IGCSE Biology
Active transport ✔✔The process in which energy is used to move the particles of a substance
against a concentration gradient, that is, from a region where they are of lower concentration to a
region where they are of higher concentration.
Adaptation ✔✔Any characteristic of an organism that improves its chances of surviving in its
environment.
Aerobic respiration ✔✔Respiration with oxygen. It's the oxidation of food substances in the
presence of oxygen with the release of a large amount of energy. Carbon dioxide and water are
released as waste products.
AIDS ✔✔An abbreviation for Acquired Immune Deficiency Syndrome.
Alleles ✔✔Different forms of a gene which occupy the same relative positions on a pair of
homologous chromosomes.
Anaerobic respiration ✔✔Respiration without oxygen. It's the oxidation of food substances in
the absence of oxygen. Anaerobic respiration releases less energy than aerobic respiration.
Anaesthetics ✔✔Drugs that make the body unable to feel pain
Arteries ✔✔Blood vessels which carry blood away from the heart.
Artificial selection ✔✔A method used by human beings to produce plants and animals with
desired qualities.
Asexual reproduction ✔✔The process resulting in the production of genetically identical
offspring from one parent, without the fusion of gametes.
Assimilation ✔✔The process whereby some of the absorbed food materials are converted into
new protoplasm or used to provide energy.
Axon ✔✔A nerve fibre that transmits impulses away from the cell body of a neurone.
, Bioaccumulation ✔✔The process by which substances collect in all parts or part of a living
organism.
Breathing ✔✔The process that brings about an exchange of gases between an organism and its
environment.
Capillaries ✔✔Microscopic thin-walled (one cell thick) blood vessels which carry blood from a
small artery (arteriole) to a small vein (venule).
Codominance ✔✔A condition where both alleles express themselves in a hybrid, as they are
both either dominant or recessive to one another. (Roughly equal expression.)
Community ✔✔Populations of organisms living together and interacting with one another under
the same environmental conditions.
Conservation ✔✔The protection and preservation of natural resources of the environment.
Consumers ✔✔Organisms which obtain their energy by feeding on other organisms.
Continuous variation ✔✔Traits with phenotypes ranging from one extreme to the other. It is
brought about by combined (or additive) effects of many genes. It is affected by environmental
conditions, e.g. intelligence, height and skin colour in human beings.
Cross-pollination ✔✔The transfer of pollen grains from one plant to the stigma of a flower in
another plant of the same species.
Decomposers ✔✔Saprotrophs and detritivores. Organisms which obtain energy by breaking
down dead organisms, faeces and excretory products.
Dendron ✔✔A nerve fibre that transmits impulses towards the cell body of a neurone.
Desertification ✔✔The destruction of land leading to desert-like conditions.
Detoxification ✔✔The process of converting harmful substances into harmless ones in the body.
Active transport ✔✔The process in which energy is used to move the particles of a substance
against a concentration gradient, that is, from a region where they are of lower concentration to a
region where they are of higher concentration.
Adaptation ✔✔Any characteristic of an organism that improves its chances of surviving in its
environment.
Aerobic respiration ✔✔Respiration with oxygen. It's the oxidation of food substances in the
presence of oxygen with the release of a large amount of energy. Carbon dioxide and water are
released as waste products.
AIDS ✔✔An abbreviation for Acquired Immune Deficiency Syndrome.
Alleles ✔✔Different forms of a gene which occupy the same relative positions on a pair of
homologous chromosomes.
Anaerobic respiration ✔✔Respiration without oxygen. It's the oxidation of food substances in
the absence of oxygen. Anaerobic respiration releases less energy than aerobic respiration.
Anaesthetics ✔✔Drugs that make the body unable to feel pain
Arteries ✔✔Blood vessels which carry blood away from the heart.
Artificial selection ✔✔A method used by human beings to produce plants and animals with
desired qualities.
Asexual reproduction ✔✔The process resulting in the production of genetically identical
offspring from one parent, without the fusion of gametes.
Assimilation ✔✔The process whereby some of the absorbed food materials are converted into
new protoplasm or used to provide energy.
Axon ✔✔A nerve fibre that transmits impulses away from the cell body of a neurone.
, Bioaccumulation ✔✔The process by which substances collect in all parts or part of a living
organism.
Breathing ✔✔The process that brings about an exchange of gases between an organism and its
environment.
Capillaries ✔✔Microscopic thin-walled (one cell thick) blood vessels which carry blood from a
small artery (arteriole) to a small vein (venule).
Codominance ✔✔A condition where both alleles express themselves in a hybrid, as they are
both either dominant or recessive to one another. (Roughly equal expression.)
Community ✔✔Populations of organisms living together and interacting with one another under
the same environmental conditions.
Conservation ✔✔The protection and preservation of natural resources of the environment.
Consumers ✔✔Organisms which obtain their energy by feeding on other organisms.
Continuous variation ✔✔Traits with phenotypes ranging from one extreme to the other. It is
brought about by combined (or additive) effects of many genes. It is affected by environmental
conditions, e.g. intelligence, height and skin colour in human beings.
Cross-pollination ✔✔The transfer of pollen grains from one plant to the stigma of a flower in
another plant of the same species.
Decomposers ✔✔Saprotrophs and detritivores. Organisms which obtain energy by breaking
down dead organisms, faeces and excretory products.
Dendron ✔✔A nerve fibre that transmits impulses towards the cell body of a neurone.
Desertification ✔✔The destruction of land leading to desert-like conditions.
Detoxification ✔✔The process of converting harmful substances into harmless ones in the body.
