 So, looking at these characteristics, what we want to look at next is an introduction to the invertebrates within the animal kingdom. And we will list the phylum names, and then we'll look at characteristics of each of these phylum. Some of them will stress more than others. I specifically like to point out the animals that are parasitic to us, you know, so that we can avoid them or deal with the diseases that come from them because they're parasitic. And so we'll spend a little more time emphasizing examples in that group. So here's my list of the representative phyla in the invertebrate group. We've got peripheral, naderia, the sea silent, tinnophora, platylementis, nemathea, rotifera, nematoda, malusca, anelida, arthropoda, equinodermata, and cordata. So you may be looking at the list and saying, well, that's every phyla in the animal kingdom, and that's correct. 97% of all the animals in the animal kingdom falls within the invertebrate group. 3% actually, vertebrates. Now what's the difference? Why invertebrates versus vertebrates? What does that really mean? So invertebrates are animals that have, does not have, a backbone. They're lacking a backbone through their embryonic development. The nautical does not develop into a solid vertebral column, doesn't develop into a backbone, so they're lacking a backbone. And vertebrates are animals that have this developed nautical that becomes a vertebral column, supports the body, and is referred to as a backbone. So that's really the difference in terms of categorizing invertebrates, vertebrates. Now let's look at each representative phylum and some characteristics of each one that we can look at. Periphera, the examples of a periphera are sponges. If you think of a sponge, commercial sponge, that you have in your kitchen, it's a resemblance of the actual animal periphera, it really does look like that type of sponge. So I said in the beginning animals are motile, they move, a sponge is going to be an exception. It's a sessile organism, it's a filter feeder, it's very simple in terms of the body development. It just has a tissue level of organization. So from the germ layers that I spoke to earlier, it will be diploblastic, doesn't have three germ layers to develop the sponge, a very simple body form that filters its food and captures its food through filter feeding. Okay, it doesn't have a body cavity, and as far as symmetry, it doesn't have a specific shape, so it's considered asymmetrical. An organism doesn't have a specific body plan or specific shape in terms of radial, bilateral, then it's asymmetrical. And periphera, the sponge is fit in that category. Next we've got nadaria, the sea is silent. So nadarians are very, very interested animals. You may have seen them wrong, the jellyfishes, obelia, hydra, other genuses that belong to this group. Nadaria does have, again, similar to the sponge, a little more complexity than the sponges, but still two embryonic germ layers, diploblastic, okay? Nadarians, they live in the water, and they are two forms in a nadarian body plan. You have, when you look at nadarians, you may have a free living and a sessile. So the sessile is the polar body form stationary, and the free living that swims around is the Medusa body form. Two body forms, characteristics of nadarians. Again, under list examples here, of the nadarians, the jellyfishes, even corals, you may not think corals, animals, you know, those beautiful coral reefs you may have seen in the ocean actually fit into this particular phylum as well. Of course, those are stationary, similar to the sponges, but they're examples of nadarians. Then we have another small group, the tinnophora, the sea being silent again. This is pronounced tinnophora, the comb jellies, similar, looking to the nadarians. A very small group, the sea walnuts are another example of these, again, living in the ocean, similar to nadarians, and, you know, sort of resemble them with a different form to their bodies. Next group is a very interesting group, because I mentioned earlier, if it's parasitic to us, we will emphasize some examples beyond. And platylementis, platylementis, commonly known as the flatworms. This is a very interesting group, because when you look at them, you have the free-living flatworms, the planarians, a lot of research has been done on them, regeneration, they have the ability, if you cut a planarian, it can regenerate its body, a very unique characteristic in the animal kingdom, to be honest, because that's a means of retaining asexual reproductive capabilities. The planarians are the free-living flatworms, but we do have two parasitic groups, okay? We have the tapeworms, okay, that are, you know, intestinal parasites, humans, mammals have a lot of these tapeworms from time to time, where the worm attaches based on the specific head region into the intestines, and literally extract nutrients out of the intestines as you feed, okay, so it's sucking you up your nutrients. And then we have the fluke, which, again, delivers the organ of the targets. You have the human liver fluke, you have sheep liver fluke that are pretty common. Examples of genuses when you go to lab that you may see that represents these platylementis would be tenea, would be the tapeworm, and clonocus would be the flute, the fluke. So remember these two genuses for lab purposes, examples of platylementis, the flatworms. Now they're called flat because literally if you cut them, if you look at them on cross-section, the body's very, very flat. Therefore they're lacking a body cavity. And so from a body cavity perspective, platylementis are referred to as acelomates, okay. They do not have a body cavity. The body does not have that additional cavity to house any of the organs, and hence the name flatworms. Next, we have a very, very small group of another group of worms called nemertia, known as the ribbonworms. Again a very small amount, only section and fifty species, probably the smallest group along with tinnophora in terms of the number of species in the animal kingdom. And of course based on their name, they resemble ribbons, so they're known as the ribbonworms. Rotifera is another neat group of aquatic animals that has a wheel of cilia that resembles a rotifer, hence the name. It looks like a propeller in the water. It's very beautiful when you look at it move. It's a very unique looking animal, very transparent body. And again a small group that lives in the water, wheel of cilia is what's characteristic of these guys, the rotifers, a lot of research when you look at them in terms of movement and motility, the rotifers are used for that. Nemotoda, so another group similar to platylementis in terms of having free living forms but also having the parasitic versions. And the nematodes also are used a lot in research, especially looking at embryonic development, nematodes. So these are known as the wrong worms, their body is more cylindrical, not flat when you look at a cross section, they do have sort of a body cavity, it's not complete, and so they're referred to as being