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Home >>Biology Dictionary >> Flagellum - Forebrain Prosencephalon
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Flagellum. A relatively long (up to 150μ) fine whip like structure present on the surface of certain cells, particularly motile reproductive cells (e.g. spermatozoa), bacteria, and certain protozoans. Flagella occur singly or in small groups. Beating of flagella produces movement of the cells but some flagella (e.g. in Hydra) beat to cause movement of the surrounding fluid.
Flexor. Muscle of tendon bending a joint; antagonizes extensor.
Flightless. Unable to fly, having secondarily lost the ability. The term is usually applied to birds such as Ratiter and penguins.
Floccose.
Covered in small hair giving a down-like appearance.
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Flatworms. See Platyhelminthes
Flora.
(1) Plant population of a particular area of epoch.
(2) List of plant species (with descriptions) of a particular area arranged in families and genera, together with a key to aid identification.
Floral diagram. Diagram illustrating relative position and number of parts in each of the sets of organ comprising a flower.
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Florigen. Hypothetical plant hormone suggested to explain transmission of flowering stimulus from leaf, where it is perceived, to growing point.
Floristics. The branch of botany concerned with the study of vegetation in terms of the number of different species, present in the flora.
Flush. Wet ground that is typified by the presence of Sphagnum moss where water comes to the surface but does not form a stream bed.
FMN. Flavin mononucleotide. An oxidizing reducing co-enzyme.
Foetal membranes.
Extra embryonic membranes of mammal.
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Foetus. Mammalian embryo after recognizable appearance of main features of fully developed animal; in man after about two months of gestation.
Folic acid. Vitamin of the B-complex; forms several co-enzymes; important for cell division.
Follicle. (Bot). Dry fruit formed from a single carpel which splits open along a single line of dehiscence to liberate its seed, e.g., larkspur, columbine (Zool).
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Follicle-stimulating hormone (FSH). Gonadotropic hormone secreted by anterior lobe of pituitary in vertebrates. Stimulates growth of ovarian follicles and their oocytes in ovary, and formation of spermatozoa in testis.
Food chain. The series of organisms through which food energy moves before it is completely spent; the path way of chemical energy within a community from producers to consumers and then to decomposers.
Food pollen. Infertile pollen (produced by special anthers) that attract insects to the flower where they also collect fertile pollen.
Food production.
The growth of animals and plant material, and subsequent cropping for human consumption.
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Foramen. An aperture is an animals part on organ, especially one in a bone or cartilage. For example, the foramen magmum is the opening at the base of the skull through which the spinal cord passes.
Forebrain (prosencephalon). One of the three sections of the brain of a vertebrate embryo. The forebrain develops to form the cerebrum, hypothalamus and thalamus in the adult.
Foreskin. The glandular and vescular fold of skin surrounding the tip of the mammalian penis.
Form. (1) An extensive used in the classification of organisms into which different types of a variety may be places (2) Any distinct variant within a species. Seasonal variants, e.g. the tawny brown (summer) and blue-white (winter) forms of the blue hare, may be called forms, as may the different types that constitute a polymorphism.
Forward mutation. A genetic change in which a wild type piece of DNA is altered to a mutant sequence.
Fossil. Remains of organism, or direct evidence of its presence, preserved in rocks. Generally hard parts only are preserved, usually partly or wholly replaced by minerals deposited from circulating water, as impression or casts.
Fovea (fovea centralise).
A shallow depression in the retina of the eye, the lens that is present in some vertebrates. This area contains a large concentrations of cones with only a thin layer of overlying nerves. It is therefore specialized for the perception of colour and sharp intense images. The clarity is enhanced when light is focused on the foveae of both retinas simultaneously.
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