top down control cascades. They're seen in ecosystems were a predator high on the food web is going to control prey populations. Now what we can see is a trophic cascade where the predator is going to lower the abundance of prey and then reduce the next trophic level from predation or in this case, that we're going to take a look at herbivorous. You see, the wolf population in Yellowstone used to keep the elk population in check. But due to over hunting of wolves for very terrible political reasons, the wolf population of Yellowstone was diminished to nothing. They were hunted to extinction, and then the elk population exploded. And this actually lead Thio. Um, you know, a lot of herbivorous, and it greatly reduced the vegetation in the area. So this was an example of a trophic cascade because those wolves were actually protecting the vegetation indirectly by controlling the elk population. Now, primary production is something we look at Nikko Systems and this is the synthesis of organic compounds from inorganic carbon dioxide. And usually we're going to see this in the form of photosynthesis. And you can see the reaction here, uh, in the Calvin cycle that will perform this carbon fixation. And we're gonna be looking at different measures of production. There is gross primary productivity's E, which is the amount of energy generated by primary producers in an area over time. So here we can see our gross primary productivity. It's just all the energy generated now. Ah, useful, uh, measure toe look at is the net primary productivity. So some of that energy that is generated by the plants is going to be used by the plants own respiration. So they're gonna be returning that carbon to co two Now what you're left with after you take the gross primary productivity and remove what the plants used for respiration is the net primary productivity. So that's the gross primary production minus the energy consumed by the primary producers own respiration. And you can think of this is the total amount of new biomass added by primary producers. Now, net ecosystem productivity looks at the total accumulation of new biomass after the respiration off all organisms. So here you can see the net ecosystem. Uh, productivity takes that neck. Primary productivity minus everything that gets diverted to the hetero troves. Respiration. So everything we're left with. All that biomass left over is the net ecosystem productivity now that let's go ahead and flip the page.
