metamerism

enUK

me·tam·er·ism

M0246800 (mĭ-tăm′ə-rĭz′əm)n. The condition of having the body divided into metameres, apparent in certain animals only in the early embryonic stages of development.

metamerism

(mɪˈtæməˌrɪzəm) n1. (Zoology) Also called: metameric segmentation or segmentation the division of an animal into similar segments (metameres). In many vertebrates it is confined to the embryonic nervous and muscular systems2. (Chemistry) chem a type of isomerism in which molecular structures differ by the attachment of different groups to the same atom, as in CH3OC3H7 and C2H5OC2H5

me•tam•er•ism

(məˈtæm əˌrɪz əm)

n. 1. the body plan of animals in which the basic structure is a series of linear segments or somites. 2. isomerism resulting from the attachment of different groups to the same atom, as C₂H₅NHC₂H₅ and CH₃NHC₃H₇. [1840–50; (definition 1) metamere + -ism; (definition 2) meta- + (iso) merism] met•a•mer•ic (ˌmɛt əˈmɛr ɪk) adj. met`a•mer′i•cal•ly, adv.

Metamerism

enUK

metamerism

[mə′tam·ə‚riz·əm] (zoology) The condition of an animal body characterized by the repetition of similar segments (metameres), exhibited especially by arthropods, annelids, and vertebrates in early embryonic stages and in certain specialized adult structures. Also known as segmentation.

Metamerism

(segmentation), in biology, division of the body in many bilaterally symmetrical animals into more or less similar repeating parts, or metameres (segments), arranged serially along the body’s longitudinal axis.

Metamerism in the form of strobilation is characteristic of parasitic tapeworms. The body of the parasite consists of proglottids, segments of identical structure that bud at the head (neck region) of the worm and form a chain, or strobila. Metamerism may be external only (pseudometamerism), or it may involve the internal organs as well (true metamerism). True metamerism can be complete, involving the entire organism, or incomplete, extending only to a few organ systems (for example, dermatomeres, or cutaneous metameres; myomeres, or muscular; scleromeres, or skeletal; and neuromeres, or neural).

A distinction is made between homonomous metamerism, where all of the metameres are structurally similar, perform identical functions, and bear identical extremities, and heteronomous metamerism, where the metameres, while retaining essentially a common structural plan, differentiate in different directions, become externally dissimilar, and bear different extremities or lose some. Complete metamerism is characteristic of annelids and arthropods, in which the metameres coalesce to form a head, thorax, and abdomen.

In chordates, metamerism is manifested in the structure of the skeleton, musculature, nervous system, cutaneous formations, circulatory system, and excretory organs. In most vertebrates, including man, metamerism is clearly expressed in the early stages of embryonic development. In the human adult, metameric features survive in the vertebral skeleton, cerebrospinal reflex centers, and roots of the spinal nerves and in the regular alternation of ribs, intercostal muscles, and nerves.

B. S. MATVEEV

Metamerism

in chemistry, a special case of isomerism relating to the position of a heterocyclic atom in a chain of aliphatic compounds. For example, methylpropyl ether CH₃OCH₂CH₂CH₃ and diethyl ether CH₃CH₂OCH₂CH₃ are metameric. The term “metamerism” was suggested by J. Berzelius in 1830. Today it is seldom used.

metamerism

(1) In colorimetry, the quality of some colors that causes them to appear different under various light sources. For example, two color samples might appear the same in natural light, but not in artificial light.

(2) In biology, repeating segments that appear the same but perform different functions. An earthworm is a common animal example.