pseudo-cylomates, remember in biology pseudo means false. So pseudo-cylomates are the nematodes, nematoda, they have a false body cavity, somewhat of a body cavity but not continuous throughout the body and hence the nematoda or the wrong worms, the species, the genus that we look at in lab a lot is ascarus as an example of the wrong worm. And then we've got maluska, second largest filer in the animal kingdom in terms of number of species, okay? Second largest, a very, very large group, again, examples of maluska, you may be familiar with these, the snails, the slugs, the clams, the squids, octopuses, 110,000 species identified. What makes these guys so successful? As we talk about these animosity, look at the number of species, there must be something within this group that enable them to be so successful. If you listen to the list as well, some of these guys we ourselves enjoy as seafoods yet they continue to exist in large numbers. So the maluska has three specific body parts that enables them to be so successful. They got a foot for locomotion, so there's motility, there's movement, they've got a mantle, and that's the key, the mantle develops a calcified shell that protects these guys, you think of a snail, for example, doesn't move very fast, but once it feels that it's under attack, it's able to retract its body mass into the shell, be protected and allow it to survive being predated upon, and most of the maluska are very similar. The squids and the octopuses are actually deep sea predators, they swim by jet propulsion and they literally can hundung any other organism and capture their prey because of the ability to swim, and one of the characteristics these guys have developed that is characteristic of the most advanced animals as well is something known as cephalization. So as we look at characteristics, we've tagged just a few, but there are many more characteristics in the animal kingdom that we can look at, 13 altogether, cephalization has to do with a well-developed head and nervous system, brain, and a lot of development in the head region that allows it again to be more effective in terms of a predator, prey relationship, they are able to escape their predators and capture their prey when there's good cephalization. And we see that for the first time basically in the maluska group, good cephalization, specifically the octopus and squids. Okay, next we have the last set of worms, the segmented worms called the anelida. You guys should be familiar with this, when you're a little kid, you go into the backyard into the garden and you play with these little worms, you know, the earthworms that kind of retract its body and it's very slimy, and if you haven't played with earthworms then you've missed a nice childhood, you need to go do that. But anelids actually do have a complete body cavity and therefore they are silomates. So anelids does have a complete or do have a complete body cavity. So if you look at, again, tagging the worms from the flatworms to the wrongworms to the earthworms, the segmented worms, then these are used as representative of body cavities or lack of as great examples. So going back to the first group, the platylementis, there were a silomates, the body's flat, no body cavity, the wrongworms has a false body cavity and the earthworms have a true body cavity, the silomates. Okay, and finally here we have, or the next group, sorry, our arthropoda. Now these guys, when you look at successful numbers, abundance, there's no other phyla, not even us, we belong to phylamcodata, not even phylamcodata, rivals, arthropoda in terms of numbers, okay? So I like to say, some of the examples, they're called jointed appendages and that's a clue to their success. These guys, these animals, examples of arthropods are some of your most feared critters on the planet, spiders and scorpions and centipedes and millipedes, crabs, lobsters, crayfish, insects. The insects really is a super class that really makes this the most successful in terms of numbers, I mean there's over, what, 900,000 species of insects identified in the phylamarthropoda. So what makes these guys so successful? Malusco was a very successful group in terms of numbers, arthropoda is another very successful group in terms of numbers, what contributes to the success? Jointed appendages, how does that benefit an animal to enable them to be so successful? Most of us always try to get rid of insects, we want to kill the housefly, we want to kill the spider, we want to kill the roaches, but yet they just seem to multiply in numbers every time we get rid of them. Why are they so successful? Well again, it has to go back to the ability to move. Those jointed appendages enables them to be so successful in terms of movement and again in the interaction of predator and prey, they are able to capture and eat by having the motility, the flexibility of their limbs and they're also able to avoid their predators. In the case of insects, developing the wings to go along with these jointed appendages makes them so elusive that they're very hard to capture and therefore that enables them, that's part of the success. They also have exoskeletons on their body that makes them a little rigid and tough, so you rarely have to try to crush it in order to kill it because of the tough exoskeleton that these guys have developed as well. So jointed appendages is one of the key characteristics to the success of atropods, remember that. The next two phyla, Ikinodermata is high upon the list, this is a very unique group because unlike some of these others which have evolved from radial to bilateral symmetry, these guys have a bilateral symmetry in the larval stage, but a radial symmetry in the adult stage, that's kind of unique because radial symmetry seems to be tacked to some of the more early or primitive animals, yet Ikinodermata is on top of the list as actually has a deuterous term development just like chordates, that's unique. So radial symmetry again, examples of Ikinodermata, the starfish or sea star, the sea animons, the sea urchins, these are all examples so they are aquatic in existence, marine environment, but yet has well developed structures, organs and tissues in the body plan similar to the more advanced animals, so that puts them in a unique group, radial symmetry but advanced animal characteristics. Okay, now the final phyla on our list that fits both the invertebrate group and the vertebrate group is phylum chordata. So this phylum is a final phyla on an animal list but it fits the invertebrate group and vertebrate group. In terms of invertebrate, there are two sub phylums that falls in that category, urocordata and cephalocordata. Urocordata and cephalocordata, the tunicates, okay, the urocordata are the tunicates and cephalocordata are the lanslets, so again these are two invertebrates, no backbone but phylum chordata in terms of chordate characteristics and then we have the phylum, sub phylum vertebrata, sub phylum vertebrata with a list of these other classes of animals that all fit into the invertebrate category.