Definitions for ALTERNATION OF GENERATIONS
al·ter·na·tion of gen·er·a·tions

Princeton's WordNetRate this definition:0.0 / 0 votes

1. alternation of generations, heterogenesis, xenogenesisnoun

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

WikipediaRate this definition:0.0 / 0 votes

1. Alternation of generations

   Alternation of generations (also known as metagenesis or heterogenesis) is the predominant type of life cycle in plants and algae. It consists of a multicellular haploid sexual phase, the gametophyte, which has a single set of chromosomes alternating with a multicellular diploid asexual phase, the sporophyte which has two sets of chromosomes. A mature sporophyte produces haploid spores by meiosis, a process which reduces the number of chromosomes to half, from two sets to one. The resulting haploid spores germinate and grow into multicellular haploid gametophytes. At maturity, a gametophyte produces gametes by mitosis, the normal process of cell division in eukaryotes, which maintains the original number of chromosomes. Two haploid gametes (originating from different organisms of the same species or from the same organism) fuse to produce a diploid zygote, which divides repeatedly by mitosis, developing into a multicellular diploid sporophyte. This cycle, from gametophyte to sporophyte (or equally from sporophyte to gametophyte), is the way in which all land plants and most algae undergo sexual reproduction. The relationship between the sporophyte and gametophyte phases varies among different groups of plants. In the majority of algae, the sporophyte and gametophyte are separate independent organisms, which may or may not have a similar appearance. In liverworts, mosses and hornworts, the sporophyte is less well developed than the gametophyte and is largely dependent on it. Although moss and hornwort sporophytes can photosynthesise, they require additional photosynthate from the gametophyte to sustain growth and spore development and depend on it for supply of water, mineral nutrients and nitrogen. By contrast, in all modern vascular plants the gametophyte is less well developed than the sporophyte, although their Devonian ancestors had gametophytes and sporophytes of approximately equivalent complexity. In ferns the gametophyte is a small flattened autotrophic prothallus on which the young sporophyte is briefly dependent for its nutrition. In flowering plants, the reduction of the gametophyte is much more extreme; it consists of just a few cells which grow entirely inside the sporophyte. Animals develop differently. They directly produce haploid gametes. No haploid spores capable of dividing are produced, so generally there is no multicellular haploid phase. (Some insects have a sex-determining system whereby haploid males are produced from unfertilized eggs; however females produced from fertilized eggs are diploid.) Life cycles of plants and algae with alternating haploid and diploid multicellular stages are referred to as diplohaplontic (the equivalent terms haplodiplontic, diplobiontic and dibiontic are also in use, as is describing such an organism as having a diphasic ontogeny). Life cycles, such as those of animals, in which there is only a diploid multicellular stage are referred to as diplontic. Life cycles in which there is only a haploid multicellular stage are referred to as haplontic.

ChatGPTRate this definition:0.0 / 0 votes

1. alternation of generations

   Alternation of generations is a biological lifecycle found in certain plants, algae, and fungi, where they alternate between two distinct forms – a sexual phase (or gametophyte) and an asexual phase (or sporophyte). This cycle involves both haploid (single set of chromosomes) and diploid (double set of chromosomes) stages. The diploid sporophyte stage produces spores, which grow into a haploid gametophyte. The gametophyte then produces gametes, or sex cells, which combine to create a new diploid sporophyte, repeating the cycle.

WikidataRate this definition:0.0 / 0 votes

1. Alternation of generations

   Alternation of generations is a term primarily used to describe the life cycle of plants. A multicellular gametophyte, which is haploid with n chromosomes, alternates with a multicellular sporophyte, which is diploid with 2n chromosomes, made up of n pairs. A mature sporophyte produces spores by meiosis, a process which reduces the number of chromosomes to half, from 2n to n. The haploid spores germinate and grow into a haploid gametophyte. At maturity, the gametophyte produces gametes by mitosis, which does not alter the number of chromosomes. Two gametes fuse to produce a zygote, which develops into a diploid sporophyte. This cycle, from gametophyte to gametophyte, is the way in which all land plants and many algae undergo sexual reproduction. The relationship between the sporophyte and gametophyte varies among different groups of plants. In those algae which have alternation of generations, the sporophyte and gametophyte are separate independent organisms, which may or may not have a similar appearance. In liverworts, mosses and hornworts, the sporophyte is less well developed than the gametophyte and is largely dependent on it. Although moss and hornwort sporophytes can photosynthesise, they require additional photosynthate from the gametophyte to sustain growth and spore development and depend on it for supply of water, mineral nutrients and nitrogen. By contrast, in all modern vascular plants the gametophyte is less well developed than the sporophyte, although their Devonian ancestors had gametophytes and sporophytes of approximately equivalent complexity. In ferns the gametophyte is a small flattened autotrophic prothallus on which the young sporophyte is briefly dependent for its nutrition. In flowering plants, the reduction of the gametophyte is much more extreme; it consists of just a few cells which grow entirely inside the sporophyte.

EntomologyRate this definition:0.0 / 0 votes

1. Alternation of generations

   where a species that occurs in both sexes periodically produces only parthenogenetic females; the latter, in turn, producing the sexed form; occurs in Cynipidae and some Homoptera: see heterogeny.

Matched Categories

1. • Organic Phenomenon

How to pronounce ALTERNATION OF GENERATIONS?

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Numerology

1. Chaldean Numerology

   The numerical value of ALTERNATION OF GENERATIONS in Chaldean Numerology is: 4

2. Pythagorean Numerology

   The numerical value of ALTERNATION OF GENERATIONS in Pythagorean Numerology is: 7

References

1. ^ Princeton's WordNet
   http://wordnetweb.princeton.edu/perl/webwn?s=ALTERNATION OF GENERATIONS
2. ^ Wikipedia
   https://en.wikipedia.org/wiki/Alternation_of_Generations
3. ^ ChatGPT
   https://chat.openai.com
4. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=ALTERNATION OF GENERATIONS
5. ^ Entomology
   https://www.gutenberg.org/files/22748/22748-h/22748-h.htm#:~:text=ALTERNATION OF GENERATIONS