Edexcel International GCSE Biology glossary
89 key terms from the Edexcel International GCSE Biology notes, A to Z. Each definition links to the note that teaches it.
A
- Active site
- The region of an enzyme with a shape complementary to its substrate, where the reaction takes place.Revise it: Enzymes as biological catalysts
- Active transport
- Movement of substances against a concentration gradient (low to high), using energy from respiration.Revise it: Diffusion
- Allele
- A different version (alternative form) of the same gene.Revise it: Alleles and genetic terms
- Antibody
- A protein released by a lymphocyte that is specific to one antigen and helps to destroy the pathogen.Revise it: White blood cells and the immune response
- Antigen
- A molecule on the surface of a pathogen that the immune system recognises as foreign.Revise it: White blood cells and the immune response
- ATP
- The molecule that provides energy for cells. It is made during respiration.Revise it: Respiration and ATP
B
- Biodiversity Biology only
- The variety of all the different species of organisms in an ecosystem, habitat or on Earth.Revise it: Biodiversity
- Biological control
- Using a living organism, such as ladybirds eating aphids, to reduce a pest population.Revise it: Fertilisers, pesticides and biological control
C
- Cell
- The basic building block of all living organisms.Revise it: Levels of organisation
- Cell differentiation Biology only
- The process by which a cell becomes specialised for a particular job.Revise it: Cell differentiation and specialised cells
- Cell membrane
- Controls the movement of substances into and out of the cell.Revise it: Bacteria
- Cell wall
- Surrounds the cell and supports it.Revise it: Bacteria
- Central nervous system (CNS)
- The brain and spinal cord.Revise it: The central nervous system and nerve impulses
- Chromosome
- A long molecule of DNA, found in the nucleus, on which genes are located.Revise it: The genome, genes and chromosomes
- Circular chromosome
- A single loop of DNA found free in the cytoplasm, not enclosed in a nucleus.Revise it: Bacteria
- Clone
- An offspring that is genetically identical to its parent, produced by asexual reproduction.Revise it: Sexual and asexual reproduction
- Cloned transgenic animal Biology only
- A cloned animal that contains a gene from another species, such as a human gene.Revise it: Cloned transgenic animals and human proteins
- Codominance Biology only
- Both alleles are expressed in the phenotype of a heterozygous organism, for example roan cattle or blood group AB.Revise it: Codominance
- Combustion
- Burning of fuels such as wood, coal, oil and gas, which releases carbon dioxide.Revise it: The carbon cycle
- Community
- All the populations of different species living in the same area.Revise it: Population, community, habitat and ecosystem
- Compensation point Biology only
- The light intensity at which photosynthesis equals respiration, so there is no net gas exchange.Revise it: Net gas exchange by day and night
- Cytoplasm
- Where the chemical reactions of the cell happen.Revise it: Bacteria
D
- Diffusion
- The net movement of particles from an area of higher concentration to an area of lower concentration.Revise it: Diffusion
- Diploid
- A cell with two sets of chromosomes in its nucleus.Revise it: Mitosis
- Dominant
- An allele that is expressed in the phenotype even when only one copy is present.Revise it: Alleles and genetic terms
- Double circulatory system
- Blood passes through the heart twice on each circuit: heart to lungs and back, then heart to body and back.Revise it: The circulation system
E
- Ecosystem
- A community together with the non-living (abiotic) parts of its environment.Revise it: Population, community, habitat and ecosystem
- Effector
- A muscle or gland that carries out the response.Revise it: Responding to change: stimulus, receptor, effector
- Emphysema
- A lung disease in which alveoli walls break down, reducing the surface area for gas exchange.Revise it: Smoking, the lungs and the circulatory system
- Enhanced greenhouse effect
- Extra warming because human activities increase greenhouse gases, which absorb more infrared radiation and send it back to Earth.Revise it: The enhanced greenhouse effect and global warming
- Enucleated egg cell Biology only
- An egg cell that has had its nucleus removed.Revise it: Cloning mammals: Dolly the sheep
- Enzyme
- A protein that acts as a biological catalyst, speeding up metabolic reactions without being used up.Revise it: Enzymes as biological catalysts
- Eutrophication
- Over-enrichment of water with minerals, such as nitrates leached from fertiliser, leading to loss of oxygen and death of aquatic life.Revise it: Eutrophication
- Examples of animals
- Mammals (for example humans) and insects (for example housefly and mosquito).Revise it: Plants and animals
- Examples of plants
- Flowering plants, such as a cereal (for example maize) and a herbaceous legume (for example peas or beans).Revise it: Plants and animals
- Excretion
- The removal from the body of the waste products of metabolism.Revise it: Excretion: lungs, kidneys and skin
- Explant Biology only
- A small piece of plant tissue taken from the parent plant to be grown in vitro.Revise it: Micropropagation (tissue culture)
F
- Food web
- A diagram of all the linked food chains in a habitat.Revise it: Food chains and food webs
G
- Gene
- A section of a molecule of DNA that codes for a specific protein.Revise it: The genome, genes and chromosomes
- Genetically identical
- Having exactly the same genetic information (the same DNA).Revise it: Mitosis
- Genome
- The entire DNA of an organism.Revise it: The genome, genes and chromosomes
- Genotype
- The alleles an organism has for a gene, for example Tt.Revise it: Alleles and genetic terms
H
- Habitat
- The place where an organism lives.Revise it: Population, community, habitat and ecosystem
- Heterozygous
- Having two different alleles of a gene, for example Tt.Revise it: Alleles and genetic terms
- Homeostasis
- The maintenance of a constant internal environment.Revise it: Homeostasis
