Non-cellular life
Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. Historically, most definitions of life postulated that an organism must be composed of one or more cells, but this is for some no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.The primary candidates for non-cellular life are viruses. Some biologists consider viruses to be organisms, but others do not. Their primary objection is that no known viruses are capable of autonomous reproduction; they must rely on cells to copy them.