Lophotrochozoans - Video Tutorials & Practice Problems
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Lophotrochozoans
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Okay, everyone. In this lesson on invertebrate organisms, we are gonna be specifically talking about Lophotrochozoans. And while they have, like, a really crazy name, I promise they're not that terrible. Lophotrochozoans, that's a superphyla. So, a super phila is gonna be 1 big group that contains many other phila. So in this super phylum sorry. Phylum is the singular. Phyla is the plural. So in this super phylum, we're gonna have many different other phyla that we are going to talk about that fall under this category. So, Lofotrocozoans have a really crazy name, but it's kind of, a smash up of 2 of the main types of organisms. As you can see, we have Lophophorates are one of the types of organisms we're gonna talk about, and then we have trochophores, another type of organism we're gonna talk about. So, Lophotrochozoans is a combination of those two names. Now, these invertebrate organisms are bilateral. Remember, that means that they are mirror images. So, we are bilateral protostomes. Remember They are protostomes. Remember, that means an embryonic development, the mouth is the first cavity that is formed. In contrast to deuterostomes, where the anus is the first cavity that is formed. Many are coelomates, meaning that they surround their digestive. Means that they have water inside of their bodies, and they're using that water pressure to keep their bodies upright to give them structure. Like our solid bone skeleton gives us structure, they have a water system inside of their bodies that gives them structure. So, now let's talk about some specific types of Lophotrochozoans. And we have the trocophores. These are gonna be any types of organisms that have larva with a ring of cilia around its body, and this is gonna be used for swimming and feeding. I'm gonna go out of the picture because this image right here is gonna show you what a trochophore actually looks like. This is a trochophore larva. Remember that that is the adolescent stage or the non adult stage of this developing organism. And you can see here that I'm highlighting in yellow this ring of cilia, and this ring of cilia is utilized to bring food into the larva and help it move around. Remember whenever we learned about cilia, these are gonna be projections from the cells and they do have movement. Some examples of organisms that are trochophores are going to be mollusks and annelids. We're not going to talk about mollusks or annelids in this particular lesson, but coming up in the next couple of lessons we will definitely talk about mollusks and annelids. So mollusks are going to be things like oysters and clams and scallops, and annelids are actually segmented worms like earthworms. And they are trochophores because they have a larva with a cilia ring. Okay. Now these trochophores have an alimentary canal. You have an alimentary canal. And these are gonna be digestive tubes with 2 openings, a mouth and an anus. That's very simple. That's common to a lot of organisms. Now, let's move on to the lophophorates. This is a different type of organism. These are going to be animals with a lophophore. A lophophore is gonna be a really specialized feeding mechanism, so a specialized structure used for suspension feeding. And we can see that in this image right here. You can see that it looks like a little crown of these little cilia or these movable projections. And commonly, you'll see this structure called a crown because it kind of sits on the organism and it'll move its little they kinda look like fingers to me. It'll move its little fingers and grab food from the water that surrounds it. This is going to be a lophophore, and it is a really interesting feeding mechanism that grabs food and then pushes it towards the mouth of the organism. Okay. So, some examples of Lophophores are gonna be ectoprocs and brachiopods. So, ectoprocs are actually what you are looking at here. These are going to be coral reef building animals, but they're not coral. Okay. We will talk about coral in a bit. Coral is actually a cnidaria, not a ectoprot. So whenever you think of coral, like an actual coral organism, those are not going to be ectoprocs. Well, ectoprocs do create coral reef structures. They actually kind of look like moss. So if you you can see here that it kinda looks like a hairy little structure that might look like a patch of moss if you saw a whole bunch of these organisms together. And they look so much like moss that another name for ectoprocs is going to be Bryozoans. And if you remember or if you've gone over the lesson on plants, the name for moss is bryophytes. So, these are bryozoans. They look like moss. So, those are two names for the same thing. Ectoprocs and bryozoans, they're the same thing, but they do look a lot like moss, and they some of them do have these hard exoskeletons that allow them to build these reef like structures. They look