Species and Speciation
Species and Speciation, basic concepts in the classification of organisms. In simple terms, a single species is a distinct kind of organism, with a characteristic shape, size, behavior, and habitat that remains constant from year to year. A biological species is defined as a group of natural populations that mate and produce offspring with one another, but do not breed with other populations. This definition includes genealogical relationships as well as physical properties, and emphasizes that species evolve independently of one another. See Evolution . THE NATURE OF SPECIES Other conceptions of species exist, the oldest of which is the typological-species concept that originated with Plato and Aristotle. According to this concept, a species represents some ideal form, of which individual variation is merely the imperfect expression. The morphological-species definition, on the other hand, is purely observational: a group of individuals that resemble one another and are separated f