Solution: In Biology, the basic unit of which all living things are composed is known as €˜cell€™. The €˜cell€™ is the smallest structural unit of living matter that is capable of functioning independently. A single cell can be a complete organism in itself, as in bacteria and protozoans. A unicellular organism also captures and digests food, respires, excretes, grows, and reproduces. Similar functions in multi-cellular organisms are carried out by groups of specialized cells which are organized into tissues and organs such as, the higher plants and animals. Hence, €˜cell€™ is known as the basic structural and functional unit of life.