Documents for "Biology: General":

• acquired characteristics modifications produced in an individual plant or animal as a result of mutilation, disease, use and disuse, or any distinctly environmental influence. Some examples are docking of tails,...

• adaptive radiation in biology, the evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat. Adaptive radiation has occurred in...

• analogy in biology, the similarities in function, but differences in evolutionary origin, of body structures in different organisms. For example, the wing of a bird is analogous to the wing of an insect,...

• astrobiology see exobiology.

• autotroph in biology, an organism capable of synthesizing its own organic substances from inorganic compounds. Autotrophs produce their own sugars, lipids, and amino acids using carbon dioxide as a source...

• Beagle naval vessel: see Darwin, Charles Robert.

• benthos see marine biology.

• biogenetic law in biology, a law stating that the earlier stages of embryos of species advanced in the evolutionary process, such as humans, resemble the embryos of ancestral species, such as fish. The law refers...

• biological clock see rhythm, biological.

• biology the science that deals with living things. It is broadly divided into zoology , the study of animal life, and botany , the study of plant life. Subdivisions of each of these sciences include cytology (the study of cells), histology (the study of tissues), anatomy or morphology, physiology, and embryology (the...

• bioluminescence production of light by living organisms. Organisms that are bioluminescent include certain fungi and bacteria that emit light continuously. The dinoflagellates, a group of marine algae, produce...

• bionics the study of living systems with the intention of applying their principles to the design of engineering systems. Drawing on interdisciplinary research in the mechanical and life sciences, bionics...

• biophysics application of various methods and principles of physical science to the study of biological problems. In physiological biophysics physical mechanisms have been used to explain such biological...

• biorhythm or biological rhythm, cyclic pattern of changes in physiology or in activity of living organisms, often synchronized with daily, monthly, or yearly environmental changes. Rhythms that vary according to the time of day...

• book gill see horseshoe crab.

• book lung terrestrial respiratory organ characteristic of arachnids such as scorpions and primitive spiders. Each book lung consists of hollow flat plates. Air bathes the outer surface of the plates and...

• carbon cycle in biology, the exchange of carbon between living organisms and the nonliving environment. Inorganic carbon dioxide in the atmosphere is converted by plants into simple carbohydrates, which are...

• category in taxonomy: see classification.

• chemosynthesis process in which carbohydrates are manufactured from carbon dioxide and water using chemical nutrients as the energy source, rather than the sunlight used for energy in photosynthesis. Most life on earth is fueled directly or indirectly by sunlight. There are, however, certain groups of bacteria, referred to as chemosynthetic autotrophs, that are fueled not by the sun but by the...

• chemotaxis see taxis.

• chemotroph see autotroph.

• circadian rhythm see rhythm, biological.

• cladistics or phylogenetic systematics , an approach to the classification of living things in which organisms are defined and grouped by the possession of one or more shared characteristics (called characters) that are derived from a common ancestor and that were not...

• class in taxonomy: see classification.

• classification in biology, the systematic categorization of organisms into a coherent scheme. The original purpose of biological classification, or systematics, was to organize the vast number of known plants and...

• cline in biology, any gradual change in a particular characteristic of a population of organisms from one end of the geographical range of the population to the other. Gradients of characteristics...

• clone group of organisms, all of which are descended from a single individual through asexual reproduction, as in a pure cell culture of bacteria. Except for changes in the hereditary material that come...

• cloning see clone.

• commensalism relationship between members of two different species of organisms in which one individual is usually only slightly benefited, while the other member is not affected at all by the relationship...

• competition in biology, relationship between members of the same or different species in which individuals are adversely affected by those having the same living requirements, such as food or space...

• creation science see creationism.

• creationism or creation science, belief in the biblical account of the creation of the world as described in Genesis , a characteristic especially of fundamentalist Protestantism (see fundamentalism ). Advocates of creationism have campaigned to have it taught in U.S. public schools along with the theory of evolution , which they dispute. In 1981 a federal judge ruled unconstitutional an Arkansas law requiring the teaching of creationism, holding it to be religious in nature; a similar Louisiana law was...

• cross-fertilization see fertilization.

• differentiation in biology, series of changes that occur in cells and tissues during development, resulting in their specialization. This, in turn, permits a greater variety of organisms. In plants, unspecialized...

• division in taxonomy: see classification.

• eukaryote a cell or organism composed of cells that have a membrane-bound nucleus and organelles (mitochondria, chloroplasts; see cell , in biology) and genetic material organized in chromosomes in which the...

• evolution concept that embodies the belief that existing animals and plants developed by a process of gradual, continuous change from previously existing forms. This theory, also known as descent with...

• Examples of Systematic Classification Examples of Systematic Classification Common Name Species Name Genus Family Order Class Phylum (Division) Kingdom Humans Homo sapiensHomo Hominidae Primates Mammalia Chordata Animalia Rhesus...

• exobiology or astrobiology, search for extraterrestrial life within the solar system and throughout the universe. Philosophical speculation that there might be other worlds similar to ours dates back to the ancient Chinese and Greeks. However, the...

• extinction in biology, disappearance of species of living organisms. Extinction occurs as a result of changed conditions to which the species is not suited. If no member of the affected species survives and...

• family in taxonomy: see classification.

• fertilization in biology, process in the reproduction of both plants and animals, involving the union of two unlike sex cells (gametes), the sperm and the ovum , followed by the joining of their nuclei. In the flowers of higher plants, the process occurs after pollination has enabled the sperm to contact the egg cell in the plant's ovary. In lower plants and in animals the sperm is actively motile and swims to the egg through an external aqueous medium or through a...

• fossil remains or imprints of plants or animals preserved from prehistoric times by the operation of natural conditions. Fossils are found in sedimentary rock, asphalt deposits, and coal and sometimes in...

