The characteristics of living organisms revision notes

Edexcel International GCSE Biology (4BI1), chapter 1: Life processes, specification point 1.1. Free lesson.

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Living organisms share eight characteristics, often remembered as MRS GREN plus control of internal conditions. Knowing what each characteristic means helps you distinguish living things from non-living things and avoid confusing nutrition, respiration, excretion and egestion.

What the first four characteristics mean

The first four letters of MRS GREN stand for movement, respiration, sensitivity and growth. Learn the meaning of each one, because exam marks are awarded for the definitions, not just the names. Movement is an action by an organism that causes a change of position or place. The organism causes the movement itself, rather than being blown along by the wind. Respiration is the chemical reactions in cells that break down nutrient molecules and release energy. Sensitivity is the ability to detect and respond to changes in the environment. Growth is a permanent increase in size…

What the other four characteristics mean

The next four are reproduction, excretion, nutrition and control of internal conditions. MRS GREN gives you seven characteristics, so learn the eighth separately. Reproduction is making more of the same kind of organism. Excretion is removing the waste products of metabolism, and substances in excess of requirements. Metabolism means the chemical reactions taking place in an organism. Nutrition is taking in materials for energy, growth and development. Control of internal conditions means keeping the inside of the body steady, whatever is happening outside. This is called…

How to tell nutrition, respiration, excretion and egestion apart

Nutrition and respiration are linked, but they are not the same. Nutrition brings materials into an organism. Respiration uses nutrient molecules in cells to release energy. Excretion and egestion are also different, because only excretion removes waste made by the organism's own reactions. Nutrition takes materials in from outside. It happens at the gut or the leaf. Respiration breaks down those materials to release energy. It happens in every living cell. Excretion removes waste made by the organism's reactions, such as carbon dioxide and urea. Egestion is the removal of food that…

How to decide whether something is living

A living organism carries out all eight characteristics. For a car, do not assume that taking in fuel, releasing energy, moving or giving off waste gases makes it alive. Give characteristics it cannot carry out biologically, with a reason for each. A car does not grow, because it has no permanent increase in size and dry mass. A car cannot reproduce by making more cars. It also has no sensitivity of its own, and has no cells in which biological respiration can happen.

How to remember the eight characteristics

Use MRS GREN to remember the seven named by the mnemonic, in order. Then add control of internal conditions as the eighth, because it is not included in the mnemonic. M: Movement R: Respiration S: Sensitivity G: Growth R: Reproduction E: Excretion N: Nutrition The eighth characteristic is control of internal conditions, also called homeostasis.