Essential Definitions

Action Potential
Rapid change (depolarisation) in membrane potential of an excitable cell (e.g. a neurone)
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Active Site
Region of enzyme molecule where substrate molecule binds
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An alternative form of a gene, occupying a specific locus on a chromosome
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Allele Frequency
The commonness of the occurrence of any particular allele in a population
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The process by which chemical substances become more concentrated at each trophic level
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An individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele
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Cellular Respiration
Controlled release (transfer) of energy from organic compounds in cells to form ATP
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An organism that uses energy from chemical reaction to generate ATP and produce organic compounds from inorganic substances
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An organism that uses energy from chemical reactions to generate ATP and obtains organic compounds from other organisms
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A branch of a phylogenetic tree containing the set of all organisms descended from a particular common ancestor which is not an ancestor of any non-member of the group
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Method of classifying living organisms that makes use of lines of descent only (rather than phenotypic similarities)
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A group of genetically identical individuals (or cells)
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Codominant Alleles
Pairs of alleles that both affect the phenotype when present in a heterozygous state
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A group of populations of organisms living and interacting with each other in a habitat
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A structural change in a protein that results in a loss (ususallu permanent) of its biological properties
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Passive movement of particles from a region of high concentration to a region of low concentration
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Dominant Allele
An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state
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The study of relationships between living organisms and between organisms and their environment- a community and its abiotic environment
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Mainly proteins (a very few are RNA) that function as biological catalysts
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The study of the occureence, distribution and control of disease
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Cumulative change in the hertiable characteristics of a population
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Removal from the body of the waste products of metabolic pathways
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A hertiable factor that controls a specific characteristic
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Gene Mutation
Change in the chemical structure (base sequence) of a gene resulting in change in the charateristics or an organism or individual cell
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Gene Pool
All the genes (and their alleles) present in a breeding population
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The genetic comlement (genes) of an organism or of an individual cell- the whole of the genetic information of an organism
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The genetic constitution of an organism- the alleles of an organism
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The locality or surroundings in which an organism normally lives or the location of a living organism
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The time taken for the ionising radiation emitted by a radioactive isotope to fall to half maximum
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Heart Rate
Number of contractions of the heart per minute
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Having two different alleles of a gene
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Homologous Chromosome
Chromosomes in a diploid cell which contain the same sequence of genes, but are derived from different parents
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Having two identical alleles of a gene
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Resistance to the onset of a disease after infection by the causative agent
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Active Immunity
Immuntiy due to the production of antibodies by the organism istelf after the body's defence mechanisms have been stimulated by antigens
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Passive Immunity
Immunity due to the production of antibodies from another organism in which active immunity has been stimulated, including via the placents, colostrum, or by injection of antibodies
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Linkage Group
The genes carried on any one chromosome
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The particular position on homologous chromosomes of a gene
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A chemical substance found in foods that is used in the human body- any substance used or required by an organism as food
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Control of the water balance of the blood, tissue or cytoplasm or a living organism
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Diffusion of free water molecules from a regions where they are more concentrated (low solute concentration) to a region where theyr are less concentrated (high solute concentration) across a partially permeable membrane
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An organism or virus that causes a disease
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Partial Pressure
The pressure exerted by each component of a gas mixture, proportional to how much of the gas is present in the mixture; the partial pressure of oxygen in the air is represented by the symbol pO2 and is expressed in kilopascals
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The characteristics or appearance (structural, biochemical etc.) of an organism
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An organism that uses light energy to generate ATP and to produce organic compounds from inorganic substances
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An organism that uses light energy to generate ATP and obtains organic compounds from other organisms
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Polygenic Inheritance
Inheritance of phenotypic characteristics (such as height, eye colour in humans) that are determined by the collectibe effects of several different genes
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A group of organisms of the same species which live in the same area (habitat) at the same time
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Gross Productivity
Total amount of organic matter produced
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Net Productivity
The organic matter or organisms less the amount needed to fuel respiration
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Recessive Allele
An allele that has an effect on the phenotype only when present in the homozygous state
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A rapid unconscious response
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The outcome when a stimulus is detected by a receptor
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Resting Potential
The potential difference across the membrane of a neurone when it is not being stimulated (repolarised)
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Sex Linkage
Genes carried on only one of the sex chromosomes and which therefore shoe a different pattern of inheritance in crosses where the male carries the gene from those where the female carries the gene
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A group of individuals of common ancetry that closely resemble each other and there are normally capable of interbreeding to produce fertile offspring
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Male germ cells (stem cells) which make up the inner layer of the lining od the seminiferous tubules, and give rise to spermatocytes
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A change in the environment (internal or external) that is detected by a receptor and leads to a response
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Stroke Volume
Volume of blood pumped out by the heart per minute
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Test Cross
Testing a suspected heterozygote by crossing it with a known homozygous recessive
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Tidal Volume
Volume of air normally exchanged in breathing
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Total Lung Capacity
Volume of air in the lungs after maximum inhalation
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Loss of water vapour from the aerial parts of platns (leaves and stem)
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Trophic Level
A levle in a food chain defined by the method of obtaining food and in which all organisms are the same number of energy transfers away from the original source of the energy (photosythesis)
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The amount of oxygen being used in the body (cm3/kgmin); with increasingly vigorous exercise, VO2 will increase initially
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VO2 Max
The maximal oxygen uptake by the body (cm3/kgmin)- even if the maximum physical effort is maintained, a situation is reached where further increase is impossible
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Venous Return
Volume of blood returning to the heart via the veins per minute
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Vital Capacity
The total possible change in lung volume- the maximum volume of air that can be exhaled after maximum inhalation
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Card 2


Active Site


Region of enzyme molecule where substrate molecule binds

Card 3




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Card 4


Allele Frequency


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Card 5




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