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Maths & Statistics

This is a compilation of words and definitions from the syllabus. You will eventually need to know most of them by the time you finish the course but not all as you will not have done all the options.

This isn't an exhaustive list of all biological terms but if there is a word missing you think should be included here, please let me know.

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Absorption The taking in of chemical substance through cell membranes or layers of cells.
Acrosome The specialised penetrating vesicle at the top of the spermatozoon.
Acrosome reaction

The release of hyaluronidase when the sperm cell membrane fuses with the acrosome. The enzyme dissolves the zona pellucida leading to fusion of sperm head and ovum.

Action potential

The localised reversal and then restoration of electrical potential between the inside and outside of a neuron as the impulse passes along it. (repolarisation)

Active immunity

Immunity due to production of antibodies by the organism itself after the body's defence mechanisms have been stimulated by invasion of foreign micro-organisms.

Active site The site on the surface of an enzyme to which substrate or substrates bind.

One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene.

Allele frequency For a specific gene, the relative proportion of each allele of that gene found in a population.

Molecules which have one hydrophobic end and one hydrophilic end. E.g. all proteins which are membrane bound must be amphipathic to be anchored in the lipid bilayer and to be functional in an aqueous environment.

Analogous characteristics

Found in various species that may have the same appearance and or function, but have different evolutionary origins. The similarities are dues to similar selective pressure, rather than common ancestry.

Antibody A globular protein that recognises an antigen.
Antigen A molecule recognised as foreign by the immune system.
Antisense strand The template strand which is transcribed.
Artificial immunity Immunity due to inoculation with vaccine.
Assimilation The process of the transformation of external substances and materials into substances and materials internal to the body.
When substance that have been absorbed are used to make new products.
e.g. nitrates are absorbed by plants and assimilated when used to make amino acids.
Autosome A chromosome that is not a sex chromosome.

An organism that produces organic matter from inorganic raw materials and an external energy source to use.
An organism that synthesises its organic molecules from simple inorganic substances.

Balanced diet A diet that provides all nutrients in the necessary proportions.
Binary fission

The process in which a parent cell splits into two daughter cells of approximately equal size. Simple cell division in single-celled organisms.

Biomagnification Process in which chemical substances become more concentrated at each trophic level.

The total mass of organic matter in organisms or ecosystems. Water is not organic matter so is not included. (The term Standing crop which is synonymous will not be used).

Biome A general type of ecosystem occupying extensive geographical areas characterised by similar plant communities, for example, deserts.

Total of all areas where living things are found; including the deep ocean and the the lower part of the atmosphere. The biosphere contains a number of biomes.

Body mass index
Cardiac output Volume of blood pumped out by the heart per minute.

An individual that has a recessive allele of a gene that does not have an effect on the phenotype.
An individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele.

Carrying capacity The maximum number of a species that can be sustainable supported by the environment.
Cell respiration The controlled release of energy from organic compounds in cells to form ATP.

Chemiosmosis is the diffusion of ions across a membrane. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane.


The points at which homologous chromosomes remain in contact as chromatids move apart during Prophase I of meiosis or a cross-shaped structure formed by crossing over between chromosomes or two chromatids.

Clade A group of species that contains the common ancestor of a group and its descendants.
Cladistics The school of evolutionary biology that seeks relationships among species based on the polarity (primitive or derived) of characters.
Classical conditioning The modification of behaviour in an animal as a result of detection of correlations between external events.

A group of organisms of identical genotype.
A group of cells descended from a single parent cell.

