Life can be
a property of matter. Matter that is alive, or life forms are organisms
of a vast variety. Properties common to the known organisms found
on Earth – plants, animals, fungi, protists, archaea and bacteria
– are that they are carbon-and-water-based, are cellular with
complex organization, undergo metabolism, possess a capacity to
grow, respond to stimuli, reproduce and, through natural selection,
adapt in succeeding generations.
An entity with the above properties is considered
to be an organism. However, not every definition of life considers
all of these properties to be essential. For example, the capacity
for descent with modification is often taken as the only essential
property of life. This definition notably includes viruses, which
do not qualify under narrower definitions as they are acellular
and do not metabolise. Broader definitions of life may also include
theoretical non-carbon-based life and other alternative biology.
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