The Hierarchy
Kingdom, Phylum, Class, Order Family, Genus, Species
Viruses
Kingdom: very small and are beyond the resolution of a light microscope. They are sub-cellar structures, which exist as chemicals outside of living cells, but which are able to reproduce once they have invaded their hosts. They have obvious significance f
Bacteria
Kingdom; represents the smallest life forms which are organized on a cellular basis. Most obtain their energy from the breakdown of living or non-living organic matter. They play an important role in the decomposition of plant and animal remains, and the
Protoctista
Kingdom; single celled organisms. They make up much of the plankton in the oceans. Each individual cell contains organelles, specialized to perform certain functions - digestion, protein synthesis, transport, etc. Some are harmful and can cause malaria, d
Fungi
Kingdom; contain no chlorophyll. They gain their food from dead organisms remains or from living hosts. Consists of multi-cellular filamentous threads called hyphae which grow over the substrate, secreting enzymes which digest the plant or animal remains
Plants
Kingdom; algae, lichens, bryophytes, pteridophytes, spermatophytes
Animals
Kingdom; coelenterates, nematodes, platyhelminths, annelids, arthropods, mollusks, echinoderms, chordates
Crustaceans
Falls under the phylum arthropods. Ex) woodlice, barnacles, crabs, shrimps
Fish
Class of chordates; fish, cartilaginous - sharks, rays, and dogfish, bony - cod, herring, mackerel. Fish live all their lives in water and breathe through gills. Cold-blooded, external fertilization, body covering of bony scales, limbs are fins.
Amphibians
Class of chordates; frogs, toads, newts. Larval forms (tadpoles) breathe through gills, adults have legs. Cold-blooded, fertilization is external and aquatic, body covering of smooth skin.
Reptiles
Class of chordates; lizards, snakes, crocodiles, turtles. Mainly terrestrial, adults have legs. Cold-blooded, internal fertilization, eggs laid in soft shell, body covering of leathery scales.
Birds
Class of chordates; sparrow, raven, ostrich. Power of flight has allowed worldwide apatite radiation. Forelimbs are wings. Warm-blooded, internal fertilization, egg laid in chalky shell body covering of feathers.
Mammals
Class of chordates; Shrew, cat, elephant, bat, dolphin, humans. Warm-blooded, internal fertilization, young born live and fed milk from female mammary gland, body covering hair (except marine mammals).
Dichotomous key
a key for the identification of organisms based on a series of choices between alternative characters