Is biodiversity greater in hot or cold areas? Why?
Biodiversity tends to be highest in the tropics and drops off as you go to higher latitudes (i.e. towards the polar regions) because life thrives best in warm and moist environments.
Life thrives best in warm and moist environments and the tropics has this in abundance, including some "hot spots" of really high diversity. But if the environment gets too hot and dry, as in desert regions, or cold and dry as in the polar regions, biodiversity also drops off. See pic. Notice how biodiversity is low (blue) near the the poles and in North Africa at the Sahara desert. And very high near the equator (red and orange)