| natural mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
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| natural passive immunity | Immunity conferred by the mother on the foetus or newborn. (14 Nov 1997) |
| natural pigment | A naturally occurring coloured compound; absorbs light in the visible range of the electromagnetic spectrum. Compare: structural colour. Synonym: biochrome. (05 Mar 2000) |
| natural products | Naturally occurring compounds that are end products of secondary metabolism; often, they are unique compounds for particular organisms or classes of organisms. (05 Mar 2000) |
| natural selection | The hypothesis that genotype environment interactions occurring at the phenotypic level lead to differential reproductive success of individuals and hence to modification of the gene pool of a population. (18 Nov 1997) |
| naturalism | 1. A state of nature; conformity to nature. 2. <psychology> The doctrine of those who deny a supernatural agency in the miracles and revelations recorded in the Bible, and in spiritual influences; also, any system of philosophy which refers the phenomena of nature to a blind force or forces acting necessarily or according to fixed laws, excluding origination or direction by one intelligent will. Origin: Cf. F. Naturalisme. Source: Websters Dictionary (01 Mar 1998) |
| naturalist | 1. One versed in natural science; a student of natural history, especially. Of the natural history of animals. 2. One who holds or maintains the doctrine of naturalism in religion. Origin: Cf. F. Naturaliste. Source: Websters Dictionary (01 Mar 1998) |