This is a quote from the book "The Virtue Of Selfishness" by Ayn Rand
...s life, or: that which is required for the organism’s survival.
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No choice is open to an organism in this issue: that which is required for its survival is determined by its natur
e, by the kind of entity it is. Many variations, many forms of adaptation to its background are possible to an organism, including the possibility of existing for a while in a crippled, disabled
or diseased condition, but the fundamental alternative of its existence remains the same: if an organism fails in the basic functions required by its nature — if an amoeba’s protoplasm stop...