protozoa

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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)
From Wikipedia, the free encyclopedia
(Redirected from Binary fission)
Jump to: navigation, search
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
1. ^ Carlson, B. M. (2007). Principals of regenerative biology.. Elsevier Academic Press. pp. 379.
ISBN 0123694396.
2. ^ 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.
3. ^ 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.16000706.2003.12450.x. http://onlinelibrary.wiley.com/doi/10.1034/j.16000706.2003.12450.x/abstract.
Retrieved from "http://en.wikipedia.org/wiki/Fission_(biology)"
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http://en.wikipedia.org/wiki/Binary_fission
Fission (biology)
From Wikipedia, the free encyclopedia
Jump to: navigation, search
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
1. ^ Carlson, B. M. (2007). Principals of regenerative biology.. Elsevier Academic Press. pp. 379.
ISBN 0123694396.
2. ^ 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.
3. ^ 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.16000706.2003.12450.x. http://onlinelibrary.wiley.com/doi/10.1034/j.16000706.2003.12450.x/abstract.
Retrieved from "http://en.wikipedia.org/wiki/Fission_(biology)"
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protozoan
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Encyclopædia Britannica (2)
- Reproduction and life cycles
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Article
Features of protozoans
Natural history
o Size range and diversity of structure
 Flagellated protozoans
 Amoebae and pseudopodia
 Ciliated protozoans
 Parasitic protozoans
o Distribution and abundance
o Ecological and industrial importance of protozoans
o Protozoans and disease
Form and function
o The protozoan cell
o Characteristics of locomotion
 Flagellar propulsion
 Cilium structure and beat
 Amoeboid movement
o Respiration and other energy-generating pathways
 Aerobic protozoans
 Anaerobic protozoans
 Hydrogenosomes
 Mitosomes and glycosomes
o Carbon acquisition and nutrition
 Mechanisms of food ingestion
 Food vacuoles
 Food selection
 Mixotrophy
 Photosynthesis and plastid acquisition
 Symbiotic mixotrophy
 Mixotrophy in planktonic protozoans
o Reproduction and life cycles
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Mechanisms of asexual reproduction
Mechanisms of sexual reproduction
 Conjugation in ciliates
 Autogamy and modified conjugation
 Parasitic protozoan life cycles
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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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Articles from Britannica encyclopedias for elementary and high school students.
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.
LINKS
External Web Sites
The topic protozoan is discussed at the following external Web sites.
Glass Protozoa
Cornell University - Protozoa and Microsporidia
Onview.net Ltd - Protozoan
Virtual Education - Protozoa
Zipcode Zoo - Protozoa
Aberystwyth University - Protozoa I
Lander University - Protozoa
Royal Society of Chemistry - Protozoan
Midwest Institute for Biological Control - Protozoa
How Stuff Works - Science - Protozoan
Monroe County Women’s Disability Network - Protozoa
History of The Universe - Protozoa
BC Parks - Protozoan
The Physics Hypertextbook - Diameter of a Protozoan
The Pennsylvania State University - Protozoan Diseases
Citations
MLA Style:
"protozoan." Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia
Britannica, 2011. Web. 29 Aug. 2011.
<http://www.britannica.com/EBchecked/topic/480488/protozoan>.
APA Style:
protozoan. (2011). In Encyclopædia Britannica. Retrieved from
http://www.britannica.com/EBchecked/topic/480488/protozoan
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single-celled organism; paramecium [Encyclopædia Britannica, Inc.]
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ciliate: locomotion [Encyclopædia Britannica, Inc.]

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cilium: structure and movement of cilia and flagella [Encyclopædia Britannica, Inc.]
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Paramecium [Encyclopædia Britannica, Inc.]
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bacteria: helping animals digest
IMAGES
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sea sparkle [Douglas P. Wilson]



amoeba [Russ Kinne/Photo Researchers]

representative protozoans [© Merriam-Webster Inc.]


