How does biological weathering take place?

Biological weathering is caused by following agents:

1. Plants — The roots of plants grow into the cracks and crevices in search of water or nourishment. They exert pressure on rocks and break them. Sometimes, the roots release carbonic acid which changes the chemical composition of minerals and help in weathering.
2. Animals — Burrowing animals cause loosening or weakening of the rocks and expose them to other agents of weathering.
3. Human activities — Construction of roads, mining, farming and deforestation lead to weathering of rocks.