland at about 71°N only about 56. The remaining three statements all describe that same gradient correctly, so (a) is the odd one out and the required answer.

Why the other options are wrong — (b) This statement is TRUE, so it cannot be the answer to a 'NOT true' question. The tropical belt (23.5°N to 23.5°S) is the richest zone on Earth for practically every taxonomic group.  (c) This statement is TRUE, so it cannot be the answer. The Amazonian rainforest of South America is the standard textbook example of the most species-rich region on the planet, counted in tens of thousands of plant species besides its fishes, birds, mammals, amphibians, reptiles and enormous invertebrate fauna.  (d) This statement is TRUE, so it cannot be the answer. It simply states the higher-latitude half of the same gradient: moving from temperate latitudes into the Arctic and Antarctic, species richness keeps falling.

Concept: The latitudinal gradient in species diversity is one of the oldest and best-documented patterns in ecology: species richness peaks in the tropics and declines towards both poles, for plants, birds, fishes and insects alike. Three explanations are usually offered. (i) Evolutionary time — temperate latitudes were repeatedly disrupted by Pleistocene glaciations, while tropical latitudes remained relatively undisturbed for millions of years, giving speciation a far longer uninterrupted run. (ii) Environmental constancy — tropical climates are less seasonal and more predictable, which favours narrow niche specialisation and lets more species coexist. (iii) Energy — more solar radiation reaches the tropics, supporting higher primary productivity and therefore a greater diversity of consumers.

State PCS 2019 Q23 — Environment & Ecology PYQ with Answer

State PCS 2019 Q23 — Environment & Ecology PYQ with Answer