Volvox: glass model of colony [Courtesy of the American Museum of Natural History, New York
City]


dinoflagellate; Ceratium tripos [Eric V. Grave]


red tide [R.F. Head—The National Audubon Society Collection/Photo Researchers]


radiolarian: glass model [Courtesy of the American Museum of Natural History, New York City]


Euplotes patella [Philip Feinberg, Fellow, New York Microscopical Society.]


oligotrich; Halteria grandinella [J.M. Langham]


trypanosome: trypanosome with human red blood cells [John J. Lee]


Trypanosoma cruzi [Dr. Myron G. Schultz/Centers for Disease Control and Prevention (CDC)
(Image Number: 613)]


blackwater fever [Centers for Disease Control and Prevention (CDC) (Image Numer: 5856)]


Trichomonas vaginalis [A.L. Leu]


amoeba: amoeba engulfing a ciliate [Roman Vishniac]


suctorian; Podophrya fixa [Walter Dawn]


Plasmodium vivax: Plasmodium vivax in red blood cell [A.L. Leu]


conjugation [Damián H. Zanette]


malaria: life cycle of a malaria parasite [Encyclopædia Britannica, Inc.]


Entamoeba coli [A.L. Leu]


plant: approximate numbers of named species [Encyclopædia Britannica, Inc.]


lysosome: intracellular digestion [Encyclopædia Britannica, Inc.]
Assorted References
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characteristics (in protist (biology): General features; in protist (biology): Ecology )
classification (in microbiology: Protozoa)
anatomy and physiology
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ciliated structures (in biological development: Development of single-celled organisms)
digestion (in digestion (biology): Ingestion)
excretory system (in excretion (biology): The contractile vacuoles of protozoans)
integumentary system (in integument (biology): Protozoans)
nervous system (in nervous system (anatomy): Organelle systems)
photoreceptive mechanisms (in photoreception (biology): Evolution of eyes)
regeneration (in regeneration (biology): Protozoans)
reproduction (in reproduction (biology): Multiple fission; in sex: The origin of sex and sexuality
)
skeletal systems (in skeleton: Calcareous structures)
behaviour



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chemoreception and directed movement (in chemoreception (physiology): Single-celled
organisms)
dormancy (in dormancy (biology): Dormancy in protozoans and invertebrates)
locomotion (in locomotion (behaviour): Microorganisms)
mating behaviour (in reproductive behaviour (zoology): Protozoans and sponges)
biotic interactions


infectious diseases (in infectious disease: Parasites)
symbiotic relationship with termites (in termite (insect): Cellulose)
evolution and research


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comparison with animals (in animal (biology): History of classification)
phylogeny (in phylogeny (biology): Major evolutionary steps)
protozoology (in protozoology)
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VIDEOS


single-celled organism; paramecium [Encyclopædia Britannica, Inc.]


ciliate: locomotion [Encyclopædia Britannica, Inc.]


cilium: structure and movement of cilia and flagella [Encyclopædia Britannica, Inc.]


Paramecium [Encyclopædia Britannica, Inc.]


bacteria: helping animals digest
IMAGES


sea sparkle [Douglas P. Wilson]


amoeba [Russ Kinne/Photo Researchers]


representative protozoans [© Merriam-Webster Inc.]


Volvox: glass model of colony [Courtesy of the American Museum of Natural History, New York
City]


dinoflagellate; Ceratium tripos [Eric V. Grave]


red tide [R.F. Head—The National Audubon Society Collection/Photo Researchers]


radiolarian: glass model [Courtesy of the American Museum of Natural History, New York City]


Euplotes patella [Philip Feinberg, Fellow, New York Microscopical Society.]


oligotrich; Halteria grandinella [J.M. Langham]


trypanosome: trypanosome with human red blood cells [John J. Lee]


Trypanosoma cruzi [Dr. Myron G. Schultz/Centers for Disease Control and Prevention (CDC)
(Image Number: 613)]


blackwater fever [Centers for Disease Control and Prevention (CDC) (Image Numer: 5856)]


Trichomonas vaginalis [A.L. Leu]


amoeba: amoeba engulfing a ciliate [Roman Vishniac]


suctorian; Podophrya fixa [Walter Dawn]


Plasmodium vivax: Plasmodium vivax in red blood cell [A.L. Leu]


conjugation [Damián H. Zanette]


malaria: life cycle of a malaria parasite [Encyclopædia Britannica, Inc.]


Entamoeba coli [A.L. Leu]


plant: approximate numbers of named species [Encyclopædia Britannica, Inc.]


lysosome: intracellular digestion [Encyclopædia Britannica, Inc.]



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