The eight characteristics all living organisms share
Every living organism — bacterium, fungus, protoctist, plant or animal — carries out all eight of these processes. If something only does some of them (a virus, a car engine, a flame), it is not classed as a living organism.
A useful memory hook is MRS GREN, but learn the proper definitions because the exam wants the biology, not the mnemonic.
| Characteristic | What it means | Concrete example |
|---|---|---|
| Nutrition | Taking in nutrients — organic substances and mineral ions — that contain raw materials and energy for growth and tissue repair | A plant makes glucose by photosynthesis; a human digests and absorbs protein from food |
| Respiration | The chemical reactions in cells that break down nutrient molecules to release energy | Glucose broken down in every living cell, 24 hours a day |
| Excretion | Removal of toxic materials, the waste products of metabolism, and substances in excess of requirements | Humans excrete urea in urine and carbon dioxide from the lungs |
| Response to surroundings | Detecting and reacting to changes (stimuli) in the environment | A shoot grows towards light; you pull your hand off a hot pan |
| Movement | An action by an organism or part of an organism causing a change of position or place | A fish swims; a sunflower head turns; roots grow downwards |
| Control of internal conditions | Keeping the internal environment constant — this is homeostasis | Body temperature held near 37 °C; blood glucose controlled by insulin |
| Reproduction | Making more of the same kind of organism | A bacterium divides; a plant produces seeds |
| Growth and development | A permanent increase in size and dry mass by an increase in cell number, cell size, or both, plus an increase in complexity | A seedling grows from a seed and develops leaves, stem and root |
Points that gain the marks
- Excretion is not egestion. Excretion removes waste made by the organism's own reactions (urea, carbon dioxide). Egestion removes undigested food that was never absorbed — faeces. Faeces is not excretion.
- Respiration is not breathing. Respiration is a chemical reaction inside cells that releases energy. Breathing (ventilation) just moves air.
- Nutrition is not just eating. Plants require nutrition too — they make their own food and take up mineral ions such as nitrate from the soil.
- Movement does not have to mean walking. Plants move — growth movements of roots and shoots, opening of flowers — so movement still counts for a plant.
- Growth means a permanent increase in size and dry mass. A balloon inflating gets bigger but is not growing; a plant that has just taken up water has gained mass temporarily, not grown.
Examiner tip. Read every word of the question stem. If it asks for two characteristics shown by the data, do not write everything you know about MRS GREN — examiners report that nervous candidates latch onto one key word and rush into an answer that never addresses what was asked.