F

F2 generation Second filial generation of a genetic cross.

Facet A small, facelike articular surface.

facette Funnel-shaped opening through the inner membrane complex of the egg of a pentastomid. It receives the product of the dorsal organ.

facial faci = the face.

facilitated diffusion Mediated transport in which a permease makes possible diffusion of a molecule across a cell membrane in the direction of a concentration gradient; contrast with active transport.

facultative anaerobes Microorganisms capable of switching pathways of respiration, depending on the presence or absence

facultative symbiont Opportunistic symbiont, establishing a relationship with a host only if the opportunity presents itself but not physiologically dependent on doing so.

FAD Abbreviation for flavine adenine dinucleotide, an electron acceptor in the respiratory chain.

falciform falci = a sickle; form = shape.

fallopian tube See uterine tube.

family The level of classification between order and genus.

family planning Controlling reproduction; planning the timing of birth and having as many babies as are wanted and can be supported.

famines Acute food shortages characterized by large-scale loss of life, social disruption, and economic chaos.

fascicle 1. Stylet bundle or combination of mouthparts used to pierce the skin in a blood-feeding arthropod. Composition of a fascicle varies according to group. 2. A small bundle, usually referring to a collection of muscle fibers or nerve axons.

fascicular cambium The layer of cambium that develops between the xylem and phloem within a vascular bundle.

fat Triglyceride that is solid at room temperature; usually of animal origin. Organic molecules containing high levels of carbon and hydrogen, but little oxygen. Oils are merely fats in liquid state.

fatigue Loss of efficiency in the performance of a motor act when that act is repeated in rapid succession.

fat-soluble vitamin Vitamins that can be stored in fatty tissues of the body; vitamins A, D, E, and K.

fatty acid Any of a series of saturated organic acids having the general formula CnH2nO2, occurs in natural fats of animals and plants.

fault A crack in the earth's crust usually formed when two pieces of crust are moving past each other.

fauna All of the animals present in a given region.

feather stars See crinoids.

fecundity The physical ability to reproduce.

feedback loops A sequence of events in which the level of a hormone or related endocrine product circulating in the blood leads to alterations in the rate of production and release of other hormones from one or more endocrine glands. Often, feedback loops involve the hypothalamic portion of the brain where specialized sensory cells monitor circulating blood levels of numerous compounds, including both hormones and products from hormone actions at various body locations.

feedback mechanisms control mechanisms in organisms and communities in which a change in a given factor either inhibits or stimulates processes controlling the production, release, or use of that factor

female defense polygyny Males controlling access to females directly by competing with other males.

femur Podomere of an insect or acarine leg fixed to the trochanter proximally and articulating with the tibia distally in insects and with the patella in acarines.

fen An area of waterlogged soil that tends to be peaty; fed mainly by upwelling water; low productivity.

fenestra fenestr = window.

feral A domestic animal that has taken up a wild existence.

fermentation (alcoholic) A type of anaerobic respiration that yields carbon dioxide and alcohol; used in commercial fermentation processes, including production of raised bakery dough products and alcoholic beverages.

fermentation Degradative pathway that begins with glycolysis and ends with the electrons being transferred back to one of the breakdown products or intermediates such as alcohols, acids, and carbon dioxide; does not require molecular oxygen.

Fertile Crescent Area between the Tigris and Euphrates Rivers in the Near East; some of the earliest documented sites of agriculture.

fertility Measurement of actual number of offspring produced through sexual reproduction; usually described in terms of number of offspring of females, since paternity can be difficult to determine.

fertilization membrane A membrane that raises off the surface of an egg after sperm penetration; prevents multiple fertilization.

fertilization The union of gametes. It can be external and take place in the water, or internal and take place within the body.

fertilizer burn When the concentration of solutes in the soil is too high due to over fertilization, plasmolysis at the roots occurs, damaging the plant.

festoons Sclerites on the posterior margin of the opisthosoma of certain hard ticks.

fetch The span of the sea surface over which the wind blows to form wind-driven waves.

fetus Postembryonic unborn. From the seventh or eighth week of gestation.

fiber Long and narrow sclerenchymous cell; functions in support; an important dietary component that provides bulk; component of fabrics, ropes, and paper.

