Plants seem to grow together as groups. Maps have been made of plant growth and these have been called climate maps. The primary patters of climate are caused by fluid flow on a spinning earth differentially warmed at the equator. All fluid flow acquires angular momentum because of the spin of the earth, a result described as Coriolis force. As a result, the earthly climate is divided into large patches or cells, wet into great gyres around ocean basins, causing different climates where they approach continents and where they depart, thereby superimposing local climatic patches on the global system.
Mountain ranges bar the reflected in the pattern of biomes.
Specific plants grow in specific biomes. A biome is defined as an ecosystem of a large geographic area in which plants are of one formation and for which climate sets the limits. Low latitudes receive more heat and plant diversity is reflective of this first law of inequality. Higher latitudes receive less heat, are cold and dry resulting in particular biomes. The earth is a spinning sphere, the equator of which is just a few degrees away from being parallel with the plane of the earth's orbit around the sun.