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Alternation of generations is defined as the alternation of multicellular diploid and haploid forms in the organism's life cycle, regardless of whether these forms are free-living. [6] In some species, such as the alga Ulva lactuca , the diploid and haploid forms are indeed both free-living independent organisms, essentially identical in ...
The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations. It is the biological process of gametogenesis during which cells that are haploid or diploid divide to create other cells.
Wilhelm Hofmeister demonstrated that alternation of generations is a feature that unites plants, and published this result in 1851 (see plant sexuality). Some terms (haplobiont and diplobiont) used for the description of life cycles were proposed initially for algae by Nils Svedelius, and then became used for other organisms.
While writing Generations, Strauss and Howe described a theorized pattern in the historical generations they examined, which they say revolved around generational events which they call turnings. In Generations, and in greater detail in The Fourth Turning, they describe a four-stage cycle of social or mood eras which they call "turnings". The ...
This type of life cycle, involving alternation between two multicellular phases, the sexual haploid gametophyte and asexual diploid sporophyte, is known as alternation of generations. The evolution of sexual reproduction is considered paradoxical, [ 12 ] because asexual reproduction should be able to outperform it as every young organism ...
Babies born in the new year, and for the 14 years following, will make up the newest generation: Generation Beta.Its members will explore new digital landscapes, many of which we likely can't ...
Fertilisation in humans is the union of a human egg and sperm, ... Algae, like some land plants, undergo alternation of generations. Some algae are isomorphic, where ...
This is called alternation of generations. Most fungi and algae are haploid during the principal stage of their life cycle, as are some primitive plants like mosses . More recently evolved plants, like the gymnosperms and angiosperms , spend the majority of their life cycle in the diploid stage.