Encyclopedia > Cell theory

  Article Content

Cell theory

The cell theory says that:
  1. All organisms are composed of one or more biological cells.
  2. The cell is the basic unit of organization of organisms.
  3. All cells come from preexisting cells.

Microscopes continued to be improved upon by scientists that studied cells. As a result, the scientists could see closer and begin to understand the internal structures of an individual cell. The internal structures of a cell are called organelles, which means "little organs." Just as our bodies are made up of organs, the "bodies" of cells are made up of organelles.

There are two basic types of cells:

  • prokaryote: do not have a nucleus or membranes surrounding its organelles. Example: bacteria.
  • eukaryotes: do have a nucleus and organelles with membranes surrounding them. Example: plants, animals.

See also: germ theory

All Wikipedia text is available under the terms of the GNU Free Documentation License

  Search Encyclopedia

Search over one million articles, find something about almost anything!
  Featured Article

... to pass urine to the outside, and also a reproductive function in the male, as a passage for sperm. The external urethral sphincter is the skeletal muscle that allows ...

This page was created in 34.5 ms