Department of Biotechnology, St. Aloysius College (Autonomous), Jabalpur

Transcription

1 Department of Biotechnology, St. Aloysius College (Autonomous), Jabalpur Page 1 of 5

2 Question:- Write a short note on:- a) Commensalism. b) Synergism SHORT NOTES Answer:- 1. Commensalism Symbiosis describes close interactions between two or more different species. It is different from regular interactions between species, because in a symbiotic relationship, the two species in the relationship live together. Many organisms are involved in symbiotic relationships because this interaction provides benefits to both species. However, there are types of symbiosis that are not beneficial and may in fact harm one or both of the species. Symbiotic relationships can be obligate or facultative. Obligate symbiosis is when two organisms are in a symbiotic relationship because they can't survive without each other. Facultative symbiosis is when the species live together by choice. There are three main types of symbiotic relationships: mutualism, commensalism, and parasitism. Definition of Commensalism One type of symbiosis is called commensalism. In commensalism, one organism benefits from the relationship while the other species involved neither benefit nor is harmed. The word "commensalism" is derived from the word "commensal", meaning "eating at the same table" in human social interaction, which in turn comes through Page 2 of 5

3 French from the Medieval Latin commensalis, meaning "sharing a table", from the prefix com-, meaning "together", and mensa, meaning "table" or "meal". Originally, the term was used to describe the use of waste food by second animals, like the carcass eaters that follow hunting animals, but wait until they have finished their meal. The commensal (the species that benefits from the association) may obtain nutrients, shelter, support, or locomotion from the host species, which is substantially unaffected. The commensal relation is often between a larger host and a smaller commensal; the host organism is unmodified, whereas the commensal species may show great structural adaptation consonant with its habits, as in the remoras that ride attached to sharks and other fishes. Examples a) The remora fish attaches to the belly of the shark by a sucker disc in it's mouth. It travels everywhere the shark goes. It eats any parasites on the shark which helps keep the shark clean. It also eats any leftover food from the shark. The remora (sucker fish) gets to eat and the shark stays clean and healthy. b) Many of the microorganisms that make up our normal microbiota arc commensals; these include the corynebacteria that inhabit the surface of the eye and certain saprophytic mycobacteria that inhabit the ear and external genitals. These bacteria live on secretions and sloughed-off cells, and they bring no apparent benefit or harm to the host. Page 3 of 5

4 1. Synergism:- Synergy is broadly defined as the combined effects of two or more organisms to produce a greater result than each would achieve individually. Synergism in nature includes altruism, reciprocity, functional interdependence, mutualism, and parasitism. Mutualistic relationships occur between two species who perform "services" for each other that they can't carry alone. For example, a bee gets its food from a flower's nectar and the nectar is fertilized by pollen carried by the bee during pollination. This kind of interaction is found in various types of environments: the ocean, on land, in bacteria, and even the human intestine. Synergism (protocooperation): Both populations benefit but the association is not obligatory and both populations can survive on their own. However, the association provides some mutual benefits. It can be difficult to judge whether the relationship is mutualistic (mutualism is an obligatory association), synergistic (not obligatory) or a commensalistic one (one population can replace the other). Some examples of synergism. o Synthesis of a product which neither population can perform on their own: For example, completion of a pathway. This type of synergism is known as syntrophy. Fungi Fungi have a mutualistic relationship with several insect species in forested habitats. Beetles and ants "farm" fungi: they help grow them by collecting and grinding up leaves and feeding the leaves to the fungi. They then use the fungi for food. The interaction is mutualistic because, although the insects consume the fungi, they also help the fungi populations to increase by providing them with nutrition. However, fungi aren't completely dependent on ants or beetles: their spores can float elsewhere to live a more independent lifestyle. Page 4 of 5

5 Intestinal Bacteria Bacteria are found in various species' intestines where they get food from helping us break down digestible materials. In moose, bacteria are needed to break down the massive amounts -- around 160 liters -- of plant material in the intestine. These bacteria have an ample supply from nutrition from aiding digestion. This type of bacteria is also found in the human small intestine where it helps break down the food we consume. Humans have a mutualistic relationship with these bacteria because we indirectly feed these bacteria when we eat food. Beneficial Viruses Most viruses are harmful, but some viruses have a mutually beneficial relationship with their hosts. A lot of viruses help their hosts by attacking their competition. For example, the hepatitis G virus slows down the growth of HIV, the virus that causes AIDS, in humans. Bacteria grow viruses inside their cells and infect competitors with those viruses. Other viruses are needed for their host's physical development. When wasps lay eggs inside other insects, their eggs are equipped with viruses. These viruses fight off the infected insect's defenses and guarantee the eggs' survival. Page 5 of 5