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Home >>Zoology Dictionary >> F1 -Frog
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Fl - Denotes the first filial feneration i.e. the first generation of descendants of a particular pair of organisms.
F2 - Second filial generation, i.e. the grandchildren of a particular pair of organisms.
Facial Nerve - The seventh cranial nerve of vertebrates.
Faces - Undigested material passed out of the food canal at the anus.
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Fallopian Tube - Funnel shaped tube in female mammals leading from ovary to uterus. Eggs are normally fertilised on their way down the tube.
Family - A category used in the classification of organisms. Zoological family names end in idae.
Fauna - The animal life of a certain region or time.
Feather - An outgrowth of the skin that is found only in birds. Feathers probably evolved from reptile scales and, although they are used for flight now, their first function was almost certainly as a protection against cold.
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Feathers are made of keratin, a horny substance produced by the uper layers of the skin, and there are four types.
Contour feathers are large and sheathe the body of the bird, as well as covering the tail and wings. The actual quill of the feather is the section of the stem which remains embedded in the skin. It is usually hollow with two small openings. One at its base and one where the quill perforates the skin surface.
The rest of contour feather above the skin's surface is called the, vane; it consists of a central, solid shaft continuous with the quill and a very large number of small branches (barbs) coming off from either side. The barbs are so closely packed together that they appear to form a continous surface. In actual fact they are separate units, though each one is attached to its neighbours by a series of hooked and notched barbules.
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Down feathers are much smaller and simpler. The quill is very small and at the surface, instead of continuing as a main stem, it divides to form a spray of slender branches. The flufly coats of young chicks are make up entirely of down feathers:
Pin-feathers are even simpler. They consist of just the quill and a short stem which divides at the top into a bunch of small barbs. Powder down feathers are possessed by only a few birds, e.g. bitterns and herons. They break down into a powder useful for removing slime and dirt from the rest of the plumage.
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Contour feathers, fitted to the wings and tails of birds, provide a large surface area to push against the air during flight. The sheath of smaller contour feathers formed over the whole body gives the bird a stream lined shaped essential for movement through the air. The smooth, flat surfaces of the contour feathers are formed by the tightly linked barbs. If the barbs become disarranged by unhooking of the barbules, the birds: preening action soon repairs them smooth, streams lined feathers are not necessary for flightless birds; ostriches have plume like contour feathers.
Down feathers are concerned with insulation of the body from the cold. They help trap a layer of air a against the skin. In adult birds they are not usually conspicuous as they are covered by the contour feathers.
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Feathers can be moved by the action of muscles just as the hairs that cover mammals can be moved. Ruft1ing of feathers occurs during cold weather (the additional trapped air gives extra warmth)and the position of contour feathers on the wings and on the tail can. be controlled in flight.
Again like hairs, feathers are supplied with nerve fibres and can be used as organs of touch. Birds that fly at night have very sensitive hair like feathers on their faces, rather like the whiskers of cats.
Femur - Thight bone.
Frinogen - A soluble protein in vertebrate blood which is converted into insoluble fibres of fibrin when blood vessels are damaged. The fibres trap corpuscles and form a clot or scab which prevents further blood loss and allows healing to begin.
Fibula - Smaller of the two bones in lower part of the hind leg.
Fibula - Smaller of the two bones in lower part of the hind eg.
Fishes - (See Teleostei: Elasmobranchil; Dipnoi).
Flageilata - (=Mastigophora). Class of protozoans in which the main stage has one or more flagella. Sex cells are formed by some species but reproduction is normally affected by simple division. There are both plant like and animal like t1agellates and some. such as Englena, that appear to be midway between the two. Many flagellates are parasitic. e.g. Trypanosoma, the organism causing sleeping sickness.
Flagellum - Fine whip like thread projecting from certain cells. There are rarely more than a few per cell. They move the cell about (in the case of protozoans or motile sex cells) or they may create a current of water in an animal (in the food cavity of Hydra and in sponges).
Flame Cell - (=Solenocyte). Excretory organ of flatworms. Nitrogen containing excretory products diffuse in solution through the body tissue into a scries of branching tubules the water vessels. There are two main tubules, one on either side of the body opening by excretory pores on the upper surface of the body, Branches of the tubules terminate in l1amecells hollowed out structures containing a number of hair like t1agella. The flickering movement of the flagella (which gives the cell its name) keeps the fluid in the tubules continually circulating. No doubt this speeds up the loss of excretory products and also helps to eliminate excess water passing into the animal's body by osmosis.
Flatworm - (See Platyhelminthes).
Flea - (See Siphonaptera).
Flexor muscle - One this bends a limb. e.g. biceps bending arm.
Fluke - A flatworm of class Trematoda.
Foetus - Mammalian embryo when all main features are recognisable.
Food Chain - Aphid eats plant; spider eats aphid, bird eats spider; birdof prey eats smaller bird. This is a typical food chain. Material passes from the plant, through several animals before it reaches the last link in the chain. The cycle is completed with the death and decay of the last animal in the chain. the simple substances formed by decay will be used again by a plant and a newcycle will start. We can make the food chain complicated by including all the other animals that eat aphids or by including all the parasites found on the birds. Every living organism belongs to one or more food chains and, if parasites are excluded, the higher up the chain one goes, the fewer individuals will be found. This must be so, for if in the example above there were more birds than spiders, the latter would soon disappear. All the food chains in a habitat link up to arm the food cycle.
Foramen - Literally a hole but normally restricted to holes in the skull through which nerves run. E.g. Foramen magnum, the large opening at the back through which the spinal cord emerges.
Foraminifera - A group of protozoans. usually with a chambered shell and fine, thread like pseudopodia. They are mainly marine and the shells sometimes accumulate in vast quantities on the sea bed to form oozes, e.g. Globigerina ooze, made up of the chalky shells of Globigerina.
Fossil - The remains of an organism preserved in the rocks. Normally only those animal with hard skeletons have been preserved and they are most commonly found in rocks that were laid down under water. The dead organism fell to the bottom and became covered with sediment. Soft parts generally decayed but the hard shells and skeletons remained while the sediments became compressed into rocks. The actual material of the skeleton has in most cased been wholly or partly replaced by minerals, leaving what is known as a cast, but this still shows the original overall structure.
in some cases the whole skeleton has been washed away by percolating water, leaving only a hollow mould but this is still a valuable clue to the structure of the dead organism. Fossils are very important for geologists and also provide strong evidence to support the theory of evolution.
Fovea - Highly sensitive part of retina.
Frog - (See Amphibia; Anura).
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