The richest area of biodiversity in the world is the:

Correct answer: (a) Tropical region

Explanation

The tropical regions, between the Tropics of Cancer and Capricorn, are the richest in biodiversity: they hold more than half of the world's plant and animal species on a small part of its surface. Reasons:

• a warm, steady climate, without harsh winters;
• plenty of sunlight and rain, so plants grow fast all year;
• a long, stable history, little disturbed by the ice ages, which gave species time to evolve.

Tropical rainforests such as the Amazon and the forests of South-East Asia are the richest of all.