The sexual life cycle involves biologya biological life cycle or just life cycle when the biological context is clear is a series of changes in form that an organism undergoes, returning to the starting state.
In some organisms, different
The sexual life cycle involves of the species succeed each other during the life cycle. For plants and many algaethere are two multicellular stages, and the life cycle is referred to as alternation of generations. The term life history is often used, particularly for
The sexual life cycle involves such as the red algae which have three multicellular stages or morerather than two. Life cycles that include sexual reproduction involve alternating haploid n and diploid 2 n stages, i.
To The sexual life cycle involves from a diploid stage to a haploid stage, meiosis must occur. In regard to changes of ploidythere are 3 types of cycles:. The cycles differ in when mitosis growth occurs.
Zygotic meiosis and gametic meiosis have one mitotic stage: Therefore, zygotic and gametic meiosis are collectively termed haplobiontic single mitotic phase, not to be confused with haplontic. Sporic meiosison the other hand, has mitosis in two stages, both the diploid and haploid stages, termed diplobiontic not to be confused with diplontic. The study of reproduction and development in organisms was carried out by many botanists and zoologists. Wilhelm Hofmeister demonstrated that alternation of generations The sexual life cycle involves a feature that unites plants, and published this result in 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 The sexual life cycle involves used for other organisms. A zygotic meiosis is a meiosis of a zygote immediately after karyogamywhich is the fusion of two cell nuclei.
This way, the organism ends its diploid phase and produces several haploid cells. These cells divide mitotically to form either larger, multicellular individuals, or more haploid cells.
Two opposite types of gametes e. The individuals or cells as a result of mitosis are haplontshence this life cycle is also called haplontic life cycle. In gametic meiosisinstead of immediately dividing meiotically to produce haploid cells, the zygote divides mitotically to produce a multicellular diploid individual or a group of more unicellular diploid cells.
Cells from the diploid individuals then undergo meiosis to produce haploid cells
The sexual life cycle involves gametes. Haploid cells may divide again by The sexual life cycle involves to form more haploid cells, as in many yeasts, but the haploid phase is not the predominant life cycle phase. In most diplonts, mitosis occurs only in the diploid phase, i. In the whole cycle, gametes are usually the only haploid cells, and mitosis usually occurs only in the diploid phase.
The diploid multicellular individual is a diplonthence a gametic meiosis is also called a diplontic life cycle. In sporic meiosis also commonly known as intermediary meiosisthe zygote divides mitotically to produce a multicellular diploid sporophyte. The sporophyte creates spores via meiosis which also then divide mitotically producing haploid individuals called gametophytes. The gametophytes produce gametes via mitosis.
In some plants the The sexual life cycle involves is not only small-sized but also short-lived; in other plants and many algae, the gametophyte is the "dominant" stage of the life cycle.
Some animals have a sex-determination system
The sexual life cycle involves haplodiploidbut this is not related to the haplodiplontic life cycle. Some red The sexual life cycle involves such as Bonnemaisonia  and Lemanea and green algae such as Prasiola have vegetative meiosisalso called somatic meiosis sexual life cycle involves, which is a rare phenomenon.
The gametophytes remain attached to The sexual life cycle involves part of the sporophyte. Vegetative non-reproductive diploid cells undergo meiosis, generating vegetative haploid cells. These undergo many mitosis, and produces gametes. A different phenomenon, called vegetative diploidizationa type of apomixisoccurs in some brown algae e.
The primitive type of life cycle probably had haploid individuals with asexual reproduction. From Wikipedia, the free encyclopedia. A series of changes of form that an organism undergoes, returning to the starting state. Alternation of generations Apomixis Eel life history Haplodiploidy Monocarpicplants bloom once and then die Parasexual cycle Parasitic life Parthenogenesis Reproductive biology Brachymeiosis Mitotic recombination Dikaryon Heterokaryon Fertilisation.
Biology of the Rhodophyta. Skottsberg"Nils Eberhard Svedelius. Nuclear Phases and Alternation in Rhodophyceae.
Beihefte zum Botanischen Centralblatt. Margulis"Archaeal-eubacterial mergers in the origin of Eukarya: The Journal of protozoology.
Cambridge University Press pp. Textbook of Algae, p. Sex and Death in Protozoa. Cambridge University Press, p.
European Journal of Phycology. Some structural and physiological aspects of meiosis in algae, fungi, and protozoa". The Evolutionary Biology of Parthenogenesis.
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