Organisms living on land are subject to a variety of physical factors. These are temperature, humidity, soil, etc. light, temperature, rainfall, etc., are considered climatic factors while properties and nature of soil are known as edaphic factors. The top fertile layer of soil is formed by weathered rock materials, nutrients and organic detritus (debris). Terrestrial organisms live on this layer of soil. Many animals are found inside it and many walk on it. Plants are anchored by their root systems. Terrestrial plants and animals are deeply influenced by water and temperature. On the basis of these two important factors, terrestrial habitat may be classified as xeric habitat (dry and hot like deserts) and mesic habitat (moist and cool like mountains, plants).