Multicellular organism

From ArticleWorld

Multicellular organisms are organisms that are made up of more than one cell and in which the cells are differentiated to perform specialized functions. The multicellular organisms are also considered as the more complex life-forms in existence. They include animals and plants, and are indeed the most clearly visible set of organisms.

Tissue level

A tissue is defined as a group of similarly differentiated cells that perform a function. A multicellular organism can work on several levels. The tissue is one such level. There are however multicellular organisms that do not function even at this level. The sponge can work on a cellular level as the different cells seem to work like many separate organisms working together. The sponges have no tissues, organs or organ systems which require organization.

There are advanced organisms such as jellyfish, corals and sea anemones that work on the tissue level as their cells aggregate to form tissues. An example of this is seen in the outer epidermis and inner gastrodermis of jellyfish.

Organ level

Even more advanced organisms are those with an organ level of development. This is where groups of tissues form organs. This includes the formation of organs such as the primitive brain in platyhelminthes. In more advanced organisms there are organ systems. This is where there are groups of organs that act together for a common purpose. Each organ in these systems performs a particular task but act together to achieve a common purpose.

An example of this would be in the digestive system where many organs work together towards the purpose of digesting food. This includes the use of the stomach, small intestine and the pancreas, to name a few.