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Symbiosis

Symbiosis

Symbiosis (pl. symbioses) (from the Greek words syn = con/plus and biono = living) is an interaction between two organisms living together in more or less intimate association or even the merging of two dissimilar organisms. The term host is usually used for the larger (macro) of the two members of a symbiosis. The smaller (micro) member is called the symbiont (plural: symbionts), or alternately, symbiote (plural: symbiotes). When a microscopic symbiont lives inside the cells of a host, it is referred to as an endosymbiont. The various forms of symbiosis include: -
- parasitism, in which the association is disadvantageous or destructive to one of the organisms and beneficial to the other (+ -)
- mutualism, in which the association is advantageous to both (+ +)
- commensalism, in which one member of the association benefits while the other is not affected (+ 0)
- amensalism, in which the association is disadvantageous to one member while the other is not affected (- 0) In some cases, the term symbiosis is used only if the association is obligatory and benefits both organisms. Symbiosis as defined in this article does not restrict the term to only the mutually beneficial interactions. Symbiosis may be divided into two distinct categories: ectosymbiosis and endosymbiosis. In ectosymbiosis, the symbiont lives on the body surface of the host, including the inner surface of the digestive tract or the ducts of exocrine glands. In endosymbiosis, the symbiont lives either in the intracellular space of the host or extracellularly. An example of mutual symbiosis is the relationship between clownfish of the genus Amphiprion (family, Pomacentridae) that dwell among the tentacles of tropical sea anemones. The territorial fish protects the anemone from anemone-eating fish, and in turn the stinging tentacles of the anemone protect the anemone fish from its predators (a special mucus on the anemone fish protects it from the stinging tentacles). sea anemone.]] Another example is the goby fish, which sometimes lives together with a shrimp. The shrimp digs and cleans up a burrow in the sand in which both the shrimp and the goby fish live. The shrimp is almost blind leaving it vulnerable to predators when above ground. In case of danger the goby fish touches the shrimp with its tail to warn it of imminent danger. When that happens both the shrimp and goby fish quickly retract into the burrow. A famous land version of symbiosis is the relationship of the Egyptian Plover bird and the crocodile. In this relationship, the bird is well known for preying on parasites that feed on crocodiles which are potentially harmful for the animal. To that end, the crocodile openly invites the bird to hunt on his body, even going so far as to open the jaws to allow the bird enter the mouth safely to hunt. For the bird's part, this relationship not only is a ready source of food, but a safe one considering that few predator species would dare strike at the bird at such close proximity to its host. The biologist Lynn Margulis, famous for the work on endosymbiosis, contends that symbiosis is a major driving force behind evolution. She considers Darwin's notion of evolution, driven by competition, as incomplete, and claims evolution is strongly based on co-operation, interaction, and mutual dependence among organisms. According to Margulis and Sagan (1986), "Life did not take over the globe by combat, but by networking". As in humans, organisms that cooperate with others of their own or different species often outcompete those that don't. However, mutualism, parasitism, and commensalism are often not discrete categories of interactions and should rather be perceived as a continuum of interaction ranging from parasitism to mutualism. In fact, the direction of a symbiotic interaction can change during the lifetime of the symbionts due to developmental changes as well as changes in the biotic/abiotic environment in which the interaction occurs.

See also


- List of symbiotic relationships

References


- Lynn Margulis and Dorion Sagan, Microcosmos: Four Billion Years of Evolution from Our Microbial Ancestors. Summit Books, New York, 1986. ISBN 0520210646
- Jan Sapp Evolution by Association, Oxford University Press, 1994. ISBN 0195088212 Category:Ecology
- ja:共生

Biological interaction

Biological interactions result from the fact that organisms in an ecosystem interact with each other, in the natural world, no organism is an autonomous entity isolated from its surroundings. It is part of its environment, rich in living and non living elements all of which interact with each other in some fashion. An organism's interactions with its environment are fundamental to the survival of that organism and the functioning of the ecosystem as a whole. In ecology, biological interactions are the relationships between two species in an ecosystem. These relationships can be categorized into many different classes of interactions based either on the effects or on the mechanism of the interaction. The interactions between two species vary greatly in these aspects as well as in duration and strength. Species may meet once in a generation (e.g. pollination) or live completely within another (e.g. endosymbiosis). Effects may range from one species eating the other (predation), to both living together with mutual benefit (mutualism). The interactions between two species need not be through direct contact. Due to the connected nature of ecosystems, species may affect each other through intermediaries such as shared resources or common enemies.

Interactions categorized by effect

Terms which explicitly indicate the quality of benefit or harm experienced by participants in an interaction are listed below:
- Neutralism is a lack of interaction. Since all species sharing an environment interact in some way, a complete lack of interaction is rarely seen in nature. However, the term can also signify a relationship in which each species derives neither benefit nor detriment to any measurable degree.
- Mutualism benefits both populations. It is often non obligatory or temporary.
- Synnecrosis is detrimental to both species. It is a rare and necessarily short-lived condition as evolution selects against it.
- Amensalism is detrimental to one species and neutral to the other.
- Commensalism benefits one organism and the other organism is neither benefited nor harmed.
- Predation is an interaction between organisms in which one organism captures biomass from another. It is often used as a synonym for carnivory but formally also includes herbivory, parasitism, and parasitoidism. It is important to note that these interactions are not always static. In many cases, two species will interact differently under different conditions. This is particularly true in, but not limited to, cases where species have multiple, drastically different life stages.

Interactions classified by mechanism


- Symbiosis is an obligatory relationship between two populations. Partners in a symbiotic relation ship are constantly in contact with each other. Often one lives inside the other. It often implies mutualism, but most formal definitions also include other types of relationships like parasitism and commensalism.
- Competition is an association between two species in which both need some limited environmental factor for growth. Category:Ecology

Endosymbiont

An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis (Greek: endo = inner and biosis = living). For instance, some nitrogen fixing bacteria (known as rhizobia) live in root nodules on legume roots, reef-building corals contain single-celled algae, and several insect species contain bacterial endosymbionts. Many other examples of endosymbiosis exist. Many instances of endosymbiosis are obligate, where neither the endosymbiont nor the host can survive without the other, such as gutless marine worms which get nutrition from their endosymbiotic bacteria. However, not all endosymbioses are obligate. Also, some endosymbioses can be harmful to either of the organisms involved. See symbiosis for further discussion of this issue. It is generally agreed that certain organelles of the eukaryotic cell, especially mitochondria and chloroplasts, originated as bacterial endosymbionts. This theory is known as the endosymbiotic theory, confirmed and popularized by Lynn Margulis.

The endosymbiont theory and mitochondria and chloroplasts

The endoymbiont theory explains the origins of organelles such as mitochondria and chloroplasts in eukaryotic cells. Lynn Margulis of the University of Massachusetts most forcefully defended the endosymbiont theory. The theory proposes that chloroplasts and mitochondria evolved from certain types of bacteria that prokaryotic cells engulfed through endophagocytosis. These cells and the bacteria trapped inside them entered an symbiotic relationship, a close association between different types of organisms over an extended time. However, more specifically, the relationship was endosymbiotic, meaning that one of the organisms (the bacteria) lived within the other (the prokaryotic cells). According to the endosymbiont theory, an anaerobic cell probably ingested an aerobic bacterium but failed to digest it. The aerobic bacterium flourished within the cell because the cell’s cytoplasm was abundant in half-digested food molecules. The bacterium digested these molecules with oxygen and gained great amounts of energy. Because the bacterium had so much energy, it probably leaked some of it as ATP into the cell’s cytoplasm. This benefited the anaerobic cell because it enabled it to digest food aerobically. Eventually, the aerobic bacterium could no longer live independently from the cell, and it therefore became a mitochondrion. The origin of the chloroplast is very similar to that of the mitochondrion. A cell must have captured a photosynthetic cyanobacterium and failed to digest it. The cyanobacterium thrived in the cell and eventually evolved into the first chloroplast. Other eukaryotic organelles may have also evolved through endosymbiosis. Scientists believe that cilia, flagella, centrioles, and microtubules may have come from a symbiosis between a spirilla-like bacterium and an early eukaryotic cell. There are several examples of evidence that support the endosymbiont theory. Mitochondria, chloroplasts, and centrioles contain their own small supply of DNA, which may be remnants of the DNA the organelles had when they were independent aerobic bacteria. In addition, there are organisms alive today, called living intermediates, that are in a similar endosymbiotic condition to the prokaryotic cells and the aerobic bacteria. Living intermediates show that the evolution proposed by the endosymbiont theory is possible. For example, the amoeba lacks mitochondria but has aerobic bacteria that carry out a similar role. A variety of corals, clams, snails, and one species of Paramecium permanently host algae in their cells. These modern organisms with endosymbiotic relationships with aerobic bacteria suggest that the endosymbiont theory, which explains the origin of mitochondria and chloroplasts, is accurate.

Bacterial endosymbionts in marine oligochaetes

Some marine oligochaetes (e.g Olavius or Inanidrillus) have obligate extracellular endosymbionts that fill the entire body of their host. These marine worms are nutritionally dependent on their symbiotic chemoautotrophic bacteria lacking any digestive or excretory system (no gut, mouth or nephridia).

Bacterial endosymbionts in other marine invertebrates

Extracellular endosymbionts are also represented in all 5 extant classes of Echinodermata (Crinoidea, Ophiuroidea, Asteroidea, Echinoidea, and Holothuroidea). Little is known of the nature of the association (mode of infection, transmission, metabolic requirements, etc.) but phylogenetic analysis indicates that these symbionts belong to the alpha group of the class Proteobacteria, relating them to Rhizobium and Thiobacillus. Other studies indicate that these subcuticular bacteria may be both abundant within their hosts and widely distributed among the Echinoderms in general.