fibril A strand of protoplasm produced by a cell and lying within the cell.

fibrillar Composed of or pertaining to fibrils or fibers.

fibrillar flight muscle Insect flight muscle responsible for indirect flight. A single nerve impulse results in many cycles of flight muscle contraction and relaxation.

fibrin Protein that forms a meshwork, trapping erythrocytes, to become blood clot. Precursor is fibrinogen.

fibrocartilage The type of cartilage made up of parallel, thick, compact bundles, separated by narrow clefts containing typical cartilage cells (chondrocytes).

fibrosis Deposition of fibrous connective tissue in a localized site, during process of tissue repair or to wall off a source of antigen. The general name for accumulation of scar tissue in the lung.

fibrous connective tissue The tissue that is made up of fibers that are very densely packed (e.g., tendons and ligaments).

fibrous roots A root system with many equally sized roots forming a mat, as in grasses. There is no primary taproot.

fibrous root system A root system in which roots are finely divided and lacking a main axis, common in monocotyledons.

fibula fibul = buckle. A leg bone.

fiddlehead The curled fern frond prior to unrolling and elongation; also known as a crozier.

fidelity A principle that forbids misleading or deceiving any creature capable of being mislead or deceived. We are to be truthful in our dealings with others.

field capacity The soil-water storage capacity; the saturated soil profile after gravitational percolation ceases to flow.

filament Part of the stamen in a flower that supports the anther.

filamentous A slender or threadlike structure or organism, in the latter consisting of a chain of interconnected cells as in filamentous algae.

filial imprinting The process by which young animals form a social attachment for a particular stimulus, often the mother.

filial An offspring generation, for example, F1, the first filial generation.

filiform Thread-like.

filipodium A type of pseudopodium that is very slender and may branch but does not rejoin to form a mesh.

filoplume feather A small thin feather that probably has sensory functions in birds (pinfeather).

filter feeder An organism that filters food particles from the surrounding fluid.

filter feeding. Any feeding process by which particulate food is filtered from water in which it is suspended.

filters A porous mesh of cotton cloth, spun glass fibers, or asbestos-cellulose that allows air or liquid to pass through but holds back solid particles.

filtration Movement of material through a membrane as a result of hydrostatic pressure.

fin ray Each of the bony spines in the fins of bony fishes.

finite resources Resources that have a limit to their availability; not boundless.

finlet small median fin on the dorsal and ventral sides of the rear parts of tuna and similar fish

fire ecology The study of the environmental effects of fire.

fire-climax community An equilibrium community maintained by periodic fires; examples include grasslands, chaparral shrubland, and some pine forests.

first law of thermodynamics The total amount of energy in the universe remains constant; more energy cannot be created and existing energy cannot be destroyed; energy can only undergo conversion from one form to another.

First World The industrialized capitalist or market-economy countries of Western Europe, North America, Japan, Australia, and New Zealand.

fish meal A fish-protein supplement used in animal feeds.

fish protein concentrate (FPC or fish flour)A fish protein supplement for human consumption.

fission Asexual reproduction in which the cell divides into two (binary fission) or more (multiple fission) daughter parts, each of which becomes an individual organism.

fitness Degree of adjustment and suitability for a particular environment. Genetic fitness is relative contribution of one genetically distinct organism to the next generation; organisms with high genetic fitness are naturally selected and become prevalent in a population.

fixed action pattern (FAP) An innate behavior pattern that is stereotyped, spontaneous, and independent of immediate control, genetically encoded, and independent of individual learning.

fjord a deep coastal embayment caused by glacial erosion

flabellum Recurved process often found on the first two thoracic exopods of branchiuran crustaceans.

flaccid Pertaining to a cell or tissue with less than full

flagella Elongated appendages of certain cells used in locomotion.

flagellar pocket Depression, sometimes long and deep, from which a flagellum arises.

flagellum Whiplike cellular structure of motility; eukaryotic flagella are composed of microtubules.

flagging behavior Alarm signaling, as with the use of the tail.

flame cell Specialized hollow excretory or osmoregulatory structure of one or several small cells containing a tuft of flagella (the "flame") and situated at the end of a minute tubule; connected tubules ultimately open to the outside. See solenocyte, protonephridium.

