As one moves from the poles towards the Equator, biodiversity generally:

In general, the number of species of plants and animals increases from the poles towards the Equator. This pattern, called the latitudinal diversity gradient, is one of the most widely observed patterns in ecology.

Examples:

• Tropical rainforests near the Equator, such as the Amazon, the Congo basin and South-East Asia, contain more than half of the world's species, though they cover only a small part of the land.
• Colombia, near the Equator, has nearly 1,400 species of birds, while New York at about 41 degrees North has about 105, and Greenland at about 71 degrees North has only 56.

Reasons for higher diversity in the tropics:

• Stable climate over long periods: Tropical regions were less affected by ice ages, giving species more time to evolve and diversify.
• Less seasonal variation: Steady conditions throughout the year allow species to specialise in narrow niches.
• More solar energy: Tropical areas receive more sunlight, which supports higher plant growth (productivity) and more food for animals.
• Warm temperatures and abundant rainfall: These allow more organisms to survive and reproduce.

Polar and high-latitude regions:

Extreme cold, short growing seasons and long periods of darkness limit the number of species that can survive.

Similar pattern with altitude:

Biodiversity usually decreases with increasing altitude on mountains, because temperatures fall and conditions become harsher.

India's biodiversity:

• India is one of the 17 megadiverse countries of the world.
• It has four of the world's 36 biodiversity hotspots: the Himalayas, the Western Ghats and Sri Lanka, the Indo-Burma region and Sundaland (including the Nicobar Islands).
• India has only about 2.4 percent of the world's land area but about 7 to 8 percent of its recorded species.

Why not the other options?

• ✗Biodiversity does not decrease or remain the same towards the Equator.
• ✗It does not become zero anywhere on the land between the poles and the Equator.