Overview of Animals - 5

by Jason Amores Sumpter
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the nervous system is one of those really especially unique things that animals have, and it actually forms from the primary germ layers. The Noto cord forms from the miso germ, and this is kind of like a primitive backbone structure that what are called core dates form. And in some animals this will develop into the actual vertebrae of the spine, whereas in others it's a transient structure that will go away during development. Now the neural tube is, ah, hollow structure that the brain and spinal cord will drive from, and that actually comes from the ectodermal folding in and creating this neural tube. You can see the tissue for it and purple over here, and it's going thio old, inward and eventually create this structure the neural tube, which will swell in certain places and that forms the embryonic brain. Those swellings Now there's a trend in animals in the evolution of animals called civilization, which is basically trend in which the nervous tissue becomes concentrated at the anterior end of an organism. And, you know, this is essentially how the brain comes to be right. This massive neurons that integrates and processes sensory information and is usually located at the anterior end of an organism. Now some organisms have a central nervous system where basically the nerves air clustered into one or more tracks that project through the body. So here we have an example of a central nervous system, right. We have this nerve cord, goes through the body and is, you know, a bundled pile of nerves. Basically, what we think of is less complex. Animals tend to have what are called nerve nets, which is basically unlike a centralized arrangement of nerves. It's a diffuse arrangement of nerves, Um, and it's found in Radio Lee Symmetric animals. So stuff like starfish like in this example here. And you can see, uh, the outline of the starfish, right? And in black, these This is the nerve net of the organism you can see that protrudes out into the little arms of the starfish. So it is not a centralized but a diffuse arrangement of nerve cells. Essentially, another pattern we see with animals is segmentation, which are basically just repeated body structures. So think of a warm. For example, worms have all those little segments. In fact, there are many animals that have segments um and we can often see this very clearly during development. So you might look at a fly and go That doesn't really look segmented. But if you look at a fly during development, you can actually see those segments a little more clearly. And if you want a better idea of all of this, I suggest you check out the video on development, which covers segmentation when talking about home box genes, which we've also mentioned here Now, vertebrates. Speaking of segmentation, vertebrates have this vertebral column that develops from that node accord. And most are dude er, soames and the vertebral vertebral column is segmented, right? It's segmented into vertebra, so even organisms like humans that don't necessarily outwardly appear segmented. Do you have segmentation invertebrates lack this vertebral column on and they will still have a segmented bodies, right? Like exterior structures that are obviously segmented. Most of these are gonna be protest owns. So just little distinction to make there. And we're gonna talk in much more depth about vertebrates and invertebrates on the chapters that cover those two organisms. Uh, there's gonna there's a chapter on vertebrates and then another chapter on invertebrates. So get a lot more detail on those in those other chapters. All right, See you guys next time