Biology IGCSE

Movement

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

Respiration

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

Sensitivity

The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.

Growth

A permanent increase in size and dry mass by an increase in cell number or cell size or both.

Reproduction

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

Excretion

Removal from organisms of the waste products of metabolism, toxic materials, and substances in excess of requirements.

Nutrition

Taking in of materials for energy, growth and development.

Species

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

Diffusion

The net movement of particles from a region of their higher concentration to a region of their lower concentration 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 to a region of lower water potential through a partially permeable membrane.

Active Transport

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.

Enzyme

A protein that functions as a biological catalyst.

Photosynthesis

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

Transpiration

The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.

Translocation

The movement of sucrose and amino acids in the phloem.

Ingestion

The intake of substances through the mouth.

Mechanical Digestion

Breaking food into smaller pieces without chemical change.

Chemical Digestion

The breakdown of large, insoluble molecules into small, soluble ones.

Absorption

Movement of digested food through the intestine wall into the blood.

Assimilation

Movement of digested food into cells for use.

Egestion

The passing out of undigested food as faeces.

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.

Synapse

A junction between two neurones.

Sense Organs

Groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals.

Hormone

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

Homeostasis

The maintenance of a constant internal environment.

Gravitropism

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

Phototropism

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

Asexual Reproduction

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

Sexual Reproduction

A process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other.

Fertilisation

The fusion of gamete nuclei.

Sexually Transmitted Infection (STI)

An infection that is transmitted via body fluids through sexual contact.

Inheritance

The transmission of genetic information from generation to generation.

Chromosome

A thread-like structure of DNA, carrying genetic information in the form of genes.

Gene

A length of DNA that codes for a protein.

Allele

An alternative form of a gene.

Haploid Nucleus

A nucleus containing a single set of unpaired chromosomes.

Diploid Nucleus

A nucleus containing two sets of chromosomes.

Mitosis

Nuclear division giving rise to genetically identical cells.

Meiosis

Nuclear division giving rise to cells that are genetically different.

Genotype

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

Phenotype

The observable features of an organism.

Homozygous

Having two identical alleles of a particular gene.

Heterozygous

Having two different alleles of a particular gene.

Dominant

An allele that is expressed if it is present.

Recessive

An allele that is only expressed when no dominant allele of the gene is present.

Sex-linked Characteristic

A characteristic in which the gene responsible is located on a sex chromosome and which makes it more common in one sex than in the other.

Gene Mutation

A change in the base sequence of DNA.

Adaptive Feature

An inherited feature that helps an organism to survive and reproduce in its environment.

Fitness

The probability of an organism surviving and reproducing in the environment in which it is found.

Food Chain

A chart showing the flow of energy from one organism to the next beginning with a producer.

Food Web

A network of interconnected food chains.

Producer

An organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis.

Consumer

An organism that gets its energy by feeding on other organisms.

Herbivore

An animal that gets its energy by eating plants.

Carnivore

An animal that gets its energy by eating other animals.

Decomposer

An organism that gets its energy from dead or waste organic matter.

Population

A group of organisms of one species, living in the same area, at the same time.

Community

All of the populations of different species in an ecosystem.

Ecosystem

A unit containing the community of organisms and their environment, interacting together.

Trophic Level

The position of an organism in a food chain, food web or ecological pyramid.

Sustainable Resource

One which is produced as rapidly as it is removed from the environment so that it does not run out.

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 to destroy pathogens or mark them for destruction.

Passive Immunity

Short-term defence against a pathogen by antibodies acquired from another individual.

Drug

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

Double Circulation

Circulation where blood flows through the heart twice for each complete circuit of the body.

Pollination

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

Co-dominance

A situation in which both alleles in a heterozygote are expressed, leading to a phenotype that shows features of both.

Genetic Modification

Changing the genetic material of an organism by removing, changing or inserting individual genes.

Cell Membrane

A partially permeable barrier surrounding the cell that controls the movement of substances into and out of the cell.

Cell Wall

A rigid outer layer made of cellulose that provides structural support and maintains the cell's shape.

Nucleus

An organelle containing genetic material (DNA) that controls all activities of the cell.

Cytoplasm

A jelly-like substance where most metabolic chemical reactions within the cell occur.

Mitochondria

Organelles where aerobic respiration occurs to release energy for the cell.

Ribosomes

Microscopic structures within a cell that serve as the site of protein synthesis.

Catalyst

A substance that increases the rate of a chemical reaction and remains unchanged at the end of the reaction.

Balanced Diet

A diet containing all the essential nutrients in the correct proportions needed to maintain health and growth.

Tissue

A group of similar cells working together to perform a specific function.

Organ

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

Organ System

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

Single Circulation

A circulatory system where blood passes through the heart only once for each complete circuit of the body.

Binomial System

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