Cell Theory

Cells of Multicellular Organisms Multicellular organisms are organisms that are made up of many cells. Animals, plants, and most fungi are multicellular organisms. Cells within a multicellular organism are specialized, which means that they have a specific job within the organism. These cells must work together, including sharing resources and communicating, in order to survive.

Cells of Unicellular Organisms Unicellular organisms are made of only one cell. Bacteria and Archaea are two types of unicellular organisms. Most unicellular organisms are small, and you need a microscope to see them. All of the processes that keep the organism alive have to happen in one cell.

Cell Theory Cell theory states that all living things are made of one or more cells, the structure and function of a living thing is determined by all of its cells working together, and that all cells come only from existing cells.

Viruses Viruses are nonliving particles that make copies of themselves inside living cells. Unlike living things, viruses are not made of cells. Drugs like antibiotics that kill living things are not effective against viruses.