Read the passage carefully and answer the questions based on the passage:
Species diversity on earth is not uniformly distributed. It is generally highest in the tropics and decreases towards the poles. Earth’s fossil history reveals the incidences of mass extinctions in the past. Earth’s rich biodiversity is vital for the very survival of mankind. It is believed that communities with high diversity tend to be less variable and more productive. The reasons of conserving biodiversity are narrowly utilitarian, broadly utilitarian and ethical. Biodiversity conservation may be in situ as well as ex-situ.
Which of the following might not account for the greater biological diversity in the tropic region?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Frequent glaciations in the past
The passage says species diversity is highest in the tropics and decreases towards the poles. This is the latitudinal gradient. Ecologists give three main reasons for the greater diversity of the tropics.
Option (1) Frequent glaciations in the past — Does not account for tropical diversity. Frequent glaciations happened in the temperate regions. They are the reason those regions have less diversity; the tropics escaped them.
Option (2) More solar energy available — Accounts for tropical diversity. More sunlight gives higher productivity, which may support more species.
Option (3) Less seasonal and more constant and predictable — Accounts for tropical diversity. A steady environment promotes niche specialisation and so more species.
Option (4) Undisturbed for million of years — Accounts for tropical diversity. Speciation needs time, and the tropics had a long evolutionary time for species diversification.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Patterns of Biodiversity – “… Ecologists and evolutionary biologists have proposed various hypotheses; some important ones are (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.”