MORPHOLOGY

in linguistics, study of the internal construction of words. Languages vary widely in the degree to which words can be analyzed into word elements, or morphemes (q.v.). In English there are numerous examples, such as replacement, which is composed of re-, place, and -ment, and walked, from the elements walk and -ed. Many American Indian languages have a highly complex morphology; other languages, such as Vietnamese or Chinese, have very little or none. Morphology includes the grammatical processes of inflection (q.v.) and derivation. Inflection marks categories such as person, tense, and case; e.g., sings contains a final -s, marker of the 3rd person singular, and the German Mannes consists of the stem Mann and the genitive singular inflection -es. Derivation is the formation of new words from existing words; e.g., singer from sing and acceptable from accept. Derived words can also be inflected: singers from singer. in biology, the study of the size, shape, and structure of animals, plants, and microorganisms and the relationships of their internal parts. Morphology implies more than simple description; it involves some principle or generalization to which form can be related. The term morphology is used rather loosely, often being confused with anatomy. Whereas anatomy describes the structure of organisms (by dissection and other means), morphology is concerned with explaining the shapes and arrangement of parts of organisms in terms of such general principles as evolutionary relations, function, and development. The interest of the early morphologists lay in the patterns they could distinguish in the forms of animals and plants. An example is the pattern of bones in the human arm, which is repeated in the leg. Another example is the similarity between the pattern of bones in the human arm, the wing of a bird, and the front leg of a frog; or the pattern of bones in the skulls of vertebrates generally. Some early morphologists went to extreme lengths in attempting to show that such widely different sorts of animals as vertebrates and insects conformed to the same pattern, but these ideas have not survived. The study of the similarities of form between different sorts of organisms received a great impetus when the idea of evolution was accepted. The pre-evolutionary biologists simply considered these similarities as a fact of nature. Charles Darwin regarded them as evidence that animals and plants evolve by successive, slow steps from earlier forms. Darwin's ideas stimulated morphologists (particularly animal morphologists) to study a very wide variety of organisms in order to discover from similarities and differences in the form of their bodies (including their embryonic stages) how closely or remotely they were related in an evolutionary sense. In the animal kingdom all animals which could reasonably be said to share the same basic pattern were classified together into the same phylum. A quite different approach to the interpretation of form is through function. The functional morphologist is interested in how the form of part or all of an organism influences its performance. For example, there is a connection between the form of a tree and how it is affected by gravity and wind, or how light reaches the leaves. And the form of an animal's wing is related to the speed and manner of its flight, a subject that can be studied by means of models in a wind tunnel. A third approach to the study of form arises from the fact that as an organism develops from ovum or seed, through embryonic stages to an adult, the particular form changes through these phases. Developmental morphology (or morphogenesis) is concerned not with describing these changes (which is the science of embryology) but with the mechanisms that bring them about. Much progress has been made in experiments designed to show how one part of an organism influences the way in which adjacent parts develop. Related to this is the way in which the inherited materials (genes) exert their control on development. in biology, the study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of the parts comprising them. The term refers to the general aspects of biological form and arrangement of the parts of a plant or an animal. The term anatomy also refers to the study of biological structure but usually suggests study of the details of either gross or microscopic structure. In practice, however, the two terms are used almost synonymously. Typically, morphology is contrasted with physiology, which deals with studies of the functions of organisms and their parts; function and structure are so closely interrelated, however, that their separation is somewhat artificial. Morphologists were originally concerned with the bones, muscles, blood vessels, and nerves comprising the bodies of animals and the roots, stems, leaves, and flower parts comprising the bodies of higher plants. The development of the light microscope made possible the examination of some structural details of individual tissues and single cells; the development of the electron microscope and of methods for preparing ultrathin sections of tissues created an entirely new aspect