Assertion (A): The diversity of bird species decreases as we move away from the equator towards the poles.
Reason (R): Colombia, located near the equator, has nearly 1,200 species of birds, while New York at 41° N has 56 species and Greenland at 71° N has only 42 species.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Assertion (A) is true, but Reason (R) is false.
Assertion (A): The diversity of bird species decreases as we move away from the equator towards the poles. — True. Species diversity generally decreases as we move away from the equator towards the poles. The tropics hold more species than temperate or polar areas. This is the latitudinal gradient in diversity.
Reason (R): Colombia, located near the equator, has nearly 1,200 species of birds, while New York at 41° N has 56 species and Greenland at 71° N has only 42 species. — False. The places are right, but the numbers are not. The book gives Colombia nearly 1,400 bird species (not 1,200), New York 105 (not 56) and Greenland only 56 (not 42). The figure of 1,200 belongs to India, and 56 belongs to Greenland, not New York.
So A is true but R is false.
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. … 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. Colombia located near the equator has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at 71° N only 56 species. India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds.”