GTLE Biology key terms

The maintenance of a stable internal environment within an organism, such as constant body temperature or blood glucose, despite changes in external conditions. It relies on negative feedback loops detecting and correcting deviations.

A control mechanism where a change from a set point triggers a response that counteracts that change, restoring the original value. Common in temperature regulation, hormone control, and blood sugar management.

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

The passive spreading of particles from a region of higher concentration to a region of lower concentration, driven by random molecular motion. Rate depends on concentration gradient, temperature, surface area, and distance.

Movement of ions or molecules across a membrane against their concentration gradient using carrier proteins and energy from ATP hydrolysis. It allows cells to accumulate substances they need at higher internal concentrations.

A biological catalyst, usually a globular protein, that speeds up reactions by lowering activation energy. Its activity depends on shape, temperature, pH, and substrate concentration, and it is not consumed.

The specific region of an enzyme where the substrate binds and the reaction occurs. Its shape is complementary to the substrate, and alteration of this shape reduces or destroys catalytic activity.

Loss of a protein's three-dimensional structure caused by heat, extreme pH, or chemicals, breaking bonds that maintain shape. For enzymes this destroys the active site and abolishes catalytic function irreversibly in most cases.

Nuclear division producing two genetically identical daughter cells with the same chromosome number as the parent. It underpins growth, repair, and asexual reproduction in eukaryotes.

Reduction division producing four haploid gametes from one diploid cell, involving two divisions and crossing over. It generates genetic variation through independent assortment and recombination.

One of two or more alternative versions of a gene occupying the same locus on homologous chromosomes. Combinations of alleles determine genotype and contribute to phenotype variation.

The genetic makeup of an organism at one or more loci, described by the alleles present, such as homozygous dominant or heterozygous. It interacts with environment to produce the observable phenotype.

The observable characteristics of an organism resulting from the interaction between its genotype and environmental factors. Examples include eye colour, blood group, and enzyme activity levels.

The process whereby individuals with inherited traits better suited to their environment survive and reproduce more successfully, increasing the frequency of those alleles in later generations.

An inherited feature or behaviour that increases an organism's chance of survival and reproduction in its habitat. Adaptations arise through natural selection over many generations.

The light-dependent synthesis of glucose from carbon dioxide and water in chloroplasts, releasing oxygen. Light energy is captured by chlorophyll and converted into chemical energy in organic molecules.

The controlled release of energy from organic molecules such as glucose, producing ATP. Aerobic respiration uses oxygen and yields carbon dioxide and water; anaerobic respiration occurs without oxygen.

Adenosine triphosphate, the universal energy currency of cells. Hydrolysis of its terminal phosphate bond releases energy that drives endergonic processes including active transport and synthesis reactions.

The green pigment in chloroplasts that absorbs mainly red and blue light for photosynthesis while reflecting green wavelengths. Different chlorophyll types absorb slightly different wavelengths.

A community of interacting organisms together with the non-living components of their environment, such as soil, water, and climate. Energy flows through it while nutrients are recycled.

A sequence showing the transfer of energy from producers through primary and secondary consumers to decomposers. Arrows indicate direction of energy flow, and energy is lost at each trophic level.

The position an organism occupies in a food chain, such as producer, primary consumer, or secondary consumer. Biomass and energy generally decrease at higher trophic levels.

The variety of living organisms in an area, encompassing species richness, genetic diversity within species, and ecosystem diversity. It supports ecosystem stability and resilience to change.

The protection and management of species, habitats, and genetic resources to maintain biodiversity and prevent extinction. Strategies include protected areas, captive breeding, and seed banks.

A learning theory holding that learners build new understanding by connecting new information to existing knowledge and experience. Teaching therefore starts from prior conceptions and uses active, hands-on tasks.

A persistent, scientifically incorrect idea a learner already holds, such as believing plants get food from soil. Effective teaching elicits and directly challenges such ideas rather than ignoring them.

Ongoing assessment used during teaching to identify what learners understand and to adjust instruction accordingly. It is low-stakes and feedback-focused, contrasting with summative assessment of final achievement.

Assessment carried out at the end of a unit or course to judge overall achievement against standards. Results are typically graded and reported, and may inform progression or certification decisions.

Learning activities in which students handle equipment and materials to investigate biological questions. Well-designed practicals develop investigative skills and support understanding of concepts and the nature of evidence.

The process of asking questions, formulating testable hypotheses, planning fair investigations, collecting and analysing data, and drawing evidence-based conclusions. It reflects how scientific knowledge is generated.

Adapting content, tasks, support, or outcomes to meet the varied readiness and needs of learners in the same class. It aims to give all students appropriate challenge and access to the curriculum.

Temporary structured support, such as models, prompts, or partially completed tasks, that enables learners to accomplish a task they could not yet do independently. Support is gradually withdrawn as competence grows.

The gap between what a learner can do unaided and what they can achieve with guidance from a more capable person. Instruction is most effective when targeted within this range.

The extent to which an assessment or investigation measures what it claims to measure. In experiments, validity requires controlling confounding variables so results can be attributed to the independent variable.

The consistency of a measurement or assessment when repeated under the same conditions. Reliable methods give similar results on repeat trials, though a reliable measure may still be invalid.

How close a measured value is to the true or accepted value. Accuracy differs from precision, which concerns the closeness of repeated measurements to each other.

How close repeated measurements are to one another, reflecting the spread of results. Precise measurements may still be inaccurate if there is a systematic error.

A factor kept constant across experimental groups so that it cannot influence the outcome. Controlling relevant variables strengthens the validity of conclusions about the independent variable.

Principles governing responsible research and teaching involving living organisms, including informed consent, animal welfare, and safe handling of microorganisms. Ethical approval and risk assessment are usually required before practical work.

A systematic identification of hazards in an activity and evaluation of the likelihood and severity of harm, followed by measures to reduce risk. It underpins safe laboratory and fieldwork practice.

A measure of the spread of data around the mean, calculated from the square root of the variance. A large value indicates widely dispersed results and greater uncertainty in the mean.

The arithmetic average of a set of values, found by summing them and dividing by the number of values. It summarises central tendency but is sensitive to extreme values.

The number of times an image is larger than the actual object, calculated as image size divided by actual size. Units must be converted consistently, usually to millimetres or micrometres.

The smallest distance at which two points can be distinguished as separate. It is limited by the wavelength of radiation used and is distinct from magnification.

The change in amount of reactant or product per unit time, often expressed per second or per minute. Graphs of product against time allow comparison of initial rates between conditions.