 So, in this video I'd like to talk about why primary productivity is important. So we have photosynthesis, so I'm drawing some grass down here, and basically that process of photosynthesis creates a biomass. So you have carbon dioxide plus protons and electrons going to organic matter, right? And then this organic matter is what makes the biomass, right? And then a lot of other organisms eat and decay that biomass by basically taking oxygen and reacting it with that biomass to go back to getting the carbon dioxide, right? So for energy, organisms that eat biomass, some of it with oxygen, but they also take some of the organic matter, and they use it in their own bodies or their own biomass, okay? So we have the primary productivity that creates this first biomass and is getting consumed in this case by a cow. Some of the grass that the cow consumes reacts with the oxygen to create carbon dioxide and water plus energy, and some of that organic matter goes into the biomass of the cow. So the proportion of these two varies a little bit, but on average 90% of what an animal eats goes into producing the energy for it to live, and only 10% goes into the biomass of creating the cow. So over time for the cow to grow, it has to eat about 10 times the amount of food as it weighs. So it's a really significant amount of energy or biomass is lost when you go from your photosynthesizers into your grazers here. So there's a lot of loss of biomass in this process. And that means that you'll have to have about 10 times more photosynthesis creating biomass than you have accumulation at the next trophic level. And then, so for example, I should say trophic level is the number of times something gets eaten and converted into another organism. So let's say that the person here, me, I'm eating my ice cream cone made from this cow's milk here, right, and it has, of course, sugar from plants. So some of that is coming from plant biomass to go into the ice cream. And then we also have to have our chickens here that laid an egg that goes into my ice cream cone as well. In each case, I only gain enough biomass of 10 percent of each of these, goes into biomass, and that other 90 percent gets consumed as energy. So in this particular case, if most of it came from the milk, it would be you lose 10 percent, or you only keep 10 percent, you lose 90 percent, you lose 90 percent. At each level on the food chain, a large proportion is lost. So to have very much biomass in an ecosystem, it requires much more primary productivity than the actual mass that you would measure. Because a lot of it gets consumed as is energy that actually maintains organisms a lot. And the other thing, so it really needs lots of primary productivity, and the second thing is that the more times things are eaten, and also the more trophic levels, and trophic levels are the number of times things are consumed. So the number of times you go from grass to cows to people, things like that, the more trophic levels requires more primary productivity. So there's this whole process of loss through the consumption of food at each level. So what that means is that the more primary productivity you have at the bottom of the food web, the more biomass can actually be maintained in an ecosystem.