Question

How many of the following statements is/are not true?
(i) Species diversity increases as we move from the poles towards the equator.
(ii) The tropical regions have been subjected to frequent episodes of glaciations in the past.
(iii) The seasonal changes in the tropical regions are less as compared to the temperate regions.
(iv) The photosynthetic productivity of the tropics is more than that of the temperate regions.

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is A 1

Biodiversity refers to the variety and variability amongst living organisms and ecosystems in a given area. Every part of this planet does not have a uniform distribution of life forms and hence the amount of biodiversity seen in different parts of the world also varies.

Species diversity increases as we move from the poles towards the equator. The tropical regions (ranging from 23.5°N to 23.5°S) have more variety of species than the polar or temperate (23.5°N to 66.5°N and 23.5°S to 66.5°S) regions. India, which majorly lies in the tropical zone, has 1200 different species of birds whereas Greenland at 71°N has only 56 different species of birds. Thus statement I is true.

The reason behind this is believed to be the fact that -

• The environmental conditions in the tropics have remained constant since a very long time whereas the temperate region has often experienced extreme disastrous events such as glaciations. This has allowed the organisms living in the tropics to evolve undisturbed over a long period of time which has led to greater species diversification. Thus, statement II is false.
• The seasonal changes in the tropics are much less compared to the temperate zones. The climate in the tropics remains warm and humid throughout the year without any extreme changes. This allows organisms to specialise their niche (role played by an organism in its ecosystem) they belong to and promote better species diversification. Thus, statement III is true.
• As the tropics receive a constantly high amount of overhead sunlight throughout the year, the photosynthetic productivity in these regions is high and hence availability of food and energy for all life forms is high which can indirectly promote higher diversity in life forms. Thus, statement IV is true.

Hence, we can conclude that only one statement is not true.