What is the main pattern observed in the distribution of species diversity worldwide?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Species diversity decreases as we move away from the equator towards the poles.
Species are not spread evenly over the earth. The best-known pattern is the latitudinal gradient: the number of species is highest near the equator and falls as we go towards the poles. The tropics (23.5° N to 23.5° S) have more species than temperate or polar areas.
Option (1) Species diversity increases as we move away from the equator towards the poles. — Incorrect. This is the reverse of the real pattern. Moving away from the equator, the number of species falls, it does not rise.
Option (2) Species diversity decreases as we move away from the equator towards the poles. — Correct. Species diversity decreases from the equator towards the poles. For example, Colombia, near the equator, has about 1,400 bird species, while Greenland, far to the north, has only 56.
Option (3) Species diversity is uniform throughout the world. — Incorrect. The book says the diversity of plants and animals is not uniform throughout the world; it shows an uneven distribution.
Option (4) Species diversity is highest at the poles. — Incorrect. The poles have the fewest species, not the most, because they lie at the far end of the gradient.
NCERT Extract:
Patterns of Biodiversity – “(i) Latitudinal gradients: The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution. For many group of animals or plants, there are interesting patterns in diversity, the most well- known being the latitudinal gradient in diversity. In general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar areas.”