Project on Symbiosis free essay sample

In 1879, the  German  mycologist  Heinrich Anton de Bary  defined it as the living together of unlike organisms. The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any types of persistent  biological interactions  (i. e. mutualistic,  commensalistic, orparasitic). Some symbiotic relationships are  obligate, meaning that both symbionts entirely depend on each other for survival. For example, many  lichens  consist of fungal and photosynthetic symbionts that cannot live on their own. Others are facultative, meaning that they can, but do not have to live with the other organism. Symbiotic relationships include those associations in which one organism lives on another (ectosymbiosis, such as  mistletoe), or where one partner lives inside the other (endosymbiosis, such as  lactobacilli  and other bacteria in humans or  Symbiodinium  incorals). Symbiosis is also classified by physical attachment of the organisms; symbiosis in which the organisms have bodily union is called conjunctive symbiosis, and symbiosis in which they are not in union is called disjunctive symbiosis. OBJECTIVE Study on Symbiosis Symbiosis can mainly be of 3 types :- i. Mutualism ii. Commensalism iii. Parasitism MUTUALISM Mutualism  is any relationship between individuals of different  species  where both individuals benefit. In general, only lifelong interactions involving close physical and  biochemical  contact can properly be considered symbiotic. Mutualistic relationships may be either obligate for both species, obligate for one but facultative for the other, or facultative for both. Many  biologists  restrict the definition of symbiosis to close mutualist relationships. A large percentage of  herbivores  have mutualistic  gut fauna  that help them digest plant matter, which is more difficult to digest than animal prey. This gut fauna is made up of cellulose-digesting protozoans or bacteria living in the herbivores intestines. Coral  reefs are the result of mutualisms between coral organisms and various types of algae that live inside them. Most land plants and land ecosystems rely on mutualisms between the plants, which  fix  carbon from the air, and  mycorrhyzal  fungi, which help in extracting water and minerals from the ground. An example of mutual symbiosis is the relationship between the  ocellaris clownfish  that dwell among the  tentacles  of  Ritteri sea anemones. The territorial  fish  protects the anemone from anemone-eating  fish, and in turn the  stinging  tentacles of the anemone protect the clownfish from its  predators. Special  mucus  on the clownfish protects it from the stinging tentacles. A further 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. When that happens both the shrimp and goby fish quickly retreat into the burrow. One of the most spectacular examples of obligate mutualism is between the  siboglinid  tube worms  and symbiotic  bacteria  that live athydrothermal vents  and  cold seeps. The worm has no digestive tract and is wholly reliant on its internal symbionts for nutrition. The bacteria oxidize either hydrogen sulfide or methane, which the host supplies to them. These worms were discovered in the late 1980s at the hydrothermal vents near the Galapagos Islands and have since been found at  deep-sea  hydrothermal vents and cold seeps in all of the worlds oceans. COMMENSALISM Commensalism describes a relationship between two living organisms where one benefits and the other is not significantly harmed or helped. It is derived from the English word  commensal  used of human  social interaction. The word derives from the Medieval Latin word, formed from  com-  and  mensa, meaning sharing a table. Commensal relationships may involve one organism using another for transportation or for housing, or it may also involve one organism using something another created, after its death. Examples of metabiosis are  hermit crabs  using  gastropod  shells to protect their bodies and spiders building their webs on  plants. PARASITISM A  parasitic  relationship is one in which one member of the association benefits while the other is harmed. This is also known as antagonistic or antipathetic symbiosis. Parasitic symbioses take many forms, from  endoparasites  that live within the hosts body toectoparasites  that live on its surface. In addition, parasites may be necrotrophic, which is to say they kill their host, or biotrophic, meaning they rely on their hosts surviving. Biotrophic parasitism is an extremely successful mode of life. Depending on the definition used, as many as half of all  animals  have at least one parasitic phase in their life cycles, and it is also frequent in  plants  and  fungi. Moreover, almost all free-living animals are host to one or more parasite  taxa. An example of a biotrophic relationship would be a  tick  feeding on the blood of its host. SYMBIOSIS AND EVOLUTION While historically, symbiosis has received less attention than other interactions such as  predation or  competition, it is increasingly recognized as an important selective force behind evolution,  with many species having a long history of interdependent  co-evolution. In fact, the evolution of all  eukaryotes  (plants, animals, fungi, and  protists) is believed under the endosymbiotic theory  to have resulted from a symbiosis between various sorts of bacteria. This theory is supported by certain organelles dividing independently of the cell, and the observation that some organelles seem to have their own nucleic acid. Vascular plants About 80% of  vascular plants  worldwide form symbiotic relationships with fungi, for example, inarbuscular mycorrhizas. Symbiogenesis The biologist  Lynn Margulis, famous for her work on  endosymbiosis, contends that symbiosis is a major driving force behind  evolution. She considers  Darwins  notion of evolution, driven by competition, to be incomplete and claims that evolution is strongly based on  operation, interaction, and  mutual dependence  among organisms. According to Margulis and  Dorion Sagan, Life  did not take over the  globe  by  combat, but by  networking. Co-evolution Symbiosis played a major role in the  co-evolution  of  flowering  plants and the animals that  pollinate  them. Many plants that are pollinated by  insects,  bats, or  birds  have highly specialized flowers modified to promote pollination by a specific pollinator that is also correspondingly adapted. The first flowering plants in the f ossil record had relatively simple flowers. Adaptive  speciation  quickly gave rise to many diverse groups of plants, and, at the same time, corresponding speciation occurred in certain insect groups. Some groups of plants developed nectar and large sticky pollen, while insects evolved more specialized morphologies to access and collect these rich food sources. In some taxa of plants and insects the relationship has become dependent,  where the plant species can only be pollinated by one species of insect. HERMIT CRAB,  CALCINUS LAEVIMANUS, WITH SEA ANEMONE. ALDER TREE ROOT NODULE LEAFHOPPERS  PROTECTED BY AN ARMY OF  MEAT ANTS PICTURE GALLERY CONCLUSION Symbiosis can mainly be of 3 types:-Mutualism , Commensalism , Parasitism. Mutualism  is any relationship between individuals of different  species  where both individuals benefit. Commensalism describes a relationship between two living organisms where one benefits and the other is not significantly harmed or helped. A  parasitic  relationship is one in which one member of the association benefits while the other is harmed. This is also known as antagonistic or antipathetic symbiosis. While historically, symbiosis has received less attention than other interactions such as  predation or  competition, it is increasingly recognized as an important selective force behind evolution,  with many species having a long history of interdependent  co-evolution. About 80% of  vascular plants  worldwide form symbiotic relationships with fungi, for example, inarbuscular mycorrhizas. The biologist  Lynn Margulis, famous for her work on  endosymbiosis, contends that symbiosis is a major driving force behind  evolution. She considers  Darwins  notion of evolution, driven by competition, to be incomplete and claims that evolution is strongly based on  operation, interaction, and  mutual dependence  among organisms. Symbiosis played a major role in the  co-evolution  of  flowering  plants and the animals that  pollinate  them. Many plants that are pollinated by  insects,  bats, or  birds  have highly specialized flowers modified to promote pollination by a specific pollinator that is also correspondingly adapted. The first flowering plants in the fossil record had relatively simple flowers.