• gamete see reproduction.

• genera in taxonomy: see classification.

• genus in taxonomy: see classification.

• gills external respiratory organs of most aquatic animals. In fishes the gills are located in gill chambers at the rear of the mouth (pharynx). Water is taken in through the mouth, is forced through...

• Gram's stain laboratory staining technique that distinguishes between two groups of bacteria by the identification of differences in the structure of their cell walls. The Gram stain, named after its developer,...

• hermaphrodite animal or plant that normally possesses both male and female reproductive systems, producing both eggs and sperm. Many plants, including most flowering plants (angiosperms), are hermaphroditic, or...

• heterotroph living organism that obtains its energy from carbohydrates and other organic material. All animals and most bacteria and fungi are heterotrophic. In contrast, autotrophs are organisms that use inorganic...

• homology in biology, the correspondence between structures of different species that is attributable to their evolutionary descent from a common ancestor. For example, the forelimbs of vertebrates, such as...

• intelligent design theory that some complex biological structures and other aspects of nature show evidence of having been designed by an intelligence. Such biological structures are said to have intricate components...

• kingdom in taxonomy: see classification.

• life although there is no universal agreement as to a definition of life, its biological manifestations are generally considered to be organization, metabolism, growth, irritability, adaptation, and...

• longevity term denoting the length or duration of the life of an animal or plant, often used to indicate an unusually long life. The average human life-span of threescore and ten years cited in the Bible...

• marine biology study of ocean plants and animals and their ecological relationships. Marine organisms may be classified (according to their mode of life) as nektonic, planktonic, or benthic. Nektonic animals are...

• mass extinction the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events. The five greatest were those of the final Ordovician period (approximately 435 million years ago), the late Devonian period (357 million years ago), the final Permian period (250 million years ago), the late Triassic period (198 million years ago), and the final Cretaceous period (65 million years ago). The most devastating was that at the end of the Permian period, when an estimated 95% of marine species and 8 of 27 insect orders were lost. The best-known mass extinction...

• microbiology see biology.

• mimicry in biology, the advantageous resemblance of one species to another, often unrelated, species or to a feature of its own environment. (When the latter results from pigmentation it is classed as protective coloration.) Mimicry serves either to protect the mimic from its predators, as when the model is inedible or dangerous, or to deceive its prey (e.g., certain ant-eating spiders that themselves resemble ants)...

• nomenclature, biological see classification.

• ontogeny see biogenetic law.

• order in taxonomy: see classification.

• parasite plant or animal that at some stage of its existence obtains its nourishment from another living organism called the host. Parasites may or may not harm the host, but they never benefit it. They...

• parasitism see parasite.

• parthenogenesis [Gr.,=virgin birth], in biology, a form of reproduction in which the ovum develops into a new individual without fertilization. Natural parthenogenesis has been observed in many lower animals (it...

• phylogeny see biogenetic law.

• phylum in taxonomy: see classification.

• pigmentation name for the coloring matter found in certain plant and animal cells and for the color produced thereby. Pigmentation occurs in nearly all living organisms. Almost all plants synthesize their own...

• recapitulation theory, stated as the biogenetic law by E. H. Haeckel , that the embryological development of the individual repeats the stages in the evolutionary development of the species. For example, the beginnings of gill clefts appear in both humans and fish,...

• reproduction capacity of all living systems to give rise to new systems similar to themselves. The term reproduction may refer to this power of self-duplication of a single cell or a multicellular animal or plant organism. In all cases reproduction consists of a basic pattern: the conversion by a parent organism...

• rhythm, biological cyclic pattern of physiological changes or changes in activity in living organisms, most often synchronized with daily, monthly, or annual cyclical changes in the environment. The exact nature of...

• secretion in biology, substance elaborated by the living material of an animal or plant. Secretions in humans can be produced by a single cell or by a group of cells commonly called a gland. Some secretions...

• sociobiology controversial field that studies how natural selection, previously used only to explain the evolution of physical characteristics, shapes behavior in animals and humans. The theory has contributed...

• species in biology, a category of classification , the original and still the basic unit in the demarcation of plant and animal types. The species marks the boundary between populations of organisms rather than between individuals. Because related...

• spore term applied both to a resistant or resting stage occurring among various unicellular organisms (especially bacteria) and to an asexual reproductive cell produced by many unicellular plants and animals and by all plants that undergo an alternation of generations. A spore is typically a cell surrounded by a cell wall; in resistant spores and in the...

• subspecies also called race, a genetically distinct geographical subunit of a species. See also classification.

• symbiosis the habitual living together of organisms of different species. The term is usually restricted to a dependent relationship that is beneficial to both participants (also called mutualism) but may...

• systematics see classification.

• taxa see taxon.

• taxis movement of animals either toward or away from a stimulus, such as light (phototaxis), heat (thermotaxis), chemicals (chemotaxis), gravity (geotaxis), and touch (thigmotaxis). The turning...

• taxon (pl. taxa), in biology, a term used to denote any group or rank in the classification of organisms, e.g., class, order, family.

• taxonomy see classification.

• tropism involuntary response of an organism, or part of an organism, involving orientation toward (positive tropism) or away from (negative tropism) one or more external stimuli. The term tropism is usually applied to growth and turgor movements in plants; an involuntary orientation of a microorganism toward or away from an external stimulus is commonly called a taxic movement, or taxis —e.g., the negative phototaxis of certain protozoans that move away from light. Tropistic stimuli include light, heat, moisture, gravity, electricity, and chemical agents. Plant stems are positively...

• tubercle [Lat.,=little swelling], small, usually solid, nodule or prominence. In anatomy the term is applied to natural prominences in certain muscles, to nerve nuclei of the central nervous system, and to...

• variation in biology: see Darwinism.