This article throws light upon the three main biological agents responsible for disintegration and decomposition of rocks and minerals. The biological agents are: 1. Man and Animal 2. Roots of Higher Plants 3. Micro-Organisms.
Biological Agent # 1. Man and Animal:
The action of human being in the disintegration of rocks is well recognised as he cuts the rocks to build dams, channels, roads and buildings etc. Due to such activities of man, the bigger size rocks are converted into smaller ones and thereby increased the surface area of rocks which favours the chemical weathering process leading to decomposition of rocks and minerals.
The role of animals is somewhat similar to man. Large number of birds, insects, worm etc. live in the rocks and by their activities, they make holes into rocks and thus help in weathering.
Biological Agent # 2. Roots of Higher Plants:
The root of trees and other plants penetrate into the joints and crevices of rocks. Due to growth and development of those trees, the roots exert a tremendous pressure because of its development and the massive and hard rock may be broken into smaller ones.
Some roots go quite deep into the soil and form a channel. The roots running in crevices in limestone or marble in search of food, produce acids which have a solvent action on carbonates and thus itch a pattern on the walls of fissures by dissolving a part of the rock with which roots come in contact. During root respiration CO2 produces and that also take part in the weathering process.
Biological Agent # 3. Micro-Organisms:
At the very initial stages of mineral decomposition and soil formation, the lower forms of plants and animals like mosses, bacteria, fungi, actinomycetes etc. play an important role. These organisms extract nutrients from the massive solid rock, nitrogen from the air and can live with a very small amount of moisture.
In due course of time, the soil develops under the cluster of mosses, algae and bacteria. These organisms act upon the decay of plants and animal remains and produce various complex organic compounds, CO2 and also nutrients. The production of CO2 and other organic compounds help in the decomposition of minerals.