Weathering refers to the set of geological processes that decompose rock on the surface of the earth. Biological weathering is a sub-process of physical and chemical weathering. It plays an important role in soil formation.
In biological weathering, living organisms, such as plants and animals, cause rock to decompose.
Plant and tree roots can work their way into the crevices of a rock, forcing it apart and ultimately causing it to fracture. Some plants give off organic acids that can chemically break down rock minerals.
Worms, termites, gophers and prairie dogs can all be responsible for biologically weathering rocks and rock particles. They physically break rocks apart during physical activities such as boring.
Some lichens will anchor themselves to the surface of a rock and weather it either chemically or physically. They can either release various organic acids that will break down rock minerals or they can grow into the pores and cracks of the rock, making it vulnerable to fracture.
When plants and animals decay, they release carbon dioxide into the air. When the carbon dioxide mixes with water, it forms carbonic acid, which can break down the minerals in rocks.