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As mitosis is less complex than meiosis, meiosis may have arisen after mitosis. [93] However, sexual reproduction involving meiosis is also a primitive characteristic of eukaryotes. [ 94 ] Thus meiosis and mitosis may both have evolved, in parallel, from ancestral prokaryotic processes.
In eukaryotes, there are two distinct types of cell division: a vegetative division , producing daughter cells genetically identical to the parent cell, and a cell division that produces haploid gametes for sexual reproduction , reducing the number of chromosomes from two of each type in the diploid parent cell to one of each type in the ...
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.
According to this theory, early eukaryotes evolved mitosis first, became established, and only then did meiosis and sexual reproduction arise. Supporting this idea are observations of some features, such as the meiotic spindles that draw chromosome sets into separate daughter cells upon cell division, as well as processes regulating cell ...
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.
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.
Human sexual reproduction, to produce offspring, begins with fertilization. Successful reproduction typically involves sexual intercourse between a healthy, sexually mature and fertile male and female. [1] During sexual intercourse, sperm cells are ejaculated into the vagina through the penis, resulting in fertilization of an ovum to form a ...
Another theory is that sexual reproduction originated from selfish parasitic genetic elements that exchange genetic material (that is: copies of their own genome) for their transmission and propagation. In some organisms, sexual reproduction has been shown to enhance the spread of parasitic genetic elements (e.g. yeast, filamentous fungi). [80]