AFU Common Entrance Exam flashcards

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

Law of the Minimum

Plant yield is governed by the scarcest essential resource, not by the total available. Supplying other nutrients generously cannot compensate for the single deficient factor.

Cation exchange capacity

The soil's capacity to hold exchangeable cations such as calcium, magnesium and potassium on clay and organic matter surfaces. Higher CEC means greater nutrient retention and less leaching.

N-P-K fertiliser label

The three numbers give percent nitrogen, phosphorus expressed as P2O5, and potassium expressed as K2O by weight. A 20-10-10 product contains twice as much N as P2O5.

C3 versus C4 photosynthesis

C3 plants fix carbon dioxide directly with RuBisCO. C4 plants first fix it into a four-carbon acid, concentrating CO2 at the enzyme and improving water-use efficiency in heat.

Legume nitrogen fixation

Rhizobia bacteria in root nodules convert atmospheric nitrogen into forms the plant can use. This requires near-neutral soil pH and the correct bacterial strain for the host species.

Conservation tillage

A tillage system leaving at least thirty percent of the soil surface covered by crop residue after planting. It reduces erosion but can delay soil warming and early crop establishment.

Crop rotation

Growing different crops in sequence on the same land. Rotating with legumes adds fixed nitrogen, interrupts pest and disease cycles, and improves soil structure compared with monoculture.

Seed germination requirements

Germination needs adequate moisture, oxygen and a temperature above the species minimum. Light is required only by certain species; some germinate better in darkness.

Rumen fermentation

Microbes in the rumen break down cellulose into volatile fatty acids that supply most ruminant energy. Saliva and rumination buffer the rumen to a pH near 6.0 to 6.8.

Rumen acidosis

A digestive disorder caused by a sudden shift to readily fermentable carbohydrate and low fibre. Rumen pH falls below about 5.5, impairing microbes and causing appetite loss.

Colostrum and gut closure

Colostrum supplies antibodies that newborn animals can absorb only during the first hours of life. After gut closure, ingested antibodies are digested rather than absorbed.

Body condition scoring

A hands-on assessment of fat cover over ribs, spine and tail head. Scores at calving or lambing extremes predict fertility problems and metabolic disease risk.

Notifiable animal diseases

Diseases such as foot-and-mouth disease and anthrax that must be reported immediately to veterinary authorities. Control relies on rapid reporting, movement restriction and official action.

Zoonosis

An infectious disease transmissible from animals to humans, including brucellosis, rabies and tuberculosis. Control combines surveillance, herd management and protective equipment for handlers.

Normal rectal temperature

Approximate normal ranges are 38.0 to 39.0 Celsius for cattle and dogs, 38.5 to 40.0 for sheep, and 38.5 to 39.5 for pigs. Fever indicates infection or heat stress.

Passive maternal antibody

Antibodies transferred from dam to young through colostrum. They protect the newborn but can block vaccine response, so vaccination timing must account for their decline.

Vaccination primary course

An initial series of doses that builds immunity, followed by booster doses to maintain protection. Timing depends on the species, vaccine type and age of the animal.

Pond dissolved oxygen

Warm-water fish culture generally needs dissolved oxygen above five milligrams per litre. Levels are lowest before dawn because respiration continues while photosynthesis has stopped.

Dawn oxygen sampling

Measuring dissolved oxygen before sunrise detects the daily minimum. Night-time respiration by plants and animals consumes oxygen without photosynthetic replacement, so stress appears then.

Pond fertilisation

Adding nutrients to stimulate plankton growth that feeds cultured fish. Excess fertiliser causes dense algal blooms and night-time oxygen depletion when the algae respire.

Pond yield calculation

Yield per unit area equals stocking density times survival rate times mean harvest weight. Improving any single factor raises output only if the others are not limiting.

Fishing mortality and MSY

Fishing mortality combined with natural mortality gives total mortality. Stock collapse risk rises when fishing mortality exceeds the level supporting maximum sustainable yield.

Hypophysation

Induced breeding of fish by injecting pituitary extract or synthetic hormone. It triggers spawning outside the natural season and allows controlled seed production in hatcheries.

Poikilothermic fish metabolism

Fish body temperature follows water temperature, so metabolic rate, feed intake and growth rise with warmth up to a species-specific optimum. Beyond that optimum, stress and disease risk increase.

Cage culture siting

Cages and pens rely on free water exchange to remove wastes and supply oxygen. Sites need adequate current, depth and flushing to prevent waste build-up beneath the stock.

Shelterwood system

A silvicultural system removing the stand in successive fellings while retaining seed trees. It provides shelter for regeneration before the final removal of the overstorey.

Diameter at breast height

Tree diameter measured at 1.3 metres above ground level. It is the standard input for volume tables, growth models and stand inventory calculations.

Mean annual increment

Total stand volume divided by stand age. Foresters often set rotation age near the point of maximum mean annual increment to optimise average wood production.

Afforestation versus reforestation

Afforestation establishes forest on land without recent tree cover. Reforestation restores forest on land recently cleared or disturbed, often after harvesting or fire.

Agroforestry

Deliberate integration of trees with crops or livestock on the same land. Nitrogen-fixing species such as Leucaena can improve soil fertility for associated intercrops.

Forest fuel load

The amount of combustible vegetation and litter in a stand. High fuel load with low humidity and wind raises fire risk; controlled early burning reduces accumulated fuel.

Reduced-impact logging

Harvesting that limits damage to residual trees and soil through planned extraction routes and directional felling. It supports regeneration and maintains future stand quality.

Wood moisture content

The water present in timber expressed as a percentage of dry weight. Green timber shrinks as it dries, and density plus moisture content affect strength and drying behaviour.