equational divisionA chromosome division in which the two chromatids of each duplicated chromosome separate longitudinally, prior to being incorporated into two daughter…
Equi-Potential LineA line, in a field of flow, such that the total head is the same for all points on the line, and therefore the direction of flow is perpendicular to the…
EquilibriumTo be in a state of perfect balance. A spinning top is a kind of equilibrium untill it falls.
Equilibrium DrawdownThe ultimate, constant drawdown for a steady rate of pumped discharge.
Equilibrium Level(EL) - On a sounding, the level above the level of free convection (LFC) at which the temperature of a rising air parcel again equals the temperature of…
Equilibrium Surface DischargeThe steady rate of surface discharge which results from a long-continued, steady rate of net rainfall, with discharge rate equal to net rainfall rate.
Equilibrium TimeThe time when flow conditions become substantially equal to those corresponding to equilibrium discharge or equilibrium drawdown.
equilibrium vapor pressureThe necessary vapor pressure around liquid water that allows the water to remain in equilibrium with its environment.
EquinoxThe two times of the year when the sun crosses the equator and night and day are of equal length; usually occurs on March 21st (spring equinox) and…
Equity financingProvision of capital through the sale of common or preferred stock to investors.
Equivalent diameter (equivalent size)The diameter of a hypothetical sphere composed of material having the same specific gravity as that of the actual soil particle and of such size that it…
Equivalent fluidA hypothetical fluid having a unit weight such that it will produce a pressure against a lateral support presumed to be equivalent to that produced by the…
Equivalent Potential TemperatureThe equivalent potential temperature is the temperature a parcel at a specific pressure level and temperature would have if it were raised to 0 mb…
ERDescribes cells that do not have a protein to which the hormone estrogen will bind.
ERAA time period dominated by a particular physical process.
ERGA unit of work done by the force of one dyne acting through a distance of one centimeter.
Erlenmeyer flaskA conical flat-bottomed laboratory flask with a narrow neck, widely used for culturing micro-organisms.
ErodeTo wear away or remove the land surface by wind, water, or other agents.
ErosionThe wearing away of land surface by wind or water, intensified by land-clearing practices related to farming, residential or industrial development, road…
ErraticBoulder transported by a glacier and left behind when the ice melted.
errorError The difference between a measured value of a quantity and its true value. Different types of errors are inherent to observations.
EruptionThe process by which solid, liquid, and gaseous materials are ejected into the Earth's atmosphere and onto the Earth's surface by volcanic activity.
EruptiveIn solar-terrestrial terms, solar activity levels with at least one radio event (10 cm) and several chromospheric events per day (Class C Flares).
Eruptive Prominence on Limb (EPL)In solar-terrestrial terms, a solar prominence that becomes activa- ted and is seen to ascend from the sun.
Erythrocyte(eh-RITH-roh-site) A cell that carries oxygen to all parts of the body. Also called RBC and red blood cell.
EscapementUnharvested spawning stocks that return to the streams.
EscarpmentA cliff or the steep slopes of a plateau edge.
Escherichia coliA commensal bacterium inhabiting the human colon that is widely used in biology, both as a simple model of cell biochemical function and as a host for…
essential amino acidAn amino acid required for normal metabolism, but which cannot be synthesized by an organism. It therefore has to be supplied via feed or food.
essential derivation of varieties(Abbreviation: EDV). Genotypes very similar to an originating cultivar, obtained, for example, by the selection of a mutant or a variant individual from…
Essential elementAny of a number of elements required by living organisms to ensure normal growth, development and maintenance.
Essential Fish Habitat (EFH)Authorized by the Magnuson-Stevens Fishery Conservation and Management Act, EFH are those waters and substrate necessary to fish for spawning, breeding…
essential nutrientAny substance required by living organisms to ensure normal growth, development and maintenance.
essential requirementIn plant cell tissue culture, comprises inorganic salts, including all of the elements necessary for plant metabolism; organic factors (amino acids…
established culture1. An aseptic viable explant (See: micropropagation ). 2. A suspension culture subjected to several passages with a constant cell number per unit time.
ester(ES-ter) A type of chemical substance that is a combination of acid and alcohol. Esters are found in essential oils (scented liquid taken from plants).
