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alternation of generations |
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alternation of generations: see gametophyte gametophyte (gəmē`təfīt'), phase of plant life cycles in which the gametes, i.e., egg and sperm, are produced. ..... Click the link for more information. ; reproduction reproduction, capacity of all living systems to give rise to new systems similar to themselves. The term reproduction may refer to this power of self-duplication of a single cell or a multicellular animal or plant organism. ..... Click the link for more information. . alternation of generationsIn biology, alternation of a sexual phase (gametophyte) and a nonsexual phase (sporophyte) in the life cycle of an organism. The two phases, or generations, are often distinct in structure and sometimes in chromosome makeup. Alternation of generations is common in algae, fungi (see fungus), mosses, ferns, and seed plants. The character and extent of the two phases vary greatly among different groups of plants and algae. During the course of evolution, the gametophyte stage has been progressively reduced. Thus in higher (vascular) plants, the sporophyte is the dominant phase; in more primitive, nonvascular plants the gametophyte is dominant. Among animals, many invertebrates (e.g., protozoans, jellyfish, flatworms) have an alternation of sexual and asexual generations. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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| In books such as the Patternist novels, published from 1976 to 1984, and the Xenogenesis trilogy, published from 1987 to 1989 and now collected in the omnibus volume Lilith's Brood, Butler employed the stuff of hard science--biological engineering, interspecies hybrids--to create settings and situations that are both literally and figuratively alien. A physical function of the Oankali and the Oankali-human constructs [in the Xenogenesis Trilogy] that intrigues me is their ability to see without eyes, by means of sensory tentacles or patches rather than human optics. From the Medusa-like appearance of the alien Oankali in her Xenogenesis Trilogy(1) and the archetypal power of the matriarchal shapeshifter Anyanwu in her 1980 novel Wild Seed to Gan's "female" reproductive function for the Tlic in "Bloodchild," Butler is deeply invested in science-fictional metaphors for the "feminine" which challenge traditional representations. |
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