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists

Dinoflagellate endosymbionts of the genus Symbiodinium, commonly known as zooxanthellae, are found in corals, mollusks (esp. giant clams, the Tridacna), sponges, and foraminifera. These endosymbionts drive the amazing formation of coral reefs by capturing sunlight and providing their hosts with energy for carbonate deposition. Previously thought to be a single species, molecular phylogenetic evidence over the past couple decades has shown there to be great diversity in Symbiodinium. In some cases there is specificity between host and Symbiodinium clade. More often, however, there is a ecological distribution of Symbiodinium, the symbionts switching between hosts with apparent ease. When reefs become environmentally stressed, this distribution of symbionts is related to the observed pattern of coral bleaching and recovery. Thus the distribution of Symbiodinium on coral reefs and its role in coral bleaching presents one of the most complex and interesting current problems in reef ecology.

Bacterial obligate endosymbionts in insects

Among bacterial endosymbionts of insects, the best studied are the pea aphid Acyrthosiphon pisum and its endosymbiont Buchnera sp. APS, and the tsetse fly Glossina morsitans morsitans and its endosymbiont Wigglesworthia glossinidia brevipalpis. As with endosymbiosis in other insects, the symbiosis is obligate in that neither the bacteria nor the insect is viable without the other. Scientists have been unable to cultivate the bacteria in lab conditions outside of the insect. With special nutritionally-enhanced diets, the insects can survive, but are unhealthy, and at best survive only a few generations. The endosymbionts live in specialized insect cells called bacteriocytes (also called mycetocytes), and are maternally-transmitted, i.e. the mother transmits her endosymbionts to her offspring. In some cases, the bacteria are transmitted in the egg, as in Buchnera; in others like Wigglesworthia, they are transmitted via milk to the developing insect embryo. The bacteria are thought to help the host by either synthesizing nutrients that the host cannot make itself, or by metabolizing insect waste products into safer forms. For example, the primary role of Buchnera is thought to be to synthesize essential amino acids that the aphid cannot acquire from its natural diet of plant sap. The evidence is (1) when aphids' endosymbionts are killed using antibiotics, they appear healthier when their plant sap diet is supplemented with the appropriate amino acids, and (2) after the Buchnera genome was sequenced, analysis uncovered a large number of genes that likely code for amino acid biosynthesis genes; most bacteria that live inside other organisms do not have such genes, so their existence in Buchnera is noteworthy. Similarly, the primary role of Wigglesworthia is probably to synthesize vitamins that the tsetse fly does not get from the blood that it eats. The benefit for the bacteria is that it is protected from the environment outside the insect cell, and presumably receives nutrients from the insect. Genome sequencing reveals that obligate bacterial endosymbionts of insects have among the smallest of known bacterial genomes and have lost many genes that are commonly found in other bacteria. Presumably these genes are not needed in the environment of the host insect cell. (A complementary theory as to why the bacteria may have lost genes, Muller's ratchet, is that since the endosymbionts are maternally transmitted and have no opportunity to exchange genes with other bacteria, it is more difficult to keep good genes in all individuals in a population of these endosymbionts.) Research in which a parallel phylogeny of bacteria and insects was inferred supports the belief that the obligate endosymbionts are transferred only vertically (i.e. from the mother), and not horizontally (i.e. by escaping the host and entering a new host). Attacking obligate bacterial endosymbionts may present a way to control their insect hosts, many of which are pests or carriers of human disease. For example aphids are crop pests and the tsetse fly carries the organism (trypanosome protozoa) that causes African sleeping sickness. Other motivations for their study is to understand symbiosis, and to understand how bacteria with severely depleted genomes are able to survive, thus improving our knowledge of genetics and molecular biology.

References

Obligate bacterial endosymbiosis in marine oligochaetes:


- Endosymbiotic sulphate-reducing and sulphide-oxidizing bacteria in an oligochaete worm. Dubilier N., Mülders C.,Ferdelman T., De Beer D.,Pernthaler A.,Klein M., Wagner M., Erseus C., Thiermann F., Krieger J., Giere O & Amann R. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11357130

Bacterial endosymbionts in echinoderms:


- Subcuticular bacteria from the brittle star Ophiactis balli (Echinodermata: Ophiuroidea) represent a new lineage of extracellular marine symbionts in the alpha subdivision of the class Proteobacteria. Burnett, W J and J D McKenzie http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=168468&rendertype=abstract

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists


- Excellent review paper covering the role of Symbiodinium in reef ecology and the current state of research: [http://arjournals.annualreviews.org/doi/abs/10.1146%2Fannurev.ecolsys.34.011802.132417?cookieSet=1 FLEXIBILITY AND SPECIFICITY IN CORAL-ALGAL SYMBIOSIS: Diversity, Ecology, and Biogeography of Symbiodinium. Andrew C. Baker, Annual Review of Ecology, Evolution, and Systematics 2003 34, 661-689]

Obligate bacterial endosymbionts in insects:


- PLOS Biology Primer- Endosymbiosis: lessons in conflict resolution http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020068
- A general review of bacterial endosymbionts in insects. P. Baumann, N. A. Moran and L. Baumann, Bacteriocyte-associated endosymbionts of insects in M. Dworkin, ed., The prokaryotes, Springer, New York, 2000. http://link.springer.de/link/service/books/10125/
- An excellent review of insect endosymbionts that focuses on genetic issues. Jennifer J. Wernegreen (2002), Genome evolution in bacterial endosymbionts of insects, Nature Reviews Genetics, 3, pp. 850-861. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12415315&dopt=Abstract
- A review article on aphids and their bacterial endosymbionts. A. E. Douglas (1998), Nutritional interactions in insect-microbial symbioses: Aphids and Their Symbiotic Bacteria Buchnera, Annual Reviews of Entomology, 43, pp. 17-37.
- Describes possible methods to control the human pathogen causing African sleeping sickness, which is transmitted by tsetse flies. Focuses on methods using the primary and secondary endosymbionts of the tsetse fly. Serap Aksoy, Ian Maudlin, Colin Dale, Alan S. Robinsonand and Scott L. O’Neill (2001), Prospects for control of African trypanosomiasis by tsetse vector, TRENDS in Parasitology, 17 (1), pp. 29-35. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11137738&dopt=Abstract
- Announces and analyzes the full genome sequence of Buchnera sp. APS, the endosymbiont of the pea aphid, and the first endosymbiont to have its genome sequenced. S. Shigenobu, H. Watanabe, M. Hattori, Y. Sakaki and H. Ishikawa (2000), Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS, Nature, 407, pp. 81-86. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10993077&dopt=Abstract
- An article that discusses one theory on how obligate endosymbionts may have their genomes degraded, in a freely-available journal. Nancy A. Moran (1996), Accelerated evolution and Muller’s ratchet in endosymbiotic bacteria, Proceedings of the National Academy of Sciences of the USA, 93, pp. 2873-2878. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8610134&dopt=Abstract Category:Symbiosis

Mutualism

For another use of the term see Mutualism (economic theory). In biology, mutualism is an interaction between two species in which both species derive benefit. Mutualisms can be lifelong interactions involving close physical and biochemical contact (known as symbiosis) such as those between trees and mycorrhizal fungi; they can also be briefer, non-symbiotic interactions, such as those between flowering plants and pollinators. Mutualisms may also be obligatory or non-obligatory (facultative). For example, bacteria known as rhizobia can reproduce either in the soil or in (usually) mutualistic symbiosis with legume plants. Mycorrhizal fungi, on the other hand, can be totally dependent on their plant hosts. Microbes often band together for mutual benefit in biofilms to break down solid food sources as in rusticles. Category:Ecology Category:Symbiosis

Amensalism

Amensalism is an biological interaction, a type of symbiosis, between two species in which one impedes or restricts the success of the other without being affected, positively or negatively, by the presence of the other. Usually this occurs when one organism exudes a chemical compound as part of its normal metabolism that is detrimental to another organism. The bread mold Penicillium is a common example of this; penicillium secrete penicillin, which is a chemical that kills bacteria. A second example is the Black walnut tree (Juglans nigra) species. Its roots secrete juglone, a chemical that often kills neighboring plants. Plants in certain biomes, such as the chaparral or desert, are very dependent on the effects of amensalism. It stabilizes the community by reducing competition for scarce nutrients in the water. Category:Ecology

Endosymbiosis

An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis (Greek: endo = inner and biosis = living). For instance, some nitrogen fixing bacteria (known as rhizobia) live in root nodules on legume roots, reef-building corals contain single-celled algae, and several insect species contain bacterial endosymbionts. Many other examples of endosymbiosis exist. Many instances of endosymbiosis are obligate, where neither the endosymbiont nor the host can survive without the other, such as gutless marine worms which get nutrition from their endosymbiotic bacteria. However, not all endosymbioses are obligate. Also, some endosymbioses can be harmful to either of the organisms involved. See symbiosis for further discussion of this issue. It is generally agreed that certain organelles of the eukaryotic cell, especially mitochondria and chloroplasts, originated as bacterial endosymbionts. This theory is known as the endosymbiotic theory, confirmed and popularized by Lynn Margulis.

The endosymbiont theory and mitochondria and chloroplasts

The endoymbiont theory explains the origins of organelles such as mitochondria and chloroplasts in eukaryotic cells. Lynn Margulis of the University of Massachusetts most forcefully defended the endosymbiont theory. The theory proposes that chloroplasts and mitochondria evolved from certain types of bacteria that prokaryotic cells engulfed through endophagocytosis. These cells and the bacteria trapped inside them entered an symbiotic relationship, a close association between different types of organisms over an extended time. However, more specifically, the relationship was endosymbiotic, meaning that one of the organisms (the bacteria) lived within the other (the prokaryotic cells). According to the endosymbiont theory, an anaerobic cell probably ingested an aerobic bacterium but failed to digest it. The aerobic bacterium flourished within the cell because the cell’s cytoplasm was abundant in half-digested food molecules. The bacterium digested these molecules with oxygen and gained great amounts of energy. Because the bacterium had so much energy, it probably leaked some of it as ATP into the cell’s cytoplasm. This benefited the anaerobic cell because it enabled it to digest food aerobically. Eventually, the aerobic bacterium could no longer live independently from the cell, and it therefore became a mitochondrion. The origin of the chloroplast is very similar to that of the mitochondrion. A cell must have captured a photosynthetic cyanobacterium and failed to digest it. The cyanobacterium thrived in the cell and eventually evolved into the first chloroplast. Other eukaryotic organelles may have also evolved through endosymbiosis. Scientists believe that cilia, flagella, centrioles, and microtubules may have come from a symbiosis between a spirilla-like bacterium and an early eukaryotic cell. There are several examples of evidence that support the endosymbiont theory. Mitochondria, chloroplasts, and centrioles contain their own small supply of DNA, which may be remnants of the DNA the organelles had when they were independent aerobic bacteria. In addition, there are organisms alive today, called living intermediates, that are in a similar endosymbiotic condition to the prokaryotic cells and the aerobic bacteria. Living intermediates show that the evolution proposed by the endosymbiont theory is possible. For example, the amoeba lacks mitochondria but has aerobic bacteria that carry out a similar role. A variety of corals, clams, snails, and one species of Paramecium permanently host algae in their cells. These modern organisms with endosymbiotic relationships with aerobic bacteria suggest that the endosymbiont theory, which explains the origin of mitochondria and chloroplasts, is accurate.

