importance of lichens:-They have the ability to separate the minerals by eroding rocks. Therefore, they also grow on empty rocks. Because of its death and dissolution, there becomes a fold of mineral and organic matter on which other plants can grow. Thus, they produce suitable conditions for other plants to grow on rocks.- In the Tundra regions, lichens are available in abundance.- They also contribute in the formation of soil by enriching it by trapping water, dust and silt. Also, when lichens die they contribute organic matter to the soil, which further improves the quality of the soil so that more plants can grow.- Lichen also plays an important role in fixing nitrogen. Due to their cooperation with algae, lichens are capable of converting nitrogen from the air into nitrate, which leads to their development. This conversion of nitrogen impacts the ecosystem because when it rains, nitrates are leached from lichens and is used by soil-based plants.- Lichen needs clean air to grow. They are not able to tolerate pollution. Therefore, to grow they absorb everything from the air including carbon dioxide and heavy metals. Scientists can determine the level of air pollution in the area with the help of lichens and if lichens are dying in one site due to harmful pollution, it can be considered as the initial warning or signal that the level of pollution is increasing at that place.

Metabolism is a term that is used to describe all chemical reactions involved in maintaining the living state of the cells and the organism. Metabolism can be conveniently divided into two categories:

Catabolism - the breakdown of molecules to obtain energyAnabolism - the synthesis of all compounds needed by the cellsMetabolism is closely linked to nutrition and the availability of nutrients. Bioenergetics is a term which describes the biochemical or metabolic pathways by which the cell ultimately obtains energy. Energy formation is one of the vital components of metabolism.