Biological life
"Life" redirects here. For other uses, see
Life (disambiguation)
.
Biological life is life instantiated in a physical biological body — the ordinary, carbon-and-water-based organic organisms of Earth and, on the accounts documented here, of other worlds. It is distinguished from the alleged forms of non-biological life said to exist alongside it: beings that regard themselves as "alive" or conscious yet possess no organic body.
Biology conventionally characterizes a biological organism by a cluster of shared properties rather than by any single trait: it is built of one or more cells, maintains internal order and homeostasis against its surroundings, takes in and transforms energy through metabolism, grows, responds to stimuli, reproduces, and — across generations — undergoes evolution by natural selection. A widely cited working definition, formulated by a NASA exobiology working group in the 1990s and given its best-known statement by the biochemist Gerald Joyce, compresses these into "a self-sustaining chemical system capable of Darwinian evolution."
Physically, a living organism is a thermodynamically open system held far from equilibrium: it does local work to preserve its own improbable order, exporting entropy to its environment rather than settling into it. Erwin Schrödinger, in his 1944 lectures published as What Is Life?, framed this as an organism "feeding on negative entropy" (negentropy) to resist the decay toward equilibrium that the second law of thermodynamics otherwise imposes. This counter-entropic, spatially bounded confinement of matter — order sustained against the pull toward equilibrium — is the property the term "biological life" is meant to pick out.
According to various alleged witnesses and contactees, certain beings who consider themselves alive or conscious — consciousness being a closely related notion, held to be necessary or sufficient for the ascription of life — do not have biological bodies. Some are described as having a non-biological body, which may be a cybernetic body or a "doll body", while others are said to have no physical body at all. Such beings are reported to exist in the same reality as the ordinary animals and humans of Earth, and the category "biological life" exists chiefly to mark the boundary between them.
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