Bacterial endosymbionts in marine oligochaetes

Some marine oligochaetes (e.g Olavius or Inanidrillus) have obligate extracellular endosymbionts that fill the entire body of their host. These marine worms are nutritionally dependent on their symbiotic chemoautotrophic bacteria lacking any digestive or excretory system (no gut, mouth or nephridia).

Bacterial endosymbionts in other marine invertebrates

Extracellular endosymbionts are also represented in all 5 extant classes of Echinodermata (Crinoidea, Ophiuroidea, Asteroidea, Echinoidea, and Holothuroidea). Little is known of the nature of the association (mode of infection, transmission, metabolic requirements, etc.) but phylogenetic analysis indicates that these symbionts belong to the alpha group of the class Proteobacteria, relating them to Rhizobium and Thiobacillus. Other studies indicate that these subcuticular bacteria may be both abundant within their hosts and widely distributed among the Echinoderms in general.

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists

Dinoflagellate endosymbionts of the genus Symbiodinium, commonly known as zooxanthellae, are found in corals, mollusks (esp. giant clams, the Tridacna), sponges, and foraminifera. These endosymbionts drive the amazing formation of coral reefs by capturing sunlight and providing their hosts with energy for carbonate deposition. Previously thought to be a single species, molecular phylogenetic evidence over the past couple decades has shown there to be great diversity in Symbiodinium. In some cases there is specificity between host and Symbiodinium clade. More often, however, there is a ecological distribution of Symbiodinium, the symbionts switching between hosts with apparent ease. When reefs become environmentally stressed, this distribution of symbionts is related to the observed pattern of coral bleaching and recovery. Thus the distribution of Symbiodinium on coral reefs and its role in coral bleaching presents one of the most complex and interesting current problems in reef ecology.

Bacterial obligate endosymbionts in insects

Among bacterial endosymbionts of insects, the best studied are the pea aphid Acyrthosiphon pisum and its endosymbiont Buchnera sp. APS, and the tsetse fly Glossina morsitans morsitans and its endosymbiont Wigglesworthia glossinidia brevipalpis. As with endosymbiosis in other insects, the symbiosis is obligate in that neither the bacteria nor the insect is viable without the other. Scientists have been unable to cultivate the bacteria in lab conditions outside of the insect. With special nutritionally-enhanced diets, the insects can survive, but are unhealthy, and at best survive only a few generations. The endosymbionts live in specialized insect cells called bacteriocytes (also called mycetocytes), and are maternally-transmitted, i.e. the mother transmits her endosymbionts to her offspring. In some cases, the bacteria are transmitted in the egg, as in Buchnera; in others like Wigglesworthia, they are transmitted via milk to the developing insect embryo. The bacteria are thought to help the host by either synthesizing nutrients that the host cannot make itself, or by metabolizing insect waste products into safer forms. For example, the primary role of Buchnera is thought to be to synthesize essential amino acids that the aphid cannot acquire from its natural diet of plant sap. The evidence is (1) when aphids' endosymbionts are killed using antibiotics, they appear healthier when their plant sap diet is supplemented with the appropriate amino acids, and (2) after the Buchnera genome was sequenced, analysis uncovered a large number of genes that likely code for amino acid biosynthesis genes; most bacteria that live inside other organisms do not have such genes, so their existence in Buchnera is noteworthy. Similarly, the primary role of Wigglesworthia is probably to synthesize vitamins that the tsetse fly does not get from the blood that it eats. The benefit for the bacteria is that it is protected from the environment outside the insect cell, and presumably receives nutrients from the insect. Genome sequencing reveals that obligate bacterial endosymbionts of insects have among the smallest of known bacterial genomes and have lost many genes that are commonly found in other bacteria. Presumably these genes are not needed in the environment of the host insect cell. (A complementary theory as to why the bacteria may have lost genes, Muller's ratchet, is that since the endosymbionts are maternally transmitted and have no opportunity to exchange genes with other bacteria, it is more difficult to keep good genes in all individuals in a population of these endosymbionts.) Research in which a parallel phylogeny of bacteria and insects was inferred supports the belief that the obligate endosymbionts are transferred only vertically (i.e. from the mother), and not horizontally (i.e. by escaping the host and entering a new host). Attacking obligate bacterial endosymbionts may present a way to control their insect hosts, many of which are pests or carriers of human disease. For example aphids are crop pests and the tsetse fly carries the organism (trypanosome protozoa) that causes African sleeping sickness. Other motivations for their study is to understand symbiosis, and to understand how bacteria with severely depleted genomes are able to survive, thus improving our knowledge of genetics and molecular biology.

References

Obligate bacterial endosymbiosis in marine oligochaetes:


- Endosymbiotic sulphate-reducing and sulphide-oxidizing bacteria in an oligochaete worm. Dubilier N., Mülders C.,Ferdelman T., De Beer D.,Pernthaler A.,Klein M., Wagner M., Erseus C., Thiermann F., Krieger J., Giere O & Amann R. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11357130

Bacterial endosymbionts in echinoderms:


- Subcuticular bacteria from the brittle star Ophiactis balli (Echinodermata: Ophiuroidea) represent a new lineage of extracellular marine symbionts in the alpha subdivision of the class Proteobacteria. Burnett, W J and J D McKenzie http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=168468&rendertype=abstract

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists


- Excellent review paper covering the role of Symbiodinium in reef ecology and the current state of research: [http://arjournals.annualreviews.org/doi/abs/10.1146%2Fannurev.ecolsys.34.011802.132417?cookieSet=1 FLEXIBILITY AND SPECIFICITY IN CORAL-ALGAL SYMBIOSIS: Diversity, Ecology, and Biogeography of Symbiodinium. Andrew C. Baker, Annual Review of Ecology, Evolution, and Systematics 2003 34, 661-689]

Obligate bacterial endosymbionts in insects:


- PLOS Biology Primer- Endosymbiosis: lessons in conflict resolution http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020068
- A general review of bacterial endosymbionts in insects. P. Baumann, N. A. Moran and L. Baumann, Bacteriocyte-associated endosymbionts of insects in M. Dworkin, ed., The prokaryotes, Springer, New York, 2000. http://link.springer.de/link/service/books/10125/
- An excellent review of insect endosymbionts that focuses on genetic issues. Jennifer J. Wernegreen (2002), Genome evolution in bacterial endosymbionts of insects, Nature Reviews Genetics, 3, pp. 850-861. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12415315&dopt=Abstract
- A review article on aphids and their bacterial endosymbionts. A. E. Douglas (1998), Nutritional interactions in insect-microbial symbioses: Aphids and Their Symbiotic Bacteria Buchnera, Annual Reviews of Entomology, 43, pp. 17-37.
- Describes possible methods to control the human pathogen causing African sleeping sickness, which is transmitted by tsetse flies. Focuses on methods using the primary and secondary endosymbionts of the tsetse fly. Serap Aksoy, Ian Maudlin, Colin Dale, Alan S. Robinsonand and Scott L. O’Neill (2001), Prospects for control of African trypanosomiasis by tsetse vector, TRENDS in Parasitology, 17 (1), pp. 29-35. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11137738&dopt=Abstract
- Announces and analyzes the full genome sequence of Buchnera sp. APS, the endosymbiont of the pea aphid, and the first endosymbiont to have its genome sequenced. S. Shigenobu, H. Watanabe, M. Hattori, Y. Sakaki and H. Ishikawa (2000), Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS, Nature, 407, pp. 81-86. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10993077&dopt=Abstract
- An article that discusses one theory on how obligate endosymbionts may have their genomes degraded, in a freely-available journal. Nancy A. Moran (1996), Accelerated evolution and Muller’s ratchet in endosymbiotic bacteria, Proceedings of the National Academy of Sciences of the USA, 93, pp. 2873-2878. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8610134&dopt=Abstract Category:Symbiosis

Exocrine

Exocrine gland refers to glands that secrete their products via a duct. This is as opposed to endocrine glands that release their products directly into the circulatory system via the capillary network. Typical exocrine glands include sweat glands, salivary glands, mammary glands and many glands of the digestive system.

