Ecdysozoans

Hi. In this video, we'll be talking about dices Owens and mainly focusing on arthropods now dices Owens. Our protest owns that grow incrementally by shedding their outer layer. This outer layer is known as the cuticle, and it's a tough external coding. In some cases, it's actually hardened into what we call an exoskeleton. Now. Every time the animal sheds its cuticle, its body then swells, allowing it to grow. If you've ever had a soft shell crab, for example, you're actually eating a crab that has recently molted and is in the process of regrowing its cuticle. That's why it has a quote unquote soft shell. Now the by and large, the biggest group of dices. Owens is the fila of animals known as arthropods. Uh, these organisms have segmented bodies. Talk about that second, and they have exoskeletons. They also have jointed appendages. Now they're exoskeletons are mostly made of chitin and in the case of crustaceans, which are organisms like shrimp or lobsters, uh, those exoskeletons air actually reinforced with calcium carbonate. Now their bodies are grouped into what are called tag Mata, and these are segments like the head, thorax and abdomen of insects. We can actually see unexamined of tag Mata right here with this organism. Technically, this is a trial. A bite thes guys. Well, they've been gone for a little while. Let's put it that way. But it nicely illustrates the three tag mata of trilobite body in these different colors. So you can see we have the cephalon thorax and pig idiom. Don't worry about these names. Just know that these are all tag Mata. Now it should be noted that changes in hawks genes which are those genes that control the development of, uh, the various segments in the animal body. These hocks genes allow for a huge variety of form and function which has led to the massive success of arthropods. Arthropods are just everywhere. There's tons of them on the planet, many different types, and part of that is the part of what allowed them to spread so effectively. Is that great diversity and form and function? I mean, think about it. Some of these, uh, you know, hocks genes have allowed for things like pincers, wings and 10 I many different sensory organs. So a lot of variety in the body plans of arthropods, thanks to these variations in the hawks jeans. Now the main body cavity of arthropods is called the him a coal, and that's due to the fluid it's filled with called him a limp, which is basically just kind of like their version of blood. And also arthropods haven't open circulatory system. So that fluid is basically going to directly bathe the organs in order todo gas exchange and you can see a simple body plan of arthropod right here. And you might be surprised to see that they actually have brains as well as hearts. But yeah, you know, things like insects on organisms like that absolutely have brains and hearts. And here you can see a insect in the process of molting. Now let's talk about one of our first groups of arthropods, that air known as Thekla's Serrata. These are organisms that have claw like feeding appendages. Uh, they actually lack antennae, and they have simple eyes as opposed Thio something we're gonna talk about momentarily called compound eyes, basically its eyes like you can see right here in this kind of cute little spider. I mean, not that spiders air cuddly or cute, but notice how it's I just has this one single lens. It's like a single dome. Later we'll look at compound eyes, which have many different lenses or rather many lenses on one. I eso Kelis, Arata include organisms like horseshoe crabs, sea spiders, scorpions, ticks, mites, all these lovely things, A swell as spiders. And we're gonna talk about rack needs right now. So organisms like spiders, and they're also the largest group of callus Arata Um, they actually have to tag Mata and we'll look at that right here on this nice little diagram of the inside of Iraq needed. There's the CFO Thor X, which is this region right here. That's the SEF alot Oops! Set flow, thorax. And then this back region called the abdomen. Right now, Rack needs have these special appendages called pet. It helps, which you can see right here. That's this appendage. And actually they're gonna use thes to reproduce and believe it or not, these guys reproduce through internal fertilization. We'll see that a lot of other arthropods reproduced through external fertilization. These guys happen to use internal fertilization. They also have the characteristic Kelly. Sorry. Those are the claw like feeding appendages. You can see right here. And also uh huh. Here on our little spider friend. So that is he Calles Sarah and Iraq needs, uh, one of the defining features of raton's I'm sure you're familiar with is therefore pairs of walking legs or eight legs. Basically, here you can see four legs. Well, there's four on this side and, you know, ostensibly four behind it on the other side for a total of eight legs. So with that, let's turn the page.

