Alternation of generations
Alternation of Generations
Alternation of generations (pronunciation: /ˌɔːltəˈneɪʃən ɒv ˌdʒɛnəˈreɪʃənz/) is a biological process in which an organism's life cycle alternates between two distinct, multicellular stages. This process is common in many plant and algae species.
Etymology
The term "alternation of generations" is derived from the Latin words "alternatio" meaning "interchange" and "generatio" meaning "generation". It was first used in the mid-19th century to describe the life cycles of plants and algae.
Definition
In the alternation of generations, one generation, the sporophyte, produces spores that grow into a separate generation, the gametophyte. The gametophyte then produces gametes, or sex cells, which combine to form a new sporophyte. This cycle continues, alternating between the sporophyte and gametophyte stages.
Related Terms
- Sporophyte: The diploid, or 2n, stage in the life cycle. The sporophyte produces spores by meiosis, which grow into gametophytes.
- Gametophyte: The haploid, or n, stage in the life cycle. The gametophyte produces gametes by mitosis, which combine to form a new sporophyte.
- Gametes: The sex cells produced by the gametophyte. These cells combine to form a new sporophyte.
- Meiosis: The process by which the sporophyte produces spores. This process reduces the number of chromosomes in each spore by half.
- Mitosis: The process by which the gametophyte produces gametes. This process maintains the number of chromosomes in each gamete.
See Also
External links
- Medical encyclopedia article on Alternation of generations
- Wikipedia's article - Alternation of generations
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