Overview of Animals

Hi. In this video we'll be going through a general introduction to animals and in later videos will explore more specifics. So animals are multi cellular header trophic. You carry outs and we feed by ingesting our food, meaning we actually pull our food into our bodies to absorb the nutrients. Now most animals are deployed and produce gametes directly by my Asus, which is different if you'll recall than how. For example, plants do it Where, um spores air actually produced by my Asus and their gametes are often produced by mitosis. Animals lack cell walls, right plants you cellulose fungi use kitten. We don't have that. Instead, we use an extra cellular matrix for support. All animals are motel, at least at some point in every animal's life. They exhibit active movement, right? Intentional active movement. Now most animals reproduce sexually, though there are some that reproduce a sexually. But for the most part, we're going to focus on, uh, what you could think of as more common animals. Now, animals also undergo embryonic development, and this is when the zygote is undergoing cleavage. And you actually, uh, we'll see more or less three patterns of birth for animals. So you have vivid Paris, which in which the embryo will actually be nourished inside the parent and the parent will give birth to live offspring. This is in contrast to you over Paris organisms, in which the parent actually lays eggs and the embryo is actually nourished by yolk in the egg, as opposed to the parent directly and in ovo Viva Paris organisms. The eggs actually will remain inside the parent until they're ready to hatch. But the embryo is still nourished by the yoke, not directly by the parents, so humans and mammals in general, are vivid Paris organisms. As you might have guessed. Now it's worth noting that during embryonic development, animals actually have a lot of similarities here. In this image, you can see the embryonic development of a fish, salamander, tortoise, chick, calf and human, and look at the similarities early on and development. As development goes on, organisms become more and more different, but early on their striking similarities. And that is because even though animals have a wide variety of different body plans and morphology ease, the genes that control the development of the body are common toe. Almost all animals and they're called Homo box jeans. And if you want to learn more about these, check out the videos on animal development. Now. Animals also have tissues, and tissues are basically organized groups of similar cells that act as a functionally unit. Nice example of a tissue. It's this right here. This is muscle tissue. Notice the what are called striations. Basically, they're sort of a line pattern to the tissue, and that has to do with the various filaments. The contract I'll filaments that allow muscle thio contract. Um, we'll learn more about that in the chapter on muscles. But for now, the important thing to take away is that all of these individual muscle cells work together is a functional unit. Thio make up this muscle tissue. Now, many tissues will actually, um, be incorporated into organs, which also act as a functional unit and are another example of how tissues can be used. The other thing that's kind of special about animals is that we have a nervous system now. Not every animal has a nervous system, but many animals have nervous systems, especially uh, animals that you might think are less complex or not complex enough to have a nervous system like a worm or a jellyfish, for example, and let me jump out of the picture here for a second. As you can see, this is a worm, and this worm, believe it or not, has a brain right there. And it has a nervous system that you can see being depicted here and here. It's this dark portion here on the bottom. We're looking, getting a top down look and here or getting a side view of the organisms. Nervous system. So those were some general features shared by animals. Let's flip the page and talk about some more specific features of animals.

