 Okay, good morning class. Today we're going to be talking about animal diversity. And from the outline, my goal is to speak to the animal diversity first in terms of the characteristics that puts every organism into this kingdom called the animal kingdom. Then we're going to look at the distribution in terms of how it's organized into invertebrates and vertebrates. These are informal phylum names, but just for classification in terms of grouping. And I'll explain that. So we'll talk about the invertebrate group. And then we'll talk about the vertebrates. So animals. Animals, when we think of an animal, we think of something that moves. And so motility is a key characteristic, but it doesn't fit every animal. For the most part, animals are motile. They're heterotrophic. That's the big characteristic that pulls them in to the animal kingdom. There are other groups that are heterotrophic, for example, fungi, but what separates the animals from the fungi in terms of their heterotrophic nutrition is animals are heterotrophic by ingestion. So they take in the food and then it fits into some digestive cavity where the food is broken down as opposed to absorption in the case of the fungi. The multicellular, many, many cells makes up an animal, along with the embryonic germ layers. You have some of the simpler animals that are, there are only two germ layers, two embryonic layers, ectoderm and endoderm. And so that's referred to as being diploblastic, just two germ layers. And some of the simpler animals, as we go down the list, I will refer back in terms of the embryonic development and the simplicity in terms of their body versus the more advanced animals that consist of three germ layers, which are triploblastic. So we got heterotrophic, we got multicellular, we got germ layers. And the other thing about animals, there are several other characteristics that we can tag, but we're going to look at body cavity. Okay, so the more advanced animals based on the embryonic germ layers have a body cavity. It's referred to as a, the body cavity is referred to as a selum. And so, again, not every animal has a complete body cavity, but as we go through the list, we have those that are lacking a selum, acelumates, those that have a false body cavity, pseudo-selumates, and then the more advanced animals with a complete body cavity, the selumates. So we'll again tag those as we go along as examples of selumates, acelumates, pseudo-selumates. The other characteristic that's pretty good to look at animals in terms of body structure is their symmetry. You either have those that are asymmetrical, the simplest of all on the list, nobody's symmetry whatsoever, they call asymmetrical versus those that have a radial symmetry. Some of the more primitive animals possess this radial symmetry. And what does that mean? Well, radial symmetry, if you dissect the animal body through any of the planes, you'll get mirror images. Okay, you'll get a mirror image. So it's sort of a star shape if you think in radial. And the more advanced animals have evolved into bilateral symmetry with a definite head and foot. And so if you cut through a longitudinal section, you'll get a definite left and right. But of course, if you cut across section, you'll get a head and you'll get a foot or head and a tail. So bilateral, more advanced, radial, sort of the more primitive animals. Now as we talk about the animals, as we go through the list, we'll see that they're, you know, they live in very different habitats from aquatic to terrestrial. So water land and again some of the earlier animals are found mostly in the aquatic, either freshwater or marine environments, similar to some of the protistae, if you remember that kingdom. Okay, so let's look at final characteristic on the animals is that embryonic development, where they're classified as either protostomes versus juderostomes in terms of their embryonic development. So what does that mean? If you remember when a sperm fertilizes an egg, develops into one cell structure called a zygote. From that point on that zygote, that one cell structure goes through cell division and there's a multiplication of the cells going through these different growth stages. And that's the embryonic development. When, as this development goes on, there's an embryonic opening that develops in some animals. And that first opening develops into the anus and that's the protostome animals. Basically all the invertebrates, most of the invertebrates fall under this developmental type. So the second embryonic opening becomes the mouth. First, the anus. Juderostome is opposite. During embryonic development, the first embryonic opening becomes the mouth. The second embryonic opening, sorry, the first embryonic opening of protostome becomes the mouth. Second becomes the anus. And then juderostome is the opposite. First embryonic opening becomes the anus. Second embryonic opening becomes the mouth. Now, let's take the cordage, the most advanced animal filer, the cordata, that have these protostomes or deuterostomes embryonic development. The question is, well, why does some animals develop the first embryonic going to open and develops into the anus versus the mouth? Well, when you think of the protostomes, that anus or that mouth has to do with feeding and getting rid of waste. Since most of the cordage, all these animals in the most advanced groups are linked and being fed, you know, in case of us humans, the babies being fed by the mom to the umbilical cord, then the need for that fetus is to get rid of the waste versus to take in food through the mouth. So that's why that first embryonic opening becomes the anus. For the other animals having the need to feed, that first opening becomes the mouth, then eventually it matures into having a place to excrete the waste. Anyhow, we'll get into that at another time. The focus here is to just keep this simple, keep this organized and understand how animals are placed within this kingdom.