Which of the following is NOT one of the explanations given for the greater species diversity of the tropics compared to temperate regions?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → More solar energy is available in temperate regions, which contributes to their higher productivity.
NCERT gives three main hypotheses for the greater species diversity of the tropics: they had more evolutionary time, because they were not disturbed by glaciations; their environment is less seasonal and more constant, which promotes niche specialisation; and they receive more solar energy, which gives higher productivity.
Option (1) Tropical environments are less seasonal, relatively more constant and predictable. — One of the explanations. A constant, predictable environment is the second hypothesis given by NCERT.
Option (2) More solar energy is available in temperate regions, which contributes to their higher productivity. — Not one of the explanations. It is the tropics, not temperate regions, that receive more solar energy and so have higher productivity. This higher productivity may in turn add to the diversity of the tropics.
Option (3) Tropical latitudes have remained relatively undisturbed for millions of years, unlike temperate regions subjected to frequent glaciations. — One of the explanations. Long undisturbed periods gave the tropics a long evolutionary time for species diversification, since speciation is a function of time.
Option (4) Constant tropical environments promote niche specialisation, leading to greater species diversity. — One of the explanations. Constant environments allow species to specialise into narrow niches, and this leads to greater species diversity.
NCERT Extract:
Patterns of Biodiversity – “… (a) Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification, (b) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity and (c) There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.”