CIE IGCSE Biology Definitions

Taken from syllabus

Movement

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 and respond to changes in the internal or external environment

Growth

Permanent increase in size and dry mass

Reproduction

The processes that make more of the same kind of organism

Excretion

The removal of the waste products of metabolism and substances in excess of requirements

Nutrition

The taking in of materials for energy, growth and development

Species

A group of organisms that can reproduce to produce fertile offspring

Binomial System

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

Organelle

A part of a cell that carries out a particular job

Cell

The basic building block of all living organisms.

Tissue

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

Organ

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

Organ System

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

Diffusion

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 (dilute solution) to a region of lower water potential (concentrated solution), 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 (against a concentration gradient), using energy from respiration

Catalyst

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

Enzyme

Proteins that are involved in all metabolic reactions, where they function as biological catalysts

Active Site

The part of an enzyme where the substrate binds

Photosynthesis

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

Limiting Factor

Something present in environment in such short supply that it restricts life processes

Balanced Diet

Consists of all food groups in correct proportions.

Ingestion

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

Physical Digestion

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

Chemical Digestion

Break down large insoluble molecules into small soluble molecules, which can be absorbed.

Absorption

The movement of digestion food molecules from the digestive system into the blood (glucose and amino acids) and lymph (fatty acids and glycerol)

Assimilation

The movement of digested food molecules into the cells of the body where they are used, becoming part of the cells

Egestion

Removal of undigested food from the body as faeces

Xylem

Transport of water and minerals from roots to stem and leaves, provides support

Phloem

Transport of sucrose and amino acids made by plant from photosynthesis to non-photosynthesising regions in the roots and stem

Transpiration

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 phloem from sources to sinks.

Source

The parts of plants that release sucrose or amino acids

Sink

The parts of plants that use or store sucrose or amino acids

Circulatory System

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

Pathogen

Disease-causing organism

Transmissible disease

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. Slow acting and provides long-lasting immunity.

Antibodies

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

Passive immunity

A short-term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk

Respiration

Series of chemical reactions that releases energy from food

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

Human Nervous System

To coordinate and regulate body functions

Sense Organs

Groups of receptor cells responding to specific stimuli

Reflex Action

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

Synapse

A junction between 2 neurons

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 of the light source

Drug

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

Asexual Reproduction

A process resulting in the production of genetically identical offspring from one offspring (clones).

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

Fusion of the nuclei of gametes

Pollination

The transfer of pollen grains from an anther to a stigma

Fertilisation

The fusion of a pollen nucleus with an ovum nucleus

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

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

STI

An infection that is transmitted through sexual contact

Chromosomes

Made of DNA, which contains genetic information in the form of genes (located in nucleus of DNA)

Gene

A length of DNA that codes for a protein, carries genetic information (control characteristics → code for proteins playing important roles in what our cells do)

Haploid Nucleus

A nucleus containing a single set of chromosomes

Diploid Nucleus

Anucleus containing two sets of chromosomes

Alleles

Different versions of a particular gene

Mitosis

Nuclear division giving rise to genetically identical cells.

Meiosis

A reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells.

Inheritance

The transmission of genetic information from generation to generation

Stem Cells

Unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions

Genotype

The genetic make-up of an organism and 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 Allele

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

Recessive Allele

An allele that is only expressed when there is no dominant allele of the gene present in the genotype

Codominance

Both alleles are expressed and the phenotype of the heterozygote is new, and there is presence of multiple alleles for one trait

Sex-linked Characteristic

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

Variation

Differences between individuals of the same species

Mutation

Random change in base sequence of DNA

Natural Selection

AA process where organisms that are better adapted to an environment will survive and reproduce.

Selective Breeding

Select individuals with desirable characteristics and breed them together to result in selection of offspring showing desirable features

Continuous Variation

Range of phenotypes between two extremes

Discontinuous Variation

A limited number of phenotypes with no intermediates

Adaptive Feature

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

Fitness

Probability of an organism in surviving and reproducing in the environment it is found

Food Chain

Showing the transfer of energy from one organism to the next, beginning with a producer

Food Web

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 material

Trophic Level

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

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

Biodiversity

The number of different species that live in an area

Sustainable Resource

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