6.What is biodegradation?

Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. 

It is generally assumed to be a natural process.

The process of biodegradation is threefold: first an object undergoes biodeterioration, 

which is the mechanical weakening of its structure; then follows biofragmentation, 

which is the breakdown of materials by microorganisms; and finally assimilation, 

which is the incorporation of the old material into new cells.