What Are the Seven Signs of Life?
The seven signs of life are moving, respiration, sensitivity, growth, reproduction, excretion and nutrition. All of these activities are present in living organisms. A non-living object sometimes manifests one or more of these activities but not all of them.
All living things, including plants, move. Respiration goes beyond the breathing process. The general meaning of respiration as it applies to a sign of life is that the chemical breakdown of complex organic substances, such as carbohydrates and fats, is necessary for energy. Sensitivity involves the ability to detect change in the world around the organism. All living things grow and mature. Reproduction, or making other living things, is necessary for sustaining life. Taking in and utilizing food, as well as eliminating waste products, are also signs of life.