hi in these videos will be talking about core dates and specifically will be looking at vertebrates, which are a group of animals that have vertebrae. But before we get there, let's actually go ahead and define what a core date is. And it is a bilateral do tourist stone animal that is going to have at some point in its life cycle for specific features. And those are the dorsal hollow nerve cord, the Noto cord, a post anal tail, and Farron Jill Gill slits. Now the dorsal hollow nerve cord is going to be a hollow tube that forms from the ectodermal, which is one of those primary germ layers, and you can see it in this image along the backside of this organism. Below it, we see the node accord, which is if formed from the miso derm, another one of those germ layers, and is going to have a variety of functions and animals, including a place for muscle attachment, which is going to be important in animal movement. In some cases, now, the dorsal hollow nerve cord, actually in some organisms, will go on to form the central nervous system that is the brain and spinal cord and likewise, the note accord in some organisms will go on to or in some coordinates, rather will go on to form the vertebra. So in in some respects, you can think of the dorsal hollow nerve coordinate accord as precursors to the central nervous system and the end the vertebra of the spinal cord, respectively. Now, the post anal tail, pretty self explanatory. Just tail that extends beyond the an issue could see it right here in this organism. And these pharyngeal gill slits thes are openings between the pharynx and the external environment. You can see them right here in the image and believe it or not, you know, humans, for example, developed these, uh, as fetuses while we develop, we actually get gills and then we lose them. So that should just reiterate the point that these four features that define coordinates are not present during the entire life of the court date. They just have to be there at some point in the life cycle. And that could be very brief Window indeed. Moving on. Let's talk about two organisms that, while are not vertebrates, are considered to be coordinates. And these are Cephalon coordinates, which are organisms like lance slits and the's are kind of like fish, in a sense, I mean, you can see a picture of one there. Uh, here is a more anatomical diagram of it. They kind of look like fish, though they are technically not fish. Uh, in fact, fish will evolve. Uh, you know, later, down the line these air very primitive organisms, and they use their pharyngeal gilles slits. Thio feed in sort of suspension feeding process. And they will have muscle attachments to that note accord that allow them to swim. And again, they're going to swim. Kind of like fish they, you know, have that sort of appearance of being fish, even though again, they're not fish. Now. We also have these quite strange organisms called your accord dates. And a new example of your court date is an organism called a tunic. It and these guys, they look kind of like this later in life. You're probably going How is that a court date? Well, they actually Onley get these coordinate features as larva. So here you can see a tunic, it larva, and you can see all the necessary features of the coordinate. Let me jump out of the image and highlight those for you. We have the nerve cord. That's gonna be that dorsal hollow nerve cord. We have a noto cord. We have. We have the tail right here, and we can't actually see it on this diagram. But these guys are gonna have some gill slits. All right, so, uh, believe they're not some tunic, its air actually eaten, in fact, considered a delicacy. For example, sea pineapples in Japan, despite having a flavor that's described to be similar to that of ammonia cleaning chemical. Apparently, it tastes very good when paired with sake. I don't know. Go figure anyhow, that let's flip the page.