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GCSE OCR Biology Definitions

OCR GCSE B1 You and Your Genes Definitions
Variation: Differences between individuals of the same species.
DNA (deoxyribonucleic acid): Molecules that code for genetic information and make up chromosomes.
Gene: A small section of DNA of a chromosome that determines a particular characteristic.
Chromosome: A long molecule found in the nucleus of all cells containing DNA.
Nucleus: The control centre of a cell, containing DNA.
Protein: Large organic compounds made of amino acids.
Allele: An alternative form of a particular gene.
Homozygous: When a pair of alleles for a characteristic are the same.
Heterozygous: When a pair of alleles for a characteristic are different.
Genotype: The genetic make-up of an organism.
Phenotype: The characteristics shown by an individual.
Sex-determining region Y: A sex-determining gene on the Y chromosome in humans and other primates.
Huntington’s disease: A hereditary, degenerative disorder of the central nervous system.
Cystic fibrosis: A recessive hereditary disorder that mainly affects the lungs and digestive system.
Fetus: An unborn human/animal baby.
In vitro fertilisation (IVF): A technique in which egg cells are fertilised outside the female body.
Pre-implantation Genetic Diagnosis (PGD): Involves removing a cell from an embryo at an early stage of development and testing it for genetic disorders.
Clone: An organism genetically identical to the parent.
Asexual reproduction: New offspring are reproduced that are identical to the parent.
Stem cell: A cell of a human embryo or adult bone marrow that has the ability to differentiate.
Embryonic stem cell: A cell able to differentiate, originating from an embryo cell.
Adult stem cell: A cell able to differentiate, originating from an adult cell.
OCR GCSE B2 Keeping Healthy Definitions
Bacteria: Single-celled microorganisms with no nucleus.
Fungi: A group of organisms including mushrooms, toadstools and yeasts.
Virus: A tiny microorganism with a very simple structure that is reliant on using a cell’s machinery to reproduce.
Immune system: The body’s defence system against infections and diseases (consists of white blood cells and antibodies).
White blood cell: A type of cell in blood that fights infection.
Antibody: Produced by white blood cells to inactivate disease-causing microorganisms.
Antigen: A marker on the surface of a disease-causing microorganism.
Natural immunity: To remain resistant or to be unaffected by a specific disease.
Side effect: A condition caused by taking medication, e.g. headache, nausea.
Mutation: A spontaneous change in the genetic code of a cell.
Antimicrobial: A chemical that kills bacteria, fungi and viruses.
Clinical trial: The process of testing a medical treatment or medicine on human volunteers for safety and effectiveness.
Artery: A muscular blood vessel that carries blood away from the heart.
Vein: A blood vessel that carries blood towards the heart.
Capillary: A blood vessel that connects arteries to veins; where the exchange of materials takes place.
Epidemiological study: A study of the factors affecting the health and illness of populations.
Homeostasis: The maintenance of a constant internal environment.
Hormone: A regulatory substance that stimulates cells or tissues into action.
Anti-diuretic hormone (ADH): A hormone that controls the concentration of urine.
Pituitary gland: The small gland at the base of the brain that produces hormones.
Hypothalamus: The part of the brain responsible for maintaining homeostasis.
OCR GCSE B3 Life on Earth Definitions
Species: Similar organisms capable of interbreeding to produce fertile offspring.
Food chain: A simple chain showing the feeding relationship between organisms in an ecosystem.
Food web: Interlinked food chains in an ecosystem.
Energy: The ability to do work; measured in joules (J).
Photosynthesis: The chemical process that takes place in green plants where water combines with carbon dioxide to produce glucose using light.
Ecosystem: A term that refers to a physical environment, including the conditions there and the organisms that live there.
Autotroph: An organism that makes its own food.
Heterotroph: An organism that is unable to make its own food; consumes other organisms.
Herbivore: An organism that only eats plants, grass, etc; a primary consumer.
Carnivore: An organism that eats other animals; a secondary or tertiary consumer.
Decomposer: An organism that breaks down dead materials and waste products.
Detritivore: An animal that feeds on dead materials.
Excretion: The removal of waste products of cell reactions.
Nitrogen fixing: The removal of nitrogen from the air.
Denitrification: Taking nitrogen from materials, e.g. nitrates.
Combustion: Burning in oxygen/air.
Indicator organism: An organism that is only found in certain conditions.
Pollution: Harmful additions to the environment.
DNA (deoxyribonucleic acid): Molecules that code for genetic information and make up chromosomes.
Common ancestor: The most recent individual from which all organisms in a group are directly descended.
Fossil: Animal/plant remains preserved in rock.
Evolution: The gradual process of adaptation of a species over generations.
Theory of evolution: The most likely scientific explanation, based on evidence, as to why organisms are the way they are.
Natural selection: A natural process resulting in the evolution of organisms best adapted to the environment.
Mutation: A spontaneous change in the genetic code of a cell.
Environmental variation: Variation that occurs as a result of a certain factor in the surroundings.
Selective breeding: The production of new varieties of animals and plants by artificial selection.
Extinction: The process by which groups of organisms die out.
Biodiversity: The range of species in an environment.
Kingdom: A classification of a group of organisms with a small number of features in common.
Biodegradable: A material that decomposes naturally.
OCR GCSE B4 The Processes of Life Definitions
DNA (deoxyribonucleic acid): Molecules that code for genetic information and make up chromosomes.
Organelles: The different parts of a cell’s structure.
Nucleus: The control centre of a cell, containing DNA.
Enzyme: A protein that speeds up that rate of reaction in living organisms (a catalyst in living things).
Denatured enzyme: An enzyme that has had its shape destroyed and can no longer catalyse reactions.
Active site: The place where the molecule fits into the enzyme.
