(in biology), a part of the body of an animal or plant that performs one or several characteristic functions. Examples of animal organs are the brain, heart, eye, liver, and stomach, while the root, stem, leaf, and flower are examples of plant organs.
An organism is able to act as a unified whole owing to the interconnection and interaction of its organs (seeCORRELATION). Organs are classified according to their principal functions; for instance, animal organs can be locomotor, digestive, respiratory, circulatory, or excretory, and plants have photosynthetic and absorptive organs. Reproductive organs are common to both animals and plants. Functionally complementary organs are united into systems that ensure the principal life functions of the organism. Each organ usually consists of a number of tissues, each of which performs a narrower function than the organ as a whole. Most organs perform several functions. In comparative studies, a distinction is made between analogous and homologous organs (seeANALOGY, HOMOLOGY).
In the development of a species, reduction or increase in the size, complexity, and function of an organ is a consequence of natural selection and of new requirements of the organism in response to environmental changes. Examples of such structural and functional modifications in organs are the reduction of eyes in burrowing and speluncar animals, the reduction of stamens in labiates and scrophulariaceous plants, the development of lungs in a number of terrestrial vertebrates, and the well-developed root system of plants that grow in arid habitats.
a multibarrel weapon used in various armies in the 16th and early 17th centuries. The name “organ” originated from its external resemblance to the musical instrument.
The organ had from six to 24 or more barrels (muskets, mortars, and small-caliber cannon) secured in several rows on a special shaft or on frames. The detonators of the barrels in each row were connected by a single groove, making it possible to fire a simultaneous volley. Organs were usually placed on wheeled carriages. Similar guns in Russia were called soroki. They went out of use with the invention of case shot.
a wind keyboard musical instrument consisting of a set of wooden and metal pipes of various sizes and a pneumatic system (an air-compressing mechanism and conductors) contained in one cabinet, and a separate control panel, or console. In addition to keyboards for the hands (manuals) and feet (pedal board), the console houses the handles of various levers that connect (couple) the keyboards and switch on the ranks, as well as devices that control the volume of sound.
An organ may have from one to seven manuals, each including up to 72 keys, and a single pedal board (usually, up to 32 keys). Some modern organs have a second pedal board. Organs may have up to several thousand pipes (sounding mechanisms), which are divided into groups called ranks, or registers. The total number of ranks in an organ depends on the size of the instrument. A small organ may have up to ten, and a large one may have several hundred. Each rank has a characteristic timbre and is controlled by a lever or button. Music for the organ is written on three staffs. Usually, the ranks are not indicated.
There are three main operating systems, or actions. In an organ with mechanical (tracker) action, the energy of the movement of the organist’s finger is transmitted from the key to the valve, which is opened by means of many trackers (rods), sliders, wooden brackets and blocks, permitting air to enter the pipe. With pneumatic action, wind pressure transmits an impulse of air through pipe-conductors to a pipe valve, opening it. Pneumatic action organs are not common. Electric action transmits the organist’s “instructions” from the keys to the pipes by means of electric cables. The best type of modern organ offers a combination of mechanical and electric action.
The volynka, the ancient Chinese sheng, and the European panpipes are predecessors of the organ. A water organ known as the hydraulus was invented in the third century B.C. in Greece.
Among the composers who have contributed to the organ repertoire are J. S. Bach, Mozart, Beethoven, Haydn, Brahms, C. Saint-Saëns, B. Britten, A. K. Glazunov, A. F. Gedike, D. D. Shostakovich, A. Kapp, and A. Kalniņŝ. The popularity of the organ in Europe increased most rapidly in the 16th through 18th centuries.