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Ecosystems and ecological networks

Biodiversity, specifically species richness, plays a crucial role in ecosystem stability and resilience. The emerging field of biodiversity-ecosystem function (BEF) studies these interactions. Higher biodiversity spreads interactions among more species, reducing the chance of ecological collapse. Ecosystems with more species and interactions are less likely to suffer negative impacts from disturbances, as crucial components are less likely to be removed. Created by California Academy of Sciences.

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  • blobby green style avatar for user Mailliw Htims
    But what about when you add humans into the mix? we can create synthetic food and other previously animal based supplies. So do humans need to protect other species or can we do without? Even if we can't live without them can't we keep their DNA samples stored somewhere to be grown when needed?
    (19 votes)
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    • purple pi purple style avatar for user Hannah Elaine
      Good question! Humans probably can make up for some the biodiversity that we lose is synthetics ways and stuff like that, but that doesn't take care of the all of the problems. For one thing, plants do a very good job performing photosynthesis. I don't think humans have ever found away to convert energy into food. Even if we have or possibly can it's probably not as efficient as a plant's photosynthesis and it would hard to reproduce that process on a scale large enough to feed millions of people. Also, plants are at the bottom of the food chains and if we lose plants we lose all other kind of living organisms.
      Another effect losing biodiversity has is on the climate and cycles of water, carbon, nitrogen etc. (Hank Green does a good job explaining them here: https://www.khanacademy.org/partner-content/crash-course1/cc-ecology/v/crash-course-ecology-08 and here: https://www.khanacademy.org/partner-content/crash-course1/cc-ecology/v/crash-course-ecology-09 ) Our climate gets messed up when the ecosystem is messed up (and our ecosystem gets messed up when the climate gets messed up...).
      Also,the problem with losing some biodiversity and trying to get along with only some other species is they are all inter-related in very complicated ways, and I don't think we fully understand them all. We have a intricate balance and if that gets messed up we might have more problems than we can predict.
      However, as we do lose biodiversity, we might have to do more with creative solution that don't make us depend on other species. But that isn't the best solution and preserving the environment, in the end, the most productive and cost-effective solution.
      (32 votes)
  • leaf red style avatar for user Jack McClelland
    At around , the author mentions Fungi. How is this pronounced (I've heard it many different ways; which is most scientifically correct?)
    (11 votes)
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  • male robot hal style avatar for user AGLUTENFREEFOOD.
    Fun"G"i, not Fun"J"i.
    (10 votes)
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  • blobby green style avatar for user seanhannonedit
    What happens to the eco system when an almost extinct animal is reintroduced back into the system. Such as wolves back to Yellowstone. They are flourishing now since being brought back; Is there a chance the larger numbers could create more problems?
    (6 votes)
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    • blobby green style avatar for user B.Grünerde
      As the video suggests, introducing wolves has created more connections. Previously, elk over-browsed (ate) shrubs and young trees growing in open areas. This led to a lack of food for beavers, which resulted in their disappearance. Without beavers, streams were not blocked with dams at any points. Without dams, ponds and wetlands didn't form. This removed a significant amount of heterogeneity from the system (less habitat types). By introducing wolves, the elk no longer "over graze" these areas, allowing willows and cottonwood to grow. These are then consumed by beavers who build the dams, allowing new habitat types to form for other species to live in. More wolves may reduce elk populations, but the produces a feedback on the wolf population. This is a well known process in ecological studies best described in Canadian lynx and hare populations.
      (9 votes)
  • hopper cool style avatar for user Grace  McIntyre
    Is it possible for there to be a positive outcome if a species is removed? For example, I have heard about how if humans are wiped away from the earth, than the carbon emissions will reduce significantly, there will be more nature, and other species will be able to flourish. Though it may be bad for some species that are dependant on us (say, domestic animals such as dogs and modern pigs), will it have a better impact on the earth?
    (6 votes)
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    • male robot donald style avatar for user Tybalt
      Probably not.

      Each species takes up an ecological niche. They perform certain roles, they have their own set of predators and prey, and they each perform their roles at different times. Remove a niche, and the ecosystem is disturbed. Predators may begin to starve, prey may begin to overpopulate, dead bodies may begin to pile up, populations cannot be controlled, species cannot benefit from each other, etc. While it may be possible for a niche to be completely removed and be beneficial to the ecosystem, this is very unlikely. Besides: another organism may just re-make the niche and any benefits an extinction may have had will be gone.