flatworms (phylum Platyhelminthes)Invertebrates that are dorsoventrally flattened and have an incomplete digestive tract, true organs, and organ systems.

flavin adenine dinucleotide A coenzyme that is a condensation product of riboflavin phosphate and adenylic acid; it forms the prosthetic group of certain enzymes; FAD.

flavin mononucleotide An electron acceptor in the electron transport scheme or aerobic respiration.

flavonoids A group of secondary compounds produced by plants and important in chemical identification of those plants; believed to be contained in petals that reflect ultraviolet patterns and thus an element in pollinator attraction.

fleshy fruit Fruit in which the cells of the pericarp are alive at maturity.

flexion flect = bend.

flocculate A process by which dissolved substances come out of solution and aggregate together to form macroscopic particles.

flood An overflow of water onto land that normally is dry.

floodplains Low lands along riverbanks, lakes, and coastlines subjected to periodic inundation.

flora All of the plants present in a given region.

floret One of the small flowers that make up the inflorescences in the composite and grass families.

florigen The hypothetical flowering hormone. This compound (or compounds) has never been identified chemically.

flower The reproductive structure of the anthophyta or angiosperms.

flowering plants Plants that have flowers, seeds, and true leaves, stems, and roots.

flue-gas scrubbing Treating combustion exhaust gases with chemical agents to remove pollutants. Spraying crushed limestone and water into the exhaust gas stream to remove sulfur is a common scrubbing technique.

fluid feeding The process by which an animal feeds on fluid.

fluid mosaic Refers to the model for the structure of membranes, consisting of a bilayer of lipids in which globular proteins are embedded and can move laterally.

fluid mosaic model Model of cell membrane structure composed of a lipid bilayer with scattered proteins; often described as a sea of lipids with protein icebergs.

fluidized bed combustion High pressure air is forced through a mixture of crushed coal and limestone particles, lifting the burning fuel and causing it to move like a boiling fluid. Fresh coal and limestone are added continuously to the top of the combustion bed while ash and slag are drawn off below.

fluke A member of class Trematoda or class Monogenea. Also, certain of the flatfishes (order Pleuronectiformes).

fluorescence Longer wavelength emissions which can result form excited electron energy, results in a glowing light.

flushing time The time required for all of the water of an estuary to be completely exchanged.

FMN . Abbreviation for flavin mononucleotide, the prosthetic group of a protein (flavoprotein) and a carrier in the electron transport chain in respiration.

focal-animal sampling A technique for recording the behavior of individual animals in which the observer concentrates on the activities of one individual for a set time period and then switches to watch another animal for a set time period.

foci Groups of cells in an embryo that differentiate into specific structures and organs.

follicle Single, dry, dehiscent fruit that splits along one seam; example: milkweed.

food aid Financial assistance intended to boost less-developed countries' standards of living.

food chain A sequence of organisms in which plants are the primary food source for herbivores, which are in turn the food source for carnivores, etc., until the top carnivore level is reached.

food security The ability of individuals to obtain sufficient food on a day-to-day basis.

food surpluses Excess food supplies.

food vacuole An organelle in the cell that functions in intracellular digestion.

food web A community food chain depicting which species feed on each other and how many interrelationships are involved.

foot 1. The basal portion of a moss sporophyte, embedded in the gametophyte. 2.The muscular locomotory structure of molluscs.

forage crops Crops that are grown as food for domesticated herbivores.

forager Hunter-gatherer group.

foraging behavior The process animals use in locating food resources.

Foramen foram = an opening.

foraminiferan ooze A biogenous sediment that consists mostly of the calcareous shells of foraminiferans.

foraminiferan A member of the class Granuloreticulosea (phylum Sarcomastigophora) bearing a test with many openings.

foraminiferans (forams) Protozoans with a calcareous shell, or test, and pseudopodia.

forebrain The forebrain consists of the diencephalon and telencephalon.

fore reef The outer part of a barrier reefor atoll.

forest management Scientific planning and administration of forest resources for sustainable harvest, multiple use, regeneration, and maintenance of a healthy biological community.

form drag Hydrodynamic drag on an organism caused by its cross-sectional area.

formed-element fraction The cellular component of vertebrate blood.

fossa foss = depression or trench.

