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F![]() |
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F1 (first filial generation) |
The first filial or hybrid offspring in a genetic cross-fertilization. |
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F2 (second filial generation) |
Offspring resulting from interbreeding of the hybrid F1 generation. |
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F factor |
A fertility factor in bacteria, a DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient. May exist as a plasmid or integrated into the bacterial chromosome. |
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facilitated diffusion |
The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients. |
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facultative anaerobe (fak-ul-tay-tiv an-uh-robe) |
An organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions. |
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FAD |
Abbreviation of flavin adenine dinucleotide, a coenzyme that functions as an electron acceptor in the Krebs cycle. |
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Fallopian tube |
See Oviduct. |
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family |
A taxonomic grouping of related, similar genera; the category below order and above genus. |
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fat (triacylglycerol) (tri-ah-sil-glis-er-all) |
A biological compound consisting of three fatty acids linked to one glycerol molecule. |
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fatty acid |
A long carbon chain carboxylic acid. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form fat. |
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feedback inhibition |
A method of metabolic control in which the end-product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway. |
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feedback systems |
Control mechanisms whereby an increase or decrease in the level of a particular factor inhibits or stimulates the production, utilization, or release of that factor; important in the regulation of enzyme and hormone levels, ion concentrations, temperature, and many other factors. |
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fermentation |
A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end-product, such as ethyl alcohol or lactic acid. |
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fertilization |
The union of haploid gametes to produce a diploid zygote. |
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fetus [L., pregnant] |
An unborn or unhatched vertebrate that has passed through the earliest developmental stages; a developing human from about the second month of gestation until birth. |
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fiber |
A lignified cell type that reinforces the xylem of angiosperms and functions in mechanical support; a slender, tapered sclerenchyma cell that usually occurs in bundles. |
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fibril [L. fibra, fiber] |
Any minute, threadlike structure within a cell. |
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fibrin (fy-brin) |
The activated form of the blood-clotting protein fibrinogen, which aggregates into threads that form the fabric of the clot. |
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fibroblast (fy-broh-blast) |
A type of cell in loose connective tissue that secretes the protein ingredients of the extracellular fibers. |
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fibrous protein |
Insoluble structural protein in which the polypeptide chain is coiled along one dimension. Fibrous proteins constitute the main structural elements of many animal tissues. |
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filament [L. filare, to spin] |
(1) A chain of cells. (2) In flowers, the stalk of a stamen. |
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filtrate |
Fluid extracted by the excretory system from the blood or body cavity. The excretory system produces urine from the filtrate after extracting valuable solutes from it and concentrating it. |
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filtration |
The first stage of kidney function; blood plasma is forced, under pressure, out of the glomerular capillaries into Bowman's capsule, through which it enters the renal tubule. |
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first law of thermodynamics (thur-moh-dy-nam-iks) |
The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed. |
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fitness |
The genetic contribution of an individual to succeeding generations relative to the contributions of other individuals in the population. |
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fixed action pattern |
A highly stereotypical behavior that is innate and must be carried to completion once initiated. |
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flaccid (flas-id) |
Limp; walled cells are flaccid in isotonic surroundings, where there is no tendency for water to enter. |
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flagellum pl. flagella (fla-jell-um) [L. flagellum, whip] |
A long cellular appendage specialized for locomotion, formed from a core of nine outer doublet microtubules and two inner single microtubules, ensheathed in an extension of plasma membrane. |
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flower |
The reproductive structure of angiosperms; a complete flower includes sepals, petals, stamens (male structures), and carpels (female structures). |
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fluid-feeder |
An animal that lives by sucking nutrient-rich fluids from another living organism. |
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fluid mosaic model |
The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids. |
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follicle (fol-eh-kul) |
A microscopic structure in the ovary that contains the developing ovum and secretes estrogens. |
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follicle-stimulating hormone (FSH) |
A protein hormone secreted by the anterior pituitary that stimulates the production of eggs by the ovaries and sperm by the testes. |
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food chain |
The pathway along which food is transferred from trophic level to trophic level, beginning with producers. |
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food web |
The elaborate, interconnected feeding relationships in an ecosystem. |
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fossil [L. fossilis, dug up] |
The remains of an organism, or direct evidence of its presence (such as tracks). May be an unaltered hard part (tooth or bone), a mold in a rock, petrification (wood or bone), unaltered or partially altered soft parts (a frozen mammoth). |
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founder effect |
A cause of genetic drift attributable to colonization by a limited number of individuals from a parent population. |
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fovea [L., pit] |
A small area in the center of the retina in which cones are concentrated; the area of sharpest vision. |
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fragile X syndrome |
A hereditary mental disorder, partially explained by genomic imprinting and the addition of nucleotides to a triplet repeat near the end of an X chromosome. |
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frameshift mutation |
A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of 3, thus resulting in improper grouping into codons. |
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free energy |
A quantity of energy that interrelates entropy (S) and the system's total energy (H); symbolized by G. The change in free energy of a system is calculated by the equation G = ![]() ![]() |
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free energy of activation |
The initial investment of energy necessary to start a chemical reaction; also called activation energy. |
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frequency - dependent selection |
A decline in the reproductive success of a morph resulting from the morph's phenotype becoming too common in a population; a cause of balanced polymorphism in populations. |
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fruit [L. fructus, fruit] |
A mature ovary of a flower that protects dormant seeds and aids in their dispersal. |
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function [L. fungor, to busy oneself] |
Characteristic role or action of a structure or process in the normal metabolism or behavior of an organism. |
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functional group |
A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and usually involved in chemical reactions. |
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
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Glossary from Biology, Fifth Edition By Campbell, Reece, Mitchell © 1998, Benjamin Cummings. Reprinted with Permission. All Rights Reserved |