Biotic weathering is carried out by plants, animals, and man.
Plants contribute to both mechanical and chemical weathering.
The roots of the plants penetrate into the joints of the rocks.
They grow longer and thicker.
In this manner, they exert pressure on the rocks and the rock joints are thereby enlarged and break into smaller fragments.
Burrowing animals like earthworms, rats, rabbits, termites and ants breakdown the rocks.
These disintegrated rocks can easily be eroded or removed by wind.
According to scientists, there is a possibility of occurrence of about 1,50,000 earthworms in an acre and they can convert 10 to 15 tonnes of a rock mass into good soil and bring it to the surface.
Human beings play a very important role in weathering of various rocks.
Man breaks a large amount of rocks in the course of his activities, like agriculture, construction of houses, roads, etc. He quarries for mining minerals, thus helps in weathering by breaking, weakening and loosening the rocks.