There's a lot of magic that happens during animal development. I mean, it's incredible to think that a single cell this is I go will eventually become a complex body like that of an animal. And to think that the genetics of that zygote will determine how it forms, and those genes will control whether or not it forms into an elefant or fish. I mean, it's totally crazy. Um, of course, it's not magic, it's biology. And it's just amazing to think about the precision control that happens during development. So let's actually take a look at animal development. So of course, you start with single celled zygote, right? And that's going to go through cleavage, which are Siris of Rapid, my ta tick divisions that lead to a blast yola, which is a hollow ball of cells. You can see it right here. And, uh, these blue cells are the outer ring of cells, this yellow stuff that is representing the hollow space inside the blast villa, which is called a blast ical case. You're curious. And, uh, it's also worth noting that, um um alien blaster is called a blastocyst, just in case you hear that term come up. So then this blast Ula is gonna go through gassed relation which leads to the formation of a gas strolla. And basically, this is the formation of the three germ layers which are sort of these layers of cells that will develop into the complex tissues and features of the animal body. So, during gas relation, the blast July will imagine eight. It will create this cavity that we call the Arken Theron. This cavity in here and the opening to that cavity is called the blast of port. And the, uh this cavity will actually become the digestive too, which is pretty crazy. What's even crazier to me is that the blast support that opening in the gas strolla will actually become either the mouth or the anus of the organism. So this first opening in this what is literally just a cluster of cells will actually lead to a major orifice of the body. Now thes three germ layers. You can see here we have the ectodermal, which is the outer layer of, um, cells. And these are going to form nerves. Organs like the glands rather like the adrenal medulla, uh, skin the brain, the eyes, the inner ear thes air, of course. Human right. Mammalian examples. But just to put it in context, uh, that is easier to grasp. But the main point is that the ectodermal is the outer layer. The end of term is the in, er lair, and the end of term is going to give rise to stuff like the lining of the digestive tract, the liver, the pancreas and lungs. And it's actually not depicted in this image, but I'm gonna draw it in. There's also a middle layer that we call the Miso Durm and the me Zod, ERM against that middle layer and the me Zo Durham is gonna give rise thio organs like the adrenal cortex, the blood bones, the go nads and soft tissues. Now I said that blast support will either turn into the anise or the mouth and turns out that this is actually a pretty important distinction in biology. Which one it becomes now Here we have a nice little image of Hey, blast Ula going through gassed relation. Right. Here's our blast of port opening up and notice how this cavity will actually eventually go all the way through the organism I mean, you haven't opening it to ends its ah, common feature of animals. Sometimes, um, you know, your professor might joke that we're all just tubes, which is kind of true in many ways. You know, our bodies were set up to just be a Siris of tubes, and we have, of course, tubes running through our bodies that open at one end and the other now getting back to the blast report depending on whether that turns into the mouth of the famous, you're either considered a proto stone or due to a stone and a proto stone is an organism like the one we see right here that is going to have its blast report developed into the mouth. That's what's being depicted here. Mouth and the other opening will end up being the anus. Do tourist stones are the opposite, Uh, in do tourist owns the blast of port will actually develop into the anus, and it's the other opening that will become the mouth. And you can see an example of a Dutra stone right here. And you might also notice there's some other details about how the music term will form the Coolum and I don't want you to worry about that too much just yet. As we haven't talked about what a column is yet. I'm just putting that in there because technically, that is that also applies Thio the definition of protest. Um, and do her stone, and you can see that that's been, uh, labeled here. We have the museum tissue here and here, and it is turning. Uh, it is, uh, depending on whether your protest, Omar Judo stone doing different things to form the column, which is a type of body cavity. Now, it's really important to realize, given all this, that humans are actually do tourist stones. Which means at one point in everyone's life, you were just nothing but nastiness right there. Just kidding. All right, let's flip the page.

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.