Types

Exocrine glands are named apocrine, holocrine, or merocrine based on how their product is secreted.
- Apocrine glands - a portion of the secreting cell's body is lost during secretion. Apocrine gland is often used to refer to the apocrine sweat glands.
- Holocrine glands - the entire cell disintegrates to secrete its substances.
- Merocrine glands - cells secrete their substances by exocytosis. Category:Exocrine glands Category:Integumentary system

Amphiprion

Twenty-seven, including:
Amphiprion allardi - Allard's Clownfish
Amphiprion melanopus - Cinnamon Clownfish
Amphiprion clarkii - Clark's Anemonefish
Amphiprion ocellaris - Ocellaris Clownfish
Amphiprion percula - Percula Clownfish
Amphiprion perideraion - Pink Skunk Clownfish
Amphiprion polymnus - Saddleback Clownfish
Amphiprion sebae - Sebae Clownfish
Amphiprion tricinctus - Three-Band Anemonefish
Amphiprion ephippium - Tomato Clownfish
Amphiprion frenatus - Fire Clownfish
Amphiprion chrysopterus - Orange-fin Anemonefish
Amphiprion akallopisos - Skunk Clownfish
Amphiprion nigripes - Black-footed Clownfish
Amphiprion sandaracinos - Orange Skunk Clownfish
Amphiprion rubacinctus - Australian Clownfish
Premnas biaculeatus - Maroon Clownfish The Clownfish, or Anemonefish, are the subfamily Amphiprioninae of the family Pomacentridae. There are currently 27 species, of which one is in the genus Premnas and the rest are in the subfamily's type genus Amphiprion. The other pomacentrids are called damselfish. Clownfish are native to wide ranges of the warm waters of the Pacific; some species ranges overlap others. Clownfish are not found in the Atlantic. Clownfish live in a mutual relationship with sea anemones, or in some case settle in some varieties of soft corals, or large polyp stony corals. Once an anemone or coral has been adopted, the clownfish will defend it vigorously. However, clownfish in an aquarium environment can exist very well without an anemone, or with a . (This may be advisable as most anemones are extremely difficult to keep alive even for experienced aquarists.) The anemone is required in nature because reef life is dangerous for small, brightly colored fish with very poor swimming abilities; in an aquarium lacking predators it is not needed. For this reason, Clownfish never stray far from their host. In an aquarium, where they don't have to forage for food, it is very common for Clownfish to remain within 6-12 inches of their host for an entire lifetime. Clownfish and Damselfish are the only species of fish which can avoid the stings of an anemone, which can be quite potent. The exact mechanism by which this is accomplished is the subject of debate, and there are several theories which may all be partly responsible. The details of these theories are complex, but they fall into two major categories. One theory is that their slime coating is based on sugar rather than proteins so anemones fail to recognize the fish as food and do not fire their nematocysts, or sting organelles. A similar theory is that the mucous coating mimicks the anemone's own coating, a theory that is bolstered by the fact that it takes several days for a Clownfish to adapt to a new species of anemone. There is no acclimation period when a Clownfish is moved to another anemone of the same species. It is interesting to note that not all anemones make suitable hosts--many can and will sting and eat Clownfish. Also, particular species of clownfish will only use particular species of host anemones in nature. In captivity, certain Clownfish species will adapt to certain other anemone species, but not many. Another likely possibility is that their unique movements, which are unlike any other fish, let the anemone know that they are not food. This theory is bolstered by the fact that juvenile Clownfish, which have no coating, will immediately seek refuge in any compatible anemone and will not be stung. Juvenile clownfish will not survive for long without the protection of an anemone, and few actually find one before being eaten. Clownfish are among the few marine fish that can be bred in captivity in commercially-viable quantities at the time of this writing. Hobbyists are advised to purchase captive-born clownfish (and other marine animals) whenever possible. The Amphiprions are attractive in colour and usually wear bright colours. Example: orange, black, and white. They are good for a marine aquarium because they are friendly and easy to feed. They adapt well in captivity and can be easily studied for scientific research. Clownfish lay eggs on any flat surface close to or under protection of their host anemones. These eggs are cared for by the male and hatched under complete darkness after a period of 7 to 10 days. Hatching occurs in a natural rhythm directly connected to the phases of the moon. Clownfish are omnivorous, their diets range from flakes to meat. They feed mostly on copepods and mysids, the undigested excrement from their host anemones. Clownfish are relatively small organisms, fish in aquaria can grow to 9 cm (3.5 inches) in length, fish in the wild can grow to a length of 12 cm (5 inches). The maximum size varies by species, with males being significantly smaller than females. captivity

Reproduction

Clownfish are protandrous hermaphrodites, meaning they are hatched as sexually immature fry. Based on signals from their environment and being physically mature (12-24 months) they will either remain sexually immature, change into a male or change into a male then female. A group of clownfish is always built into a hierarchy of this type, with the female (the largest and most aggressive) at the top. The change from juvenile to male, and male to female is irreversible. If the female should die or be removed from the group, the most dominant male then changes into a female, and the rest of the males move up a rank on the hierarchy. In typical home aquaria, a juvenile only several months old can make the change from juvenile to male to female in as little as a month. Because of this, pairing clownfish can be a tricky proposition, as most hobbyists tend to select the largest and most dominant specimen (presumably a female) to mate with their own female. Usually two females will tend to fight regularly, and frequently lock jaws (some hobbyists describe it as kissing). In a successful pair, the male will exhibit submissive behavior. Usually, this behavior entails the more aggressive female darting at the male, and the male turning sideways and quivering. captivity Most common species of clownfish (A. ocellaris, A. percula etc.) are fairly easy to breed in the home aquarium. The female will be the larger of the pair, and the two fish will usually stay close to each other in one area of the tank or in a host anemone. After several months in a successful pair, the fish will begin spawning. The female's abdomen will bulge with eggs, ready to be deposited. She will usually find a flat surface near her host anemone (if present) to lay her eggs before they can be fertilized by the male. The eggs will normally hatch in 6-11 days depending on temperature and other water parameters. In home aquaria, the fry must be reared in a separate aquarium on a diet of rotifers then baby brine shrimp to have any chance of survival.

References in media

Clownfish featured prominently in the 2003 Pixar-animated movie Finding Nemo. Despite the content of the movie - wherein a young clownfish's father must rescue his son after being taken as a aquarists pet - public demand for clownfish as pets has tripled shortly after its release. Some environmental protection activists regard this as a catastrophe as clownfish are already facing the threat of extinction due to a reduction of their natural habitat (coral reefs) which in turn is due to global climate changes as well as pollution of the seas. It is also feared that people may have attempted to send fish back into the open sea by flushing them down the toilet as demonstrated in the film; they will however not be able to survive the canalisation or the sewage plant. Another problem is that many buyers lack basic knowledge and understanding to take care of such speciality fish. Category:Pomacentridae Category:Symbiosis ko:흰동가리

Sea anemone


- Suborder Endocoelantheae
  - Family Actinernidae
  - Family Halcuriidae
- Suborder Nyantheae
  - Infraorder Athenaria
    - Family Andresiidae
    - Family Andwakiidae
    - Family Edwardsiidae
    - Family Galatheanthemidae
    - Family Halcampidae
    - Family Halcampoididae
    - Family Haliactiidae
    - Family Haloclavidae
    - Family Ilyanthidae
    - Family Limnactiniidae
    - Family Octineonidae
  - Infraorder Boloceroidaria
    - Family Boloceroididae
    - Family Nevadneidae
  - Infraorder Thenaria
    - Family Acontiophoridae
    - Family Actiniidae
    - Family Actinodendronidae
    - Family Actinoscyphiidae
    - Family Actinostolidae
    - Family Aiptasiidae
    - Family Aiptasiomorphidae
    - Family Aliciidae
    - Family Aurelianidae
    - Family Bathyphelliidae
    - Family Condylanthidae
    - Family Diadumenidae
    - Family Discosomidae
    - Family Exocoelactiidae
    - Family Haliplanellidae
    - Family Hormathiidae
    - Family Iosactiidae
    - Family Isanthidae
    - Family Isophelliidae
    - Family Liponematidae
    - Family Metridiidae
    - Family Minyadidae
    - Family Nemanthidae
    - Family Paractidae
    - Family Phymanthidae
    - Family Sagartiidae
    - Family Sagartiomorphidae
    - Family Stichodactylidae
    - Family Thalassianthidae
- Suborder Protantheae
  - Family Gonactiniidae
- Suborder Ptychodacteae
  - Family Preactiidae
  - Family Ptychodactiidae Named after a terrestrial flower, the anemone, the sea anemone is a group of water-dwelling, filter feeding animals of the order Actinaria. As a cnidarian, it is closely related to coral and jellyfish. The anemone is a (usually) solitary polyp with stinging cells (cnidocytes) in its tentacles. These stinging cells serve to paralyze and capture the prey, which is then moved by the tentacles to the mouth for digestion inside a central cavity. cnidocyte (Heteractis magnifica) home]] cnidocyte cnidocyte Other close relations to the sea anemone are the solitary, tube-dwelling anemones and the hydras. The sea anemone has a foot which in most species attaches itself to rocks or anchors in the sand. Some species attach to kelp and others are free-swimming. Although not plants and therefore incapable of photosynthesis themselves, many sea anemones form an important symbiosis with certain single-celled green algae species which reside in the animals' gastrodermal cells. These algae may be either zooxanthellae, zoochlorellae or both. The sea anemone benefits from the products of the algae's photosynthesis, namely oxygen and food in the form of glycerol, glucose and alanine; the algae in turn are assured a reliable exposure to sunlight, which the anemones actively maintain. The preponderance of species inhabit tropical reefs, although there are species adapted to relatively cold waters, intertidal reefs, and sand/kelp environments. Some sea anemones form symbiotic relationships with crabs and anemone fish, also known as clownfish. In the former situation, anemones will either attach or be attached to the shell of a hermit crab (by the crab's own volition), providing additional protection for the crab and allowing the anemone to eat scraps when the crab feeds. A similar relationship can be formed between a sea anemone and a clownfish. The clownfish presses itself into the anemone, living comfortably within the stinging tentacles: This is possible because of a protective mucus that covers the clownfish. The clownfish benefits from this symbiotic relationship because it is protected by the anemone. The anemone benefits because the anemone gets food scraps from the clownfish. Category:Cnidarians ja:イソギンチャク

Goby

Many, e.g.
Amblyeleotris
Gobius
Pomatoschistus
Microgobius
Periophthalmus The Gobies form the family Gobiidae, and are one of the largest families of fish, with over 2000 known species. Most are relatively small, typically less than 10 cm (4 in) in length. The smallest vertebrates in the world are gobies of the genera Trimmatom and Pandaka, which are under 1 cm (3/8 in) long when fully grown. There are some large gobies, such as species of Gobioides, that can reach well over 30 cm (1 ft) in length, but that is exceptional. Although few are important as food for humans, they are of great significance as prey species for commercially important fish like cod, haddock, sea bass, and flatfish. Several gobies are also of interest as aquarium fish, in particular the bumblebee gobies of the genus Brachygobius. The most distinctive aspect of goby morphology are the fused pelvic fins that form a disc-shaped sucker. In function this sucker is analogous to the dorsal fin sucker possessed by the remora or the pelvic fin sucker that the lumpfish has, but is anatomically a quite distinct structure, and thus any similarities are the product of convergent evolution. Gobies can often be seen using the sucker to adhere to rocks and corals, and in aquaria they will happily stick to glass walls of the tank as well. convergent evolution Gobies are primarily fish of shallow marine habitats including tide pools, coral reefs, and seagrass meadows; they are also very numerous in brackish water and estuarine habitats including the lower reaches of rivers, mangrove swamps, and salt marshes. A small number of gobies (unknown exactly, but in the low hundreds) are also fully adapted to freshwater environments. These include the Asian river gobies (Rhinogobius spp.), the desert gobies of Australia (Redigobius), and the European freshwater goby Padagobius martensii.

