In microbiology the roles of mutation and selection in evolution are coming to be better understood through the use of bacterial cultures of mutant strains.
I declare that The Beatles are mutants. Prototypes of evolutionary agents sent by God, endowed with a mysterious power to create a new human species, a young race of laughing freemen.
(n.) Change; alteration, either in form or qualities.
How is it that you keep mutating and can still be the same virus?
It wasn't torpor that kept her - she was often restless to the point of irritability. She simply liked to feel that she was prevented from leaving, that she was needed.