Characteristics of living organisms

• Movement

  In all living cells, structures in the cytoplasm move. Animals move their entire bodies. Plants move parts of their body in responses to external stimuli e.g. light
• Respiration

  A series of reactions that occur in living cells to release energy from nutrients
• Sensitivity

  Living organisms can detect and respond changes in their external and internal conditions
• Homeostasis

  The ability of an organism to control its internal conditions within narrow limits whilst adjusting to the external environment
• Growth

  Permanent increase in size or dry mass of cells or the whole body of an organism. The mass of a biological sample after the water content has been removed. Dry mass accommodates for the changes that occur due to diet and water intake
• Reproduction

  The production of more individuals of that kind of organisms
• Excretion

  Removal of waste products (often toxic) from the body produced because of metabolic reactions in the cell
• Nutrition

  Taking in of nutrients, e.g. organic substances and mineral ions, into the body
• Viruses do not have a cell structure or cytoplasm, so they do not respire or sense their surroundings. Viruses do not feed or excrete
• Viruses infect cells e.g. plant, animal or bacterial cell so that they can cause that cell to make many new copies of the virus. So, they show the capacity to reproduce
• Viruses are obligate parasites as they can only reproduce inside the cells of organisms they have infected
• Viruses are not considered living organisms