Lebanese University Faculty of Agronomy Entrance Examination key terms

A type of cell division in which one cell produces two genetically identical daughter cells, each with the same chromosome number. It supports growth, tissue repair and asexual reproduction in many organisms.

A specialised division producing four cells, each with half the chromosome number of the parent. It occurs in the formation of gametes and generates genetic variation through crossing over and independent assortment.

The process by which plants, algae and some bacteria use light energy to convert carbon dioxide and water into sugars, releasing oxygen. It takes place mainly in chloroplasts and underpins most food chains.

Loss of water vapour from plant surfaces, mainly through stomata in leaves. It drives the upward movement of water and dissolved minerals in the xylem and helps cool the plant.

Movement of water across a semi-permeable membrane from a region of lower solute concentration to one of higher solute concentration. It explains water uptake by roots and the turgor pressure of plant cells.

One of the alternative forms of a gene at a given position on a chromosome. Different alleles may produce different traits, and a diploid organism inherits one from each parent.

The maintenance of a stable internal environment within narrow limits despite changes outside. Examples include body-temperature regulation and blood glucose control, achieved through feedback mechanisms.

A protein that speeds up a biochemical reaction by lowering its activation energy. Enzymes are specific to their substrates and their activity is affected by temperature and pH.

The system of naming species with two Latin-based words: the genus name, capitalised, followed by the species epithet in lower case. Both are italicised in printed text.

The amount of substance containing as many elementary entities as there are atoms in 12 grams of carbon-12, namely 6.022 × 10^23. It links mass, particle number and gas volume.

The concentration of a solution expressed as moles of solute per litre of solution. It is temperature-dependent because the volume of a solution changes with temperature.

A logarithmic scale, roughly from 0 to 14, measuring hydrogen-ion activity in a solution. Values below 7 are acidic, 7 is neutral and values above 7 are basic.

A volumetric procedure in which a solution of known concentration is added gradually to a measured volume of unknown concentration until the reaction reaches its endpoint, shown by a colour change or an instrument.

A solution that resists large changes in pH when small amounts of acid or base are added. It usually contains a weak acid together with its conjugate base.

A chemical bond formed when two atoms share one or more pairs of electrons. It is typical of organic molecules and is usually strong and directional.

A specific group of atoms within a molecule that gives it characteristic chemical properties and reactivity, such as the hydroxyl, carboxyl, amino or carbonyl groups found in organic compounds.

One of two or more compounds that share the same molecular formula but have different arrangements of atoms, and therefore different physical or chemical properties.

A process in which an atom, ion or molecule loses electrons, usually accompanied by an increase in oxidation number. It always occurs together with reduction in a redox reaction.

The rate at which a function changes with respect to its variable, defined as the limit of the difference quotient. Geometrically it gives the slope of the tangent to the curve.

The value that a function or sequence approaches as its input approaches a specified point or infinity. Limits underlie the definitions of continuity, derivative and integral.

A number between 0 and 1 expressing how likely an event is. For equally likely outcomes it equals the number of favourable outcomes divided by the total number of outcomes.

A measure of how widely the values in a data set spread around their mean. It is the square root of the variance and is expressed in the same units as the data.

The exponent to which a fixed base must be raised to produce a given number. For example, the base-10 logarithm of 1000 is 3.

The net force acting on an object equals its mass multiplied by its acceleration. It links force, mass and acceleration and is written F = ma when the mass is constant.

For a conductor at constant temperature, the current through it is proportional to the potential difference across it. Resistance is the constant of proportionality, giving V = RI.

The change in direction of a wave when it passes from one medium into another in which its speed differs. It explains lenses, prisms and the apparent bending of a stick in water.

Energy cannot be created or destroyed in an isolated system, only converted between forms. The change in internal energy equals the heat added minus the work done by the system.

The upward force exerted by a fluid on an object immersed in it, equal to the weight of the fluid displaced. It determines whether an object floats or sinks.

The relative proportions of sand, silt and clay particles in a soil. Texture influences water retention, drainage, aeration and how easily roots can penetrate the soil.

A permeable geological formation that stores and transmits groundwater in usable quantities. Water enters through recharge areas and is extracted through wells and springs.

The warming of a planet's surface because certain atmospheric gases absorb and re-emit infrared radiation. It keeps Earth habitable, but human emissions of these gases intensify it.

The variety of living organisms at genetic, species and ecosystem levels. It supports ecosystem stability, resilience and services such as pollination and soil formation.

The detachment and transport of soil or rock by water, wind, ice or gravity. On farmland it removes fertile topsoil and is worsened by bare ground and steep slopes.

A short summary placed at the start of a scientific paper or report, stating the objective, methods, main results and conclusion so that readers can decide whether to read the full text.

The evaluation of a research manuscript by independent specialists in the same field before publication. It checks validity, significance and clarity, although it does not guarantee that the work is correct.

Presenting another person's words, data or ideas as one's own without proper attribution. In science it is a serious breach of research ethics and can lead to correction or retraction.