Taxonomy (classification) of living beingsThe basic unit of biological classification is species. By species they denote an aggregate of organisms of similar structure of the body, similar way of life, and capable of mating and producing reproduction-capable offspring. Similar species are combined into genera, genera into families, families into orders, orders into classes, classes into phyla (in case of animals) or divisions (in case of plants), phyla and divisions into kingdoms. There are also additional terms, like suborder, subclass, etc. Let us start with the most large taxonomic units kingdoms: 1. Viruses (Vira). They are of non-cellular structure. 2. Anucleate prokaryotes (Prokaryota). It includes bacteria and cyanobacteria (the latter are often called blue-green algae, but they are bacteria, in essence). 3. Plants (Plantae). They are subdivided into lower and higher. The subkingdom of lower (Thallophyta) comprises algae and lichens. The subkingdom of higher plants (Cormophyta) includes: mosses (Bryophyta), ferns (Pteridophyta), gymnosperms or conifers (Gymnospermae), and angiosperm or flowering plants (Angiospermae, Anthophyta) (the rest of the higher plants, including trees with leaves, shrubs and undershrubs, flowers and grasses). 4. Fungi (Mycota). Formerly, botanists classified fungi as plants. But then it was discovered that fungi, contrary to plants, do not have chlorophyll in their cell. Like insects, they have chitin in cells membranes. Therefore it was decided to classify them as a separate group, which is intermediate between plants and animals. What most people call mushrooms are just fungal fruiting bodies growing on mycelia developing in soil or in wood. There are several classes of fungi, including moulds and pathogenic kinds parasitizing on tissues of bodies of people, animals, plants. The fungal fruiting bodies gathered by people are produced fungi of only one division: basidiomycetes (Basidiomycota). 5. Animals (Animalia or Zoa). They are subdivided into a) protozoan (Protista), this group includes amebas, infusoria, and other unicellular organisms; and b) multicellular (Metazoa), comprising sponges, worms, mollusks, arthropods (insects, spiders, crustaceans, etc) and chordates (Chordata) Chordates includes, in particular, vertebrates. Vertebrates comprise the following classes: cyclostomes (lampreys and myxini), fishes (Pisces), amphibians (Amphibia) (frogs, toads, tritons, salamanders, etc), reptiles (Reptilia) (lizards, snakes, tortoises, crocodiles, etc), birds (Aves), and
mammals (Mammalia). The class of mammals (i.e. feeding their young with milk produced by mammary glands) comprises three subclasses: prototheria (platypus and echidna), lower animals or marsupials (Metatheria), higher animals or placentals (Eutheria or Placentalia) which are represented by the following orders:
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