A person lying in coma is not conscious of its surrounding environment. Thus, he/she is not capable of responding to the external environmental stimuli.The person is supported by machines for various functions of the body.The person is otherwise brain dead.Some of these patients never come back to normal life. They can neither be called living nor non-living or dead.

A person lying in coma is not conscious of its surrounding environment. Thus, he/she is not capable of responding to the external environmental stimuli. The person is supported by machines for various functions of the body. The person is otherwise brain dead. Some of these patients never come back to normal life. They can neither be called living nor non-living or dead.

Reproduction is required for the perpetuation of a population. It is not necessary for the survival of living organism. Many organisms, e.g., mules, sterile worker bees, infertile human couples are not able to reproduce, while they have all other defining properties of life, so they can be called as living.
Sexual reproduction involves the formation and fusion of two kinds of gametes to produce an offspring. In asexual reproduction, new individuals can arise by the specialised parts of body or without the fusion of gametes.

Amoeba shows various characteristics such as growth, reproduction, metabolism, etc., that are specific to living organisms. On the other hand, a sand particle does not show any reproduction and metabolism therefore, it is considered as non-living matter. Though, the sand particle shows growth which is also a characteristic of living things, but in this the growth is only external due to aggregation of many sand particles and not internal. Therefore, Amoeba is a living matter while a sand particle is a non-living matter.

Metabolic reactions can be demonstrated outside the body in cell-free systems. When an isolated metabolic reaction is performed outside the body of an organism in a test tube, it is neither living nor non-living. Hence, while metabolism is a defining feature of all living organisms without exception, isolated metabolic reactions in vitro are not living things, but are living reactions. Here, it can also be said that cellular organisation of the body is the defining feature of life forms.