 Let's begin by drawing a cladogram, shall we? But of course. Let's start out with the out group to all animals. Who was that guy? Do you remember? It was the coanoflagellates, and that was a protist group, and I'm actually going to show you a picture of a coanoflagellate here in just a second. But I want you to remember that coanoflagellates, do they have a blastula? However, they share signaling proteins with us. And think about that. Messages are made out of the same molecule. So again, the more similarities we have, the more fundamental similarities we have with other critters, the more likely we are to have shared a common ancestor. Now, they're not animals. So everybody beyond this point has the blastula. And our first group of animals that branches off with the blastula is the sponges. They're called peripherals, but you can go ahead and call them sponges. So we're going to look at sponges. We're going to look at coanoflagellates. I want you to see a picture of a coanoflagellate first. Whoa. Now look at that thing. This is a single-celled critter. Here's its body. It has this like little frill, neck frill, like a collar, a collar. In fact, we're going to see some collar cells here in a second. Don't you kind of want to wear one of those things? And then this is crazy cool. They have flagella, like sperm. This is like a single-celled sperm with a collar. Wow. I bet if our sperms saw those, they'd be like, dude, why don't I have a collar? I want a collar. Well, if they were cool, like coanoflagellates, they would have a collar. Coanoflagellates use that flagellum to create currents in the water, and that draws stuff in to the cell and they filter feed. So they trap crap from the water in those little bristles, and then they yumselize whatever gets trapped in the bristles. And the flagellum creates the currents that bring the water in. Okay. That's awesome. Like, we could spend an entire class looking at coanoflagellates. What? Those things are awesome. They're not animals. They're single-celled protists. But do not forget what that looks like, because now we're going to look at our peripherals. This is an example of a lovely sponge. And again, like, I mean, I could call that a plant all day long that totally looks like one of those pitcher plants, like those carnivorous plants that the flies climb down to the bottom, and there's all those digestive juices down at the bottom, before little flies fall in and drown in digestive juices and feed the plant. I mean, I could see that being one of these things, but no, this had a blastula. All right, that's cool. But guess what kind of cells are found inside that thing? Seriously? Take a look. Does this look familiar to anyone? What? Dude, that thing? It's the koaniflagellate. I'm sorry. Look at that. It's the collar cell in a sponge. It's how sponges do their filtering. Sponges are filter feeders just like koaniflagellates. Go back. Look at the koaniflagellate. Go back. Look at the koaniflagellate. Dude, they're like identical. Can you see why humans decided, this makes a lot of sense, that koaniflagellates decided to become multicellular? Hey, you guys, let's be colonial. Let's work together. And if we all make a big tube, we can like make big currents happen, and then we can deliciousify. We can filter out the water that comes through with our big currents and be more efficient than if we did not have such a setup. It's pretty much unbelievable. And they're primitive animals. Sponges are primitive, but you can see why we thought they were related to koaniflagellates. Okay. Sponges are really simple. If you were to chop them up, you would see that they don't actually have a tissue level of organization. They really are like just a colonial multicellular critter, but the cells themselves haven't specialized to do jobs. We have tissues. We have cardiac muscle in our hearts where the cells have specialized to become contractile and do a special job, and they all work together to do that job. That's what a tissue is. They don't have tissues, but guess who's coming up next and guess what they have.