cell

The cell is the basic structural and functional unit of all forms of life or organisms. The term comes from the Latin word cellula meaning 'small room'. A biological cell basically consists of a semipermeable cell membrane enclosing cytoplasm that contains genetic material. Most cells are only visible under a microscope. Except for highly-differentiated cell types (examples include red blood cells and gametes) most cells are capable of replication, and protein synthesis. Some types of cell are motile. Cells emerged on Earth about four billion years ago.

All organisms are grouped into prokaryotes, and eukaryotes. Prokaryotes are single-celled and include archaea and bacteria. Eukaryotes can be single-celled or multicellular, and include protists, plants, animals, most species of fungi, and some species of algae. All multicellular organisms are made up of many different types of cell. The diploid cells that make up the body of a plant or animal are known as somatic cells, which excludes the haploid gametes.