Hello, everyone. In this lesson, we're going to continue our discussion of EC Tice's Owens specifically talking about Miria pods, crustaceans and hex iPods. So the first group of animals here that we're going to talk about are going to be the Miria pods and they are going to be invertebrate organisms. And they are going to be what you think of whenever you think of millipedes and Centipedes, those little bug like structures that have a million legs on them. Those were going to be Miria pods, and they have segmented bodies and legs coming from each segment. And Miria pod is actually a very interesting name for them, and it actually makes a lot of sense when you break it down. A myriad of something in English means a huge quantity of something, so this actually means many. And if you guys remember, pod actually means legs or foot, so many legs. So the myriad or Miria pods are many legs, and they do in fact have many, many legs. If you've ever seen a centipede or a millipede, in fact, they have a believe. I think the lowest number of legs that they can have is 10 but the highest number of legs ever recorded was 750. So 700 divinity legs, That's many legs. So definitely a merry a pod. I believe that's around 16,000 species of millipedes and Centipedes that belong in this particular category. Okay, so now let's move on to crustaceans. These they're gonna be animals that I believe are a little bit more familiar with, um These are going to be animals that live in aquatic and terrestrial environments that could be in fresh water. They can also be in salt water and these air going to include things that we eat commonly like lobsters, crab, crayfish, shrimp and barnacles. Those listed there are all aquatic. Um, however, I also wanted to list some terrestrial ones for you. Three Onley Terrestrial crustacean I can think of is going to be what's called a wood lice Thes air. Gonna be terrestrial, which means they live out of the water. And a wood lice is also called a roly Poley. If you have ever seen a little roly poly, they kind of look like insects. But they're not. They're actually crustaceans. These are wood lice, and they can actually roll themselves up to protect themselves into a little Paul into a little ball. Which is why they're commonly called Rowley police. And those are terrestrial crustaceans, which are pretty neat. Okay, So an interesting thing to know about crustaceans is that they are all going to have 19 appendages and two pairs of antennae, so they have a ton of appendages. They're also gonna have to tag Maada. Remember that tag Mata are gonna be body segments and they have a CFL. Oh, thorax and abdomen. Okay, so what is a CFL oath or ex? Well, the word CF alot means head and the word abdomen. You can think of it as the belly. The head is going to contain all of the sensory structures and the brain. So things like the eyes, things like the mouth, the brain are going to be in the head structure in the belly. We're gonna have the digestive system, all this digestive organs, and you can think of the thorax as the rage and in between, maybe like the chest area off the organism, which is gonna hold all of the respiratory and circulatory structures like the lungs and the heart. So the reason they have a cephalopod. Thorax is going to be because their head and they're kind of like chest region. So I guess we can think of the thorax is the chest. Their head and chest regions are actually fused together. So we have to separate regions. We have ahead Ah, chest in a belly but their head and their chest are fused together. So that's why we have a cephalopod thorax instead of just a head and thorax. So crustaceans have those two components fused together. Now their abdomen is its own separate tag Mata, and this is obviously going to hold all of the different digestive organs. Now a lot of crustaceans will have what's called a carapace. And this is going to be a hard exoskeleton piece, kind of like a piece of armor that they put over their CFL oath or ex their head and their chest area for protection. Now remember, these are organisms with an exoskeleton, which means any time that they want thio grow or they want to increase in size, they're going to have to shed that exoskeleton including the carapace, and create a new exoskeleton. This is molting. This could make them very, um, susceptible to predation. But it allows them to continue to grow and then they have armor Whenever that exoskeleton comes back Now I believe there are e think there's like 67,000 species of crustaceans. It's insane how many there are, and they come in a huge wide variety. They could be really tiny. They could be really gigantic. I think the tiniest one is like 10.1 millimeter and then the largest one. I think it's 3.8 m, which is like 12 point 12.5 ft wide. And I believe that's the Japanese spider crab. You guys should look it up. It's gigantic, but they come in a huge variety off body types and builds. But they're all gonna have those 19 appendages, two pairs of antennae and SFO, thorax and abdomen. And the smaller species that I talked about are going to be able to perform gas exchange just through their their skin, their cuticle, while larger species like that giant crab, that Japanese spider crab that I talked about a lot of lobsters, they're gonna have gills that they utilize for their respiratory system. So that's gonna be the basis of what we know about crust stations. So now let's move on to the hex. A pods. Oh, before I stop. Just so you all know, this section here is the CF alot thorax. And then this section here, which I will do in blue. This section right here is going to be the abdomen of this particular crustacean. So that is what it means when the head and the neck or the head and the chest area are fused together, that is acceptable thorax. And you can see here that this whole kind of armory structure here that is covering the CFO thorax is gonna be the carapace which they label for you. Right there. That's the carapace. Their armor that covers their Sefolosha thorax. Okay. All right, so now let's go down and let's talk about Hex iPods. Okay, Hex. A ponds are going to be, I believe, the most successful animals on the planet. They're definitely the largest group of arthropods for shore. So hex a pods, we commonly call them insects. I believe there's over a million species of insects, probably more. And they are incredibly diverse. They can be terrestrial. They're mostly terrestrial. But they can also be aquatic and they have inhabited so many areas of our planet. They're very successful group of organisms, and some of the characteristics that are unique to them is they're gonna have three pairs of walking legs on their thorax and many of them have successfully had wings. So three pairs of legs, always on all insects. But some insects do in fact have wings. Now they are going to have three tag Mata three body segments. They're gonna have