What is "cell theory"

Cellular \Cel"lu*lar\ (s[e^]l"[u^]*l[~e]r; 135), a. [L. cellula a little cell: cf. F. cellulaire. See Cellule.]

1. Consisting of, or containing, cells; of or pertaining to a cell or cells.

2. porous; containing cavities.

3. pertaining to or using a system of transmission of telephone signals by radio, in which areas are divided into geographical parts (cells), each of which is served by a transmitter whose range is limited to that region, thus permitting a single transmission frequency to be used simulataneously in different parts of the same area. Cellular telephones are typically small and battery powered, allowing a subscriber with such a telephone to carry the telephone in a pocket or purse, over the entire area served, and to be contacted by a single telephone number. The system became widespread and popular in the 1980's and 1990's; as, cellular telephones sometimes lose their link unpredictably. Cellular plants, Cellular cryptogams (Bot.), those flowerless plants which have no ducts or fiber in their tissue, as mosses, fungi, lichens, and alg[ae]. Cellular theory, or Cell theory (Biol.), a theory, according to which the essential element of every tissue, either vegetable or animal, is a cell; the whole series of cells having been formed from the development of the germ cell and by differentiation converted into tissues and organs which, both in plants and animals, are to be considered as a mass of minute cells communicating with each other. Cellular tissue.

   1. (Anat.) See conjunctive tissue under Conjunctive.

   2. (Bot.) Tissue composed entirely of parenchyma, and having no woody fiber or ducts.

Cell \Cell\, n. [OF. celle, fr. L. cella; akin to celare to hide, and E. hell, helm, conceal. Cf. Hall.]

1. A very small and close apartment, as in a prison or in a monastery or convent; the hut of a hermit.

   The heroic confessor in his cell.
   --Macaulay.

2. A small religious house attached to a monastery or convent. ``Cells or dependent priories.''
   --Milman.

3. Any small cavity, or hollow place.

4. (Arch.)

   1. The space between the ribs of a vaulted roof.

   2. Same as Cella.

5. (Elec.) A jar of vessel, or a division of a compound vessel, for holding the exciting fluid of a battery.

6. (Biol.) One of the minute elementary structures, of which the greater part of the various tissues and organs of animals and plants are composed.

   Note: All cells have their origin in the primary cell from which the organism was developed. In the lowest animal and vegetable forms, one single cell constitutes the complete individual, such being called unicelluter orgamisms. A typical cell is composed of a semifluid mass of protoplasm, more or less granular, generally containing in its center a nucleus which in turn frequently contains one or more nucleoli, the whole being surrounded by a thin membrane, the cell wall. In some cells, as in those of blood, in the am[oe]ba, and in embryonic cells (both vegetable and animal), there is no restricting cell wall, while in some of the unicelluliar organisms the nucleus is wholly wanting. See Illust. of Bipolar.

   Air cell. See Air cell.

   Cell development (called also cell genesis, cell formation, and cytogenesis), the multiplication, of cells by a process of reproduction under the following common forms; segmentation or fission, gemmation or budding, karyokinesis, and endogenous multiplication. See Segmentation, Gemmation, etc.

   Cell theory. (Biol.) See Cellular theory, under Cellular.

n. (context biology English) the theory that all living organisms are made of cells as the smallest functional unit

n. (biology) the theory that cells form the fundamental structural and functional units of all living organisms; proposed in 1838 by Matthias Schleiden and by Theodor Schwann [syn: cell doctrine]

In biology, cell theory is a scientific theory which describes the properties of cells. These cells are the basic unit of structure in all organisms and also the basic unit of reproduction. With continual improvements made to microscopes over time, magnification technology advanced enough to discover cells in the 17th century. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, also known as cell biology. Over a century later, many debates about cells began amongst scientists. Most of these debates involved the nature of cellular regeneration, and the idea of cells as a fundamental unit of life. Cell theory was eventually formulated in 1838. This is usually credited to Matthias Schleiden and Theodor Schwann. However, many other scientists like Rudolf Virchow contributed to the theory. Cell theory has become the foundation of biology and is the most widely accepted explanation of the function of cells.

The three tenets to the cell theory are as described below:

1. All living organisms are composed of one or more cells. (However, this is controversial because non-cellular life such as viruses are disputed as a life form. See Non-cellular life.)
2. The cell is the basic unit of structure and organization in organisms.
3. Cells arise from pre-existing cells.