Terminology Bacteria are single-celled microorganisms found in nearly all natural environments. Outward appearances of the cell such as size, shape, and arrangement are referred to as morphology. The cocci may be further grouped by their tendencies to cluster. Diplococci attach in pairs, streptococci in chains, staphylococci bunch like grapes, and sarcinae produce a cuboidal arrangement. Bacterial cells have definite characteristic structures such as the cell wall, cytoplasm, and nuclear structures.
Viruses are extremely small parasites.
They require living cells of plants, animals, or bacteria for growth. The virus is mainly a packet of genetic material which must be reproduced by the host. Yeast and mold are fungi which do not contain chlorophyls. They range in size from single-celled organisms to large mushrooms. Although some are multi celled, they are not differentiated into roots, stems and leaves.