The distribution of biomes results from 2 major factors - climate and terrain (or geography). The key climatic factors are 1. the atmosphere and its circulation systems, which determine where moisture-carrying air masses do and do not go; and 2. the energy source of those circulatory systems - the sun. read more
The temperature and amounts of water and sunlight an area gets make up the basic building blocks of the climate. Somewhere with low rainfall, high temperatures and large amounts of sunlight leads to a dry, arid climate, for example. This in turn creates a desert-like biome. read more