Cambridge IGCSE Biology Key Vocabulary

Binomial system

An internationally agreed system in which the scientific name of an organism is made up of two parts, showing the genus and the species.

Excretion

Removal of waste products of metabolism and substances in excess of requirements.

Growth

A permanent increase in size and dry mass.

Movement

An action by an organism or part of an organism causing a change of position or place.

Nutrition

The taking in of materials for energy, growth and development.

Reproduction

The processes that make more of the same kind of organism.

Respiration

The chemical reactions in cells that break down nutrient molecules and release energy for metabolism.

Sensitivity

The ability to detect and respond to changes in the internal or external environment.

Species

A group of organisms that can reproduce to produce fertile offspring.

Morphology

The study of the form, or outward appearance, of organisms.

Anatomy

The study of the internal structure of organisms, as revealed by dissection.

Cell

The smallest basic unit of an animal or plant; it is microscopic and acts as a building block.

Magnification

The observed size of an image divided by the actual size of the image.

Organ

A structure made up of a group of tissues working together to perform a specific function.

Organ system

A group of organs with related functions working together to perform a body function.

Organism

A living thing that has an organised structure, can react to stimuli, reproduce, grow, adapt, and maintain homeostasis.

Tissue

A group of cells with similar structures working together to perform a shared function.

Active transport

The movement of particles through a cell membrane from a region of their lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration.

Diffusion

The net movement of particles from a region of their higher concentration to a region of lower concentration (i.e. down a concentration gradient), as a result of their random movement.

Osmosis

The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane.

Catalyst

A substance that increases the rate of a chemical reaction and is not changed by the reaction.

Enzyme

Proteins that function as biological catalysts and are involved in all metabolic reactions.

Photosynthesis

The process by which plants synthesise carbohydrates from raw materials using energy from light.

Absorption

The movement of nutrients from the intestines into the blood.

Assimilation

The uptake and use of nutrients by cells.

Balanced diet

A diet that contains all the essential nutrients in the correct proportions to maintain good health.

Chemical digestion

The breakdown of large insoluble molecules into small soluble molecules.

Digestion

The breakdown of food.

Egestion

The passing out of food that has not been digested or absorbed, as faeces through the anus.

Ingestion

The taking of substances (e.g. food, drink) into the body through the mouth.

Physical digestion

The breakdown of food into smaller pieces without chemical change to the food molecules.

Transpiration

The loss of water vapour from leaves.

Translocation

The movement of sucrose and amino acids in the phloem from sources to sinks.

Circulatory system

A system of blood vessels with a pump and valves to ensure one-way flow of blood.

Pathogen

A disease-causing organism.

Transmissible disease

A disease in which the pathogen can be passed from one host to another.

Active immunity

Defence against a pathogen by antibody production in the body.

Antibodies

Proteins that bind to antigens, leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes.

Aerobic respiration

The chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.

Anaerobic respiration

The chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.

Deamination

The removal of the nitrogen-containing part of amino acids to form urea.

Gravitropism

A response in which parts of a plant grow towards or away from gravity.

Homeostasis

The maintenance of a constant internal environment.

Hormone

A chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.

Phototropism

A response in which parts of a plant grow towards or away from the direction of the light source.

Reflex action

A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands).

Sense organ

A group of receptor cells responding to specific stimuli, such as light, sound, touch, temperature and chemicals.

Synapse

A junction between two neurones.

Set point

The physiological value around which the normal range fluctuates.

Drug

Any substance taken into the body that modifies or affects chemical reactions in the body.

Asexual reproduction

The process resulting in the production of genetically identical offspring from one parent.

Fertilisation

The fusion of the nuclei from a male gamete (sperm) and a female gamete (egg cell).

Pollination

The transfer of pollen grains from the anther to a stigma.

Sexual reproduction

A process involving the fusion of gametes (sex cells) to form a zygote and the production of offspring that are genetically different from each other.

Sexually transmitted infection (STI)

An infection that is transmitted through sexual contact.

Cross-pollination

The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species.

Self-pollination

The transfer of pollen grains from the anther of a flower to the stigma of the same flower, or a different flower on the same plant.

Allele

An alternative form of a gene.

Dominant

An allele that is expressed if it is present in the genotype.

Gene

A length of DNA that codes for a protein.

Genotype

The genetic make-up of an organism in terms of the alleles present.

Heterozygous

Having two different alleles of a particular gene; therefore, a heterozygous individual will not be pure breeding.

Homozygous

Having two identical alleles of a particular gene; two homozygous individuals that breed together will be pure breeding.

Inheritance

The transmission of genetic information from generation to generation.

Phenotype

The observable features of an organism.

Recessive

An allele that