of morphologythat involving the detailed structure of cells. Electron microscopy has gradually revealed the amazing complexity of the many structures comprising the cells of plants and animals. Other physical techniques have permitted biologists to investigate the morphology of complex molecules such as hemoglobin, the gas-carrying protein of blood, and deoxyribonucleic acid (DNA), of which most genes are composed. Thus, morphology encompasses the study of biological structures over a tremendous range of sizes, from the macroscopic to the molecular. A thorough knowledge of structure (morphology) is of fundamental importance to the physician, to the veterinarian, and to the plant pathologist, all of whom are concerned with the kinds and causes of the structural changes that result from specific diseases. Additional reading Overviews are provided by Robert D. Barnes, Invertebrate Zoology, 6th ed. (1994), an excellent modern treatment of invertebrate morphology; Peter C. Wainwright and Stephen M. Reilly (eds.), Ecological Morphology: Integrative Organismal Biology (1994); Milton Hildebrand et al. (eds.), Functional Vertebrate Morphology (1985), technical and conceptual approaches to old problems; and Claude A. Villee, Warren F. Walker, Jr., and Robert D. Barnes, General Zoology, 6th ed. (1984), a standard college-level text on vertebrate and invertebrate morphology and its relation to function. The principles governing growth and form of organisms are the subject of the classic work by D'Arcy Wentworth Thompson, On Growth and Form, 2nd ed. (1942, reissued 1992), also available in an abridged ed. edited by John Tyler Bonner (1961, reissued 1992), still a fascinating work. Renato Dulbecco, The Design of Life (1987), also treats the fundamental principles in the design of living systems. Another classic work is J.B.S. Haldane, On Being the Right Size and Other Essays, ed. by John Maynard Smith (1985). Of related interest is Knut Schmidt-Neilsen, Scaling: Why Is Animal Size So Important? (1984), on the scaling of body size and relative dimensions.Plant and animal anatomy is addressed by Katherine Esau, Plant Anatomy, 2nd ed. (1965), a beautifully illustrated text; Alfred Sherwood Romer and Thomas S. Parsons, The Vertebrate Body, 6th ed. (1986), a standard college-level text on comparative anatomy of the vertebrates; and Warren F. Walker, Jr., and Karel F. Liem, Functional Anatomy of the Vertebrates: An Evolutionary Perspective, 2nd ed. (1987), a comprehensive textbook that connects structure, function, and evolution.E.D.P. De Robertis, Francisco A. Saez, and E.M.F. De Robertis, Jr., Cell Biology, 6th ed. (1975; originally published in Spanish, 1946), is an excellent text describing the cytological features of animal and plant cells. Don W. Fawcett, The Cell, 2nd ed. (1981), collects superb electron micrographs of several kinds of cells and cell organelles, with a brief description of each.General studies focusing specifically on embryology include Bruce M. Carlson, Patten's Foundations of Embryology, 6th ed. (1996), a mechanistic approach to chick and human development; Jan Langman, Langman's Medical Embryology, 7th ed. by T.W. Sadler (1995), on human development and congenital anomalies; Scott F. Gilbert, Developmental Biology, 4th ed. (1994), contemporary developmental biology from molecule to organ; J.M.W. Slack, From Egg to Embryo: Regional Specification in Early Development, 2nd ed. (1991), focusing on concepts, theory, and future directions; and Jonathan Bard, Morphogenesis: The Cellular and Molecular Processes of Developmental Anatomy (1990), emphasizing the many unanswered questions. The short book by Lewis Wolpert, The Triumph of the Embryo (1991), is intended for the nonspecialist reader, yet it includes sufficient information to provide an account of the major themes of the subject with modern flavour. David De Pomerai, From Gene to Animal: An Introduction to the Molecular Biology of Animal Development, 2nd ed. (1990), also conveys the main ideas on the subject as of its publication date. D.M. Glover and B.D. Hames (eds.), Genes and Embryos (1989), focuses principally on early events in development, especially the genetic control of embryogenesis, during which time the fates of most cells become established. T.J. Horder, J.A. Witkowski, and C.C. Wylie (eds.), A History of Embryology (1986), provides a chronicle of history, data, and concepts from the early 19th century through the origins of molecular genetics.Works on embryology at a more advanced level are Leon W. Browder (ed.), Developmental Biology: A Comprehensive Synthesis, 7 vol. (198591), treating a diversity of topics from molecule to organ; Brian K. Hall, Evolutionary Developmental Biology (1992), a history and analysis of concepts; and Michael Akam et al. (eds.), The Evolution of Developmental Mechanisms (1994), on the development, paleontology, and evolution of living organisms. Gerald M. Edelman, Topobiology: An Introduction to Molecular Embryology (1988), discusses general principles of spatial and temporal organization of living cells with reference to their molecular basis. Claude A. Villee The Editors of the Encyclopdia Britannica