multicellular organism,
an organism composed of many cells, which are to
varying degrees integrated and independent. The development
of multicellular organisms is accompanied by cellular specialization
and division of labour; cells become efficient in one process
and are dependent upon other cells for the necessities of life.
Specialization in single-celled organisms exists at the subcellular
level; i.e., the basic functions that are divided among
the cells, tissues, and organs of the multicellular organism
are collected within one cell. Unicellular organisms are sometimes grouped together
and classified as the kingdom Protista.
Copyright (c) 1994, Encyclopaedia Britannica, Inc.
Michael Lachmann /
Stanford University / dirk@charles.stanford.edu