The characteristics that all living things share are cells, growth, reproduction, adaptation, homeostasis, use of energy and response to the environment. Using these characteristics, it is easy to determine if something is living, dead or non-living.
All living things are composed of cells. Some organisms, such as algae, are composed of a single cell (called unicellular organisms), while others, such as animals, are composed of many (called multicellular organisms).
All living things grow and develop. Their cells increase in number or grow in size, and they develop different characteristics as they do so. Reproduction either sexually or asexually is another characteristic of living things. This is the ability to produce offspring.
Adaptation means that living things alter themselves to adjust to their changing environments. Homeostasis of living things means having the ability to maintain an internal stable condition.
Living organisms also take in and use energy. Plants take in the energy from the sun and use it to produce food, and animals eat other organisms. This taking of energy from one source and using it to create energy in another way is done through a complex chemical process called metabolism.
Lastly, living organisms respond to their environment. A rock will not move if it is stepped on because it is not living, but a living thing, such as a cat, will respond to being stepped on by moving and letting out a cry.