      As for humans going extinct, while it may result in more nature, less carbon, and less species being threatened to death, consider the other systems humans manage. For instance, how about the hundreds of running nuclear power plants all over the world? Nuclear plants have to be constantly monitored and be controlled with precision. Nobody is going to do that if humans just suddenly disappeared from Earth. Sure, the animals recovered from Chernobyl and Fukushima, but how about if all of them detonated for weeks on end? What about all of the urban land and desertification? Where are the animals going to go now? Plus, animals like foxes and dolphins are being domesticated more thanks to interactions with humans. What about them? What about animals in captivity?

      I have no idea if such a planet would be better or worse for animals, but our disappearance would change it drastically.
      (9 votes)
  • blobby green style avatar for user Alyisa Caryl
    I love the visualizations, and appreciate all the interconnections. But I wonder if the emphasis in the trod unction on the bigger species be it google or a whale is maybe misleading, or better said leads our thinking away from the smaller species that place a very crucial role, and the first one that comes to mind is the honey bee - but even in your example the plankton maybe equally if not more important than the larger species. I think we too often are focused environmentally on those bigger mascot species.
    (7 votes)
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  • blobby green style avatar for user masonjr91
    What if a species doesn't have any other species left to feed on, can that species adapt to another food source? Or will the species just die off?
    (4 votes)
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  • blobby green style avatar for user Debarshi Das
    I could not ask in the previous video...Is poaching a density-dependent or density-independent factor ?
    (6 votes)
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    • female robot grace style avatar for user RazzRack
      In a way both, because you could consider poachers to be like any other sort of predator. The more animals there are (Higher density) the easier the animals will be to hunt and so the animals will die more often. But at the same time that's not really the case because humans aren't normal predators. While a normal predator might think "hey there's not very many of these rabbits. I better go hunt for something else". A human wouldn't care how rare the rabbits are because they want them for money not for food. So somewhere in the middle leaning towards density-independent I'd say.
      (5 votes)
  • piceratops ultimate style avatar for user Kyle Wyonch
    This seems like such a fragile system, why haven't humans or other "invasive species" destroyed this yet? Or do we and it's on such a small scale scale that it doesn't matter?
    (4 votes)
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    • purple pi pink style avatar for user PERCE-NEIGE
      It takes a lot of time to destroy it (for the whole system to collapse), because the systems constantly try to adapt themselves, but we already killed so many micro and miso-ecosystems, than the macro ones are wounded and very ill now (our body is an ecosystem too) Balances are always fragile, because they are balances, too much weigh and the whole is ruined. A chance they are "clever" balance and have adaptation faculties, but if you upset the balance faster than it repairs itself, the collapse is inevitable.
      (6 votes)
  • male robot hal style avatar for user intern
    At , the diagram has a few sections of where one organism is getting energy from another organism, but the other organism is getting energy from the same organism. How can this be?
    (5 votes)
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    • leaf orange style avatar for user siiky
      "Getting energy from" doesn't necessarily mean predation, it could be, for example, a goat feeding on grass, and that grass being fed by the goat's feces. (Also note that the interaction is on a species level, not in an individual level)
      (3 votes)

Video transcript

- [Narrator] 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 gonna 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 decompose into, and they, plus the physical environment, 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 as 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 directional 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 would 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 goin' 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 Mister Whale over here. That's what these lines represent. They represent the flow of energy through the ecosystem. Eventually, the whale succumbs to life and dies. And, poor Mister Whale ends up on the sea floor. Are things over at that point? Definitely not, because at that point, he's gonna 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 comes 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 whale's been accumulating from these producers, the plankton that it's been feeding on, is returned to the environment cycled 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's 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 in ecosystem function. If you take the whales out of the equation by over-hunting them, you get this drop in ecosystem function, 'cause 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 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, there are places where that network's going to show a lot of stuff going on. A major hub in the internet. A lot of messages are flowing through. Like Google's 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 gonna be places like my desktop, where I'm just messaging my kid to tell him 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 gonna 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 gonna reduce the chance that a perturbation or a disturbance is gonna have a really negative impact. Because you're just reducing the chance that you're gonna 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 ailerons. Imagine this aircraft flying along. If you take out, say, the curtains that are in the window, you're probably not gonna 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 wing's gonna fall off, and we're gonna have a problem. 'Cause before you know it, the airplane's going to crash. Same thing with the ecosystem. Everything's doing something different. Some things will matter more than others if you remove them. The more bolts, the better.