a head authorites and and abdomen. They don't have a scuffle, authorities, because their head and their thorax are not fused together. They're independent structures now. Hex A pods or insects are very famous for their compound eyes. You can see a compound I in this fly right here. And if you've ever seen a fly up close, you know their eyes like really unusual. And they are going have a compound eye, which is going to have many, many, many lenses on their eye. So we don't have a compound eye, but a lot of insects dio and the reason they have these many lenses is it allows them to have better vision specifically for movement they don't have great resolution. They can't see images in fine detail. And with really sharp details. They can't see all that, but they can see things move. They can see quick movements, changes enlightened dark. Really, Really well, So that is a compound I Some crustaceans also have compound eyes as well, but this is mostly famous for the hex of pods. Now they are going to have an open circulatory system. And this open circulatory system is is characterized by these openings in the cuticle or their skin layer called spirituals. So these are going to be basically little holes or valves in the surface of the insect. And these air gonna act like little mouths that pull in air, And these spirituals are going to pull in air, and they're going to pull it into the trachea Will tubes. So an example of this can be seen right here. This is gonna be the spirituals. So this area where you can see the tubes air meeting the surface off the insect, those they're gonna be the spirituals, which you're gonna be open pulling in air, and then they pull air into the insect and the reason they do This is because they don't have lungs like we dio. They pull air through all of their different Spiric ALS and into the tubes so that their tissues can have gas exchange can have oxygen and can get rid of CO two. This is the way they do that. The air moves through the spirituals and through the trachea tubes that lead deeper into the body, which allows the body to do gas exchange because they don't have lungs. So pretty cool. Pretty unusual. But this is gonna be a neat characteristic of hex iPods. Now most of them do reproduce sexually, and most of them do reproduce with internal fertilization. OK, so now let's go down a little bit in this image. Here, you can see the different tag model that I was talking about. The head, the thorax and the abdomen, and the head and thorax are not fused crustaceans. Okay. And if you were wondering, this is a developing insect, I believe it's probably a fruit fly that is developing, and they were taking images off its circulatory system and its respiratory system. Okay, so now let's talk about metamorphosis because this is going to be another characteristic off text iPods or insects. We've all seen a caterpillar turned into a butterfly. That is an example of metamorphosis. But I want you to know that there are actually two types of metamorphosis that these insects are able to go through. They can go through complete metamorphosis and incomplete metamorphosis. So whenever we think of a caterpillar turning into this butterfly here, that's complete metamorphosis. And that is different than incomplete metamorphosis. Because during complete metamorphosis, the larva looks completely different from the adult. I mean that caterpillar looks nothing like this butterfly, and that is complete metamorphosis, a complete drastic change. So the larva stages morphological E distinct from the adult form. They're also going to have very different functions in life, very different goals in life. The goal of the larva is to eat and eat and eat until it becomes a Pupi. And then the adult main job is generally going to be for mating and creating the next the next generation off offspring. So they're gonna have two very different goals. The largest goal is to get big enough to go through the process of metamorphosis, and then the adults goal is to reproduce with other butterflies, I guess, um, to create the next generation. So some examples of organisms that go through complete metamorphosis obviously, butterflies. Bees also go through complete metamorphosis. Wasps also and beetles. I believe Beatles also go through complete metamorphosis. Okay, so how is that different from incomplete metamorphosis when incomplete metamorphosis. The juveniles are not called larva. They're called nymphs, and they look really, really similar to the adults. So they have similar appearances two adults, But they cannot reproduce. So basically, it's hard to tell the difference between an adult and an IMF. The only difference is, is the adult is able to reproduce, and the nympho goes through these not so drastic changes but small changes until it gets into the adult stage. This is incomplete metamorphosis, because the two stages look really, really similar, and there's not a big, drastic event that changes the body form of these insects. So some examples of insects that go through incomplete metamorphosis are aphids. Dragonflies, um, praying mantises also do this, and grasshoppers also do this as well. There's tons of insects that do these different types of metamorphoses. I just wanted you all to have some examples of them everyone. So now let's go on to our next topic

the last IQ dices owns. We're gonna be talking about our nematodes and these are not arthropods, but they are dices Owens. So they're still going to have that body covered in a cuticle that they shed periodically to grow kind of hard to see here in this image. But there's such small creatures that you're you know, it's hard to visualize those things in an image thes our bilateral organisms, and they're actually, uh, un segmented worms. So we looked at analysts before, and those were segmented worms. These air un segmented worms sometimes, uh, casually referred to as roundworms. They have a suitor, Cole. Um, and they actually exhibit sexual dime or fizz. Um, believe it or not, uh, meaning that the males and females of the species have morphological differences. They appear different now. Uh, you'd have to be an expert to tell by looking at them, though obviously, this is these air subtle differences that our untrained eyes they're not going to readily pick up on. However, I do want Thio briefly mentioned the picture that we have here, and this guy is C elegance, and you probably if you haven't already seen that name in biology. You'll definitely see it come up later. This is one of the most studied organisms in laboratory experiments. It's actually so well studied that scientists basically know how every single cell in the C. Elegans body develops. I mean, it's really, really, really well studied organism. So, you know, if you see that name come up in the future now, you know it's this little nematode. All right with that, we'll send the video here. I'll see you guys next time.