In which parts of the earth is the greatest concentration of living organisms observed? And why?

For active growth and reproduction, all living organisms need a warm climate and sufficient nutrition. The most predisposing factors for this are closer to the equator in the tropical zone. It is here that the rarest animals and plants are found. After all, the habitat is conducive to an increase in the population. In the tropics, there is enough water, long daylight hours, the air temperature is suitable for the life of a huge species of plants. Many plants feed on herbivores and this is one of the favorable factors for reproduction. And predatory animals also have something to eat.