Overview of Animals - 3

by Jason Amores Sumpter
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Hello, everyone. In this lesson, we're going to be talking about how the embryos of different types of animals are going to develop into the entire organism. Alright, so we've talked about protest OEMs and we've talked about do tourist stones already and protest OEMs and Dudar stones are going to develop their embryos in slightly different ways. So the first thing that we're going to talk about is the different types of cleavage that can occur within the embryo. Remember, cleavage is going to be a specialized form of cell division that is going to occur very early in the development of the embryo. And this particular type of cell division is where the cells divide, but they don't get any larger. So the mass of the embryo is not changing, but the number of cells is. And as you guys can see, there's many different types of cleavage there spiral radiant indeterminant and determine int. So we are going to have these two different types are four different types of cleavage. Now spiral cleavage and determine it. Cleavage are going to be most associated with proto stones, while radio cleavage and indeterminant cleavage are going to be associated with do Therese stones. Now, spiral cleavage is going to be depicted right here. Spiral cleavage is here, and radial cleavage is here. Spiral cleavage is that when the plane of cell division is diagonal to the vertical axis of the embryo, that's kind of confusing for me to understand. But basically what it is is you guys can see that the cells don't sit directly on top of one another. The cell sits in between the two bottom cells, so it's kind of spiraling the position of the cells. The position of the cells kind of moves every time the cells divide, so they're spiraling. If you guys were wondering what this would look like from top down, so we have a lateral view here. If we had a top down view, we would have the four cells that air first formed and then in red. So these cells here we would have them positioned like this over the meeting area of the cells. So, as you guys can see, they're not stack directly on top of one another, they are actually spiraling or moving their position. So this is the top view. This is the lateral view this is just one way that the embryo can divide itself is one form of cleavage better than the other. Now there's different ways to do it now. You also have radio cleavage where the plane of cell Division is parallel or perpendicular to the vertical axis of the embryo. As you guys can see here, in radial cleavage, the cells sit directly on top of one another. What is that going to look like from the top down view? What we have are four cells that were created from the first round of cleavage and then in blue. I'm going to draw these cells here. Second round of cleavage. They're going to sit directly on top off the original cells, so that is going to be the difference between radio and spiral cleavage. So this is the top view. This is the lateral view. Like I said, no one form of cleavage is better than the other. It's just a different way to do it. Different types of organisms do it different ways now. There's also indeterminant, cleavage and determinant cleavage, and this is going to be talking about the fate off these cells. Indeterminant cleavage is where the cells that arise can do can develop into anything in the organism. They're not determined. Their fate is not determined. They're not going to become liver cells. They're not going to become leg cells. These cells air indeterminant. They could become anything that they need to be. Now determine it. Cleavage, the exact opposite the cells that arise are committed to differentiation. These cells that arise have already determined their fate. They are determinedly cleaved. They have already determined their fate. They already know what types of cells they will be. Where indeterminant cleavage. They don't know what types of cells they will be. So remember protest. OEMs have spiral and determinant cleavage, while dude or stones have radio and indeterminant cleavage. All right, so now let's scroll down and let's talk about the different germ layers that you can have inside of an organism. So whenever you're talking about an embryo, it is going to start dividing. It sells, and it's going to organize themselves in a particular way, and it's gonna organize itself into primary germ layers. Primary germ layers are going to be layers of cells in the embryo that air distinct, and that will form very particular features of the organism, so you can have two different types of organisms. Depending on their germ layers, you can have diplo blasts and trip low blasts dip low blasts have to germ layers while trip blow blasts have three germ layers. So in diplo blast, they are on Lee going to have an ectodermal and an Indo Durham in their blast villa. Or in they're embryo and triple blasts are gonna have the three primary germ layers. And these are going to be the Indo Derm, the miso Durham and to the ectodermal you guys were wondering were triple A plastic organisms. We have three germ layers in our embryos. So a representation off the embryos is given here. And as you guys can see, this is a diplo blast embryo, and this is a trip low blast embryo. Now these different