Parasitism - Wikipedia
Commensalism is a type of relationship where one of the organisms benefits greatly In some of these parasitic relationships the host dies and in others, it is . Parasitism is a relationship between two different organisms where one of the Aphids are a type of insect parasite that feed on the sap of the host plant. A parasitic relationship is one in which one organism, the parasite, lives off of another organism, the host, harming it and possibly causing death. The parasite.
They cannot fly or hop, but can crawl.
Head lice are passed from person to person when there is direct contact with the infested person's hair. In other words, when two people's heads touch.
Ticks Ticks love to feast on blood. They are commonly associated with living on dogs and cats, but will use humans as hosts, too. Ticks will attach to their host by burying their head into their skin. Their bodies fill up and expand as they drink, most often falling off when they're full. Mosquitoes Did you know that the deadliest animal on Earth is the mosquito? The diseases that some mosquitos can carry and pass on to people by biting them kill several million people around the world every year.
In commensalism, one organism benefits from the relationship while the other is neither helped nor hurt. If there are a lot of commensals on a single "host" then it stands to reason that the host will be hurt and the relationship will slide towards the parasitic Note: This latter definition makes many commensal relationships appear parasitic.
The photosynthetic zooxanthellae provide the coral with sugars in return for nitrogen and other nutrients from the coral. Obligate relationships - such as a human tapeworm in our gut - are considered "tight", while facultative ones - a squirrel living in a tree - are considered "loose".
Some ecologists place the 3 types of relationships first, that is there are parasitic, commensalistic, and mutualistic relationships, and only the obligate ones in any of these 3 categories are called symbioses. Parasitism tight and loose: The Catalpa Worm above is being parasitized by tiny wasp larvae. The adult wasps right sting the caterpillar, injecting their eggs.
The eggs hatch and devour the caterpillar from the inside, being careful not to disrupt any vital functions. Eventually they emerge and spin cocoons of silk in which they transition from larvae to adult.
Technically, these insects are parasitoids, since, unlike true parasites, they kill their hosts. Much looser parasitism is shown by ectoparasites, which feed from the outside.
Mosquitoes below right of course suck blood only the females at that; they need the protein to make eggs. Oak Treehoppers below suck sugar-rich juices from the phloem of trees. Often these relationships are not species-specific; the mosquitoes would probably go after any other warm-blooded prey and the oak treehoppers pictured were in fact on a sycamore tree.
The squawroot left may look like a fungus, but it is actually a flowering plant. It is parasitic on trees, usually oaks, and gets its energy by tapping into the oak's roots.
It betrays its true nature when it comes time to reproduce, however. I'm not sure about squawroot in particular, but other related plants are often self-pollinating and thus don't even need showy flowers to attract pollinators. The squawroot is a distant relative of the magnolia. Many would argue that a flicker making its home in a cactus below left is a good example of commensalism.
In a forest, such a relationship usually is commensalistic; the flicker below has excavated its nest in the dead wood of a living sycamore tree. To my eye, the desert bird has gone through some living tissue to make its nest.
Still, the overall damage to the cactus is small. The white-winged dove left has a mutualistic relationship with the Saguaro Cactus.
The cactus provides food for the bird in the form of a large fruit. The bird consumes the fruit, also ingesting the cactus' seeds.
The bird then flies off, and later deposits the seeds in a new location with a nice dose of fertilizer to boot! In this way, the cactus gets its seeds transported away from the parent plant, allowing it to potentially colonize new places. This type of mutualism is known as a dispersive mutualism. The Cattle Egret below left is often seen in the company of grazing animals. The grazers stir up insects, which the egret then eats.
This is probably a loose sort of commensalism; there is no apparent benefit to the cattle. The commensalism is loose because the egrets will follow any cattle; in Florida, in fact, I have seen them following mowers. On the other hand, the oxpecker not pictured is a bird that rides around on the backs of cattle and other large animals such as rhinos.
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! 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.
What is a Parasite? - Definition, Types & Examples
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.Extreme Animal Relationships - Earth Unplugged
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.
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- Definition of a Parasite
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. Parasitic plants and fungi can attack animals. A fungus causes lumpy jaw, a disease that injures the jaws of cattle and hogs. There are also parasitic plants and fungi that attack other plants and fungi.
A parasitic fungus causes wheat rust and the downy mildew fungus attacks fruit and vegetables. Some scientists say that one-celled bacteria and viruses that live in animals and harm them, such as those that cause the common cold, are parasites as well. However, they are still considered different from other parasites. Many types of parasites carry and transmit disease. Lyme disease is trasmitted by deer ticks.