How does biodiversity vary with respect to latitude, from the equator…

The correct answer is Option (1) → Decreases

Biodiversity is not spread evenly over the earth. The best-known pattern is the latitudinal gradient: species diversity is highest near the equator and falls steadily as we move towards the poles. The tropics (23.5° N to 23.5° S) have more species than temperate or polar areas. For example, Colombia, near the equator, has nearly 1,400 species of birds, while New York at 41° N has 105 species.

Option (1) Decreases — Correct. Species diversity decreases from the equator towards the poles, so this is the pattern.

Option (2) Increases — Incorrect. An increase towards the poles is the reverse of what is seen. The tropics, not the poles, are richest in species.

Option (3) Remains the same — Incorrect. Diversity is uneven over the earth. It changes with latitude, so it does not remain the same.

Option (4) First decreases, then increases — Incorrect. There is no rise again near the poles. Diversity keeps falling all the way from the equator to the poles.

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.”