Mudskippers

Highly specialised members of the family are the mudskippers, usually ascribed to the subfamily Oxudercinae; these gobies are able to survive for extended periods on land through a combination of behavioural and physiological adaptations, including pectoral fins that act as simple legs; the ability to breathe through their skins (like frogs); and the digging of damp burrows to avoid drying out. Periophthalmus argentilineatus (= Periophthalmus barbarus) is one of the most widespread mudskippers and can be found in mangroves and mudflats of East Africa and Madagascar east through South East Asia to Australia, Hong Kong and Japan. It grows to a length of about 6 in (15 cm) and feeds on small crabs and other crustaceans. It will also eat mosquito larvae and small fish that it can catch.

Symbiosis

convergent evolution Some goby species live in symbiosis with burrowing shrimps. The shrimp maintains a burrow in the sand in which both the shrimp and the goby fish live. The shrimp has poor eyesight compared to the goby, but if it sees or feels the goby suddenly swim into the burrow, it will follow. The goby and shrimp keep in contact with each other, the shrimp using its antennae, and the goby flicking the shrimp with its tail when alarmed. These gobies are thus sometimes known as 'watchman gobies'. Another example of symbiosis is demonstrated by the neon gobies (Gobiosoma spp.). These gobies are cleaner fish, and remove parasites from the skin, fins, mouth, and gills of a wide variety of large fish. The most remarkable aspect of this symbiosis is that many of the fish that visit the cleaner gobies' cleaning station would otherwise treat such small fish as food (for example groupers and snappers).

Sleeper Gobies

Sleeper gobies belong to the family Eleotridae that is closely related to the Gobiidae. Like the true gobies they are generally small, mostly marine fish that live on the substrate, often amongst vegetation, in burrows, or in crevices within rocks and coral reefs. Although goby-like in many ways, sleeper gobies lack the pelvic fin sucker, and that, together with other morphological differences, is used to distinguish the two families. It is widely believed that the Gobiidae and Eleotridae share a common ancestor, and they are both placed in the order Gobioidei, along with a few other small families containing goby-like fishes. Dormitator and Eleotris are two of the most widespread and typical genera, including a variety of species that inhabit marine, estuarine, and freshwater habitats. Dormitator maculatus for example grows to about 1 ft (30 cm) and is widely found in brackish and shallow marine waters of the South Eastern United States and Mexico. There are some predatory sleeper gobies that get much bigger, such as the marbled sleeper goby, Oxyeleotris marmorata, a freshwater species from South East Asia that can grow up to 2 ft (60 cm) long. However, most are much smaller, such as the fresh and brackish water species from Australia like Hypseleotris spp., known locally as gudgeons (not to be confused with the Eurasian freshwater cyprinid Gobio gobio, also known as the gudgeon).

See also


- List of fish common names
- List of fish families
- Dragonet (a similar family often confused with gobies)

External link


- [http://www.fishbase.org/Summary/FamilySummary.cfm?ID=405 FishBase entry on Gobiidae]
- [http://www.gobiidae.com Gobioid Research Institute]
- [http://homepage2.nifty.com/PhD-mukai/ Takahiko Mukai's Encyclopaedia of Goby (mostly Japanese)]
- [http://www.ozemail.com.au/~thebobo/goby.htm Richard Mleczko's Mudskipper & Goby Page]
- [http://www.wetwebmedia.com/clnrfaqs.htm Article on cleaner gobies in aquaria]
- [http://homepage.mac.com/nmonks/aquaria/brackfaqpart6.html#gobiidae Brackish Water Aquarium FAQ entry on gobies]
- Category:Symbiosis zh-min-nan:Khōng-khiang-á ja:ハゼ

Egyptian Plover


The Egyptian Plover, Pluvianus aegyptius, is a wader, the only member of the genus Pluvianus (Vieillot, 1816). Formerly placed in its own monotypic family Pluvianidae, it is now regarded as the sole member of the subfamily Pluvianinae, part of the pratincole and courser family, Glareolidae. It is also sometimes referred to as the Crocodile Bird because it is famous for its quasi-symbiotic relationship with crocodiles, wherein the crocodiles lay on the shore with their mouths open, and the plovers fly into the crocodiles' mouths so as to feed on bits of decaying meat that are lodged between the crocodiles' teeth. The crocodiles do not eat the plovers, as the plovers are providing the crocodiles with greatly-needed dentistry. Egyptian Plover is a localised resident in tropical sub-Saharan Africa. It breeds on sandbars in large rivers. Its two or three eggs are not incubated, but are buried in warm sand, temperature control being achieved by the adult sitting on the eggs with a water-soaked belly to cool them. The chicks are precocial, and can run as soon as they are hatched, but the adults will bury them in the sand temporarily if danger threatens. Egyptian Plover is a striking and unmistakable species. The 19-21 cm long adult has a black crown, back, eye-mask and breast band. The rest of the head is white. The remaining upperpart plumage is blue-grey, and the underparts are orange. The longish legs are blue-grey. In flight, it is even more spectacular, with the black crown and back contrasting with the grey of the upperparts and wings. The flight feathers are brilliant white crossed by a black bar. From below, the flying bird is entirely white, apart from the orange belly and black wing bar. The sexes are similar, but juveniles are duller and the black marking are intermixed with brown. This usually very tame bird is found in pairs or small groups near water. It feeds by pecking for insects, and by extracting fragments of meat from between crocodile teeth. The call is a high-pitched krrr-krrr-krrr.

Reference

Shorebirds by Hayman, Marchant and Prater ISBN 0-7099-2034-2 Category:Glareolidae

Parasite

A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host, but without immediately killing the host. The biological interaction between the host and the parasite is called parasitism. Parasitism is a type of symbiosis, by one definition, although another definition of symbiosis excludes parasitism, since certain types of DNA, such as transposable elements and B chromosomes, may also be considered as parasites of the host genome. Some organisms are parasitic only during a part of their lifecycle. Many cuckoos, for example, are brood parasites: their young are parasitic on the host species, but adult cuckoos fend for themselves.

Examples


- Endoparasites (endo = within; parasites that live inside their hosts)
  - Plants
    - Rafflesia
  - Animals
    - Acanthocephala
    - Candiru (Vampire fish of Brazil)
    - Clonorchis sinensis (the Chinese liver fluke)
    - Cymothoa exigua
    - Dracunculiasis (Guinea Worm Disease)
    - Enterobius vermicularis
    - Strepsiptera
    - Strongyloides stercoralis
  - Fungi (such as ringworm)
    - Gymnosporangium and other rusts
  - Protists (Protozoa)
    - Plasmodium (malarias)
    - Kinetoplastid protists of the Trypanosoma and Leishmania genera (sleeping sickness, Chagas disease and leishmania)
    - Balantidium coli (the only ciliated protozoan to infect humans)
    - Giardia lamblia (the most common intestinal protozoan in the United States)
    - Entamoeba histolytica (causes Amebiasis, common in developing countries)
- Ectoparasites (ecto = outside; parasites that live on but not within their hosts, for example, attached to their skin)
  - Plants
    - Cuscuta
    - Mistletoe
    - Toothwort
    - The wood rose, Dactylanthus taylorii
  - Animals
    - Hirudinea (some leeches)
    - Phthiraptera (Lice)
    - Siphonaptera (Fleas)
    - Acarina (Ticks)
    - Tantulocarida

See also


- Intestinal parasite
- Saprophyte
- Malarial parasite
- Teratology
- Successful parasite

References


- Centers for Disease Control and Prevention
  - [http://www.cdc.gov/ncidod/dpd/ Division of Parasitic Diseases]
    - [http://www.dpd.cdc.gov/dpdx/ DPDx] - Laboratory Identification of Parasites of Public Health Concern - Reference and Training as well as Diagnostic Assistance Category:Parasitology Category:Ecology ko:기생충 ja:寄生虫

Lynn Margulis

Lynn Margulis (born 1938) is a biologist and a professor at the University of Massachusetts Amherst. In 1967 she proposed a contentious new hypothesis which became her most important scientific contribution as the endosymbiotic theory of the origin of mitochondria as separate organisms that long ago entered a symbiotic relationship with eukaryotic cells through endosymbiosis. :"She is best known for her theory of symbiogenesis, which challenges a central tenet of neodarwinism. She argues that inherited variation, significant in evolution, does not come mainly from random mutations. Rather new tissues, organs, and even new species evolve primarily through the long-lasting intimacy of strangers. The fusion of genomes in symbioses followed by natural selection, she suggests, leads to increasingly complex levels of individuality." [http://www.geo.umass.edu/faculty/margulis/] :"After the proposal of the endosymbiotic theory, Margulis predicted that if organelles were prokaryotic symbionts, then the organelles will have their own DNA that would be different from the DNA of the cell. This prediction was actually proven in the 1980's in mitochondria, centrioles, and chloroplasts." [http://www.immaculata.edu/bioinformatics/esehi/lynn%20margulis.htm] She was criticized as a radical and her scientific work was rejected by mainstream biology for many years. Her work has more recently received widespread support and acclaim. Prominent evolutionary biologist Richard Dawkins recently [http://www.edge.org/documents/ThirdCulture/n-Ch.7.html said] that her theory that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells "is one of the great achievements of twentieth-century evolutionary biology, and I greatly admire her for it." Margulis was inducted into the World Academy of Art and Science, the Russian Academy of Natural Sciences, and the American Academy of Arts and Sciences between 1995 and 1998. She is also a proponent and co-developer of the modern version of Gaia theory, based on an idea developed by the English atmospheric scientist James Lovelock. She was the first wife of astronomer Carl Sagan and is the mother of Dorion Sagan, popular science writer and co-author, Jeremy Sagan, software developer and founder of Sagan Technology, Zachary Margulis, lawyer and Jennifer Margulis, teacher and author.

