UAE TLS Biology Test key terms

A thin, flexible barrier of phospholipids and proteins that surrounds every cell. It controls which substances enter and leave, allowing the cell to keep a stable internal environment.

A protein that speeds up a specific chemical reaction inside living things without being used up. Each enzyme has a shaped active site that fits only particular substrate molecules.

Adenosine triphosphate, the small molecule that carries usable energy around a cell. Energy released when its terminal phosphate bond breaks powers muscle contraction, transport and many synthesis reactions.

The net movement of water across a partially permeable membrane from a region of higher water potential to one of lower water potential. It is passive and needs no energy input.

An organelle with a folded inner membrane where aerobic respiration takes place. It produces most of the ATP a cell needs, so busy cells such as muscle fibres contain many of them.

One of two or more alternative versions of the same gene, occupying the same position on a chromosome. Different alleles produce slight variations in the protein that the gene codes for.

The particular combination of alleles an organism carries for one or more genes. It is usually written as pairs of letters, such as AA, Aa or aa.

A family tree diagram using standard symbols to show how a trait or disorder passes through several generations. It helps reveal whether an allele is dominant, recessive or sex-linked.

A type of cell division that produces four genetically different gametes, each with half the normal chromosome number. Two successive divisions follow one round of chromosome duplication.

The maintenance of a steady internal environment, such as constant body temperature, blood glucose and water balance, despite changes outside the body. It depends on negative feedback loops.

The microscopic filtering unit of the kidney. Each one filters blood at a glomerulus, then reabsorbs useful substances and secretes wastes along its tubule.

The tiny gap where one neurone passes a signal to another cell. A chemical neurotransmitter diffuses across and binds to receptors on the next membrane.

The process by which individuals with inherited features suited to their environment tend to survive and reproduce more successfully, so those features become more common over generations.

Body parts in different species that share a similar underlying structure because of common ancestry, even when they perform different jobs today, such as a human arm and a bat wing.

The basic unit of classification: a group of organisms that can interbreed to produce fertile offspring and are reproductively isolated from other such groups.

The two-part scientific naming system introduced by Linnaeus. The first word names the genus and is capitalised; the second names the species and is lower case.

The largest population of a species that a particular habitat can support over a long period, given the food, water, space and shelter available.

A feeding position in a food chain, such as producer, primary consumer or secondary consumer. Energy is lost at each transfer, so higher levels hold far less biomass.

The series of processes by which nitrogen moves between the atmosphere, soil and living things, including nitrogen fixation, nitrification, assimilation, ammonification and denitrification by microorganisms.

The variety of life in an area, measured at the level of species, genetic variation within species, and the ecosystems they form. High biodiversity usually makes communities more resilient.

Plant tissue made of dead, hollow cells that transports water and dissolved minerals from the roots upward to the leaves, also helping to support the stem.

The process by which green plants, algae and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen inside chloroplasts.

The loss of water vapour from the leaves of plants, mainly through stomata. It pulls water up the xylem and cools the leaf.

A permanent growth response of a plant towards or away from a one-sided stimulus, such as light, gravity or contact. Shoots usually grow towards light.

A laboratory technique that copies a chosen DNA sequence millions of times. Repeated cycles of heating and cooling use a heat-stable polymerase and short primers.

A small circular piece of DNA found in bacteria, separate from the main chromosome. Plasmids are widely used as vectors to carry foreign genes into host cells.

A bacterial protein that cuts DNA at a specific base sequence. Scientists use these enzymes to cut out genes or to check the pattern of fragments on a gel.

A technique that separates DNA fragments by size. Fragments are loaded into a gel and pulled by an electric current; smaller ones travel further than larger ones.

In an experiment, the group that does not receive the treatment being tested. It shows what would happen otherwise, so the effect of the independent variable can be judged.

The factor that a researcher deliberately changes or sets at different values between trials, so that its effect on the measured dependent variable can be observed.

How closely repeated measurements agree with each other. A set of readings can be highly precise yet still inaccurate if the instrument is badly calibrated or biased.

Items worn in the laboratory to reduce exposure to hazards, such as safety goggles, gloves, a lab coat and, where needed, a face shield or respirator.

Ongoing check of student understanding during teaching, used to adjust instruction and give feedback. It is not usually graded and contrasts with end-of-unit summative assessment.

A clear statement of what students should know or be able to do by the end of a lesson or unit, usually written with an observable action verb.

An approach in which students investigate questions, design procedures and interpret evidence themselves, with the teacher guiding rather than simply giving answers.

A firmly held idea that conflicts with accepted science, such as believing plants get their food from the soil. Good teaching deliberately surfaces and challenges them.