What are the four criteria for life?

Planet earth is the only known region of the universe to host life and so the basic criteria for life is based on observations made here. For an entity to be considered a living organism it must contain DNA or some other means of storing genetic information. The second criteria is that it must have some way of extracting nutrients from its surroundings. The organism must be able to respond to environmental stimulus and last but not least it must be able to reproduce.