Homologous

Homologous [ Biology ]	Dictionary of botanic terminology - index of names
Synonyms: Homologue, Homolog, Homologic, Homological Antonyms: Analogous, Autologous, Heterologic, Heterological, Heterologous Noun: Homology


	Corresponding or similar in position or structure or function or characteristics

Compare with: Analogous

(1) Homologous [ Biology ]


	Of anatomical structures within different organisms derived from the same structure of a common ancestor.

From the Greek homos = same, and logos = word, hence a part with similar morphology but different function.

Referring to anatomical structures that show a fundamental similarity within different organisms because originated from a structure or trait of a common ancestry rather than a product of a similar environment (compare: Analogous, Homoplastic).
Homologous structures in related species have the same evolutionary origin although their functions may differ widely. The structures in their current forms may not necessarily perform the same functions in each organism, nor perform the functions it did in the common ancestor. They may even have become completely unused and therefore vestigial. "the wing of a bat, the flippers of a seal and the arm of a man are homologous"

(2) Homologous [ Genetics ]


	a) Of a chromosome having the same morphology and linear sequence of gene loci as another chromosome. Containing the same linear gene sequences, each derived from one parent. b) Of a genes in a genome sharing a similar DNA base sequence with an other genes because they arose by duplication of an ancestral gene..

(3) Homologous [ Chemistry ]


	Of organic chemical compounds belonging to the same type or series; corresponding in composition and properties.

In molecular biology, often "homologous" is used loosely to mean similar.

Advertising

Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994