Publications and bibliography


- Margulis, Lynn, 1970, Origin of Eukaryotic Cells, Yale University Press, ISBN 0300013531
- Margulis, Lynn, 1982, Early Life, Science Books International, ISBN 0867200057
- Margulis, Lynn and Dorion Sagan, 1986, Origins of Sex : Three Billion Years of Genetic Recombination, Yale University Press, ISBN 0300033400
- Margulis, Lynn and Dorion Sagan, 1987, Microcosmos: Four Billion Years of Evolution from Our Microbial Ancestors, HarperCollins, ISBN 004570015X
- Margulis, Lynn and Dorion Sagan, 1991, Mystery Dance: On the Evolution of Human Sexuality, Summit Books, ISBN 0671633414
- Margulis, Lynn, ed, 1991, Symbiosis as a Source of Evolutionary Innovation: Speciation and Morphogenesis, The MIT Press, ISBN 0262132699
- Margulis, Lynn, 1992, Symbiosis in Cell Evolution: Microbial Communities in the Archean and Proterozoic Eons, W.H. Freeman, ISBN 0716770288
- Margulis, Lynn and Dorion Sagan, 1997, Slanted Truths: Essays on Gaia, Symbiosis, and Evolution, Copernicus Books, ISBN 0387949275
- Lynn Margulis and Karlene V. Schwartz, 1997, Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth, W.H. Freeman & Company, ISBN 0613923383
- Margulis, Lynn, 1998, Symbiotic Planet : A New Look at Evolution, Basic Books, ISBN 0465072712
- Margulis, Lynn and Dorion Sagan, 2002, Acquiring Genomes: A Theory of the Origins of Species, Perseus Books Group, ISBN 0465043917
- Margulis, Lynn, et. al., 2002, The Ice Chronicles: The Quest to Understand Global Climate Change, University of New Hampshire, ISBN 1584650621

External links


- [http://www.bio.umass.edu/faculty/biog/margulis.html UMass Bio Dept. (includes a partial list of technical publications)] Accessed 3/11/05.
- [http://www.geo.umass.edu/faculty/margulis/ UMass Geo Dept.] Accessed 3/11/05.
- [http://www.immaculata.edu/bioinformatics/esehi/lynn%20margulis.htm www.immaculata.edu] Accessed 3/11/05.
- [http://www.isepp.org/Pages/San%20Jose%2004-05/MargulisSaganSJ.html San Jose Science, Technology and Society, 2004-2005 Linus Pauling Memorial Lectures] Accessed 3/11/05.
- [http://www.biology.iupui.edu/biocourses/N100/2k2endosymb.html The Endosymbiotic Theory] Accessed 3/11/05.
- [http://www.edge.org/documents/ThirdCulture/n-Ch.7.html Gaia Is a Tough Bitch]
- [http://blog.connectingforchange.org/wp-content/podcasts/lynnmargulis.mp3 Interview with Lynn Margulis on Gaia] 5 minute MP3 from October 2005 Margulis, Lynn Margulis, Lynn ko:린 마굴리스 ja:リン・マーギュリス

Endosymbiosis

An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis (Greek: endo = inner and biosis = living). For instance, some nitrogen fixing bacteria (known as rhizobia) live in root nodules on legume roots, reef-building corals contain single-celled algae, and several insect species contain bacterial endosymbionts. Many other examples of endosymbiosis exist. Many instances of endosymbiosis are obligate, where neither the endosymbiont nor the host can survive without the other, such as gutless marine worms which get nutrition from their endosymbiotic bacteria. However, not all endosymbioses are obligate. Also, some endosymbioses can be harmful to either of the organisms involved. See symbiosis for further discussion of this issue. It is generally agreed that certain organelles of the eukaryotic cell, especially mitochondria and chloroplasts, originated as bacterial endosymbionts. This theory is known as the endosymbiotic theory, confirmed and popularized by Lynn Margulis.

The endosymbiont theory and mitochondria and chloroplasts

The endoymbiont theory explains the origins of organelles such as mitochondria and chloroplasts in eukaryotic cells. Lynn Margulis of the University of Massachusetts most forcefully defended the endosymbiont theory. The theory proposes that chloroplasts and mitochondria evolved from certain types of bacteria that prokaryotic cells engulfed through endophagocytosis. These cells and the bacteria trapped inside them entered an symbiotic relationship, a close association between different types of organisms over an extended time. However, more specifically, the relationship was endosymbiotic, meaning that one of the organisms (the bacteria) lived within the other (the prokaryotic cells). According to the endosymbiont theory, an anaerobic cell probably ingested an aerobic bacterium but failed to digest it. The aerobic bacterium flourished within the cell because the cell’s cytoplasm was abundant in half-digested food molecules. The bacterium digested these molecules with oxygen and gained great amounts of energy. Because the bacterium had so much energy, it probably leaked some of it as ATP into the cell’s cytoplasm. This benefited the anaerobic cell because it enabled it to digest food aerobically. Eventually, the aerobic bacterium could no longer live independently from the cell, and it therefore became a mitochondrion. The origin of the chloroplast is very similar to that of the mitochondrion. A cell must have captured a photosynthetic cyanobacterium and failed to digest it. The cyanobacterium thrived in the cell and eventually evolved into the first chloroplast. Other eukaryotic organelles may have also evolved through endosymbiosis. Scientists believe that cilia, flagella, centrioles, and microtubules may have come from a symbiosis between a spirilla-like bacterium and an early eukaryotic cell. There are several examples of evidence that support the endosymbiont theory. Mitochondria, chloroplasts, and centrioles contain their own small supply of DNA, which may be remnants of the DNA the organelles had when they were independent aerobic bacteria. In addition, there are organisms alive today, called living intermediates, that are in a similar endosymbiotic condition to the prokaryotic cells and the aerobic bacteria. Living intermediates show that the evolution proposed by the endosymbiont theory is possible. For example, the amoeba lacks mitochondria but has aerobic bacteria that carry out a similar role. A variety of corals, clams, snails, and one species of Paramecium permanently host algae in their cells. These modern organisms with endosymbiotic relationships with aerobic bacteria suggest that the endosymbiont theory, which explains the origin of mitochondria and chloroplasts, is accurate.

Bacterial endosymbionts in marine oligochaetes

Some marine oligochaetes (e.g Olavius or Inanidrillus) have obligate extracellular endosymbionts that fill the entire body of their host. These marine worms are nutritionally dependent on their symbiotic chemoautotrophic bacteria lacking any digestive or excretory system (no gut, mouth or nephridia).

Bacterial endosymbionts in other marine invertebrates

Extracellular endosymbionts are also represented in all 5 extant classes of Echinodermata (Crinoidea, Ophiuroidea, Asteroidea, Echinoidea, and Holothuroidea). Little is known of the nature of the association (mode of infection, transmission, metabolic requirements, etc.) but phylogenetic analysis indicates that these symbionts belong to the alpha group of the class Proteobacteria, relating them to Rhizobium and Thiobacillus. Other studies indicate that these subcuticular bacteria may be both abundant within their hosts and widely distributed among the Echinoderms in general.

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists

Dinoflagellate endosymbionts of the genus Symbiodinium, commonly known as zooxanthellae, are found in corals, mollusks (esp. giant clams, the Tridacna), sponges, and foraminifera. These endosymbionts drive the amazing formation of coral reefs by capturing sunlight and providing their hosts with energy for carbonate deposition. Previously thought to be a single species, molecular phylogenetic evidence over the past couple decades has shown there to be great diversity in Symbiodinium. In some cases there is specificity between host and Symbiodinium clade. More often, however, there is a ecological distribution of Symbiodinium, the symbionts switching between hosts with apparent ease. When reefs become environmentally stressed, this distribution of symbionts is related to the observed pattern of coral bleaching and recovery. Thus the distribution of Symbiodinium on coral reefs and its role in coral bleaching presents one of the most complex and interesting current problems in reef ecology.