Codominant alleles Alleles which have a partial effect on the phenotype when present in heterozygotes but a greater effect in homozygotes. (Note: the terms incomplete and partial are no longer used).
Pairs of alleles that both affect the phenotype when present in a heterozygote. (The terms incomplete and partial dominance are no longer used.)
Cohesion The attraction between molecules of a liquid resulting from intermolecular forces.
Community A group of populations living and interacting with each other in a habitat.
Competitive Exclusion The elimination of one species from a community by another species with the same requirements.
Consumer An organism that ingests other organic matter that is living or recently killed.
Degeneracy Having more than one base triplet to code for one amino acid.
Denaturation A structural change in a protein that results in a loss (usually permanent) of its biological properties.
Detritivore An organism that ingests non-living organic matter.
Diffusion The passive movement of particles from a region of high concentration to a region of low concentration.
Dominant allele An allele which had the same effect on the phenotype whether it is present in the homozygous or heterozygous state.
Ecology The study of relationships between living organisms and between organisms and their environment.
Ecosphere All of the ecosystems on the Earth.
Ecosystem A community and its abiotic environment.
Endergonic A reaction that involves the absorption of energy.
Endotoxins Lipopolysaccharides in the walls of gram-negative that cause fever and aches.
Enzyme A globular protein functioning as a biological catalyst.
Epidemiology The study of the occurrence, distribution and control of disease.
Evolution The cumulative change in the heritable characteristics of a population.
Excretion The removal from the body of the waste products of metabolic pathways.
Exergonic A reaction that involves the release of energy.
Exon Any part of the DNA sequence giving rise to the translated polypeptide sequence.
Exotoxins Specific proteins secreted by bacteria that cause symptoms such as muscle spasm (tetanus) and diarrhoea.
F1 hybrid vigour Vigour due to high levels of heterozygosity.
Fertilisation The fusion of male and female gametes.
Fitness The physical condition of the body which suits it to the particular exercise which it performs.
Gas exchange The movement of oxygen and carbon dioxide between the blood and the air in the lungs.

A heritable factor that controls a specific characteristic, consisting of a length of DNA occupying a position on a chromosome known as a locus.

Gene mutation A change in the base sequence of a gene.
Gene pool The collective genetic information contained within a population of sexually reproducing organisms.
Genetic screening Testing a population for the presence or absence of a gene.
Genome The total genetic material of an organelle, cell or organism.
The whole of the genetic information of an organism.
Genotype The alleles possessed by an organism.
Gross production The amount of organic matter produced by photosynthesis in plants.
Habitat The environment in which a species normally lives.
The location of a living organism.
Half life The time during which the radioactivity falls to half it's original level.
Hardy-Weinberg Principle

If two alleles A and a are segregating at a locus, and each has a frequency of p and q respectively, then the frequencies of the genotypes AA, Aa and aa are p2, 2pq and q2 respectively.

Harvestable dry biomass The dry biomass of the part of the plant of commercial value (e.g. for cereal crops the dry biomass of the grains only).
Heart rate Number of contractions of the heart per minute.
Heterotroph An organism that obtains energy and organic matter from other organisms.
An organism that obtains organic molecules from other organisms.
Heterozygous Having two different alleles of a gene.
Highly repetitive sequences The sequences are typically between 5 and 300 base pairs per repeat, and may be duplicated as many as 105 times per genome.

Chromosomes with the same gene loci in the same sequence which are capable of pairing up to form bivalents during the first prophase of meiosis.

Homologous characteristics Characteristics derived from the same evolutionary origins and hence having similar anatomy.
Homozygous Having the two identical alleles of a gene.
Imprinting An attachment to an object encountered during a short period after birth, usually a parent.
Inbreeding Reproduction involving fusion of gametes produced by genetically related individuals.
Innate behaviour Behaviour which normally occurs in all members of a species despite natural variation in environmental influences.
Insight learning A form of intelligent activity and a function of cognitive effort, which contrasts with more passive trial and error mode of learning.
Interphase The period between one division of the nucleus of a cell and the next division.
Interspecific hybridisation Sexual reproduction between members of different species.
Intron A part of the DNA sequence which is transcribed but is not translated. It is usually spliced out during RNA processing.
Joint A joint is the area where two bones are attached for the purpose of motion of body parts.

The movement (as opposed to growth) of an organism or a cell in response to a stimulus such that depends on intensity but not direction of the stimulus.


