Mutualism, Commensalism, and Parasitism
Mutualism, Commensalism, and Parasitism
Mutualism, commensalism, and parasitism. All three of these can be considered a form of symbiosis, which is a close and often long-term relationship between two or more different species.
All three of these are going to be a type of close, long-term relationship between two different species. Let’s look at each one. Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits.
They have a mutual benefit. They are both going to benefit. It is mutual. They both get something good here. An example would be the clown fish and sea anemone. The clownfish is protected by the sea anemone because it has a poison on the outside of it and other fish will be harmed by that, where the clownfish has built up a resistance to that toxin and is safe.
In return, the clownfish fights off predator fish that would eat the sea anemone. They have a mutualistic relationship, because they are each protected by the other. Another example would be hummingbirds and flowers.
This could apply to other birds as well, but birds that go and drink nectar from certain flowers, they benefit, because they are eating that nectar. Then, if they go to other flowers, they are carrying pollen with them and they are pollinating for those flowers.
They are helping the flower. The flower is being pollinated by the bird. They have a mutualistic relationship. Both benefit. Commensalism is the way two organisms of different species exist in a relationship where one organism benefits and the other is unaffected.
They have this close relationship. One of the species is benefiting from it and the other one isn’t being harmed, but it isn’t being benefited. It is just unaffected. An example would be whale barnacles and baleen whales. The whale barnacles attach themselves to the whale.
It gives them a mode of transport where they’re able to filter plankton into the ocean, but they don’t harm the baleen whales at all and they also don’t help the baleen whales. The whales are unaffected, but the barnacles have a mode of transportation.
Another example would be army ants and birds. Army ants go through attacking their ground insects and they stir up the flying insects in the area. Birds can follow behind them and eat those flying insects. They aren’t taking anything from the army ants, but they are benefiting.
The army ants are unaffected, but the birds are benefiting in that they are having their food stirred up for them without them having to go hunt for it. Parasitism is the way two organisms of different species exist in a relationship where one organism benefits and the other is harmed.
This is good for one species, but bad for the other. Instead of being unaffected, they’re now harmed. Instead of them both being benefiting, one is benefiting and the other is being harmed. An example would be tapeworms and vertebrates.
If a tapeworm gets inside of a vertebrate and is living in there, the tapeworm is going to be taking all of that vertebrate’s nutrition, or at least the majority of it. Anything the vertebrate’s eating is going to that tapeworm instead of to the vertebrate.
The vertebrate is going to become malnourished, where the tapeworm is going to be benefiting and becoming healthier and growing. Another example would be the cuckoo and other birds. They do something called “brood parasitism”, where the cuckoo will leave their own egg in another bird’s nest and leave it there for that other bird to sit on, and hatch, and raise as their own, so that the cuckoo doesn’t actually have to do the work there.
Now, it may seem like the other bird isn’t going to be harmed by that, but sometimes if the other bird notices the cuckoo bird’s egg, the other bird will push that egg out of the nest. The cuckoo will retaliate by coming and attacking the nest and maybe destroying some of the other eggs, which makes the other bird more likely to cooperate and hatch the cuckoo egg next time.
Another thing that the cuckoo might do is to throw out one of the eggs or push out and destroy one of the other bird’s eggs in place of its own egg that it’s putting there.
It puts in a cuckoo egg and pushes out one or the other bird’s eggs, so when that bird comes back it says, “Oh, look. I still have five eggs. Everything’s good.” It won’t notice an extra, even though the cuckoo bird- or the cuckoo’s egg is probably going to be a different size and color than the bird’s eggs that are already there.
One other way the cuckoo might harm the other birds is that, once the baby cuckoo hatches, it could push the other birds or the other eggs out of the nest, so that it’s the primary one getting nutrition and getting attention from that mother bird.
There are different ways that the cuckoo might harm the other bird in this relationship where the cuckoo is benefiting. It isn’t having to do any work, but its eggs are getting hatched and it is being able to procreate.
These are all different relationships that can be considered a form of symbiosis. Mutualism is going to be where both parties benefit mutually. Commensalism is when one party benefits but the other is unaffected. Parasitism is when one party benefits and the other is harmed.