like mollusks. They kinda look like bivalves. They look like molluscum, they look like mollusks. They kinda look like bivalves, but they're not. They're not bivalves even though they look a lot like bivalves. So, brachiopod, so, brachio or, let me see. I did that wrong. Brachio actually is a word that means arm. Pod is actually a word that means foot. So their name actually means arm foot. And their arm foot, you can see right here, is utilized to hold them in place, to give them structure, to give them, the a place thing to hold on to. They use this arm foot to actually dig into the sand or the dirt and hold themselves in place. And no, it's not called an arm foot. It does have its own name, and this is actually going to be a pedicle. So their pedicle, or their arm foot is used to hold them in place. They're mostly marine animals, but they're not bivalves. Even though they do have 2 shells that close, they're actually not bivalves. Bivalves will have a left and a right shell, and they commonly open their shells like this. They have a left and a right. However, brachiopods have a bottom and a top shell, and they commonly open their shells like this. And the foot will stick out the back. So that is what a brachiopod is, which can kinda be confusing with bivalves. But these are lymphotrochozoans. Okay. So now let's scroll down, and let's look at some other lymphotrochozoans, which are pretty interesting. Phylum, they also have a really crazy name, but most people generally just call these flatworms. And flatworms, there's a ton of different types of flatworms. They come as saltwater. They can live in the saltwater. They can live in freshwater. They some of them are even parasitic. A lot of human parasites are actual flatworms. And flatworms are a coelomate, meaning that they have no body cavity, no internal body cavity. They are triploblasts, they have 3 cell layers, and they have a rudimentary digestive system. And what this means, rudimentary digestive system, means that they only have one digestive opening. They only have a mouth, and food goes into the mouth, is digested in their digestive system, and then waste comes out of the mouth. So, they only have a very rudimentary digestive system. Now, they are some of the simplest Bilateral Organisms, and they lack gas exchange organs. They don't have lungs, and they don't have gills. So, what they do is they actually do the elimination of nitrogenous waste and gas exchange across their body surface via the process of diffusion. So, because they use diffusion, that means they can't be incredibly large. So, most of these flatworms won't be very big at all. The maximum size, I think, is they get, like, maybe this big, and that's because they have to do diffusion, and they don't have circulatory system, and they don't have a respiratory system. So, these organisms can perform sexual and asexual reproduction, and they are very commonly parasitic. So some require hosts to reproduce. So, for example, tapeworms and flukes, which are 2 human parasites, are going to be flatworms. They're gonna be in the group Platyhelminthes, and you guys can see a saltwater flatworm right here. Okay. So now we're also going to talk about rotifers. Rotifers belong to the phylum Rotifera, which I will write for you. They belong to the phylum rotifera, and rotifers are pretty cool. They are actually gonna be I'm standing in front of a picture of one here. I'll let you guys see it. They are actually going to be microscopic organisms. Well, my button's not working. But anyways, you can see here, they're actually going to be microscopic organisms. You can only see these under a microscope. And, they are also gonna have bilateral symmetry. Even though they don't really look like it, They do have bilateral symmetry, so do flatworms. Remember, that means that if you cut them in half, they're gonna have mirror images of one another. They are pseudo coelomates, meaning that they have a body cavity, but it's not a true coelom that surrounds their digestive tract. And they're gonna be named for the ring of cilia around their mouths which you guys can see is this structure Now, they Now, they're going to utilize parthenogenesis. This is a very unique way of reproducing. It is an asexual reproduction in which females produce unfertilized eggs that rise into more females. So basically, what it is is the female is going to be, making clones of herself. So she's gonna be making more females, and they can use this asexual reproduction called parthenogenesis. These rotifers are also very, very important for, freshwater ecosystems. They are mostly freshwater and they're gonna be one of the components of of zooplankton that are gonna be very very important for all the fish and crabs and different things that live in freshwater lakes and streams. They're gonna need these rotifers to eat. So they're a major food source. Okay, everyone. So now we're going to talk about more invertebrate organisms, and we're going to move on to mollusks. Okay, everyone. Let's go into our next topic.