Investing more resources into development and long term survival. This involves a longer life span and late maturity, and is more likely to involve parental care, the production of few offspring and reproducing more than once.

Leaf area index The ration between the total area of leaves of a plant crop and the area of soil available to it.
Learned behaviour Behaviour that develops as a result of experience.
Ligament A flexible band of fibrous tissue that connects the bones and binds the joints together.
Limiting factor Variable factors which control the rate of a process when nearer their minimum than other factors.
Lincoln index

Used to estimate a population size.
n1 = number of individuals initially caught
n2 = number of individuals caught in second sample
n3= number of marked individuals in the second sample

Linkage group A group of genes whose loci are on the same chromosome.
Locus The particular position on homologous chromosomes of a gene.

x250 means the picture is 250 smaller in real life.
x0.5 means the picture is 2 times bigger in real life.
Length of scale bar divided by size scale bar represents is equal to magnification:

Always remember to convert numbers to the same units when calculating magnification.

Malnutrition The result of feeding on a diet that is not balanced.
Mark - capture - recapture See Lincoln index
Mean The "average" value obtained by dividing the total of a set of values by the number of values.
Median The central value in a set of observations arranged in order (i.e., the value which divides the ordered set into 2 equal parts).
Meiosis Nuclear division that produces four nuclei, each with half as many chromosomes as the original parent nucleus.
Minerals Elements in an ionic form.
Mitosis Nuclear division that produces two nuclei each genetically identical to each other and to the original parent nucleus.
Mode The most frequent value in a set of observations.

An interaction between individuals of different species that live together (in close proximity) and by which both benefit and neither suffer (the term symbiosis will not be used).

Natural immunity Immunity due to infection.
Negative feedback

The control of a process by the results or effects of the process in such a way that an increase or decrease in the results or effects is reversed.

Net Assimilation Rate
The net increase in plant biomass per unit leaf area per unit time.
Net production The part of gross production that is not used in plant respiration.
Niche A species' share of a habitat and the resources in it. An organism's ecological niche depends not only on where it lives but on what it does. The part of the habitat which a species can inhabit in the absence of competitors and predators is the fundamental niche. The part it actually occupies is its realised niche.
Nucleosome A packing unit of eukaryotic chromosomes with DNA wound around a histone core.
Nutrient A substance needed in the diet of an organism.
A chemical substance found in foods that is used in the human body.
Operant conditioning A learning procedure in which reinforcement follows a particular response on a proportion of occasions.
Organ A group of at least two tissue types combines to carry out a function together (e.g., plant root, animal kidney).
Organ system An integrated group of organs with a common (shared) function (e.g., vascular system, endocrine system).
Organic Compounds containing carbon that are found in living organisms (except hydrogen carbonates, carbonates and oxides of carbon).

The control of the osmotic and water potential in a cell or inside a living organism.
The control of the water balance of the blood, tissue or cytoplasm of a living organism.


The passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.

Outbreeding Reproduction involving fusion of gametes produced by genetically unrelated individuals.
Oxidation Involves the loss of electrons from an element and frequently involves gaining oxygen or losing hydrogen.
Partial pressure

The pressure exerted by each component in a mixture. The pressure of a gas in a mixture is the same as it would exert if it occupied the same volume alone at the same temperature (Dalton's Law).

Passive immunity

Immunity due to the acquisition of antibodies from another organism in which active immunity has been stimulated including via the placenta or in colostrum.