Aerobic respiration: Respiration using oxygen; releases energy and produces carbon dioxide and water.
Anaerobic respiration: The process of releasing energy from glucose in living cells in the absence of oxygen to produce a small amount of energy very quickly.
Polymer: A large molecule made up from many similar units (monomers).
Photosynthesis: The chemical process that takes place in green plants where water combines with carbon dioxide to produce glucose using light.
Chlorophyll: The green pigment found in most plants; responsible for photosynthesis.
Quadrat: A defined area used to sample a location.
Transect: A fixed path across an area of study.
Diffusion: The net movement of particles from an area of high concentration to an area of low concentration.
Active transport: The movement of a substance against a concentration gradient.
Osmosis: The movement of water from a dilute to a more concentrated solution across a partially permeable membrane.
OCR GCSE B5 Growth and Development Definitions
Tissue: A collection of similar cells to carry out a function.
Organ: A collection of tissues to carry out a function.
Mitosis: The cell division that forms two daughter cells, each with the same number of chromosomes as the parent cell.
Meiosis: The cell division that forms daughter cells with half the number of chromosomes as the parent cell.
Chromosome: A long molecule found in the nucleus of all cells containing DNA.
Gamete: A specialised sex cell formed by meiosis.
Fertilisation: The fusion of the male gamete with the female gamete.
Zygote: A cell formed by the fusion of the nuclei of a male sex cell and a female sex cell (gametes).
Embryo: A ball of cells that will develop into a human/animal baby.
Gene: A small section of DNA of a chromosome that determines a particular characteristic.
Nucleus: The control centre of a cell, containing DNA.
Messenger RNA (mRNA): The molecule that carries the genetic code out of the nucleus.
Stem cell: A cell of a human embryo or adult bone marrow that has the ability to differentiate.
Meristem: An area where unspecialised cells divide, producing plant growth.
Clone: An organism genetically identical to the parent.
Auxin: A plant hormone that affects the growth and development of a plant.
Phototropism: A plant’s response to light.
OCR GCSE B6 Brain and Mind Definitions
Stimulus: A change in an organism’s environment.
Central nervous system: The brain and spinal cord; allows an organism to react to its surroundings and coordinates its responses.
Neuron: A specialised cell that transmits electrical messages or nerve impulses when stimulated.
Receptor: The part of the nervous system that detects a stimulus.
Effector: The part of the body, e.g. a muscle or a gland, which produces a response to a stimulus.
Axon: The thread-like extension of a nerve cell.
Synapse: A small gap between adjacent neurons.
Reflex action: A fast, automatic response.
Conditioned reflex: A reflex action brought about by a learned stimulus.
Cerebral cortex: The part of the human brain most concerned with intelligence, memory, language and consciousness.
Memory: The ability to store and retrieve information.
OCR GCSE B7 Further Biology (Peak Performance) Definitions
Vertebrate: An organism with an internal skeleton.
Bone: Rigid connective tissue that makes up the human skeleton.
Muscle: Tissue that can contract and relax to produce movement.
Ligament: The tissue that connects a bone to a joint.
Tendon: Tissue that connects a muscle to a bone.
Antagonistic pair: A pair of muscles that work together to create movement; when one contracts, the other relaxes.
Symptom: A visible or noticeable effect of a disease, illness or injury.
Diagnosis: The decision reached regarding the identification of a condition.
Body mass index (BMI): A measure of fitness.
Sprain: A stretch or tear in a ligament.
Dislocation: The displacement of a part, especially the displacement of a bone at the joint.
Atrium: One of the upper chambers of the heart, which receives blood coming back to the heart.
Ventricle: One of the lower chambers of the heart, which pumps blood out of the heart.
Valve: A device that ensures the flow of a liquid (e.g. blood) in the right direction.
Double circulation system: Blood returns to the heart twice on each circuit of the body.
Deoxygenated: A substance low in oxygen.
Oxyhaemoglobin: Haemoglobin with oxygen bound on.
Oxygenated: A substance rich in oxygen.
Artery: A muscular blood vessel that carries blood away from the heart.
Vein: A blood vessel that carries blood towards the heart.
Capillary: A blood vessel that connects arteries to veins; where the exchange of materials takes place.
Receptor: The part of the nervous system that detects a stimulus.
Effector: The part of the body, e.g. a muscle or a gland, which produces a response to a stimulus.
Hypothalamus: The part of the brain responsible for maintaining homeostasis.
Vasodilation: The widening of the blood vessels to increase heat loss from the surface of the skin.
Vasoconstriction: The narrowing of the blood vessels to decrease heat loss from the surface of the skin.
Insulin: A hormone that causes sugar to be taken from blood.
Diabetes: A medical condition where blood sugar levels are too high.
OCR GCSE B7 Further Biology (Learning from Ecosystems) Definitions
Closed loop system: An ecosystem where waste from one part is used by another.
Desertification: Turning land to desert conditions.
Greenhouse effect: Climate change/global warming due to pollution.
Eutrophication: The process that leads to the stagnation of fresh water.
Bioaccumulation: The build-up of toxic materials inside living cells.
Sustainable: Capable of being continued with minimal long-term effect on the environment.
OCR GCSE B7 Further Biology (New Technologies) Definitions
Fermenter: A controlled environment that maintains ideal conditions for microorganisms to carry out fermentation.
Antibiotic: A type of antimicrobial that kills bacteria and fungi, but not viruses.
Genetic modification: The change in the genetic make-up of an organism.
Vector: An organism (often a microorganism) used to transfer a gene, or genes, from one organism to another.
Nanotechnology: The science of working with structures that are extremely small.
Stem cell: A cell of a human embryo or adult bone marrow that has the ability to differentiate.
Biomedical engineering: Using artificial devices to replace natural parts of an organism.