Excretion

Excretion is one of the most basic functions of life. It is the process of eliminating waste products of metabolism and other non-useful materials.^[1] It is an essential process in all forms of life. It contrasts with secretion, where the substance may have specific tasks after leaving the cell.

In single-celled organisms, waste products are discharged directly through the surface of the cell. Multicellular organisms use more complex methods. Higher plants eliminate gasses through the stomata on the surface of leaves. Animals have special excretory organs.

1. ↑ Beckett, B. S. (1986). Biology: a modern introduction. Oxford University Press. p. 110. ISBN 0199142602.