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Competition, predation, and mutualism

Predatory interactions may reduce the number of organisms or eliminate whole populations of organisms. Mutually beneficial interactions, in contrast, may become so interdependent that each organism requires the other for survival. Although the species involved in competitive, predatory, and mutually beneficial interactions vary across ecosystems, the patterns of interactions of organisms with their environments, both living and nonliving, are shared. Created by Sal Khan.

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Video transcript

- [Instructor] All across ecosystems, we know that organisms interact in specific ways and scientists use special words to describe these types of interaction, competition, predation and mutualism. So let's first talk about competition which we have already talked about in other videos. In this picture here, do you see competition? Pause this video and think about that. Well, one limited resource that these animals need to survive is water. There's only a limited amount in this watering hole over here and so you could imagine there is competition not just amongst the members of a population let's say between the zebra but also between members of different species, between different populations in a community. The zebras are not just competing for water with each other but also with these antelope or with these buffalo over here. There might also be competition for food. It doesn't seem like there's a lot of grass to eat for all of these animals that like to graze on grass. So now let's move on to predation. Predation is when one organism eats another organism usually to its own benefit. Do you see any predation happening here? Well, we don't see any of these animals chasing and killing each other. There might be other animals like lions offscreen that might hunt and kill and eat these animals right over here but we know that these animals do eat grass and as I said, it's not just about hunting and killing and eating from one animal to another. It could be one organism to another. So the eating of the grass by these animals could actually be considered a form of predation especially if it kills the grass. A more obvious form of predation is this brown bear here that has gotten the salmon out of this river. It is clearly hunting and killing the salmon for its benefit and it is likely that each of these bears are in competition with other bears for this limited resource. So last but not least, let's think a little bit about mutualism. Mutualism happens when two organisms benefit from interacting with each other. Right over here, we have these starlings that actually hang out on this buffalo and pick lice and ticks off the buffalo's fur. This is mutualism because both parties benefit. The starlings are able to get food and the buffalo no longer have these parasites, these things that are living off of the buffalo sucking its blood out of its body and also probably not itching as much. Now, based on how I just described it, there's not just mutualism here. There's also predation because these birds are actually hunting and killing the lice and the ticks on the buffalo's body. Now, related to being a predator is another word known as being a parasite and that's what the lice and the ticks are doing where they're sucking the blood of the buffalo but they're not considered predators. They're more parasites because they don't kill the buffalo. They're just taking some resources away from it. So I'll leave you there. I encourage you when you look at nature, when you go to a park next time, when you go watch a documentary, I encourage you to think about how competition, predation and mutualism is happening in an ecosystem that you are seeing or that you're a part of.