Bacterial obligate endosymbionts in insects

Among bacterial endosymbionts of insects, the best studied are the pea aphid Acyrthosiphon pisum and its endosymbiont Buchnera sp. APS, and the tsetse fly Glossina morsitans morsitans and its endosymbiont Wigglesworthia glossinidia brevipalpis. As with endosymbiosis in other insects, the symbiosis is obligate in that neither the bacteria nor the insect is viable without the other. Scientists have been unable to cultivate the bacteria in lab conditions outside of the insect. With special nutritionally-enhanced diets, the insects can survive, but are unhealthy, and at best survive only a few generations. The endosymbionts live in specialized insect cells called bacteriocytes (also called mycetocytes), and are maternally-transmitted, i.e. the mother transmits her endosymbionts to her offspring. In some cases, the bacteria are transmitted in the egg, as in Buchnera; in others like Wigglesworthia, they are transmitted via milk to the developing insect embryo. The bacteria are thought to help the host by either synthesizing nutrients that the host cannot make itself, or by metabolizing insect waste products into safer forms. For example, the primary role of Buchnera is thought to be to synthesize essential amino acids that the aphid cannot acquire from its natural diet of plant sap. The evidence is (1) when aphids' endosymbionts are killed using antibiotics, they appear healthier when their plant sap diet is supplemented with the appropriate amino acids, and (2) after the Buchnera genome was sequenced, analysis uncovered a large number of genes that likely code for amino acid biosynthesis genes; most bacteria that live inside other organisms do not have such genes, so their existence in Buchnera is noteworthy. Similarly, the primary role of Wigglesworthia is probably to synthesize vitamins that the tsetse fly does not get from the blood that it eats. The benefit for the bacteria is that it is protected from the environment outside the insect cell, and presumably receives nutrients from the insect. Genome sequencing reveals that obligate bacterial endosymbionts of insects have among the smallest of known bacterial genomes and have lost many genes that are commonly found in other bacteria. Presumably these genes are not needed in the environment of the host insect cell. (A complementary theory as to why the bacteria may have lost genes, Muller's ratchet, is that since the endosymbionts are maternally transmitted and have no opportunity to exchange genes with other bacteria, it is more difficult to keep good genes in all individuals in a population of these endosymbionts.) Research in which a parallel phylogeny of bacteria and insects was inferred supports the belief that the obligate endosymbionts are transferred only vertically (i.e. from the mother), and not horizontally (i.e. by escaping the host and entering a new host). Attacking obligate bacterial endosymbionts may present a way to control their insect hosts, many of which are pests or carriers of human disease. For example aphids are crop pests and the tsetse fly carries the organism (trypanosome protozoa) that causes African sleeping sickness. Other motivations for their study is to understand symbiosis, and to understand how bacteria with severely depleted genomes are able to survive, thus improving our knowledge of genetics and molecular biology.

References

Obligate bacterial endosymbiosis in marine oligochaetes:


- Endosymbiotic sulphate-reducing and sulphide-oxidizing bacteria in an oligochaete worm. Dubilier N., Mülders C.,Ferdelman T., De Beer D.,Pernthaler A.,Klein M., Wagner M., Erseus C., Thiermann F., Krieger J., Giere O & Amann R. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11357130

Bacterial endosymbionts in echinoderms:


- Subcuticular bacteria from the brittle star Ophiactis balli (Echinodermata: Ophiuroidea) represent a new lineage of extracellular marine symbionts in the alpha subdivision of the class Proteobacteria. Burnett, W J and J D McKenzie http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=168468&rendertype=abstract

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists


- Excellent review paper covering the role of Symbiodinium in reef ecology and the current state of research: [http://arjournals.annualreviews.org/doi/abs/10.1146%2Fannurev.ecolsys.34.011802.132417?cookieSet=1 FLEXIBILITY AND SPECIFICITY IN CORAL-ALGAL SYMBIOSIS: Diversity, Ecology, and Biogeography of Symbiodinium. Andrew C. Baker, Annual Review of Ecology, Evolution, and Systematics 2003 34, 661-689]

Obligate bacterial endosymbionts in insects:


- PLOS Biology Primer- Endosymbiosis: lessons in conflict resolution http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020068
- A general review of bacterial endosymbionts in insects. P. Baumann, N. A. Moran and L. Baumann, Bacteriocyte-associated endosymbionts of insects in M. Dworkin, ed., The prokaryotes, Springer, New York, 2000. http://link.springer.de/link/service/books/10125/
- An excellent review of insect endosymbionts that focuses on genetic issues. Jennifer J. Wernegreen (2002), Genome evolution in bacterial endosymbionts of insects, Nature Reviews Genetics, 3, pp. 850-861. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12415315&dopt=Abstract
- A review article on aphids and their bacterial endosymbionts. A. E. Douglas (1998), Nutritional interactions in insect-microbial symbioses: Aphids and Their Symbiotic Bacteria Buchnera, Annual Reviews of Entomology, 43, pp. 17-37.
- Describes possible methods to control the human pathogen causing African sleeping sickness, which is transmitted by tsetse flies. Focuses on methods using the primary and secondary endosymbionts of the tsetse fly. Serap Aksoy, Ian Maudlin, Colin Dale, Alan S. Robinsonand and Scott L. O’Neill (2001), Prospects for control of African trypanosomiasis by tsetse vector, TRENDS in Parasitology, 17 (1), pp. 29-35. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11137738&dopt=Abstract
- Announces and analyzes the full genome sequence of Buchnera sp. APS, the endosymbiont of the pea aphid, and the first endosymbiont to have its genome sequenced. S. Shigenobu, H. Watanabe, M. Hattori, Y. Sakaki and H. Ishikawa (2000), Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS, Nature, 407, pp. 81-86. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10993077&dopt=Abstract
- An article that discusses one theory on how obligate endosymbionts may have their genomes degraded, in a freely-available journal. Nancy A. Moran (1996), Accelerated evolution and Muller’s ratchet in endosymbiotic bacteria, Proceedings of the National Academy of Sciences of the USA, 93, pp. 2873-2878. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8610134&dopt=Abstract Category:Symbiosis

Competition

Competition is the act of striving against another force for the purpose of achieving dominance or attaining a reward or goal, or out of a biological imperative such as survival. Competition is a term widely used in several fields, including biochemistry, ecology, economics, business, politics, and sports. Competition may be between two or more forces, life forms, agents, systems, individuals, or groups, depending on the context in which the term is used. Competition may yield various results to the participants, including both intrinsic and extrinsic rewards. Some, such as survival advantages, including favorable territory, are intrinsic biological factors that occur as a result of ecological competition between organisms. Others, such as business dominance and political power, involve competition between humans. In addition, extrinsic symbols, such as trophies, plaques, ribbons, prizes, or laudations, may be given to the winner(s). Such symbolic rewards are commonly used wherever the rewards inherent in the competition are primarily intrinsic, such as at human sporting and academic competitions. In general, the rewards range widely but usually help reinforce the advantage that one participant has over the other participant(s).

Sizes and levels of competition

Competition may also exist at different sizes; some competitions may be between two members of a species, while other competitions can involve entire species. In an example in economics, a competition between two local stores would be considered small compared to competition between several mega-giants. As a result, the consequences of the competition would also vary- the larger the competition, the larger the effect. In addition, the level of competition can also vary. At some levels, competition can be informal and be more for pride or fun. However, other competitions can be extreme and bitter; for example, some human wars have erupted because of the intense competition between two nations or nationalities.

Consequences of competition

nationalities Competition can result in both beneficial and detrimental results. For example, inter-species competition, including between humans, is the driving force of adaptation and ultimately, evolution. Social darwinists claim that competition also serves as a mechanism for determining the best-suited group, politically, economically, and ecologically, however this belief is very questionable. However, competition can also have negative consequences, particularly on the human species. Potential detrimental effects include the injury of other organisms and the drain of valuable resources and energy for competition. In addition, human competition may also require large amounts of money (such as in political elections, international sports competitions, and advertising wars) and can also lead to the compromising of ethical standards in order to gain an advantage in the competition. For example, several athletes have been caught using banned steroids in professional sports in order to boost their own chances of success or victory. Finally, competitive striving can also be harmful for the participants. Examples include athletes that injure themselves because they exceed the physical tolerances of their bodies, and companies that pursue unprofitable paths while engaging in competitive rivalries.

Competition in different fields

Economics and business competition

Seen as the pillar of capitalism in that it may stimulate innovation, encourage efficiency, or drive down prices, competition is touted as the foundation upon which capitalism is justified. According to microeconomic theory, no system of resource allocation is more efficient than pure competition. Competition, according to the theory, causes commercial firms to develop new products, services, and technologies. This gives consumers greater selection and better products. The greater selection typically causes lower prices for the products compared to what the price would be if there was no competition (monopoly) or little competition (oligopoly). However, competition may also lead to wasted (duplicated) effort and to increased costs (and prices) in some circumstances. Similarly, the psychological effects of competition may result in harm as well as good. Three levels of economic competition have been classified. The most narrow form is direct competition (also called category competition or brand competition), where products that perform the same function compete against each other. For example, a brand of pick-up trucks competes with several different brands of pick-up trucks. Sometimes two companies are rivals and one adds new products to their line so that each company distributes the same thing and they compete. The next form is substitute competition, where products that are close substitutes for one another compete. For example, butter competes with margarine, mayonnaise, and other various sauces and spreads. The broadest form of competition is typically called budget competition. Included in this category is anything that the consumer might want to spend their available money on. For example, a family that has $20,000 available may choose to spend it on many different items, which can all be seen as competing with each other for the family's available money. Competition does not necessarily have to be between companies. For example, business writers sometimes refer to "internal competition". This is competition within companies. The idea was first introduced by Alfred Sloan at General Motors in the 1920s. Sloan deliberately created areas of overlap between divisions of the company so that each division would be competing with the other divisions. For example, the Chevy division would compete with the Pontiac division for some market segments. Also, in 1931, Proctor and Gamble initiated a deliberate system of internal brand versus brand rivalry. The company was organized around different brands, with each brand allocated resources, including a dedicated group of employees willing to champion the brand. Each brand manager was given responsibility for the success or failure of the brand and was compensated accordingly. This form of competition thus pitted a brand against another brand. Finally, most businesses also encourage competition between individual employees. An example of this is a contest between sales representatives. The sales representative with the highest sales (or the best improvement in sales) over the a period of time would gain benefits from the employer. It should also be noted that business and economical competition in most countries is often limited or restricted. Competition often is subject to legal restrictions, which usually provide for fair and equal business competition. Such laws may include the banning of monopolies and price gouging. Depending on the respective economic policy, the pure competition is to a greater or lesser extent regulated by competition policy and competition law. Competition between countries is quite subtle to detect, but is quite evident in the World economy, where countries like the US, Japan, the European Union and the East Asian Tigers each try to outdo the other in the quest for economic supremacy in the global market, harkening to the concept of Kiasuism.Such competition is evident by the policies undertaken by these countries to educate the future workforce. For example, East Asian economies like Singapore, Japan and South Korea tend to emphasize education by allocating a large portion of the budget to this sector, and by implementing programmes such as gifted education, which some detractors criticise as indicative of academic elitism.

