What does the change of natural zones depend on?

The change in natural zones depends on the amount of solar heat received by the earth’s surface: the farther from the equator, the colder. This leads to climate change (it becomes more severe and colder closer to the poles), and then to a change in flora and fauna (vegetation becomes poorer the further from the equator, animals also become smaller, they are adapted to life in harsh conditions: they have warm fur, can get food from under the snow (deer), hunt in icy water (seals, polar bears).