fossil Any evidence of pre-existing life which is preserved in the earth's crust. In addition to the remains of entire, or parts of, organisms, fossils also include indirect evidence such as animal tracks and footprints, as well as the impression of leaves.

fossil fuels Organic molecules derived from partially decayed plant and animal matter, produced primarily during the Carboniferous period; includes oil, gas, and coal.

fossorial Characterized by digging or burrowing.

fouling organisms Organisms that live attached to submerged surfaces such as boats and pilings.

fouling. Contamination of feeding or respiratory areas of an organism by excrement, sediment, or other matter. Also, accumulation of sessile marine organisms on the hull of a boat or ship so as to impede its progress through the water.

founder effect Changes in gene frequency that occur when a few individuals from a parental population colonize new habitats; the change is a result of founding individuals not having a representative sample of the parental population's genes.

Fourth World A political/economic category describing very poor nations that have neither market economies nor central planning and are either not developing or are developing very slowly. Also used to describe indigenous communities within wealthier nations.

fovea A small pit or depression; especially the fovea centralis, a small rodless pit in the retina of some vertebrates, a point of acute vision.

fraction I protein Equivalent to RUBP carboxylase; the primary leaf protein in many green plants.

fragmentation Division into smaller units. A type of asexual reproduction whereby a body part is lost and then regenerates into a new organism.

frame shift See deletion mutant; insertion mutant.

frame-shift mutation A mutation caused by the insertion or deletion of nucleotides (less than three or a number not a multiple of three) resulting in the improper grouping into codons.

free energy. The energy available for doing work in a chemical system.

free-running rhythm The activity cycle that an animal exhibits when placed in a constant environment; its period is different from any known cyclic environmental variable.

free-threshing grain Grain that separates easily from enclosing bracts.

freezing condensation A process that occurs in the clouds when ice crystals trap water vapor. As the ice crystals become larger and heavier, they begin to fall as rain or snow.

fresh water Water other than seawater; covers only about 2 percent of earth's surface, including streams, rivers, lakes, ponds, and water associated with several kinds of wetlands.

freshwater ecosystems Ecosystems in which the fresh (nonsalty) water of streams, rivers, ponds, or lakes plays a defining role.

frictional drag the resistance created by an animal's body surface when it moves through a fluid medium

fringing reef a large coral-reef formation that closely borders the shoreline

frond The photosynthetic leaf blade of a fern.

front The boundary between two air masses of different temperature and density.

frontal plane. A plane parallel to the main axis of the body and at right angles to the sagittal plane.

Frontal frons = brow, foliage.

frontier mentality The idea that the world has an unlimited supply of resources for human use regardless of the consequences to natural ecosystems and the biosphere.

frontier An unexploited natural area at the leading edge of human settlement.

fructose Six-carbon monosaccharide; often referred to as fruit sugar.

fruit A mature ovary.

fruiting body The reproductive structure of certain fungi.

frustule The siliceous, box-like cell wall of diatoms.

fucoxanthin An accessory brown pigment found in brown algae and some protists.

fuel assembly A bundle of hollow metal rods containing uranium oxide pellets; used to fuel a nuclear reactor.

fuel-switching A change from one fuel to another.

fuelwood Branches, twigs, logs, wood chips, and other wood products harvested for use as fuel.

fugitive emissions Substances that enter the air without going through a smokestack, such as dust from soil erosion, strip mining, rock crushing, construction, and building demolition.

functional neuroanatomy The study of the size, structure, and arrangement of cells within the nervous system, particularly the brain.

functionalists People who conduct studies involving attempts to discern how the mind works, as opposed to studies of its structure.

fundamental niche The multidimensional space that an animal would occupy under optimal conditions in the absence of competitors; also called preferred niche. Contrast with realized niche.

fungi One of the five kingdom classifications; consists of nonphotosynthetic, eukaryotic organisms with cell walls, filamentous bodies, and absorptive nutrition.

fungicidal A compound that is able to kill a fungus and stop an infection.

fungicide A chemical that kills fungi.

fungistatic A compound that slows or stops the growth of a fungus.

funiculus The stalklike structure connecting an ovule to its placental surface within an ovary.

funnel The siphon of cephalopods.

fusiform Spindle shaped; tapering toward each end.