Commensalism - Wikipedia
Organisms live in complex assemblages in which individuals and species interact in In this relationship, if the squirrel population increases, then the mouse population Symbiosis is an interaction characterized by two or more species living in which one individual benefits while the other is neither helped nor harmed. 6 Types of Symbiotic Relationships EXPLAINED (with examples)” is Competitive Exclusion Principle: Two different species cannot share the same in which one species benefits, but the other is neither harmed nor helped. Quizlet flashcards, activities and games help you improve your grades. A symbiotic relationship in which one species benefits and the other species is neither helped nor harmed. Competition. A harmful interaction between two or more organisms that can occur when organisms compete for the same resource in the same.
Dogs[ edit ] The dog was the first domesticated animal, and was domesticated and widely established across Eurasia before the end of the Pleistocenewell before the cultivation of crops or the domestication of other animals.
Examples of Symbiosis
The wolves more likely drawn to human camps were the less-aggressive, subdominant pack members with lowered flight response, higher stress thresholds, and less wary around humans, and therefore better candidates for domestication.
In contrast, cats may have become fully dependent on a commensal lifestyle before being domesticated by preying on other commensal animals, such as rats and mice, without any human provisioning.
Debate over the extent to which some wolves were commensal with humans prior to domestication stems from debate over the level of human intentionality in the domestication process, which remains untested.
Although these two populations spend a period of the year in the same place, and though there was evidence of gene flow between them, the difference in prey—habitat specialization has been sufficient to maintain genetic and even coloration divergence.
The skull shape, tooth wear, and isotopic signatures suggested these remains were derived from a population of specialist megafauna hunters and scavengers that became extinct while less specialized wolf ecotypes survived.
Aspergillus and Staphylococcus Numerous genera of bacteria and fungi live on and in the human body as part of its natural flora. The fungal genus Aspergillus is capable of living under considerable environmental stress, and thus is capable of colonising the upper gastrointestinal tract where relatively few examples of the body's gut flora can survive due to highly acidic or alkaline conditions produced by gastric acid and digestive juices.
While Aspergillus normally produces no symptoms, in individuals who are immunocompromised or suffering from existing conditions such as tuberculosisa condition called aspergillosis can occur, in which populations of Aspergillus grow out of control.
Staphylococcus aureusa common bacterial species, is known best for its numerous pathogenic strains that can cause numerous illnesses and conditions.
However, many strains of S. Other Staphylococcus species including S. Arguments[ edit ] Whether the relationship between humans and some types of gut flora is commensal or mutualistic is still unanswered. Some biologists argue that any close interaction between two organisms is unlikely to be completely neutral for either party, and that relationships identified as commensal are likely mutualistic or parasitic in a subtle way that has not been detected.
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The oxpecker feeds on ectoparasites of the cattle such as ticks and warns the animals of approaching predators; thus both organisms benefit in a loose mutualism. On the other hand, the oxpeckers also pick at scabs and wounds on the animals and may ingest bits of flesh and blood thus making them more like parasites.
The natural world is complicated!
Examples of Symbiosis
Symbiosis in the seas: Some of the best examples of symbiosis are found in the oceans - not surprising since life has had longer to evolve and form close associations in the oceans. Above, the corals are perhaps the best example of a mutualistic symbiosis.
Tiny coral animals which individually resemble this freshwater hydra form huge colonies, with each hydroid encased in stone secreted by the animals. Collectively, these colonies can grow very large. Brain coral above right typically forms huge colonies; the dark "boulder" to the left of the picture immediately right is actually a colony of brain coral that may be thousands of years old the fish is 5 feet long.
Each hydroid in turn may harbor cells of photosynthetic algae usually dinoflagellates ; these algal endosymbionts are called zooxanthellae and give the coral its brown or green appearance. As mentioned above, the zooxanthellae "trade" sugars for nutrients; it's convenient that the wastes of the coral CO2, ammonia, etc.
Interestingly, both the corals and the zooxanthellae can survive without the other at least for a while ; under conditions of stress the corals are known to expel the endosymbionts in a phenomenon known as coral bleaching.
Under happier times, the corals direct their growth to maximize sun exposure for their algal guests; you can see this clearly in the photo of the Elkhorn Coral above.
This jellyfish spends its time upside down in the shallows of mangrove swamps exposing its algal endosymbionts to the sun. Two other mutualistic symbioses found on the coral reef are pictured to the right, although they are not as tight as the endosymbioses of coral and zooxanthellae.
In the photo to the right, a barracuda takes an unusual heads-up posture. He has arrived at the large brain coral, which makes a conspicuous landmark seamark?
When the barracuda takes this pose, the Cleaning Fish know it is safe for them to approach - the 'cuda is looking for a cleaning, not a meal. The tiny fish will scour the skin, mouth and gills of the Barracuda, removing any ectoparasites they find and getting a good meal out of it. There was a line of about 6 barracuda waiting to get cleaned here; the others were behind me in the line.
Finally, everyone who has seen "Finding Nemo" knows about the association between Clownfish and Anemones. By working its way carefully into the anemone, the clownfish gradually accustoms the anemone to the chemical makeup of the fish's skin; this gradual acclimatization prevents the anemone from stinging the clownfish while fish with a different "taste" will be stung and eaten.
