Homology definitions and example sentences on Wordnik

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noun The quality or condition of being homologous.
noun A homologous relationship or correspondence.
noun Chemistry The relation of the elements of a periodic family or group.

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The state or character of being homologous; correspondence. Specifically— In biology, that relation between parts which results from their development from corresponding embryonic parts, either in different animals, as in the case of the arm of man, the fore leg of a quadruped, and the wing of a bird, or in the same animal, as in the case of the fore and hind legs in quadrupeds, or of the segments or rings and their appendages of which the body of a worm, a centiped, etc., is composed. Homology in this sense implies genetic relationship, and consequently morphological likeness or structural affinity; and it is distinguished from analogy, which usually results from physiological adaptation of unlike parts to like functions, and therefore implies a merely adaptive modification, which brings about a superficial resemblance between things quite unlike in structure, as between the wing of a bird and that of a butterfly. Several kinds of homology are distinguished: (1) general, which is the relation of an organism, or of any of its parts, to the general type or plan of such organisms or parts; (2) serial, which is the correspondence of metamerically multiplied parts in any organism, as of successive ribs, legs, vertebræ, etc., with one another; (3) special, which is the correspondence of a part or organ of one animal with the same part in another, as the homology between a horse's fore “knee” and the humau wrist, etc. See homologous, homologue. In the great class of mollusks, though it can easily be shown that the parts in distinct species are homologous, but few serial homologies can be indicated: that is, we are seldom enabled to say that one part is homologous with another part in the same individual. Darwin, Origin of Species, p. 393.
In geometry, the relation between two corresponding figures lying in the same plane which are such that corresponding points are collinear With a fixed point called the center of homology, while corresponding lines intersect on a fixed line called the axis of homology.
Axis of homology. See axis.

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One of the major evidences for the evolution of man is homology, that is, the similarity of either anatomical or genetic features between species. — Recently Uploaded Slideshows
The reality of convergence implies that anatomical features arise because of One of the major evidences for the evolution of man is homology, that is, the similarity of either anatomical or genetic features between species. — Recently Uploaded Slideshows

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