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Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. [6] [7] Sexual reproduction also occurs in some unicellular eukaryotes. [2] [8] Sexual reproduction does not occur in prokaryotes, unicellular organisms without cell nuclei, such as bacteria and archaea.
The simple multicellular eukaryote Volvox carteri undergoes sex in response to oxidative stress [13] or stress from heat shock. [14] These examples, and others, suggest that, in simple single-celled and multicellular eukaryotes, meiosis is an adaptation to respond to stress. Prokaryotic sex also appears to be an adaptation to stress.
The sexual cycle of N. crassa is heterothallic. Sexual fruiting bodies (perithecia) can only be formed when two mycelia of different mating type come together. Like other ascomycetes, N. crassa has two mating types that, in this case, are symbolized by ‘A’ and ‘a’. There is no evident morphological difference between the ‘A’ and 'a ...
The criterion for "sexuality" varies from all cases of restitutional meiosis, [4] to those where the nuclei fuse or to only those where gametes are mature at the time of fusion. [3] Those cases of automixis that are classified as sexual reproduction are compared to self-fertilization in their mechanism and consequences.
Animal reproduction occurs by two modes of action, including both sexual and asexual reproduction. [1] In asexual reproduction the generation of new organisms does not require the fusion sperm with an egg. [1] However, in sexual reproduction new organisms are formed by the fusion of haploid sperm and eggs resulting in what is known as the ...
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism.
Sexual systems play a key role in genetic variation and reproductive success, and may also have led to the origin or extinction of certain species. [4] In flowering plants and animals, sexual reproduction involves meiosis, an adaptive process for repairing damage in the germline DNA transmitted to progeny. [5]
[1] [2] Transitions of form may involve growth, asexual reproduction, or sexual reproduction. In some organisms, different "generations" of the species succeed each other during the life cycle. For plants and many algae, there are two multicellular stages, and the life cycle is referred to as alternation of generations.