Life processes

Every living thing carries out all seven life processes at some point in its life. Remember them as MRS GREN. Doing only some of them, like a fire or a robot, is not enough.

	Process	What it means
M	Movement	A living thing moving itself, or part of itself. Plants move slowly: leaves turn to face the light, flowers open and close.
R	Respiration	A chemical reaction in every living cell that releases energy from food (glucose). It is not breathing.
S	Sensitivity	Detecting changes in the surroundings (stimuli) and responding to them. Plants do it too.
G	Growth	A lasting increase in size, or repairing damage, by making new cells.
R	Reproduction	Making offspring: new living things of the same kind.
E	Excretion	Getting rid of waste made by cells, such as carbon dioxide and urea. Faeces do not count: that is egestion.
N	Nutrition	Taking in or making food. Animals eat; plants make their own food by photosynthesis.

Respiration is not breathing. Breathing moves air in and out of the lungs. Respiration is a chemical reaction in every living cell that releases energy from glucose: glucose + oxygen → carbon dioxide + water. Breathing brings the oxygen in and takes the carbon dioxide away.

Excretion is not egestion. Excretion gets rid of waste made by cells: carbon dioxide from the lungs, urea in urine. Egestion gets rid of undigested food (faeces), which never became part of the cells.

Movement only counts when a living thing moves itself, or part of itself. A crisp packet in the wind does not count; a leaf turning to the light does. Plants do all seven: they move slowly, sense light and gravity, make their own food and respire all the time, day and night.