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Studying for a test? Prepare with these 8 lessons on Ecology.
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if we think about our biodiversity tutorials as an archipelago then today we visit this island to discover why biodiversity is so important in terms of biodiversity we mean a lot of different things in this case we're going to talk about something that's known as species richness because that's something that we can measure because counting up the number of species going out and finding out how many species there are in a given environment is something that we can actually do there are different species of plants there are many different species of animals many different species of microbes and many different species of fungi and they all interact in their environment to create what we would call an ecosystem eco is an interesting word it's an ancient word that means house so it's a system of what goes on in your house that is where we all live all of these different organisms are interacting they're behaving together they're interacting with one another some of them eat each other some of them eat what others decomposed into and they plus the physical environment or or the house form the ecosystem why would the number of species in other words species richness be crucial to the way an ecosystem functions what is it about the number of species that makes the ecosystem work better and contribute to the resiliency or the stability of the ecosystem scientists are really beginning to study this and the emerging field is referred to as BEF biodiversity ecosystem function we can think of any ecosystem a species that network one to another they have interactions with each other they can be a lot of different interactions they can live on top of one another like certain birds nesting in trees or even more crucially these things might eat one another this is a diagram a network diagram of believe it or not a relatively simple ecosystem in which the organisms are interacting one with the other we can draw lines between the species to indicate those interactions and we can make the lines direct to show that material or matter and energy are moving from one species to another when one organism takes a bite of another it not only gets a mouthful of matter or food but that food contains energy so these arrows show the direction that energy is flowing from one species to another the most important thing about these webs is that the strength of these interactions can vary that is the interdependence of the organisms in the web can vary and here's something that might be counterintuitive these interactions become less important the more species you have within a network you can think of it as the interactions being spread among more players but what happens when there are fewer players let's say we've got a really super simple set of interactions where this owl is eating that Mouse but can also eat this squirrel this gives the owl options if we remove one of these take that guy right out of there then we only have two species that are interacting with each other and it's really easy to disturb this system this guy will just eat all of these guys and boom you can cause total ecological collapse so the higher the biodiversity or species richness in a system or in a network the stronger it is the more stable it will be because of all the additional options open to the organisms in it think of that old saying about putting all your eggs in one basket not all interactions within a given ecosystem or network are exactly the same strength because some species have stronger interactions with each other than they do with some other species for example let's imagine that somewhere in here you've got one of these guys and he's eating plankton the microscopic organisms living in the water plankton are going in these guys are the producer end of things the ones who can photosynthesize and make chemical energy from sunlight and remember food equals energy so what we're talking about is a lot of energy flowing from the producers to the consumer represented by mr. Weil over here that's what these lines represent they represent the flow of energy through the ecosystem eventually the whales that comes to life and dies and poor mr. whale ends up on the seafloor a things over at that point definitely not because at that point he's going to give up stuff that ends up as part of the producers food web it's shown actually we're starting to get some really great new evidence that these events where whales fall onto the sea bottom start an ecosystem of their own in ways this is known as a whale fall don't get under one it's always best not to be under one but when the whale does hit the bottom all kinds of interesting stuff happens lots of organisms come and feed on the whale there's a succession of organisms that is organismal communities that change over time as the condition of the whale itself changes that turn this whale from a fleshy organism to bones and eventually even the bones are eaten so this huge influx of energy that the whales been accumulating from these producers the plankton that it's been feeding on is returned to the environment cycle back through the ecosystem you might imagine that that complex set of events that I just diagrammed here are part of this little bit of web it turns out that where you get concentrated clusters of things happening in these webs it's usually because energy is being run through the larger organisms in the system and when you disturb a bit of that where you've got large amounts of energy flowing through the system you can get a real drop an ecosystem function if you take the whales out of the equation by overhunting them you get this drop in ecosystem function because there's this removal of an entire major energy flow system from this network think of it a little bit like this tremendous thing that we have now this this internet if you draw a diagram of the interactions amongst all of the servers and all of the things that push messages through the internet they're places where that networks going to show a lot of stuff going on a major hub in the internet a lot of messages are flowing through like Google servers for example Google is going to be at the center of one of these big clusters of a lot of messages going through other servers may not be so important those servers are going to be places like my desktop where I'm just messaging my kid to tell them to come home for dinner if you take my server out of the system it's not going to disturb the entire web but you can see what happens if you suddenly take Google out of the system you're going to greatly perturb that particular ecosystem so these webs of interaction throughout an ecosystem are really really important if the system is bigger with more species and more interactions you're going to reduce the chance that a perturbation or a disturbance is going to have a really negative impact because you're just reducing the chance that you're going to take out something that's really crucial the other thing about this is that all of these things are doing something different they're all doing different things in the ecosystem so if you imagine one of my favorite things I love planes here's a complicated plane with four engines lots of moving parts piston engines roaring away you've got a rudder here you've got a Lauren's imagine this aircraft flying along if you take out say the the curtains that are in the window you're probably not going to bring the plane down but if you do something like remove a couple of the crucial bolts at the base of the wing here where it connects to the fuselage then the wings going to fall off and we're going to have a problem because before you know what airplanes going to crash same thing with the ecosystem everything is doing something different some things will matter more than others if you remove them the more bolts the better you