The fish gets a safe house and some tidbits; the anemone gets cleaned and has the clownfish working as lures to bring in potential prey, or chasing away fish that would harm the anemone.
Some scientists do not see any benefit for the anemone and classify this as a commensalism. The Sea Lamprey, above left, is a sort of temporary parasite. It latches onto a fish and uses the teeth to hold on and rasp away the skin, leaving an open wound for the lamprey to feed on. It drops off, usually without killing the "host". Sea Lampreys are not specific on any species of fish; they will latch onto any living thing and try to feed.
The wasp above has stung and paralyzed a spider. It will take the spider to a nest and lay an egg on it. The larvae will consume the still-living spider; often from the inside. This is usually considered to be a parasitoid relationship. Two more mutualistic relationships from the Costa Rican forests. These algae help to camouflage the sloth against the lichen-covered tree note the brown fur of the baby, not yet covered with algae. There is even a moth that lives only in the sloth's fur and consumes the algae; this is a commensal relationship between the moth and the sloth.
Below, a mutualistic relationship. The Acacia Tree is partially protected by large thorns, but it gets extra protection from Acacia Ants. The plant does 3 things to lure in the ants. First, the large thorns are hollow and provide a place for the ants to live.
Second, the plants have swollen glands, nectaries, which produce a sugary solution the ants drink. The nectaries are obvious in the photo below. In return for the room and board the ants chase off herbivores, kill and eat herbivorous insects, and destroy and plants that try to compete with the acacia.
The horsehair worm starts life as an egg laid in a puddle. The puddle dries out and a grasshopper or similar insect comes along and eats the egg, which promptly hatches and burrows through the gut of the insect into its body cavity or hemolymph.
Here, surrounded by the nutritious blood of the insect it grows until it reaches adulthood. At that point it starts producing chemicals which take over the brain of the insect and cause the insect to seek out water, which it jumps into.
The worm then exits the hopper and lives in the puddle, mating and laying more eggs. The grasshopper, if it doesn't drown, may survive the ordeal. Below, a social parasite. This cricket lives in an ant nest. It disguises itself with a chemical signature that fools the ants into thinking it is just another ant.
It is free to roam the nest and it even gets the ants to feed it. The Brown-Headed Cowbirds above are nest parasites. They originally followed the bison on the Great Plains, feeding on insects kicked up by the large herds. Since the bison themselves migrated, following the melting snows and eating the fresh spring grass, the cowbirds had to move as well. This presented a problem, as it's hard to incubate eggs on the move. Lay the eggs in other birds' nests, and trick the other birds into raising your young.
The cowbirds hatch out first, push the other eggs out of the nest, and the nest-builders often much smaller than the rapidly growing cowbird end up feeding it instead of their own young. Even though the other birds may pattern their eggs the cowbirds are up to the challenge. Cowbirds hesitate entering forests, but roads, farms, powerlines and other human intrusions give them a pathway deep into the woods where they are free to parasitize the nests of birds which until the arrival of humans didn't have to worry about the cowbirds.
Some of these bird species are on the verge of extinction as a result. Bromeliads left, above left avoid the hassle of crating a trunk to lift their leaves above the forest floor and closer to the sun.
They simply grow on the branches of trees. Since the bromeliads don't take any nutrients from the trees this is usually classified as a commensalism, but if there are a lot of bromeliads left the tree will need to add extra wood to support the weight a bromeliad can trap up to 10 gallons 80 pounds of water in its leaves.
So, if there are a lot of bromeliads the relationship overall turns into a negative for the tree. The bromeliads also host a number of organisms in the water they trap; the wastes from the animals living there undoubtedly fertilizes the bromeliad in a mutualistic relationship. The tree at lower left is absolutely covered with epiphytes.
Leeches below left are usually thought of as ectoparasites although some are predators. They attach to a vertebrate host and take a blood meal before dropping off.
Most aren't adapted to a single vertebrate host, but they are highly adapted to sucking blood; their saliva includes anesthetics to help keep the host from noticing the bite, as well as anticoagulants to keep the blood flowing. Below is a larval mussel freshwater clam. If there is any case of "good" parasitism, this may be it. The little mussels go into the mouth and pass over the gills. Here, they clamp down by closing the shell and digging in with the little teeth pictured at the edge of the shell.
The fish provides a meal and transport upstream moving is not something mussels do well over long distances, particularly upstream. Lichens above and left are mutualistic associations between a fungus and an algae or cyanobacteria.
They are the terrestrial equivalents in some ways of corals. The fungus provides a tough, waterproof body able to withstand extreme environments on rocks and tree trunks. It is good at obtaining water and secretes acids to dissolve minerals from the rocks.
It also produces carbon dioxide. All of these materials are then funneled to the endosymbiotic algae or cyanobacteria, which use the materials in photosynthesis and produce sugars which are then shared with the fungus.
Some studies have shown that the fungus benefits from this relationship more so than the algae; at least under good conditions algae grown without the fungus grow faster then they do with the fungus. This wasp has stung and paralyzed a stink bug and is dragging it to its underground lair.
Here it will deposit an egg and the larvae that hatches from the egg will eventually consume the bug. Keeping the bug alive but paralyzed ensures it doesn't rot. The two lice to the right parasitize humans.