Pathogen An organism causing disease.
Phenotype All the characteristics of an organism.
Phosphorylation The transfer of a phosphate group by a phosphatase.
Plan diagram Showing the outline of areas of each tissue but showing no detail of cells.
Pollination The transfer of pollen from the anther to the stigma.
Polygenic inheritance A characteristic controlled by more than one gene.
Polyploidy Having more than two haploid set of chromosomes.
Population A group of organisms of the same species living in the same area at the same time and capable of interbreeding.
Primary succession Succession that occurs in an environment, such as bare rock, in which no trace of a previous community is present.
Protein hormones Bind to receptors in the membrane, which causes the release of a secondary messenger inside the cell.
Random sample A method to ensure that every individual in a population has an equal chance of being observed.
Recessive allele An allele that only has an effect on the phenotype when present in the homozygous state.
Recombination The reassortment of genes or characters into different combinations from those from the parents.
Reduction Involved a gain of electrons from an element and frequently involves losing oxygen or gaining hydrogen.
Reflex A rapid unconscious response.
Resolution The least value of a measured quantity that can be distinguished.
E.g: the accuracy at which a given map scale can depict the location and shape of geographic features. The larger the map scale, the higher the possible resolution. As map scale decreases, resolution diminishes and feature boundaries must be smoothed, simplified, or not shown at all.

An action resulting from the perception of a stimulus. It is a reaction to a change perceived by the nervous system. The total of responses to stimuli is often called behaviour.

Resting potential An electrical potential across a cell membrane when not propagating an impulse. (Depolarisation)

Investing more resources into producing many offspring, having a short life span early maturity, reproducing only once and having a small body size.


An organism that feeds on dead organic matter using extra cellular digestion.
An organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

Satellite DNA See Highly repetitive sequences.
Secondary succession Succession of species on soil already formed, in which the community has been distributed.
Seed dispersal

The method by which a plant scatters its offspring away from the parent plant to reduce competition. Methods include: wind, insects and animals.

Sense strand The coding strand which has the same base sequence as mRNA (but with uracil instead of thymine).
Sex chromosome A chromosome that helps to determine the sex of an individual.
Sex linkage Genes carried on sex chromosomes.
Simpson diversity index D = diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
Single-copy genes The genes that carry our genetic information as outlined by Mendelian genetics. They only make up about 1.5% of the human genetic material.
Somatic cell Any cell in the body that is not a sperm or egg cell.
Species A group of organisms which could interbreed and produce fertile offspring.
Standard deviation Used to summarise the spread of values around the mean, 68% of the values fall within one standard deviation (sd, s or σ) of the mean.
Standing crop See Biomass.
Steroid hormones Enter cells and interact with genes directly.
Stimulus A change in the environment (internal or external) that is detected by a receptor and elicits a response.
Stroke volume Volume of blood pumped out with each contraction of the heart.
Synapse The gap between neurons across which neurotransmitters diffuse.

Locomotion of an organism in a particular direction in response to an external stimulus (e.g., phototaxis to light and chemotaxis to gradients of dissolved substances).

Tendon A tough, fibrous band of tissue that attaches muscle to bone.
Test cross Testing a suspected heterozygote by crossing with a known homozygous recessive (The term backcross is no longer used).
Tidal volume Volume of air taken in or out with each inhalation or exhalation.
Tissue A group of cells of one type with similar structure and function (e.g., plant parenchyma and squamous epithelium).
Total lung capacity Volume of air in the lungs after a maximum inhalation.

The process through which a DNA sequence is copied by an RNA polymerase to produce a complementary RNA. Or, in other words, the transfer of genetic information from DNA into RNA.

Translation The process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm.
Translocation The movement of substances from one part of a plant to another in the phloem.
Transpiration The loss of water vapour from the leave and stems of plants.
Trophic level

In ecology, the trophic level (Greek trophē, food) is the position that an organism occupies in a food chain - what it eats and what eats it.

Unique genes See Single-copy genes.
Universal Found in all living organisms.
Venous return Volume of blood returning to the heart via the veins per minute.
Ventilation The process of moving air into and out of the lungs.
Ventilation rate Number of inhalations or exhalations per minute (breathing rate is not used).
Vital capacity Maximum volume of air that can be exhaled after a maximum inhalation.
Vitamins Organic compounds.
VO2 Volume of oxygen taken up per minute.
VO2 max The highest possible volume of oxygen taken up per minute by a specific individual.
Water potential

A measure of the tendency of water to move between regions. In practice it is the force acting on water molecules in solution when separated from pure water by a membrane permeable to water only (i.e., partially permeable).