GACE Agriculture (709) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Independent variable

The factor a researcher deliberately changes in a controlled experiment; the dependent variable is the measured response, and all other conditions are held constant.

Monohybrid cross ratio

Crossing two heterozygotes (Aa x Aa) yields a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio when one gene with complete dominance is involved.

Polymerase chain reaction

A laboratory technique that repeatedly copies a targeted DNA segment through cycles of denaturation, primer annealing, and extension, producing millions of copies for analysis.

Heritability

The proportion of total phenotypic variation in a population attributable to genetic differences; high heritability means selection should produce rapid response.

Ruminant stomach compartments

Rumen, reticulum, omasum, and abomasum. Microbes in the rumen ferment fiber; the abomasum is the true glandular stomach secreting acid and enzymes.

Expected progeny difference

A prediction of how an animal's offspring will perform for a trait compared with offspring of an average animal; used to compare sires across herds.

Feed conversion ratio

Units of feed consumed per unit of body weight or product gained; a lower ratio means more efficient conversion of feed into meat, milk, or eggs.

Estrus

The receptive period of the reproductive cycle when a female stands to be mounted; ovulation timing relative to estrus determines breeding or insemination schedules.

Cation exchange capacity

The soil's capacity to hold exchangeable positively charged nutrients; clay and organic matter raise it, improving retention of calcium, magnesium, and potassium.

Liebig's law of the minimum

Plant growth is limited by the essential nutrient in shortest supply relative to need, not by nutrients present in abundance.

Nitrification

The microbial conversion of ammonium to nitrite and then nitrate in soil; nitrate is readily taken up by plants but also easily leached or denitrified.

Economic threshold

The pest population level at which the cost of control equals the value of crop loss prevented; treatment is justified only above this level.

Vegetative propagation

Asexual reproduction using cuttings, grafting, budding, layering, or tissue culture to produce plants genetically identical to the parent.

Break-even output

Fixed costs divided by the difference between unit price and unit variable cost; the quantity at which total revenue exactly covers total cost.

Marginal revenue equals marginal cost

The profit-maximizing production rule: expand output while each added unit brings in more revenue than it costs, stopping where the two are equal.

Price elasticity of demand

Percent change in quantity demanded divided by percent change in price; demand for staple foods is inelastic, so price changes strongly affect farm revenue.

Basis

The local cash price of a commodity minus the relevant futures price; it reflects transportation, storage, and local supply and demand conditions.

Debt-to-asset ratio

Total liabilities divided by total assets; a solvency measure showing what proportion of assets is financed by borrowed funds.

Universal Soil Loss Equation

A = R x K x LS x C x P, predicting average annual soil loss from rainfall, soil erodibility, slope length and steepness, cover, and supporting practices.

Eutrophication

Nutrient enrichment of water, mainly by nitrogen and phosphorus, causing algal blooms whose decomposition depletes dissolved oxygen and kills aquatic life.

Watershed

All the land area that drains surface water to a common outlet such as a stream, lake, or river; management upstream affects water quality downstream.

Land capability classes

USDA-NRCS classes I through VIII ranking land by erosion risk and productive limits; classes I-IV suit cultivation, V-VII pasture or forest, VIII little use.

Four-stroke engine cycle

Intake, compression, power, and exhaust strokes; the crankshaft makes two revolutions per power stroke, and a spark plug ignites the fuel-air mixture.

Rollover protective structure

A frame or cab that protects the operator if a tractor overturns; it must be used with a fastened seat belt to be effective.

Power take-off

A splined shaft on a tractor that transfers engine power to implements, standardized at 540 or 1000 rpm and requiring shields during operation.

Ohm's law

Voltage equals current multiplied by resistance (V = I x R); electrical power in a circuit equals voltage multiplied by current (P = V x I).

Shielded metal arc welding

Stick welding using a consumable electrode coated with flux that shields the molten weld; requires eye protection and ventilation.

Precision agriculture

Use of GPS guidance, sensors, yield monitors, and variable-rate equipment to apply inputs where they are needed rather than uniformly across a field.

Three-component agricultural education model

Programs combine classroom and laboratory instruction, FFA leadership development, and supervised agricultural experience for work-based learning.

FFA degree sequence

Progression from Discovery (middle school) to Greenhand, Chapter, State, and American degrees, each with increasing membership and project requirements.

Supervised agricultural experience

A planned, documented work-based learning project in entrepreneurship, placement, research, or service that develops occupational skills outside the classroom.

Point of order

A parliamentary inquiry that calls attention to a breach of rules; it requires no second, is not debatable, and the chair rules immediately.