Edexcel IGCSE Biology Revision

Keywords and definitions for Triple award IGCSE Science (only Biology)
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Active Transport
When a substance moves against/up a concentration gradient, from a region where they are of lower concentration to a region where they are of higher concentration.
Adaption
Any characteristic of an organism that improves its chances of surviving in its environment.
Aerobic respiration
Respiration with oxygen.
Anaerobic respiration
Respiration without oxygen. It releases less energy than aerobic respiration.
Alleles
Different forms of a gene which occupy the same relative positions on a pair of homologous chromosomes.
Arteries
Blood vessels which carry blood away from the heart.
Anaesthetics
Drugs that make the body unable to feel pain.
Artificial selection
A method used by humans to produce plants and animals with desired qualities.
Natural selection
When organisms better adapted to their environment tend to survive and produce more offspring.
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.
Breathing
The process that brings about an exchange of gases between an organism and its environment.
Ventilation
The inhalation and exhalation of air.
Respiration
The inhalation and exhalation of air.
Capillaries
Microscopic thin-walled 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.
Differentiation
The process by which a cell becomes specialized for a specific function.
Digestion
The process by which large food molecules are broken down into small, soluble and diffusible molecules that can be absorbed by the body cells.
Diploid cell
Cells that contain the full number of chromosomes.
Haploid cell
Cells that contain half the number of chromosomes as a diploid cell.
Dominant
A form of a gene that is expressed and masks the recessive gene. It gives the same phenotype in both homozygous and heterozygous conditions as it expresses itself.
Ecosystem
An ecological system formed by the interaction of living organisms and their non-living environments.
Egestion
The removal of undigested matter from the body.
Enzymes
Biological catalysts made of protein.
Excretion
The process by which metabolic waste products and toxic materials are removed from the body of an organism.
Fertilisation
The process by which the male gamete fuses with the female gamete to form a zygote.
Food chain
A series of organisms through which energy is transferred in the form of food.
Food web
Two or more food chains interlinked together.
Gamete
A reproductive cell containing the haploid number of chromosomes.
Gene
Something controls a particular characteristic and codes for a specific protein.
Genetic engineering
A technique used to transfer genes from one organism to another.
Genotype
The combination of genes in an individual.
Gland
A cell, tissue or an organ that secretes chemical substances.
Habitat
The place where an organism lives.
Heterozygous
Having different alleles for a particular trait.
Homologous pairs
Chromosomes which have the same genes, shape and length.
Homozygous
Having identical alleles for a particular trait.
Meiosis
A form of cell division that produces haploid cells.
Mitosis
A form of cell division that produces diploid cells.
Mutation
The sudden or spontaneous change in gene structure or a chromosome, or even the chromosome number, and may be inheritable.
Nutrition
The intake of food and the processes that convert food substances into living matter.
Osmosis
The net movement of water molecules from a region of high concentration to a region of low concentration, through a partially permeable membrane. (down a concentration gradient)
Oxygen debt
The amount of oxygen required to oxidize the lactic acid produced in muscles during anaerobic respiration and convert it into harmless substances.
Partially permeable membrane
A membrane that allows selected substances to pass through.
Peristalsis
The wave-like contractions of the walls of the gut.
Phenotype
The physically expressed characteristics of an individual, e.g. height and eye colour.
Photosynthesis
The process in which light energy absorbed by chlorophyll is transformed into chemical energy.
Pollination
The transfer of pollen grains from an anther to a stigma.
Recessive
A form of a gene that expresses itself usually only in the homozygous condition.
Self pollination
The transfer of pollen grains from the anther the stigma of the same flower or of a different flower on the same plant.
Sexual reproduction
The process involving the fusion of two gametes to form a zygote, resulting in the production of genetically dissimilar offspring.
Species
A group of similar organisms. Organisms within a species can breed.
Tissue
A group of similar cells which work together to perform a specific function.
Transpiration
The loss of water vapour from aerial parts of a plant, especially through the stomata of the leaves.
Variation
The differences that can be observed within a species.
Veins
Blood vessels which carry blood towards the heart.
Animalia
All multicellular animals.
Plantae
All green plants.
Fungi
Moulds, mushrooms, yeast.
Prokaryotae
Bacteria, blue-green algae.
Protoctista
Amoeba, Paramecium.