Competition in biology and ecology

Competition is also present in biology, and more specifically, ecology. Competition between members of a species is the driving force of evolution and natural selection- the competition for resources, such as food, water, territory, and sunlight, results in the ultimate survival and dominance of the variation of the species best suited for survival. According to Darwin's Theory of Evolution, this intraspecies competition results in the organisms best suited for survival producing the most offspring. As a result, the species would evolve over time and adapt to the environment in which the organisms lived. Competition is also present between species. First, a limited amount of resources are available, and several species may depend on these resources. Thus, each of the species competes with the others to gain the resources. As a result, several species less suited to compete for the resources may either adapt or die out. In addition, competition is also prominent in predator-prey relationships. Both the predator and prey are competing against one another for survival; the predator is seeking food, and the prey is seeking to survive.

Competition in politics

Competition is also found in politics. In democracies, an election is a competition for an elected office. In other words, two or more candidates strive and compete against one another to attain a position of power. The winner gains the seat of the elected office for a set amount of time, when another election is usually held to determine the next holder of the office. In addition, there is inevitable competition inside a government. Because several offices are appointed, potential candidates compete against the others in order to gain the particular office. Departments may also compete for a limited amount of resources, such as for funding. Finally, where there are party systems, elected leaders of different parties will ultimately compete against the other party for laws, funding, and power. Finally, competition is also imminent between governments. Each country or nationality struggles for world dominance, power, or military strength. For example, the United States competed against the Soviet Union in the Cold War for world power, and the two also struggled over the different types of government (in this case, representative democracy and communism). The result of this type of competition often leads to worldwide tensions and may sometimes erupt into warfare.

Sports competition

While some sports, such as fishing, have been viewed as primarily recreational, most sports are considered competitive. The majority involve the competition between two or more persons, (or animals and/or mechanical devices typically controlled by humans as in horse racing or auto racing). For example, in a game of basketball, two teams compete against one another to determine who can score the most points. While there is no set reward for the winning team, many players gain an internal sense of pride. In addition, extrinsic rewards may also be given. Athletes, besides competing against other humans, also compete against nature in sports such as kayaking or mountain climbing, where the goal is to reach a destination, with only natural barriers impeding the process. While professional sports have been usually viewed as intense and extremely competitive, recreational sports, which are often less intense, are considered a healthy option for the competitive urges in humans. Sport provides a relatively safe venue for converting unbridled competition into harmless competition, because sports competition is not unrestrained. On the contrary, the competitions are governed by codified rules ageed upon by the participants. Violating these rules is considered to be unfair competition. Sports, in addition, is also considered artificial and not natural competition; for example, competing for control of a ball or defending territory on a playing field is not an innate biologal factor in humans. Athletes in sports like gymnastics and competitive diving actually compete against a conceptual ideal of a perfect performance, which incorporates measurable criteria and standards that are translated into numerical ratings and scores. Sports competition is generally broken down into three categories: individual sports, such as archery, dual sports, such as doubles tennis, or team sports competition, such as soccer. While most sports competitions are recreation, there exists several major and minor professional sports leagues throughout the world, and the Olympic Games, held every four years, is a pinnacle of sports competition.

Competition in education

Competition is also very evident in education. On a global scale, national education systems, intending to bring out the best in the next generation, encourage competitiveness among students by scholarships. Countries like Singapore and the United Kingdom have a gifted education programme which caters to gifted students, prompting charges of academic elitism. Upon receipt of their academic results, students tend to compare their grades to see who is better. For severe cases, the pressure to perform in some countries is so high that it results in stigmatisation of intellectually deficient students or even suicide as consequence of failing the exams, Japan being a prime example (see Education in Japan). This resulted in critical revaluation of examinations as a whole by educationists (see Exam). Competitions also make up a large proponent of extracurricular activities that students partake in. Such competitions include TVO's broadcasted Reach for the Top competition, FIRST Robotics and the University of Toronto Space Design Contest.

The study of competition

Competition has been studied in several fields, including psychology, sociology, and anthropology. Social psychologists, for instance, study the nature of competition. They investigate the natural urge of competition and its circumstances. They also study group dynamics to detect how competition emerges and what its effects are. Sociologists, meanwhile, study the effects of competition on society as a whole. In addition, anthropologists study the history and prehistory of competition in various cultures. They also investigate how competition manifested itself in various cultural settings in the past, and how competition has developed over time.

Competitiveness

Many philosophers and psychologists have identified a trait in most living organisms that drive the particular organism to compete. This trait, called competitiveness, is viewed as an innate biological trait that coexists along with the urge for survival. Competitiveness, or the inclination to compete, though, has become synonymous with aggressiveness and ambitiousness in the English language.

See also


- Biological interaction
- Competitor analysis
- Cooperative
- Co-operation
- Ecological model of competition
- Microeconomics
- Perfect competition
- Planned economy
- Monopolistic competition
- Imperfect competition
- Perverse competition
- "Winning isn't everything; it's the only thing." Category:Ecology ja:競技

Interaction

:Interaction is also a Science fiction convention Interaction is a kind of action which occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction instead of a one-way causal effect. Combinations of many simple interactions can lead to surprising emergent phenomena. It has different tailored meanings in various sciences. Casual examples of interaction outside of science include:
- communication of any sort, for example two or more people talking to each other, or communication among groups, organisations, nations or states: trade, migration, foreign relations, transportation; etc.
- the feedback during operation of a machines such as a computer or a tool, for example the interaction between a driver and the position of his or her car on the road: by steering the driver influences this position, by looking this information returns to the driver;

Chemistry and medicine

In medicine, most medications can be safely used with other medicines but particular combinations of medicines need to be monitored for interactions, often by the pharmacist. Interactions between drugs fall generally into one of two main categories; pharmacodynamic (involving the actions of the two interacting drugs), and pharmacokinetic (involving the absorption, distribution, metabolism, and excretion of one or both of the interacting drugs upon the other). Sometimes two or medications are used together to create an extra effect - e.g. two different pain killers to provide more complete pain control. These interactions are usually intentional but need to be monitored by the doctor because patients can end up with more effect than is actually required. Sometimes two or more medications work against each other. These interactions are usually well-known and avoided unless both medicines are essential. Careful monitoring is used to prevent problems from the results of the interaction. Other interactions may cause one medicine to have less or more effect than expected and these are usually managed by a dosage adjustment.

Communications

In communications, interactive communication occurs when sources take turns transmitting messages between one another. This should be distinguished from transactive communication, in which sources transmit messages simultaneously.

Media

In media, interactivity is a feature of the media in question. As a result of digitalization and convergence the consumption of media is becoming more interactive. In media the strive for interaction is also a cultural trend.

Physics

In physics, an interaction specifically refers to the action of one physical object upon another and results in an interaction energy - the physical objects under consideration may range from point particles to quantum fields. For example, the interaction of charged particles takes place through the mediation of electromagnetic fields, whereas beta decay occurs by means of the weak interaction. There are believed to be four fundamental interactions in Nature.

Sociology

In sociology, social interaction is a dynamic, changing sequence of social actions between individuals (or groups) who modify their actions and reactions due to the actions by their interaction partner(s). Social interactions can be differentiated into:
- accidental - not planned and likely not repeated. For example, asking a stranger for directions or shopkeeper for product availabity.
- repeated - not planned, bound to happen from time to time. For example, accidentaly meeting a neighbour from time to time when walking on your street;
- regular - not planned, but very common, likely to raise questions when missed. Meeting a doorman or a security guard every workday in your workplace, dining every day in the same restaurant, etc.
- regulated - planned and regulated by customs or law, will definitely raise questions when missed. Interaction in a workplace (coming to work, staff meetings, etc.), family, etc. Social interactions form the basis for social relations.

See also


- Computability logic
- Game semantics
- Interaction Design
- Interactive computation
- Interactivity
- Transaction Category:Communication Category:Sociology Category:Pharmacology ja:相互作用

List of symbiotic relationships

This is an incomplete list of notable mutualistic symbiotic relationships, in which different species have a cooperative or mutually dependent relationship.
- Algae with fungi in lichens
- Vascular plants with fungi in mycorrhiza
- Anglerfish with the bioluminescent bacteria that illuminate its 'lure'
- Ants with aphids and with some caterpillars
- Cleaner fish or cleaner shrimp with other large fish like groupers, sharks and moray eels
- Corals with zooxanthella
- Flowering plants with pollinators such as bees
- Goby fish with shrimp
- Humans with cultivated plants and with domesticated animals
- Leafcutter ants with the fungus they 'farm'
- Legumes with Rhizobia (nitrogen-fixing bacteria)
- Deep-sea pompeii worm and the thermophilic bacteria which grow on it
- Ratel or 'honey badger' with the honeyguide bird
- Ruminants such as cows and their intestinal bacteria which break down cellulose
- Sea anemones with clownfish, crabs or shrimps
- Termites with their intestinal bacteria which digest cellulose
- Egyptian plovers with crocodiles
- acacia ant(Pseudomyrmex ferruginea) and a swollen thorn acacia tree
- Oxpeckers with the rhinoceros
- Polydnavirus with parasitoid wasps (though not necessarily mutually dependant)
- shark with remora
- Corner Liquor Store with BYOB Restaurant (non-biological example, but symbiosis nonetheless)

Note

Some of these relationships are so close that we speak of the composite of two species as one unit, for example, we speak of the composite of algae and fungi as lichens. This is analogous to our speaking of a modulator and a demodulator as a modem. (See list of equipment pairs.)

Reference

Awake! (magazine), September 8, 2005, pages 3-10, describes at least 20 mutualistic symbiotic relationships between different species, and at least three among members of the same species. Counting depends on how narrowly one subdivides categories. Seventeen full-color photographs, including one on the front cover and one on the second page, illustrate some of these relationships.
-

Category:Ecology

Ecology is the branch of science that studies the distribution and interactions between living things and between living things and the physical environment. This category does not cover environmentalism, or ethics topics. Category:Earth sciences Category:Environmental science ecology Category:Academic disciplines category:Agronomy ko:분류:생태학 ja:Category:生態学

Category:Symbiosis

Category:Ecology Category:Evolutionary biology

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