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Living organisms are classified into groups depending on their structure and characteristics. This system was developed in the eighteenth century by Carl Linnaeus.
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Living organisms are classified mainly to avoid confusion, to make study of organisms easy and learn how various organisms are related to each other. Scientists classified living organisms into different kingdoms, phylum, class, etc and are based on different criteria.
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- From the Greeks to the Renaissance
taxonomy, in a broad sense the science of classification, but more strictly the classification of living and extinct organisms—i.e., biological classification. The term is derived from the Greek taxis (“arrangement”) and nomos (“law”). Taxonomy is, therefore, the methodology and principles of systematic botany and zoology and sets up arrangements of the kinds of plants and animals in hierarchies of superior and subordinate groups. Among biologists the Linnaean system of binomial nomenclature, created by Swedish naturalist Carolus Linnaeus in the 1750s, is internationally accepted.
Popularly, classifications of living organisms arise according to need and are often superficial. Anglo-Saxon terms such as worm and fish have been used to refer, respectively, to any creeping thing—snake, earthworm, intestinal parasite, or dragon—and to any swimming or aquatic thing. Although the term fish is common to the names shellfish, crayfish, and starfish, there are more anatomical differences between a shellfish and a starfish than there are between a bony fish and a man. Vernacular names vary widely. The American robin (Turdus migratorius), for example, is not the English robin (Erithacus rubecula), and the mountain ash (Sorbus) has only a superficial resemblance to a true ash.
Biologists, however, have attempted to view all living organisms with equal thoroughness and thus have devised a formal classification. A formal classification provides the basis for a relatively uniform and internationally understood nomenclature, thereby simplifying cross-referencing and retrieval of information.
The usage of the terms taxonomy and systematics with regard to biological classification varies greatly. American evolutionist Ernst Mayr has stated that “taxonomy is the theory and practice of classifying organisms” and “systematics is the science of the diversity of organisms”; the latter in such a sense, therefore, has considerable interrelations with evolution, ecology, genetics, behaviour, and comparative physiology that taxonomy need not have.
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People who live close to nature usually have an excellent working knowledge of the elements of the local fauna and flora important to them and also often recognize many of the larger groups of living things (e.g., fishes, birds, and mammals). Their knowledge, however, is according to need, and such people generalize only rarely.
However, some of the earliest forays into formal, but limited, classification were undertaken by the ancient Chinese and ancient Egyptians. In China a catalog of 365 species of medicinal plants became the basis of later hydrological studies. Although the catalog is attributed to the mythical Chinese emperor Shennong who lived about 2700 bce, the catalog was likely written about the beginning of the first millennium ce. Similarly, ancient Egyptian medical papyri dating from 1700 to 1600 bce provided descriptions of various medicinal plants, along with directions on how they could be used to treat illnesses and injuries.
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The first great generalizer in Western classification was Aristotle, who virtually invented the science of logic, of which for 2,000 years classification was a part. Greeks had constant contact with the sea and marine life, and Aristotle seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time, however, in separating invertebrate animals into different groups and was aware that whales, dolphins, and porpoises had mammalian characters (that is, observable features, or traits, of an organism) and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life.
The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature—i.e., what it really is, as against superficial resemblances—requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing—what makes it what it is and thus cannot be altered; the essence is, of course, immutable. The model for this procedure is to be seen in mathematics, especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge, since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn. But the Aristotelian procedure applied to living things is not by deduction from stated and known axioms; rather, it is by induction from observed examples and thus does not lead to the immutable essence but to a lexical definition. Although it provided for centuries a procedure for attempting to define living things by careful analysis, it neglected the variation of living things. It is of interest that the few people who understood Charles Darwin’s Origin of Species in the mid-19th century were empiricists who did not believe in an essence of each form.
- Kingdom. When Linnaeus first described his system, he named only two kingdoms – animals and plants. Today, scientists think there are at least five kingdoms – animals, plants, fungi, protists (very simple organisms) and monera (bacteria).
- Phylum. Below the kingdom is the phylum (plural phyla). Within the animal kingdom, major phyla include chordata (animals with a backbone), arthropoda (includes insects) and mollusca (molluscs such as snails).
- Class. Each phylum is then divided into classes. Classes within the chordata phylum include mammalia (mammals), reptilia (reptiles) and osteichthyes (fish), among others.
- Order. The class will then be subdivided into an order. Within the class mammalia, examples of an order include cetacea (including whales and dolphins), carnivora (carnivores), primates (monkeys, apes and humans) and chiroptera (bats).
Animals can be divided into groups or 'classified' by looking at the similarities and differences between them. Animals are divided into two main groups. Animals that have a...
In biology, classification is the process of arranging organisms, both living and extinct, into groups based on similar characteristics. The science of naming and classifying organisms is called taxonomy. The term is derived from the Greek taxis (“arrangement”) and nomos (“law”).
Sep 27, 2024 · Taxonomy - Classification, Organisms, Groups: Recent advances in biochemical and electron microscopic techniques, as well as in testing that investigates the genetic relatedness among species, have redefined previously established taxonomic relationships and have fortified support for a five-kingdom classification of living organisms.