germ layers are going to become different things. Ectodermal germ layer is going to become your your skin, your outer layer of your body. Your miso Durham is going to become things like your muscles and the different organs in your body, and your Indo derm is going to create the inner lining of your body. Okay, everyone. So that's why we have are three different germ layers. But some organisms only have two germ layers, and it still works out perfectly fine. It's just a different way to build the embryo and the organism. All right, So now let's talk about body cavities because body cavities begin to form even as the embryo is forming, even in very early stages. And one of the main ways that we differentiate different types of animals is going to be based on the type of body cavity that they have, and you guys will find that this concept is gonna be highly tested upon in your lessons. Thesis alone is a very important structure in determining the type of organism or the type of animal that you're looking at. So what is the sea loam? Thesis alone is going to be basically a body cavity inside of an animal, and it's specifically surrounds the digestive tract, and it is going to be divide derived from the Meso Durham. This is important. The salam is a body cavity that surrounds the digestive tract is on Lee made from the Meso Durham. If it is a body cavity that surrounds the digestive tract that's made by something other than the Miso Durham. Then it's not the seal. Um, it's got very specific regulations now, since this body cavity forms from the Meso Durham. What kind of organism can it come from? It can Onley come from a triple Oh blast IQ embryo or Atripla plastic organism because it has to have that Miso Durham DIPLO Plastic organisms don't have those Miso Durham's Now. There's also something called the pseudo seal Um, or the fake SAlomar or not true Siloam. And this is also a body cavity that also surrounds the digestive tract. But the difference here is that the pseudo Siloam forms from the miso Durham and the Indo Derm, while a truce Eelam Onley forms from the miso Durm so you can have organisms with C loans with pseudo see loans and without see loans and an organism that has a true see loam. It's gonna be called a cell, a mate, and you guys can actually see an analytic, which this is probably an earthworm is going to be a true sell, a mate, and it's Salone is going to be here in white, and as you guys can see the Miso Durham is going to be in red. So let me write that out for you guys. The knees. A Durham here, in all of these examples is in red. The ectodermal it's gonna be in blue and I don't have a yellow. So I'm just going to write the Indo Durm. Oh, did not spell that correctly. Indo Durm is in yellow. So as you guys can see, thesis alone is completely surrounded by red. And that is because it is on Lee made up of the Meso Durham. So it's completely surrounded and created from the Meso Derm. Now we also have the pseudo Cee Lo mate. So those organisms that have a pseudo salone and these are also triple a plastic organisms and they're gonna have their body cavity form from their miso Durham. And there, Indo Durham and you guys can see a pseudo Salo mate down here. This is a nematode, a particular type of worm and these air roundworms. If you guys were wondering analysts air segmented worms, nematodes, roundworms, and we'll get to flatworms in just a second. So nematodes are going to have a pseudo seal. Um, you guys can see that the pseudo Salone is between the red and the yellow. So it's between the Indo Durham and the Miso Durham. And that's because it is made from the Indo Durham and the Miso Durham, while the true Siloam is inside of the Miso Durham. Because it's on Lee made from the Miso Durham. Now we also have a Salo mates. These air gonna be organisms that lack a seal. Um, they lack a pseudo asylum or a truce. Ealham, they lack a body cavity. As you guys can see here. This flatworm lacks an internal body cavity. We don't see any white, so I'll write that as well. White, the body cavity. There's no white in this particular cross section of this worm. If you guys were wondering what these are, these are If you cut the worm in half and then you look down the lateral view. This is a cross section of all of these worms. So as you guys can see, I'll get out of the way so you can see the labels. As you all can see, we have this flatworm that doesn't have any body cavity, has no body cavity, no white section at all. So this is an a c l o mate. It has no body cavity. So let me just make sure you guys can see this one is the flatworm. This one is the nematode, and this one is the analytics. So these are the different types of organisms. If you guys were wondering, we are Salo mates. We have a true Siloam true body cavity. But just remember that organisms animals are going to form themselves differently, their embryos air going to cleave differently. They're going to form different types of germ layers. They're going to form different types of body cavities. Now, these forms of cleavage, these forms of determination, thes forms of germ layers and body cavities are all going to be methods that scientists and you yourself are going to need to utilize to be able to identify and differentiate the different types of animals. All right, everyone, let's go on to our next topic.