 So, I'd like to use Greenland as an example of an ecosystem with a low primary productivity. This is an image of the edge of the Greenland ice sheet towards the southwest part of Greenland. This area is dark for a large part of the time in the winter, of course, because it's a very high latitude. And the area is also very cold, in part because it doesn't get sunlight in the winter, and also because of the cooling effect of the large ice sheet. So in this area, there is very little vegetation. There are just lichens and a few small grass and mosses growing in this area. And this is one of my photos in this area here. These are these termigans, which are birds that eat the plants. One of the only other grazers is the reindeer. This is an image that I took from the web. So in this particular environment, because of the high latitude, either lack of light in the winter and the cold temperatures, we have low primary productivity. So the initial amount of biomass is low. And because it's low, and only 10% of it gets into the mass of the grazers, only 10% can go into these larger organisms like the reindeer and the termigan. So basically even the grazers are sparse or rare in this environment because there's such a low biomass. And in fact, there are so few reindeer and a termigan, there are not any major predators in this part of Greenland, except occasionally humans. So I'd like to use the Amazon Tropical Rainforest as an example of a high primary productivity region. The Amazon Rainforest is near equatorial latitudes, and it is warm and gets sunlight all year round. And there's a very, very large biomass. So this is an overview image of a dense forest. And in parts of the forest, you have a huge diversity of plants and primary productivity. Some capture the sunlight at the top of the forest canopy. And then all sorts of other plants grow beneath that upper canopy. And that leads to a very high biomass that can be consumed by grazers and then all sorts of other animals that include predators like the jaguar or frogs that eat insects, insects that eat plants or other insects, a variety of birds. And so when you have this very, very high primary productivity, you end up with a large biomass and you can get a very diverse food web with lots of members in it. And those members play different roles in the ecosystem and they interact with each other. And to have sort of that wide diversity of specialized organisms, because only 10% of the biomass is transferred to each trophic level where something's consumed, you have to have a very, very high primary productivity. And so the rainforest, one of the reasons they're so valuable on earth is they have this high diversity. They also have this high biomass. They store a lot of carbon. And there are places where the interactions among animals can lead to a huge diversity in terms of evolution and ecosystem function. Thanks for watching.