as animal bodies develop, they start to form various types of symmetry along certain axes of the body. And what were you often will think of? His less complex organisms tend to show what's called radial symmetry, where basically the body parts are all arranged around one main axis. And you can see um, example of radial symmetry right here in this hydra. And basically the way to think of it is that, um if you put a plane in any direction through the top of this hydra, uh, it would look the same on both sides, right? Each side of the plane would mirror the other, no matter how you shifted it, right? So if we took, uh, for example, this plane and then shifted it over to this position, we'd still have more or less the same looking halves of a hydra on either side. Now, organisms that we typically think of when we think of animals are violet Terrians. And basically that means that they have a bilateral symmetry and this is ah, body plan that's divided into roughly two equal halves. So essentially, there is a, uh, in these animals bodies. You can draw a line through a particular point and you will have a mirror image on either side. But you can't shift that plane around right. We can't shift it this way or this way, because then we'll end up with uneven halves, right? The haves won't mirror each other anymore, which is not the case for these organisms that have radial symmetry. So just to be clear, this is bilateral symmetry here and here. This is actually an example of Hey, symmetry. This organism doesn't show any symmetry, its's type of sponge, and, uh, there are some organisms, some animals that don't show symmetry. However, most that we're used to thinking of are going to show bilateral symmetry. And as as we learn, that's because there was an explosion of bilateral fila during the what's called the Cambrian Explosion. All right now, there are also some important body axes to know, and that's because there's some terminology used to describe the position of things. So here we have our person. Uh, so, of course, this person has bilateral symmetry, right? And these terms are going to refer thio, uh, different directions along three axes of this person's body. So anterior anterior is things that point towards the head. That's anterior. The opposite of anterior is posterior, which is things that point toward the tail more or less. Of course, humans don't have tails. We still have a little tailbone. There you get the general direction. That's why sometimes your teacher might call your but your posterior, sort of a polite, I guess, way of saying it now. There's also ventral and dorsal and those they're going to go along those directions. They're gonna be perpendicular to anterior and posterior. So ventral is toward the belly and dorsal is toward the back. And you might recall that dolphins, for example, have what's known as a dorsal fin, right? It's a thin on their backs. That's where the term comes from. So, uh, make sure you know these terms because they will be used to describe the position of things when talking about anatomy. Alright, that let's flip the page

the nervous system is one of those really especially unique things that animals have, and it actually forms from the primary germ layers. The Noto cord forms from the miso germ, and this is kind of like a primitive backbone structure that what are called core dates form. And in some animals this will develop into the actual vertebrae of the spine, whereas in others it's a transient structure that will go away during development. Now the neural tube is, ah, hollow structure that the brain and spinal cord will drive from, and that actually comes from the ectodermal folding in and creating this neural tube. You can see the tissue for it and purple over here, and it's going thio old, inward and eventually create this structure the neural tube, which will swell in certain places and that forms the embryonic brain. Those swellings Now there's a trend in animals in the evolution of animals called civilization, which is basically trend in which the nervous tissue becomes concentrated at the anterior end of an organism. And, you know, this is essentially how the brain comes to be right. This massive neurons that integrates and processes sensory information and is usually located at the anterior end of an organism. Now some organisms have a central nervous system where basically the nerves air clustered into one or more tracks that project through the body. So here we have an example of a central nervous system, right. We have this nerve cord, goes through the body and is, you know, a bundled pile of nerves. Basically, what we think of is less complex. Animals tend to have what are called nerve nets, which is basically unlike a centralized arrangement of nerves. It's a diffuse arrangement of nerves, Um, and it's found in Radio Lee Symmetric animals. So stuff like starfish like in this example here. And you can see, uh, the outline of the starfish, right? And in black, these This is the nerve net of the organism you can see that protrudes out into the little arms of the starfish. So it is not a centralized but a diffuse arrangement of nerve cells. Essentially, another pattern we see with animals is segmentation, which are basically just repeated body structures. So think of a warm. For example, worms have all those little segments. In fact, there are many animals that have segments um and we can often see this very clearly during development. So you might look at a fly and go That doesn't really look segmented. But if you look at a fly during development, you can actually see those segments a little more clearly. And if you want a better idea of all of this, I suggest you check out the video on development, which covers segmentation when talking about home box genes, which we've also mentioned here Now, vertebrates. Speaking of segmentation, vertebrates have this vertebral column that develops from that node accord. And most are dude er, soames and the vertebral vertebral column is segmented, right? It's segmented into vertebra, so even organisms like humans that don't necessarily outwardly appear segmented. Do you have segmentation invertebrates lack this vertebral column on and they will still have a segmented bodies, right? Like exterior structures that are obviously segmented. Most of these are gonna be protest owns. So just little distinction to make there. And we're gonna talk in much more depth about vertebrates and invertebrates on the chapters that cover those two organisms. Uh, there's gonna there's a chapter on vertebrates and then another chapter on invertebrates. So get a lot more detail on those in those other chapters. All right, See you guys next time