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Current time:0:00Total duration:8:12

Interactions between populations

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Video transcript

in the introduction to ecology we introduced the idea of a community which is all about different populations that are in the same habitat that share the same area or that are in the same area so populations and if we're thinking in terms of water or in the air could be the share share is similar volume even populations sharing sharing a habitat sharing a habitat and in particular in this video we're going to focus on the interactions between those populations the interactions between the different species the technical term for that is interspecific interactions I like to just say interactions between species now the first one that is often thought about is the notion of competition competition and this is when different populations different species are competing for the same resources you can imagine a forest where you have different populations of plants that are competing for sunlight that are competing for water that are competing for nutrients in the soil even in this picture right over here this is a picture of a community all of these different populations of fish and other things sea anemones and coral they are sharing this same region and many of them could be in competition with each other they might be going after the same food that we or they might be going after the same shelter someplace and oftentimes when people are talking about these interspecies or interspecific interactions you'll see something like this a - slash - or a negative sign slash a negative sign and that means that this type of interaction when you have two species or two populations that are in competition with each other the more that you have of one it's going to have a negative effect on the other and vice versa if I'm a plant and if I'm in competition with another plant and that one's taking my light and if there's more of it taking my light that's going to have a negative impact on me advice versa if I'm in competition with you and we eat the same thing the more of me that there's around eating your food that's going to have a negative impact on you and vice versa so the next form of interspecific in action or interaction between species is predation is predation this is when one population likes to eat another population and you might often associate predation with pictures like this that you see on on television shows on documentaries you see a cheetah hunting it looks like a cheetah hunting a a gazelle or a deer of some kind actually it says right here it's a young Bush back and this is predation and but this is not the only form of predation this picture here of the goat eating grass this is also predation it's not quite as bloody and is violent but it is still predation because you have one species eating another put species in this case you have this animal the goat that is eating the grass and this type of predation the specific type of predation is called herbivore a herbivore but it is a type of predation so we could say predation / herbivore let me do a little slash here / herbivore II which is a special case of predation and you'll often see a + / - the more of let's say this species that you have the the species that is being eaten it's going to benefit the predator but the more of the predator that you have it's going to have a negative effect on the actual prey now the next the next types of interactions are ones where you have long term very fairly intimate interactions they are the where you have organisms that that often time live with each other or even on each other and this general term of organisms that have these long term intimate interactions is symbiosis symbiosis now in everyday language when people talk about symbiosis they're often talking about organisms that really benefit each other but technically symbiosis isn't just about benefiting each other it could be that they're even hurting each other in some way or that maybe one benefits while the other one really doesn't care and so there are several types of symbiosis the first that we could talk about is parasitism para Pera sit ISM and this looks a lot like predation where the more the more the the parasite benefits the more of the host that there is but the host is actually hurt by the parasite and there's all sorts of examples of parasitism we have right over here a zoomed in picture of a louse so why is this parasitism well if this lice of this louse I should say so this is parasitism parasitism and we would call the this right the light the louse here a parasite parasitism and this benefits by living in your hair because that's where it gets its food from it can lay or living on your scalp it gets your food by sucking your blood it can also lay eggs in your hair in some ways you could view it as almost shelter from from the rest of the environment but it's negative for you it will make you itchy it is taking your blood it is uncomfortable and so parasitism once again it's good for the parasite just like predation is good for the predator but not so good for the host in the case of parasitism now you have another situation where it is benefiting both sides and that is called mutualism mutualism let me do that in a different color so mutualism this is where both sides benefit and oftentimes when people talk about symbiosis they're really talking about mutualism which is a specific type of symbiosis where both species were both animals organisms benefit they don't have to just be animals this is an example of mutualism right here let me do that in a color you can see so this is mutualism where you have where you have a clownfish living within a sea anemone the sea anemone is providing the clownfish shelter while the clownfish is keeping away other fish that might eat that sea anemone so they are both benefiting from that interaction and so that is mutualism now you have another category we're one where one species is benefiting and the other one is maybe a little bit more and different so one species is benefiting and then the other one well maybe it is a little bit indifferent and we call that commensalism amensalism and once again there's many examples of commensalism this right here is a picture of bacteria living on your skin and you do have bacteria living on your skin right now except it's actually well oftentimes it's a good thing sometimes it's mutualism that it's providing protection from harmful bacteria but sometimes it the bacteria is surely benefiting it's its living off of nutrients on your skin the skin is its habitat but often times it doesn't really have an impact on you now commensalism let me write this soo down commensalism often times the more that we study it and the more that we understand it we realize that actually maybe maybe the host actually is benefiting in which it is mutualism or maybe the host actually is getting hurt in which case it is parasitism so oftentimes commensalism isn't completely neutral for the host it could go either way and so these are all the different types of interactions so I encourage you look around you look at the world around you and don't just limit yourself to animals think about bacteria think about plants and think about within a habitat what are all of the different interspecies interactions and how you might want to classify them
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