Definitions IGCSE Flashcards
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
Excretion
Removal from organisms of the
waste products of metabolism (chemical
reactions in cells including respiration),
toxic materials, and substances in excess of
requirements
Nutrition
The taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water
Species
A group of organisms that can
reproduce to produce fertile offspring
Binomial system of
naming species
An internationally agreed
system in which the scientific name of an
organism is made up of two parts showing the
genus and species
Tissue
A group of cells with similar
structures, working together to perform a shared
function
Organs
A structure made up of a group
of tissues, working together to perform specific
functions
Organ systems
A group of organs with
related functions, working together to perform
body functions
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 (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 using energy from respiration
Catalyst
A substance that increases the rate of a chemical reaction and is not changed by the reaction
Photosynthesis
The process by which plants manufacture carbohydrates from raw materials using energy from light
Limiting factor
Something present in the environment in such short supply that it restricts life processes
Ingestion
The taking of substances, e.g. food and drink, into the body through the mouth
Mechanical Digestion
The breakdown of food into smaller pieces without chemical change to the food molecule
Chemical digestion
The breakdown of large, insoluble molecules into small, soluble molecules
Absorption
The movement of small food molecules and ions through the wall of the intestine into the blood
Assimilation
The movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
Egestion
The passing out of food that has not been digested or absorbed, as faeces, through the anus
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
