This cheat sheet explains the seven characteristics that all living things share, using the memory aid MRS GREN. Students need it to decide whether something is living, once living, or nonliving. It gives a simple way to organize important biology ideas about plants, animals, fungi, and microorganisms.
The goal is to help students remember the full list and use it in examples.
Key Facts
- MRS GREN stands for Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition.
- Movement means a living thing can move its whole body or move parts of itself, such as a plant stem bending toward light.
- Respiration is the process living cells use to release energy from food, often summarized as food plus oxygen gives energy plus carbon dioxide plus water.
- Sensitivity means a living thing can detect and respond to changes in its environment, such as light, sound, touch, heat, or chemicals.
- Growth means a living thing can increase in size or change as it develops during its life cycle.
- Reproduction means living things can make new living things of the same kind, either with one parent or two parents.
- Excretion means a living thing removes waste materials made by its body, such as carbon dioxide, urine, or extra water.
- Nutrition means a living thing gets or makes food for energy and materials, such as animals eating food or plants making sugar by photosynthesis.
Vocabulary
- Organism
- An organism is any individual living thing, such as a plant, animal, fungus, bacterium, or protist.
- MRS GREN
- MRS GREN is a memory aid for the seven characteristics of living things.
- Respiration
- Respiration is the process cells use to release energy from food.
- Stimulus
- A stimulus is a change in the environment that a living thing can sense and respond to.
- Excretion
- Excretion is the removal of waste substances made by a living thing.
- Nutrition
- Nutrition is how a living thing gets or makes the food and materials it needs to survive.
Common Mistakes to Avoid
- Thinking movement only means walking or running is wrong because plants and many tiny organisms move slowly or move only parts of themselves.
- Confusing respiration with breathing is wrong because breathing moves air in and out, while respiration happens in cells to release energy.
- Saying fire is alive because it grows and uses oxygen is wrong because fire does not have cells, reproduce as an organism, or carry out all seven life processes.
- Forgetting excretion is wrong because living things must remove waste products made by their bodies to stay healthy.
- Thinking plants do not need nutrition is wrong because plants make their own food using light, carbon dioxide, and water.
Practice Questions
- 1 Write out what each letter in MRS GREN stands for.
- 2 A seedling grows from 4 cm tall to 13 cm tall. How many centimeters did it grow?
- 3 A rabbit has 6 babies, and each baby grows into an adult. Which two MRS GREN characteristics are shown most clearly?
- 4 A toy robot can move, make sounds, and respond to a button press. Explain why it is not a living thing using MRS GREN.
Understanding Seven characteristics of living things (MRS GREN) Memory Aid
The seven features are linked because they happen in cells. Cells need a steady supply of materials, release energy for their work, notice changes around them, and get rid of substances they no longer need. A living thing does not need to show every feature clearly every minute.
A seed may seem inactive while it waits for water and warmth. It is still alive because its cells remain capable of carrying out life processes. This is why scientists use evidence over time rather than one quick observation.
Respiration is often confused with breathing. Breathing moves air into and out of lungs or other gas exchange surfaces. Respiration happens inside cells and provides usable energy for life processes.
Plants respire all the time, including when they are not in sunlight. Photosynthesis is different because it uses light energy to make sugar. Excretion is another word that needs care.
It means removing waste made by chemical reactions in the body. Carbon dioxide leaves through the lungs in humans.
Urine contains several wastes removed by the kidneys. Faeces are mainly undigested food, so passing faeces is not usually classed as excretion.
Movement and sensitivity often work together. A person pulls away from a hot surface after detecting heat and pain. A plant can grow towards light or close its leaves after touch.
These actions may be slow, but they are still responses. Growth is more than getting larger. It can include making more cells and changing body parts during development.
A tadpole becoming a frog is a clear example. Nonliving things can grow too.
A crystal can become bigger as more material collects on it. It does not carry out the full set of cell processes, so size alone is not proof of life.
Reproduction is best understood as something a kind of organism can do, not something every individual must do. A mule may be unable to reproduce, yet it is alive. Some plants reproduce from seeds, while others make new plants from runners or bulbs.
Nutrition provides both energy and building materials. Animals obtain these by eating, while green plants make sugars from simple substances using light. When classifying an object, watch for tricky cases such as fire, clouds, robots, seeds, and viruses.
Fire can spread and use fuel, but it has no cells or biological reproduction. Viruses can copy themselves only inside host cells, so most scientists do not describe them as independently living. Good answers explain the evidence instead of relying only on the memory aid.