The reason we have seasons is that the earth is tilted as it goes around the sun. The Earth's axis is tilted at an angle around 20-30 degrees. This means that at least one side of the world is morning and the other side is night. And since we have the Earth tilted, we have equinoxes. There are 4 equinoxes since we have 4 seasons, spring, summer, fall, and winter. And the reason why we have climate zones are because of varied landscapes that can be either dense or none at all. It's also variables based on heights like mountains and depressions or where the sun is facing.