A Protozoan Undergoes Binary Fission - with Some Help!

A protozoan undergoes "binary fission" - with some help!

by Ron Neumeyer

These images, captured from video using a Snappy video grabber, illustrate the final stages of protozoan asexual reproduction (a process known as "binary fission"). The organism undergoing division, a small ciliate, gets a helping hand from one of its "cohorts" during the final stage, separation of the two daughter cells.

/ A second protozoan (lower centre) approaches the protozoan (centre) undergoing binary fission
The second protozoan forces it's way between the two daughter cells /
/ Aiding the binary fission process in a rather unorthodox way!

Binary fission generally produces daughter cells with genetic material (DNA) identical to that of the parent. It is an efficient way for protozoa to increase in number during periods when environmental conditions are relatively stable. However, when environmental conditions begin to change, sexual reproduction generally becomes more prevalent. Sexual reproduction allows for the mixing of DNA among the various strains (asexual daughters) of a local protozoan population. Shuffling the deck in this manner produces cells which are genetically different from each other, an important characteristic as genetic make-up determines how cells respond to their environment. A genetically diverse population has more "options" in the face of changing conditions. In the biological world survival of the species is the ultimate objective. The more diverse a species gene pool, the greater the likelihood that it will persist.

Comments to the author Ron Neumeyer welcomed.

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Fission (biology)

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Binary fission

In biology, fission is the carp of a body, population, or species into parts and the regeneration of those parts into separate individuals.[1][2][3] Binary fission, or prokaryotic fission, is a form of asexual reproduction and cell division used by all prokaryotes, some protozoa, and some organelles within eukaryotic organisms. This process results in the reproduction of a living prokaryotic cell by division into two parts that each have the potential to grow to the size of the original cell.

Mitosis and cytokinesis are not the same as binary fission. To be specific, binary fission cannot be divided into prophase, metaphase, anaphase, and telophase because prokaryotes have no nucleus and no centromeres. The ability of some multicellular animals, such as echinoderms and flatworms, to regenerate two whole organisms after having been cut in half, is also not the same as binary fission. Neither is vegetative reproduction of plants.

[edit] References

^ Carlson, B. M. (2007). Principals of regenerative biology.. Elsevier Academic Press. pp.379. ISBN0123694396.
^ Boulay, R. L.; Galarza, J. A.; Che, B.; Hefetz, A.; Lenoir, A.; van Oudenhove, L.; Cerda, X. (2010). "Intraspecific competition affects population size and resource allocation in an ant dispersing by colony fission.". Ecology 91 (11): 3312–3321. doi:10.1890/09-1520.1. http://www.esajournals.org/doi/full/10.1890/09-1520.1.
^ Hubbell, S. (2003). "Modes of speciation and the lifespans of species under neutrality: a response to the comment of Robert E. Ricklefs.". Oikos 100 (1): 193–199. doi:10.1034/j.1600-0706.2003.12450.x. http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0706.2003.12450.x/abstract.

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Fission (biology)

From Wikipedia, the free encyclopedia

Jump to: navigation, search

Binary fission

[edit] References

^ Carlson, B. M. (2007). Principals of regenerative biology.. Elsevier Academic Press. pp.379. ISBN0123694396.
^ Boulay, R. L.; Galarza, J. A.; Che, B.; Hefetz, A.; Lenoir, A.; van Oudenhove, L.; Cerda, X. (2010). "Intraspecific competition affects population size and resource allocation in an ant dispersing by colony fission.". Ecology 91 (11): 3312–3321. doi:10.1890/09-1520.1. http://www.esajournals.org/doi/full/10.1890/09-1520.1.
^ Hubbell, S. (2003). "Modes of speciation and the lifespans of species under neutrality: a response to the comment of Robert E. Ricklefs.". Oikos 100 (1): 193–199. doi:10.1034/j.1600-0706.2003.12450.x. http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0706.2003.12450.x/abstract.

Retrieved from "http://en.wikipedia.org/wiki/Fission_(biology)"

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o protozoan

o schizogony (reproduction)

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protozoan

Reproduction and life cycles

Asexual reproduction is the most common means of replication by protozoans. The ability to undergo a sexual phase is confined to the ciliates, the apicomplexans, and restricted taxa among the flagellated and amoeboid organisms. Moreover, sexual reproduction does not always result in an immediate increase in cell numbers but may simply be a means of exchanging genetic material between individuals of the same species (i.e., conjugation). Free-living protozoans normally resort to sexual reproduction only when environmental conditions become adverse, because this mode of reproduction enhances genetic variation through mechanisms such as mutation and chromosomal ... (100 of 13348 words)

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Protozoan - Children's Encyclopedia (Ages 8-11)

Protozoans are simple organisms, or living things. They belong to a group of organisms called protists, which are neither plants nor animals. Most protozoans are so tiny that they can be seen only with a microscope. Amoebas and paramecia are types of protozoan.

protozoan - Student Encyclopedia (Ages 11 and up)

Protozoans are typically microscopic, single-celled organisms. Unlike bacteria and archaea, they are eukaryotic. This means that they have a distinct nucleus. Also, unlike single-celled algae, protozoans cannot make their own food, so they eat other organisms. For this reason, protozoans were once considered animals. The term protozoan comes from the Greek words protos, meaning "first," and zoion, meaning "animal." Protozoans make up a variety of groups of organisms within the kingdom Protista, though these groups do not necessarily share a common evolutionary history.