All living organisms, from small to big; whether they are single-celled or multicellular, plants or animals, share characteristics that separate the living elements in nature from the non-living ones.

There are seven characteristics of living organisms:

(Note: red highlighted text below refers to definitions required for the extended syllabus)

• Movement - an action by an organism causing a change of position or place.

• Respiration - the chemical reactions in cells that break down nutrient molecules and release energy.

• Sensitivity - the ability to detect and respond to changes in the environment.

• Growth - the permanent increase in size.

• Reproduction - the processes that make more of the same kind of organism.

• Excretion - the removal from organisms of toxic materials and substances in excess of requirements.

• Nutrition - the taking in of materials for energy, growth and development.
  

One way of remembering the list of characteristics of living things is by using the mnemonic MRS GREN. The letters stand for the first letters of the characteristics.

MovementRespirationSensitivity GrowthReproductionExcretionNutrition

If you are studying the extended syllabus, you need to learn more detailed definitions of some of the characteristics of living things.

• 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 or sense stimuli in the internal or external environment and to make appropriate responses.

• Growth - a permanent increase in size and dry mass by an increase in cell number or cell size or both.

• Reproduction - the processes that make more of the same kind of organism.

• Excretion - the removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials, and substances in excess of requirements.

• Nutrition - the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water