EstheticsAn emotional judgment about what is beautiful or pleasing.
estimated breeding value(Abbreviation: EBV). Twice the expected progeny difference. The difference is doubled because breeding value is a reflection of all the genes of an…
EstrogenA type of hormone made by the body that helps develop and maintain female sex characteristics and the growth of long bones.
EstuaryA water body where salt and fresh water meet resulting in brackish water. These areas usually have associated marshlands and are critical nursery and…
Esturine watersDeepwater tidal habitats and tidal wetlands that are usually enclosed by land but have access to the ocean and are at least occasionally diluted by…
Esturine ZoneThe area near the coastline that consists of estuaries and coastal saltwater wetlands.
ETA1. The Eta Model, now referred to as North Amercian Meso (NAM) an 84-hour numerical model of the atmosphere run four times daily by NCEP.
Eta ModelNow referred to as North Amercian Meso (NAM) is one of the operational numerical forecast models run at NCEP.
ethanolCommonly used to disinfect plant tissues, glassware utensils and working surfaces in tissue culture manipulations; to precipitate aqueous solutions of…
Ethanol (C2 5OH)Otherwise known as ethyl alcohol, alcohol, or grain spirit. A clear, colorless, flammable oxygenated hydrocarbon with a boiling point of 78.
Ethyl Tertiary Butyl Ether (ETBE)A chemical compound produced in a reaction between ethanol and isobutylene (a petroleum-derived by-product of the refining process).
ethyleneA gaseous plant growth regulator acting on various aspects of vegetative growth, fruit ripening and abscission of plant parts. Synonym: ethene.
ethylenediamine tetraacetic acid(Abbreviation: EDTA). A chelating compound. Used to keep nutrients, such as iron, bound in a soluble form that leaves them still available to the plant…
etiolationAn abnormal increase in stem elongation, accompanied by poor (if any) leaf development.
euchromatinChromosomal material that is stained less intensely by certain dyes. Thought to be the chromosomal domains which are gene-rich, since the DNA in these…
EugenicsThe application of the principles of genetics to the 'improvement' of humankind. Wholly discredited as a scientific approach since the Nazi period.
EukaryoteAn organism whose cells possess a nucleus and other membrane-bound vesicles, including all members of the protist, fungi, plant and animal kingdoms; and…
euploidAn organism or cell having a chromosome number that is an exact multiple of the haploid number.
EutecticA mixture of substances that has a melting point lower than that of any mixture of the same substances in other proportions.
Eutectic SaltsSalt mixtures with potential applications as solar thermal energy storage materials.
EutrophicHighly fertile waters characterized by warm, nutrient-rich shallow basins.
EutrophicationThe natural aging process of water bodies, by siltation and organic decomposition, which reduces both water volume and oxygen levels.
Evacuated-Tube CollectorA collector is the mechanism in which fluid (water or diluted antifreeze, for example) is heated by the sun in a solar hot water system.
EvacuationThe fifth of five Early Warning System components consisting of the plans, personnel, equipment, and facilities needed to move the population at risk to…
Evacuation warningA public warning message that local officials would issue following declaration of Response Level III by personnel of the dam operating organization.
EvaporationThe conversion of a liquid to a vapor (gas), usually by means of heat.
Evaporation PanA pan used to hold water during observations for the determination of the quantity of evaporation at a given location.
Evaporation pondsShallow man-made ponds designed to contain liquid effluents and concentrate the residual waste through evaporation.
Evaporation RateIn hydrologic terms, the quantity of water, expressed in terms of depth of liquid water, which is evaporated from a given surface per unit of time.
Evaporation-mixing FogFog that forms when the evaporation of water raises the dew point of the adjacent air.
Evaporative CoolingThe physical process by which a liquid or solid is transformed into the gaseous state.
Evaporator CoilThe inner coil in a heat pump that, during the cooling mode, absorbs heat from the inside air and boils the liquid refrigerant to a vapor, which cools the…
EvaporimeterAn instrument which measures the evaporation rate of water into the atmosphere.
EvapotranspirationThe net water loss (in vapour form) per unit area of land, both directly from the land surface, and indirectly through transpiring leaves.