alternation of generations

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The regular alternation of forms or of mode of reproduction in the life cycle of an organism, such as the alternation between diploid and haploid phases, or between sexual and asexual reproductive cycles.

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• noun biology metagenesis

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the alternation of two or more different forms in the life cycle of a plant or animal