 I don't know, I don't know if there is a way to really grasp how phenomenal photosynthesis is. And when I say go kiss a tree, I mean it like a big hug and a kiss for the next tree you see, because it's like, it's incredible, I'm going to tell you some things. First of all, photosynthesis evolved two billion years ago. That's a long time. In this class, we're going to talk about evolution and we're going to look at the history of life on earth. And I want to say, I can't remember, I'm not going to give you a 3.5 billion years ago life evolved, maybe it was 3.7. We'll have a number at some point, I should have looked it up before this. What two billion years ago is when life figured out photosynthesis, when photosynthesis first evolved in some little single celled critter, a little prokaryote likely, when that happened, there was like this explosion of change. And there were two things, so like an explosion of biodiversity. Two billion years ago, photosynthesis evolved and the result was, good graciousness, biodiversity explosion, an explosion of biodiversity when photosynthesis evolved. So we started getting like all these different cool critters with photosynthesis. Why? Well, there were two things that occurred. One, oxygen became plentiful. In fact, I want to say some, and the significance of this, of oxygen as a thing, the oxygen in the atmosphere. It started out with like none, no oxygen in the atmosphere. And then some critter figured out photosynthesis and started producing oxygen as a byproduct. And oxygen levels in the atmosphere increased. And as they increased, as oxygen levels increased, critters changed. In like dinosaur times, what, 65 million years ago? Or maybe that? I can't remember. Right now, because I don't have them on hand. But there was a time, there was a prehistoric time around dinosaurs when the oxygen concentration in the atmosphere was more than it is now. And the critters were bigger and wilder. Like you've seen really humongous bugs and like crazy huge dragonflies. It's because there was more oxygen to fuel their energy needs. When oxygen levels drop, our capacity for energy drops. When oxygen levels rise, our capacity to have energy increases. We can become more complicated. We can become more resilient with more oxygen. So you had this biodiversity explosion because oxygen became more plentiful. The other thing that I think is really interesting is that as oxygen began to be produced in the atmosphere, the ozone layer was formed. And that was protective. So the ozone layer is has protected critters from all that crazy light and electromagnetic radiation that's coming from the sun. Not all of it gets through because of the ozone layer. And that served as a protective field to allow this increase in biodiversity. I think that's all I have to tell you about oxygen. But it's not messing around. It is the reason that there's so many cool things out there. So I love photosynthesis. I think cellular respiration is amazing. And we're next headed into how DNA works, which, oh my gracious, that's going to be another whole cool thing too. Okay, energy, our energy sandwich is done. So maybe now I'm going to go get our other sandwich. Bye-bye.