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How biodiversity is distributed globally

AP Bio: SYI‑3 (EU), SYI‑3.D (LO), SYI‑3.D.1 (EK)

Video transcript

- [Narrator] Life is everywhere. It's hard to find a place on the planet where there isn't life. Sometimes you might have to look really close, but you'll find it. One place where you find life where you might not expected is underneath a couple miles of ice. If you go down to the Antarctic, which is one of my favorite places, the ice sheets are very thick, and basically composed of snow that keeps falling, compacting and compacting and compacting until all the air is squeezed out of it. You get these enormous sheets of ice because the snow never melts. Underneath that, the pressure is so great that the water that's trapped underneath these ice sheets never becomes completely solid, and you'll have this lens, a layer of water known as Lake Vostok that forms below the ice sheet. Recently, a group of Russian geologists built themselves a drilling rig, and they drilled down through the ice to sample the water way down in Lake Vostok, and guess what they found? Evidence of what might be a sub-ice ecosystem with lots of species of bacteria and maybe even more complex life forms that they don't think came down with the drilling equipment. And if this isn't extreme enough or you, we can go to the other extreme, to places where it's really, really hot. A famous example of that would be in these amazing bubbling boiling cauldrons of water that are welling up from volcanic action in the middle of Yellowstone Park. You can do these fantastic tours and you see these amazing colors in all these pools and these colors, for the most part, are being produced in part by minerals but they're also being produced by life, single-celled microbes such as bacteria, huge colonies of them. We're talking about organisms that can withstand upwards of 80 degree Celsius, which would translate to somewhere in the neighborhood of 180 degrees Fahrenheit. So we're getting really close to boiling, and that actually prompts the question from some scientist, what is the upper temperature tolerance level of life? One issue that I think we need to look at here when we talk about life being everywhere is that we're also talking about something called biomass. We're talking about the different types of organisms that live in places, and the numbers of those organisms combine to give us the weight or mass of those organisms in a given place. When I say life is everywhere, it's everywhere, but it's also really abundant. Earth in some ways is a kind of living planet. People have said this before, but it's really true when you think about it in terms of the biomass being distributed everywhere across the earth. An important second point is that life is not evenly distributed. There are ranges, habitats and distributions that are characteristic for each species on earth. These are characteristics of any organism that can be studied. The ranges can be big, or the ranges can be small, but every species, every type of organism, has a specific place or places on earth that it calls home. One of my favorite examples of how we need to be careful about what we say or imply about the ranges or distributions of organisms is those cola commercials you see where polar bears are comforting with penguins. The only place where that can happen is in a zoo, and I'm pretty sure the zookeepers wouldn't be very happy about it. In nature, of course, polar bears occur in northern latitudes. They occur towards the North Pole. Penguins, on the other hand, occur only in the Southern Hemisphere, towards the South Pole. Mostly in the southern regions of the earth. So in nature, of course, they never mix, because they have different ranges. The study of the species distribution phenomenon is something we call biogeography. Graphy just means writing it down, getting it figured out, measuring it. Geo, of course, means earth. Bio, put the prefix, bio, in front of all of that, and what we're actually studying is where life occurs on the earth and we're describing what those patterns look like and how they come to be. This brings us back to the concept of species richness that we mentioned before. How many different types of species live in a particular place? We wanna measure species richness in order to understand some of these biogeography patterns. We have different ways of measuring species richness. We go out and do surveys and things like that and we find that in some areas, we have greater species richness and other areas have many fewer species. There will also be variation in how many individuals there are making up each species of what those population sizes are. So if you take a drive anywhere, just hop in a car and drive anywhere, you can see this uneven distribution in the types of organisms and in the number of organisms as you drive by. Let's start our rather longish drive in the Arctic tundra. Even though it's kind of a desert there, you have a complete ecosystem. There are different types of organisms that contribute to that ecosystem, but the number of species that live in that tundra is kind of low. The population sizes may be very high for some of those species, but the number of species is actually relatively low. Except for the tiny microscopic-sized organisms, you could actually see most of the species that occur in the tundra from the window of your car. Let's head south and say drive down the Isthmus of Panama and enter the Amazon region. You could look out the window of your car and you'd see diversity that's almost too huge to comprehend as you drive by. The types and numbers and ranges and distributions of organisms are almost uncountable, and we're working on trying to count them, but it's a big deal. It's a huge challenge for science. In the Amazon, we're talking about an enormous species richness. Same thing if you go snorkeling say right here off California, it's a fantastic place to go snorkeling. There are wonderful organisms, lots and lots of them. But now, think about, besides being much more comfortable in the warmer water, if you go snorkeling in the Philippines instead. The diversity and the species richness and even the actual biomass of the organisms that you see in a coral reef in the Philippines is much higher than you'd see along any rocky shore in California. And that makes a really great demonstration that not only do you see these differences in patterns on land, but you see it in the ocean as well. On earth, life is everywhere. It's just more abundant in some places than in others.