- Homozygous
- Having two identical alleles of a gene, for example TT or tt.Revise it: Alleles and genetic terms
- Hormone
- A chemical messenger secreted by a gland into the blood, which affects a target organ.Revise it: Nervous and hormonal communication compared
L
- Leaching
- Dissolved minerals being washed out of the soil by rain.Revise it: Eutrophication
- Ligase
- An enzyme that joins pieces of DNA together.Revise it: Restriction enzymes, ligase and vectors
- Limiting factor
- A factor in short supply that stops the rate of a process from increasing.Revise it: Factors affecting the rate of photosynthesis
M
- Memory cells Biology only
- Lymphocytes that stay in the body after exposure to an antigen and respond quickly if the pathogen returns.Revise it: Vaccination and memory cells
- Micropropagation Biology only
- Growing new plants from small pieces of tissue (explants) in vitro, in sterile conditions on nutrient medium.Revise it: Micropropagation (tissue culture)
- Mitosis
- Division of a diploid cell to produce two cells that contain identical sets of chromosomes.Revise it: Mitosis
- Mutation
- A rare, random change in genetic material that can be inherited.Revise it: Mutations and the phenotype
- Mycelium
- The body of a fungus, made from thread-like hyphae that contain many nuclei.Revise it: Plants and animals
O
- Organ
- A group of different tissues that work together to perform a specific function.Revise it: Levels of organisation
- Organ system
- A group of organs that work together to carry out a major job in the body.Revise it: Levels of organisation
- Organelle
- A structure inside a cell that has a particular job, such as the nucleus or a mitochondrion.Revise it: Levels of organisation
- Osmosis
- The diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane.Revise it: Diffusion
P
- Pathogen
- A microorganism that causes disease.Revise it: White blood cells and the immune response
- Percentage cover
- The percentage of the quadrat covered by a species. Used where individuals are hard to count, such as grass.Revise it: Practical: population size with quadrats
- Peristalsis
- Waves of contraction of circular and longitudinal muscles that squeeze food along the gut.Revise it: The alimentary canal and peristalsis
- Phenotype
- The characteristic that is expressed and can be observed, for example tall.Revise it: Alleles and genetic terms
- Photosynthesis
- The process by which plants make glucose from carbon dioxide and water, using light energy absorbed by chlorophyll.Revise it: Photosynthesis and its equations
- Plasmids
- Small rings of extra DNA, separate from the circular chromosome.Revise it: Bacteria
- Pneumococcus
- A spherical bacterium that is the pathogen causing pneumonia.Revise it: Bacteria
- Pollination
- The transfer of pollen grains from an anther to a stigma.Revise it: Insect- and wind-pollinated flowers
- Polygenic inheritance
- A feature controlled by several genes working together, such as height. Most features are polygenic.Revise it: Polygenic inheritance
- Population
- All the organisms of one species living in the same area.Revise it: Population, community, habitat and ecosystem
- Producers
- Organisms, usually plants and algae, that make glucose by photosynthesis. They are the first trophic level.Revise it: Trophic levels
- Protoctist
- A microscopic single-celled eukaryotic organism.Revise it: Plants and animals
Q
- Quadrat
- A square frame used to sample the organisms in a small, known area.Revise it: Practical: population size with quadrats
R
- Recessive
- An allele that is only expressed in the phenotype when two copies are present, so no dominant allele is there.Revise it: Alleles and genetic terms
- Respiration
- The chemical process in cells that releases energy from food, such as glucose, and uses it to make ATP.Revise it: Respiration and ATP
- Restriction enzyme
- An enzyme that cuts DNA at a specific base sequence.Revise it: Restriction enzymes, ligase and vectors
- Runner
- A stem that grows sideways along the ground and forms new plantlets, a natural method of asexual reproduction, e.g. in strawberry.Revise it: Asexual reproduction in plants
S
- Saprotrophic nutrition
- Secreting digestive enzymes onto food outside the body, then absorbing the organic products.Revise it: Plants and animals
- Selective breeding
- Humans choosing which organisms to breed so that desired characteristics are passed on to the next generation.Revise it: Selective breeding of plants and animals
- Sticky ends
- Short, unpaired DNA strands left at a cut, which pair with matching sticky ends.Revise it: Restriction enzymes, ligase and vectors
- Synapse
- A gap between two neurones.Revise it: Synapses and neurotransmitters
T
- Tissue
- A group of cells with a similar structure and function.Revise it: Levels of organisation
- Transgenic
- Describes an organism with genetic material transferred from one species to a different species.Revise it: Restriction enzymes, ligase and vectors
- Transpiration Biology only
- The evaporation of water from the surface of a plant.Revise it: Transpiration
- Transpiration stream Biology only
- The continuous flow of water up the xylem to replace water lost from the leaves.Revise it: Transpiration
- Trophic level
- The position of an organism in a food chain. Producers are level 1.Revise it: Trophic levels
U
- Ultrafiltration Biology only
- High pressure in the glomerulus forces small molecules out of the blood into the Bowman's capsule.Revise it: The nephron and ultrafiltration
V
- Vasoconstriction
- Blood vessels supplying the skin narrow, so less blood flows near the surface and less heat is lost.Revise it: The skin and temperature control
- Vector
- A plasmid or virus that takes up a piece of DNA and inserts this recombinant DNA into other cells.Revise it: Restriction enzymes, ligase and vectors
Z
- Zygote
- The cell produced when a male gamete fuses with a female gamete in fertilisation.Revise it: Sexual and asexual reproduction
Test yourself on these terms with the Edexcel International GCSE Biology flashcards, or tick them off on the specification checklist.