Mollusks

by Jason Amores Sumpter
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molluscs are kind of the star of the show for the low Fetrow cause Owens. And that's because they come in a wide variety of classes that have bunch of different morphological features that air quite diverse. Now, molluscs as a whole are kulum mates, and their bodies tend to have these three characteristic pieces what we call the foot, which is basically a large muscle. Usually it's gonna be used for movement. We'll see pretty interesting exception with creatures like squid. So anyways, this bottom piece right here on our example that is going to be the foot. We also have the visceral mass which basically the internal organs of the organism and its external gills. And that's all this mess here. This is our visceral mass. Just gonna right VM for visceral mass. And the cavity inside of this is called the Chemical. And it's named for the fluid. Uh, inside of it called him a lymph, which is ah, similar to blood. Basically So uhh the he Michael that's the cavity, and it's filled with that fluid that is gonna act similarly Toe blood and that fluid is actually going thio directly bathe the organs because these organisms. Mostly there's gonna be an exceptional talk about later. Have a new open circulatory system. So, uh, the all right, You know, the fluids that air going thio carry gas is to the organs are not going to move through veins or arteries or anything like that. It's just kind of floating around in the coal. So, uh, the feeding structure briefly, I want to mention it's part of the visceral mass is called the Regula. It's at the anterior end. What you could, I guess, kind of think of like the head. And it's a little hard to see in this image, but the Rachael A is right there. Basically this'll feeding structure is it functions kind of like a rasp. So, you know, think about unum brace, Ivo edge or abrasive surface kind of rubbing on the food to break it down like a grinding type way now. Uhh. Not all molluscs have a rad, Djula. Um, but many of them do so that's why I mention it. Here is sort of a general feature of molluscs. The last structure that's common to molluscs is the mantle, and this is basically just a covering for the visceral Mass, so you can see that it's actually this layer here, this layer just under that outer shell in the picture that is, he mantle. And it often forms a hardened calcium carbonate shell, which we can see right here. This is the shell, but this is not always the case again. We'll see some exceptions. So it's worth noting that in some species there's something called a mantle cutting, and it's basically a water filled chamber containing the gills and the anise. And you can you see that little mantle cavity right there. Now we're gonna talk about a bunch of different classes of mollusc and the first one not a ton to say about these guys air called kittens. They totally look like some type of prehistoric organism. And what defines them is that they have a shell, which you can see on the top right here. This is the shelves, and the shell is made up of eight dorsal plates. You can see there's like eight segments to this shell. You can also kind of see the foot poking out from underneath this chitin. Now gastro pods, probably an organism. You're much more familiar familiar with these are slugs and snails. They're gonna live both in, uh, marine and terrestrial environments. And while many of them have shells, not all do. Of course, are snail pictured right here has a shell. Um, but, you know, there's plenty of these organisms thes gastro pods that don't have shells. Now, many of these species actually reproduce through sexual reproduction. If you ever want to see, like a wild YouTube video, look up like slug reproduction something like that pretty crazy acrobatic act, acrobatic act. Some species, however, perform parthenogenesis, which is that type of a sexual reproduction we discussed previously. With that, let's turn the page.