单词	metamerism
释义	metamerism enUK me·tam·er·ism M0246800 (mĭ-tăm′ə-rĭz′əm)n. The condition of having the body divided into metameres, apparent in certain animals only in the early embryonic stages of development. metamerism (mɪˈtæməˌrɪzəm) n1. (Zoology) Also called: metameric segmentation or segmentation the division of an animal into similar segments (metameres). In many vertebrates it is confined to the embryonic nervous and muscular systems2. (Chemistry) chem a type of isomerism in which molecular structures differ by the attachment of different groups to the same atom, as in CH3OC3H7 and C2H5OC2H5 me•tam•er•ism (məˈtæm əˌrɪz əm) n. 1. the body plan of animals in which the basic structure is a series of linear segments or somites. 2. isomerism resulting from the attachment of different groups to the same atom, as C₂H₅NHC₂H₅ and CH₃NHC₃H₇. [1840–50; (definition 1) metamere + -ism; (definition 2) meta- + (iso) merism] met•a•mer•ic (ˌmɛt əˈmɛr ɪk) adj. met`a•mer′i•cal•ly, adv. Metamerism enUK metamerism [mə′tam·ə‚riz·əm] (zoology) The condition of an animal body characterized by the repetition of similar segments (metameres), exhibited especially by arthropods, annelids, and vertebrates in early embryonic stages and in certain specialized adult structures. Also known as segmentation. Metamerism (segmentation), in biology, division of the body in many bilaterally symmetrical animals into more or less similar repeating parts, or metameres (segments), arranged serially along the body’s longitudinal axis. Metamerism in the form of strobilation is characteristic of parasitic tapeworms. The body of the parasite consists of proglottids, segments of identical structure that bud at the head (neck region) of the worm and form a chain, or strobila. Metamerism may be external only (pseudometamerism), or it may involve the internal organs as well (true metamerism). True metamerism can be complete, involving the entire organism, or incomplete, extending only to a few organ systems (for example, dermatomeres, or cutaneous metameres; myomeres, or muscular; scleromeres, or skeletal; and neuromeres, or neural). A distinction is made between homonomous metamerism, where all of the metameres are structurally similar, perform identical functions, and bear identical extremities, and heteronomous metamerism, where the metameres, while retaining essentially a common structural plan, differentiate in different directions, become externally dissimilar, and bear different extremities or lose some. Complete metamerism is characteristic of annelids and arthropods, in which the metameres coalesce to form a head, thorax, and abdomen. In chordates, metamerism is manifested in the structure of the skeleton, musculature, nervous system, cutaneous formations, circulatory system, and excretory organs. In most vertebrates, including man, metamerism is clearly expressed in the early stages of embryonic development. In the human adult, metameric features survive in the vertebral skeleton, cerebrospinal reflex centers, and roots of the spinal nerves and in the regular alternation of ribs, intercostal muscles, and nerves. B. S. MATVEEV Metamerism in chemistry, a special case of isomerism relating to the position of a heterocyclic atom in a chain of aliphatic compounds. For example, methylpropyl ether CH₃OCH₂CH₂CH₃ and diethyl ether CH₃CH₂OCH₂CH₃ are metameric. The term “metamerism” was suggested by J. Berzelius in 1830. Today it is seldom used. metamerism (1) In colorimetry, the quality of some colors that causes them to appear different under various light sources. For example, two color samples might appear the same in natural light, but not in artificial light. (2) In biology, repeating segments that appear the same but perform different functions. An earthworm is a common animal example. metamerism enUK me·tam·er·ism (me-tam'ĕr-izm), 1. A type of anatomic structure exhibiting serially homologous metameres; in primitive forms, such as the annelids, the metameres are almost alike in structure; in vertebrates, specialization in the cephalic region masks the underlying metamerism, which is still clearly evident in serially repeated vertebrae, ribs, intercostal muscles, and spinal nerves, and in young vertebrate embryos. 2. In chemistry, rarely used synonym for structural isomerism. metamerism (mĭ-tăm′ə-rĭz′əm)n. The condition of having the body divided into metameres, apparent in certain animals only in the early embryonic stages of development. me·tam·er·ism (me-tam'ĕr-izm) A pattern of anatomic structure exhibiting serial repetition of homologous structures, as vertebrae, ribs, intercostal muscles, and spinal nerves. ThesaurusSeemetameric
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