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Mollusks
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6m
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Mollusks are kind of the star of the show for the lofotropozoans. And that's because they come in a wide variety of classes that have a bunch of different morphological features, that are quite diverse. Now, mollusks, as a whole, are collimates 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 a 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. I'm just gonna write vm for visceral mass. And the cavity inside of this is called the hemichole and it's named for the fluid, inside of it called hemolymph, which is similar to blood, basically. So, the hemichole, that's the cavity, and it's filled with that fluid that is gonna act similarly to blood, and that fluid is actually going to, directly bathe the organs because these organisms mostly, there's gonna be an exception we'll talk about later, have an open circulatory system. So, the, you know, the fluids that are going to carry gases 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 hemichole. So, the feeding structure, briefly, I want to mention, as part of the visceral mass is called the radula. 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 radula is right there. And basically, this feeding structure is, it functions kind of like a rasp. So, you know, think about, an abrasive edge or abrasive surface kinda rubbing on the food to break it down, like, in a grinding type way. Now, not all mollusks have a radula, but many of them do, so that's why I mention it here as 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 a 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, so Again, we'll see some exceptions. So, it's worth noting that in some species there's something called a mantle cavity. And it's, basically a water filled chamber, containing the gills and the anus. And you can, see that little mantle cavity right there. Now, I'm gonna talk about a bunch of different classes of mollusc, and the first one, not a ton to say about. These guys are called chitons. 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 shell. And the shell is made up of 8 dorsal plates. You can see there's like 8 segments to this shell. You can also, kind of see the foot poking out, from underneath this chitin. Now, gastropods, probably an organism you're much more familiar familiar with, these are slugs and snails. They're gonna live both in marine and terrestrial environments. And while many of them have shells, not all do. Of course our, snail, pictured right here, has a shell, but, you know, there's, plenty of these organisms, these gastropods, that don't have shells. Now, many of these species actually reproduce through sexual reproduction. If you ever wanna 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 asexual reproduction we discussed previously. With that, let's turn the
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Annelids
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Bivalves are arguably the most delicious mollusks. Though, I think it's up for debate with cephalopods. Now, all species of bivalves are aquatic and contain their body within 2 shells. And these are organisms like clams, mussels, oysters, which you can see right here, and, very important feature of, oyster anatomy is lemon and of course, inside here, menue sauce. Very important for oysters. Of course, I'm kidding here. However, when you look at that sort of meaty body inside the shell, what you're looking at is both the foot and the the visceral mass. And the shell itself is, kind of, acting as the mantle here. So, you know, looks different from the picture we saw on the previous page when we discussed the anatomy, but all those parts are still here. Now, most bivalves are suspension feeders, and they lack that radula, that, rasp like, eating apparatus. Instead, they, you know, move water through their bodies and pick up on little particles of food that are suspended in the water, and they trap this food in their gills. And you can see these tubes coming out of these clams over here, and those are the structures that they're using to feed. Now, cephalopods, as I said, kind of also in the running for most delicious mollusc. Really hard to say. Yeah. Real this is really difficult. It's such a toss-up. I mean, calamari here, really important cephalopod. I I don't know what we do without squid. Most cephalopods are marine predators that have, a foot that basically evolved into tentacles. That's what I was, referring to earlier when I said, you know, see an example of the foot taking really interesting morphology. Well, it's tentacles on these cephalopods. And these are, you know, organisms like squid, like this nautilus here. And these guys move in a really cool way. They use this structure called a siphon, which is this muscular tube, right there, to eject water. And this actually allows them to travel through what is technically jet propulsion, believe it or not. So these are nature's jets, basically. Now, they're the only mollusks to have a closed circulatory system, and cephalopods, in general, are pretty advanced organisms. They actually have, sophisticated nervous systems and pretty complex brains. They also have some pretty cool sensory organs and, a variety of other adaptations. You know, great example are cuttlefish, which are able to camouflage themselves. They have, you know, very sophisticated nervous system. There's also some pretty famous and funny examples of octopi tricking researchers studying them, proving that these animals actually have some pretty sophisticated cognition. Now, unfortunately, the last type of creature I want to discuss is kinda yucky and is not a mollusc. It's pretty important to note. Annalids are not a type of mollusc. They're their own phyla, And, they are colimates, most are segmented worms, and, they both live in aquatic environments and in damp soil. And we're gonna see 2, sort of, basic kinds of annelids. They're these polyketa, which have parapodia. And you can see all these little parapodia here is little, you know, leg like structures along the worm body coming out of, the segments of the worm. And these parapodia have what are called chaetae, which are basically these, chitinous bristles that the worms use to propel themselves through the water. And if you look, you can see there's, sort of these, like, light projections sticking out of the tips of the parapodia. Those are the key tape. Those are the bristles that the worm uses to, you know, almost swim, you can think of it as. So the other type of worm is going to be, stuff that you're probably a little more familiar with. These are organisms like earthworms and leeches. They're, they're called clitulata, and these organisms are hermaphrodites, meaning they, can reproduce sexually. And the organism has both the male and the, female parts. Although, some species will actually reproduce asexually. That's the end of this video. I'll see you guys.