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General Biology

Learn the toughest concepts covered in Biology1&2 with step-by-step video tutorials and practice problems by world-class tutors

31. Invertebrates

Porifera and Cnideria


Porifera and Cnideria

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hi in this video will be talking about peripheral and Nigeria to Philo, which, despite appearances, are actually animals now peripheral arm or commonly known as sponges and their hermaphroditic organisms, for the most part, meaning that they're capable of reproducing sexually. But we also often seep sponges or peripheral reproduce a sexually. Now sponges are filled feeders, meaning that they eat particles that air suspended in water. And they're going to do this by actually drawing water through their bodies. And we can actually see a little model of a sponges body right here. And they have this central cavity that's known as the sponge Akel and this opening through which the water moves. That's called the OSCE Killem. Now the actual inside of the sponge Ecole is lined with these cells called Cohen A sites, and you can see a Cohen, a site here and these air flag elated cells. There's R Fla Gela, and these cells air what the sponge uses to actually feed on those suspended food particles and also bacteria. And they're going to use their flu gelatin, capture the various particles, and then they're actually going to eat them by faggot site Asus, which is that process where they take the particle into the cell and then they're going to perform intracellular digestion. So unlike you and I, who actually digest our food outside of ourselves, right in our elementary canals, these organisms will digest their food within the cell in the cytoplasm. Now this gray barrier that kind of separates the red and yellow portions of the sponges body is known as the me so ill, so that is basically a barrier that separates or shouldn't say barrier. It za demarcate er between the two regions of the sponge body, and it's basically this gelatinous matrix. It's, you know, kind of gooey, goopy stuff, and the amoeba sites are going to be very important for the me. So ill because they create these rigid structural fibers can almost think of it like the skeleton for the sponge. In a sense, they give the sponge body Cem support structures. They also are responsible for transporting nutrients, which is going to be super important for any animal now turning to Nigerians. These are creatures like jellyfish, probably a little easier for you to think of them as animals as opposed to sponges, which are just so alien it's hard to even think of them as living organisms. Nigerians are also like very evolutionary simplistic organisms. And they're gonna have a radial body plan which remember means that if we were thio sort of like look down on it, we could divided into four quadrants. This is as opposed to the bilateral body plan that will see later on down the evolutionary line. Now, uh, their bodies are basically just sacks for their gastro vascular cavity, which is basically the cavity that is going to be responsible for gastro eating, nutrient absorption and vascular as in transporting stuff around. So basically, it's it's the big everything cavity again, these air super basic organisms, you know, they're not gonna have closed vascular systems with veins and arteries that sort of stuff like we do now. Nigeria come in two flavors. You can almost think of it. It's more like two body plans. You have the polyp, which you can see right here. These are polyps. This is a hydra, actually. And basically a The polit body plan is a sort of cylindrical section which you can see right here and then let me jump out of the frames. You could see what I'm drawing and, uh, attached to this cylindrical sections. And we have thes tentacles which are used for capturing prey and also, uh, this segment right here that is responsible for adhering Teoh a surface. So ah, polyp organisms tend to cling to something and feed while they're clung to a surface. But they are not Cecil, meaning they don't say sedentary forever, like a barnacle or something. They can let go of whatever they're clinging. Thio escape a predator, for example. Now the other form of Nigerian that we'll see. It's probably the form you're more familiar with. This is like what jellyfish look like, and this is called a Medusa. You can see Medusa body plan over here and notice that it's almost like a nen vert ID polyp, right? Like the tentacles kind of. Or rather, I mean, like an upside down polyp. Almost right. So the tentacles, instead of being on the topside, are now flipped under the creature, and so is the entryway into gastro vascular cavity writes on the underside. Where is in the polyp? It's sort of on the topside Now. Nigerians have these specialized cells that are used for what we tend to think of as stinging right jellyfish like sting their prey. It was a little more going on here. These specialized stinging cells air called night of sites and they contain a structure called a new Mattis ist. And basically, this is a, uh a penetrating barb that can be fired out of the night a site. And the nomad assist is technically an organ l of the night of sight. Its main function is to shoot out that barb penetrate, Uh, a, uh you know, some sort of pray for the Nigerian, and it's going thio sting it, immobilize it potentially and allow the night Arian to then eat it. Now these guys, you can tell they are mushy, right? If you've ever seen a jellyfish washed up on the beach or maybe even floating around water I mean, it's pretty clear that these air just like gooey, squishy organisms, and that's because they have hydrostatic skeleton. Basically, their body is this fluid filled cavity right, filled with water, and it's surrounded by muscle. So the pressure of the fluid in the body that fluid pressure actually is what gives the body its structure it Basically the sort of tension between the muscles and the fluid in the body supports the body almost like a skeleton. Now, uh, the last type of Nigerian I want to briefly mentioned are called an tha's oa and the's are Nigerians that air like coral and sea and enemies. Um, what defines a lot of these organisms or something that, you know we can point Thio that makes them different from the guys we just talked about is ah lot of them have these endo skeleton rather exoskeletons that are made of calcium carbonate. Right? If you've ever seen a coral reef Ah, lot of the ah, a lot of the stuff in the Coral reef has like a hard structure to it. Not all of it. I mean, you know, there's like, seeing enemies that kind of look like those dudes that flop around it like a used car salesman. A lot or something. Um, Anyways, this is just the last type of Nigerian worth pointing out thes are going to be, you know, look different from the Medusa and ah, you know, like Hydra as other forms that we might see. Alright, that let's turn the page