 There are many different interactions that can occur between different types of organisms. And one of the ways we can categorize them is by how much benefit or harm those interactions have to either organism. So a lot of times organisms support each other and help each other. And so one example would be so we could have organism number one and organism number two and maybe they both experience a benefit here. In that case it's mutually beneficial and we say that is mutualism. Both organisms benefit from the interaction that they have. The organisms might live in the same environment but they don't really impact what happens with each other and there might be no effect on either one and we usually call that neutralism. Sometimes organisms can harm each other when they interact in the same environment. So for example if we have two different things like maybe two different types of grass that are competing for space both of those take energy and the competition between those two can be harmful to both species. So competition usually takes energy and that is harmful to both. So all three of these examples had the same influence between species one and two but sometimes one organism can benefit whereas another organism gets harmed. So let's say we start with if one organism eats another organism there's benefit to the one that's doing the eating and there's harm to the one that's being eaten. So these sorts of relationships are for example predation. Usually with predation the organisms are one organism, the organisms are about the same size or one is larger and the predator kills the prey. And then we also have and I can see the orange doesn't show up very well so I'll write it in red. We also have parasites, parasitisms. And this is the case usually when one organism is much smaller than the other and it takes resources from the larger organism without actually killing it. So an example of a parasite would be for example a tick. It sucks blood and it doesn't usually kill the host organism and so it can get resources from it for a long time. The case of both predation and parasitism only one organism benefits and the other one is harmed. There are also examples where one organism might benefit and one is neutral. So in this particular case so an example might be cattle egrets which eat insects. It's much easier for them to catch the insects if there are cattle or other livestock antelope deer walking around stirring up those insects. So this particular case is commensalism because one organism benefits relative to the others. It can also have a process where one organism doesn't really get any benefit but its activity harms another organism. And so that would be a case of for example animals walking on a path. They actually step on insects present or new sprouts of plants and so they don't really get much benefit from stepping on those plants except maybe it's nice to have a trail which is why they keep using them but they do cause harm to other organisms. And so of course we sort of have these different categories but the level of benefit and harm varies a great deal and there are often feedbacks in those relationships through more than one species that make these interactions really complicated and very rich. They're the types of things that lead to complex ecosystems the way we know them on earth and appreciate them on earth. Thanks for watching.