Lebanese University Faculty of Agronomy Entrance Examination flashcards

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

Cell theory

All living organisms are composed of one or more cells, cells are the basic unit of life, and new cells arise from pre-existing cells through division.

Photosynthesis equation

6CO2 + 6H2O + light energy → C6H12O6 + 6O2; light reactions occur in thylakoid membranes and the Calvin cycle in the stroma of chloroplasts.

Mendel law of segregation

During gamete formation, the two alleles of a gene separate so each gamete carries only one allele; random fertilization restores pairs in offspring.

Xylem versus phloem

Xylem transports water and dissolved minerals upward from roots, driven mainly by transpiration; phloem transports sucrose and organic solutes bidirectionally between sources and sinks.

Binomial nomenclature

Two-part scientific naming system: capitalized genus name followed by lowercase specific epithet, both italicized or underlined; for example, Homo sapiens.

DNA base pairing

In DNA, adenine pairs with thymine by two hydrogen bonds and guanine pairs with cytosine by three; strands are antiparallel and replication is semiconservative.

Mole concept

One mole contains 6.022×10^23 entities; mass in grams numerically equals molar mass, and one mole of ideal gas occupies 22.4 L at STP.

pH definition

pH equals minus log10 of hydrogen ion concentration; at 25°C pH 7 is neutral, below 7 acidic, above 7 basic, and pH plus pOH equals 14.

Carboxylic acid group

Organic functional group -COOH, consisting of carbonyl carbon bonded to hydroxyl; it is acidic because the conjugate base is resonance-stabilized.

Beer-Lambert law

Absorbance equals molar absorptivity times path length times concentration (A = εlc); used in spectrophotometry to determine concentration of colored solutions.

Le Chatelier principle

When a system at equilibrium is disturbed by concentration, pressure, or temperature change, it shifts in the direction that partially counteracts the disturbance.

Quadratic formula

For ax² + bx + c = 0 with a ≠ 0, solutions are x = (-b ± √(b² - 4ac)) / (2a); the discriminant b² - 4ac determines number of real roots.

Chain rule

Derivative of composite function f(g(x)) is f'(g(x)) times g'(x); used to differentiate nested functions such as sin(3x²).

Conditional probability

P(A|B) equals P(A ∩ B) / P(B), provided P(B) > 0; it gives probability of event A when event B is known to have occurred.

Normal empirical rule

For a normal distribution, about 68% of observations lie within one standard deviation of the mean, 95% within two, and 99.7% within three.

Combination formula

Number of ways to choose r objects from n distinct objects without regard to order is nCr = n! / [r!(n - r)!].

Ohm law

Current through a conductor is directly proportional to voltage and inversely proportional to resistance: V = IR, where V is volts, I amperes, R ohms.

Archimedes principle

Buoyant force on a body immersed in fluid equals weight of displaced fluid: Fb = ρfluid × Vdisplaced × g; it determines floating or sinking.

Snell law

For light crossing an interface, n1 sin θ1 = n2 sin θ2, where n is refractive index and angles are measured from the normal.

First law thermodynamics

Change in internal energy equals heat added to system minus work done by system: ΔU = Q - W; energy is conserved in all thermodynamic processes.

Carnot efficiency

Maximum theoretical efficiency of a heat engine operating between hot and cold reservoirs is η = 1 - Tc/Th, with temperatures in kelvin.

Soil cation exchange capacity

CEC is the soil's capacity to hold exchangeable cations such as Ca²⁺, Mg²⁺, K⁺, and Na⁺ on clay and humus surfaces; higher CEC improves nutrient retention.

Greenhouse effect

Atmospheric gases such as CO2, methane, and nitrous oxide absorb outgoing infrared radiation and re-emit it, warming Earth's surface and lower atmosphere.

Trophic ten percent rule

In a food chain, only about 10% of energy at one trophic level is transferred to the next; the rest is lost mainly as heat through respiration.

Nitrogen fixation

Conversion of atmospheric N2 into ammonia or related compounds by bacteria such as Rhizobium or by industrial Haber-Bosch; makes nitrogen available to living organisms.

Weather versus climate

Weather describes short-term atmospheric conditions at a place; climate is the long-term average and variability of weather over decades or more.

Renewable resource

Natural resource replenished by natural processes at a rate comparable to or faster than human consumption, such as solar energy, wind, and sustainably managed forests.

IMRaD structure

Standard scientific article format: Introduction, Methods, Results, and Discussion; it organizes research reports so readers can follow rationale, procedures, findings, and interpretation.

Significant figures

Digits in a measurement that carry meaningful information about precision; rules govern zeros, multiplication, and addition when reporting calculated results.

Independent variable

Variable deliberately changed or manipulated in an experiment; it is plotted on the x-axis, while the dependent variable is measured on the y-axis.

Plagiarism definition

Presenting someone else's words, ideas, data, or images as one's own without proper attribution; avoided by quoting, paraphrasing, and citing sources correctly.

SI prefix micro

Prefix meaning one millionth (10^-6), symbolized μ; for example, 1 micrometer equals 0.000001 meter or 1000 nanometers.