The seven characteristics — MRS GREN
Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition. The acronym is a recall aid only — it earns no marks on its own; every mark comes from the full two-element definition of the term. An organism counts as living only if it shows all seven. One characteristic in isolation proves nothing: a river moves, a crystal increases in size, a flame gives off waste gases — none of them is alive.
Two-element definitions carry the marks
Each of the seven definitions has two parts, and the mark is withheld when only one appears. Movement needs the organism AND the change of position; respiration needs chemical reactions in cells AND energy from nutrient molecules; sensitivity needs detect AND respond; growth needs permanent AND dry mass; excretion needs metabolic waste AND excess substances; nutrition needs materials taken in AND energy, growth and development. Reproduction: more of the same kind.
Testing an unfamiliar specimen — run all seven
Given a fungus, a virus, a crystal or a flame, work down the list rather than answering from one observation. Does it move by its own action, not by wind or current? Does it respire? Does it detect and respond? Does it grow by a permanent increase in size and dry mass, not by adding layers from outside? Can it make more of the same kind? Does it excrete metabolic waste? Does it take in materials for energy, growth and development? Only if all seven hold is it living.
Drawn from real examiner reports.
Excretion ≠ respiration
Respiration releases energy — the chemical reactions in cells that break down nutrient molecules. Excretion removes waste — the waste products of metabolism plus substances in excess of requirements. The link between them is what causes the confusion: carbon dioxide is a waste product of respiration, so removing it is excretion, not respiration.
Flagged Nov 2022 P13 Q1; Nov 2023 — excretion confused with respiration when attributing characteristics
Growth needs "permanent" and "dry mass"
The definition is a permanent increase in size and dry mass. "An increase in cell size" or "in the number of cells" describes the underlying cause, not the definition, and drops both key words. Permanent rules out temporary swelling from water uptake; dry mass rules out a rise in fresh mass that is only water. Both elements are needed for the mark.
Flagged Nov 2023 P42 Q10(b)(iii) — growth given only as an increase in cell size/number
Movement defined without the organism
The definition is an action by an organism, or part of an organism, causing a change of position or place. Candidates give only the change of position and omit that the organism itself must cause it. As written, that would credit a leaf blown across a lawn by the wind — an external force, not the biological characteristic of movement.
Flagged Jun 2023 P43 Q10(b)(i) — movement defined without naming the organism
Gas direction reversed in respiration
Asked whether an unfamiliar organism such as an insect respires, candidates write that it takes in carbon dioxide and releases oxygen. It is the other way round: in aerobic respiration every living cell takes in oxygen and releases carbon dioxide. Insects respire exactly as humans do — respiration is not limited to organisms with lungs.
Flagged Nov 2023 P11 Q8 — insects respire (oxygen in, carbon dioxide out); many candidates reversed this
Respiration ≠ breathing
Respiration is chemical and happens in every living cell all the time. Breathing is only the mechanical movement of air into and out of the lungs, a way of supplying oxygen and removing carbon dioxide in some animals. Plants and insects respire without breathing at all, so "breathing" can never be offered as the definition of respiration.
Excretion ≠ egestion
Excretion removes substances the organism made itself — carbon dioxide, urea, surplus water and salts. Egestion removes undigested food (faeces) that was never absorbed into the body, so it is not a product of metabolism and is not excretion. Egestion is not named in B1.1 itself, but it is the standard trap set against the excretion definition.
One characteristic does not prove life
Candidates decide from a single observation — "it grows, so it is alive". Non-living things mimic one characteristic easily: a salt crystal enlarges as salt is deposited on it from solution, a river moves, a flame releases waste gases. A specimen is classed as living only when all seven characteristics hold, so always test the full list before committing.
MRS GREN recalls; definitions score
Two steps. First use MRS GREN to check you have covered all seven terms — that step earns nothing by itself. Then write the complete two-element definition of each one. Naming the characteristics alone scores zero, however many of them you list.
Link the definition to the named organism
When a question names an organism — "explain how a locust shows nutrition" — do not restate the generic definition. Apply it: the locust takes in plant material, supplying energy for flight and letting it grow. Definition first, then the evidence from the question.
"Define" and "describe" both want both elements
"Define movement" and "Describe the characteristic of growth" demand the same thing: the full two-element definition. Neither is satisfied by a single word or by an example on its own. A one-word answer to a 1-mark define question is the commonest way to throw that mark away.
Cambridge 0654 spec reference: Section B1 "Characteristics of living organisms", sub-topic B1.1 (the only sub-topic in B1; ALL-CORE content, no Supplement material). This leaf covers the definitions of the seven characteristics shared by all living organisms: movement, respiration, sensitivity, growth, reproduction, excretion and nutrition.
Out of scope for B1.1 (covered by later leaves, not here): the detailed word equation and reactants/products of respiration (B12), gas exchange structures (B11), digestion and food groups (B7), photosynthesis (B6).
Recall the seven terms with the acronym MRS GREN, but remember the acronym earns no marks -- only the full two-element definition does.
| Characteristic | Mark-scheme-precise definition |
|---|---|
| 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 and respond to changes in the internal or external environment |
| Growth | A permanent increase in size and dry mass |
| Reproduction | The processes that make more of the same kind of organism |
| Excretion | The removal of waste products of metabolism and of substances in excess of requirements |
| Nutrition | The taking in of materials for energy, growth and development |
The one idea that unlocks the topic: an organism is only classed as "living" if it shows all seven characteristics -- showing just one (e.g. a candle flame appears to "grow", a river "moves") is not enough evidence of life.
Define growth and reproduction as characteristics of living organisms.
Describe the characteristics of living organisms by defining each of the following:
(a) movement
(b) growth
(c) excretion
(3 marks)
