homologous



homologous defined in 1951 year

homologous - homologous;
homologous - An organ of one animal is said to be homologous with an organ of another when both have a fundamental similarity of structure and/or position relative to other organs, manifested especially during embryonic development; regardless of their functions in the adult, which may be very different; e.g. mammalian ear-ossicles are homologous with bones concerned in fish jaw attachment. The degree of similarity which constitutes 'fundamental similarity3 is a matter of opinion, so that homology is not a clear-cut concept. The similarity is assumed to be due to descent of the organisms from a common ancestor. The presumption is that a developmental process that occurred in a common ancestor has become modified in two different directions in two descendant species, without the divergence obscuring the common origin. Evolution has evidently generally occurred, not by sudden origin of quite new embryonic processes, but by slight modification of existing ones, the changes taking effect particularly at later stages of development; resulting in the persistence of the similarities between related organisms, especially between their embryos, denoted by homology. Homology of organs implies relationship of the organisms bearing the organs, and it is the main concept of evolutionary comparative anatomy. Compare with: Analogous.

near homologous in Knolik


homokaryonhome
letter "H"
start from "HO"
homologous chromosomes

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