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Home >>Biology Dictionary >> Hemicelluloses - Hapaticae
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Heart. A muscular, pulsatile pump with valves, in the blood vascular, in the blood vascular system, responsible for the circulation of blood. In mammals, birds and crocodiles the heart produces two separate circulations (in other tetrapods, partially separate), the pulmonary to the lungs and the systematic to the rest of the body (double circulation).
Heart wood. The central mass of wood in trees in which there are no living cells and which serves only for mechanical support.
Heath. A lowland plant community that is dominated by heather or live on a sandy soil or shallow peat.
Heavy metal. Any element with an atomic number greater than 20.
Helminth.
A worm, usually a parasitic one.
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Helminthology. Study of parasitic worms.
Helophytes. Class of Raunkiaer’s Life Forms.
Hemicelluloses.
Heterogeneous group of long-chain polysaccharides distinct from cellulose (basic units are arabinose, xylose, mannose or galactose) forming part of the cell wall of plants, especially in lignified tissue; may function as reserve food materials especially in seeds; e.g. endosperm of date seeds.
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Hemiparasite. An organism that derive part of its sustenance from other organisms.
Hemiptera (Rhynchota). Large order of insects, including scale insects, leaf-hoppers, cochineal-insects, lac-insects, bed-bugs, green-files. They such with their piercing mouth parts.
Hemizygous. Term applied to a region of a chromosomes of a diploid for which there is not homologue in the cell. The X-chromosome in organisms of the heterogametic sex is largely hemizygous.
Heparin.
Substance which prevents blood clotting by stopping conversion of prothrombin to thrombin and by neutralizing thrombin. Extractable from various tissues, especially lung. Contained in mast cells, which occur in connective tissue. Sulphur-containing complex polysaccharide.
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Hepatic. Denoting to the liver.
Hepaticae.
Liverworts, class of Bryophyta. Living in wet conditions, on soil or as epiphytes or in water. Consisting of a thin, plant body or a creeping central axis up to a few inches long, provided with leaf-like expansions; attached to soil by rhizoids from under surface. Sexual organs, antheridia and archegonia, variously grouped, male gametes motile by flagella. Fertilization is followed by development of a capsule containing spores which, being shed, germinate mostly in the form of a short, thalloid protonema from which new liverwort plants arise.
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Hepatocyte. Main kind of cell of vertebrate liver.
Herb. Plant which no persistent parts above ground, as distinct from shrubs and trees.
Herbaceous. Having the characters of a herb.
Herbarium. A reference collection of preserved plants.
Herbivore. Any animal feeding on plants.
Heredity. The transmission of characteristics from one generation to another via a mechanism involving GENES and chromosomes.
Hermaphrodite. (Bisexual).
Of a flowering plant or flower having both stamens and carpels in the same flowers.
(2) Of an individual animal producing both male and female gametes. Among unisexual animals hermaphrodities may occur as aberrations.
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Heroin. A white crystalline powder manufactured from morphine used as a sedative and narcotic in the hydrochloride form.
Heterocercal fin. The type of tail fin found on sharks where the ventral lobe is large and the dorsal Lobe small.
Heterochromatin. Parts of chromosomes showing strongly basophilic staining in interphase. It apparently has little or no genetical actively. Sex chromosexes, especially the Y-chromosome of many animals, tend particularly to have large heterochromatic regions.
Heterodont. Having teeth of different kinds, as in most mammals, which have incisors, canines, molars.
Heteroecious.
Having different spore forms on different host plants.
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