Cell, Sea anemone, Anemone, Biology 28 Part1
On this particular slide, so to start off, as we talked about invertebrates, what were meaning by this is these are animals that are going to lack a backbone. Typically, when we think about animals in our minds were visualizing vertebrates, so those are animals that have a backbone made up of vertebrae. These are not going to have that, but these are animals that are very diverse, theres a lot of them, and in fact this is going to be about 95 of the animals. So there are a lot more invertebrates than there are vertebrates altogether. We have about 32 phyla were definitely not going to look at all 32 in this chapter were going to look at a subset of those and were going to talk about the characteristics of just that subset of animals. If we start out, though, with a look at a phylogenetic tree of the animal kingdom, the animal kingdom is monophyletic. So by saying that its monophyletic, we do have one common ancestor that its thought that all animal groups diverged from and were also including all of the diverged descendants from this ancestor. The ancestor, as was mentioned in the last chapter, is thought to have been a flagel ated protist and that flagellated protists is thought to be similar to what we call kawana flageolets. So if we look at the groups on this slide in this phylogenetic tree, most of these are going to be invertebrate species and were going to look at many of these different ones that you see listed here.
If you look at the first branching point that we have or the first thing that really breaks this down into two groups thats this part here – and this has to do with the evolution of true tissues, so were going to look at the first group that branched Off, which is the porifera group and these dont have true tissues, so this will be our one group of animals, our one phyla of animals, that does not have true tissues. So if we start looking at this phylum, this is phylum Porifera, and this is the sponges. The sponges are unique, first of all because they dont have true tissues. So when we talk about tissues were talking about specialized cells that work together for a specific function and theyre, also separated off by membranes, so were not going to have that. In this case, and when you look at sponges, they look very plant light. So these are sessile, meaning theyre not going to be something that moves around theyre non moving, theyre, typically going to be anchored in some specific location and in addition to that, these are going to have asymmetric shapes to them. So in the last chapter we talked about radial symmetry and bilateral symmetry. In this case, they dont have either one of those they are asymmetric. They dont have really a top bottom right left front back any of that. So these are considered to be the simplest of all of the animal groups.
Now these have. These are what we call suspension, feeders and as suspension feeders. That means that they are going to basically be filtering water and then consuming the plankton and small animals bacteria and things that you have inside that water. Here we have an example of the structure of a typical sponge. When we look at a sponge, they do have a central cavity in the middle and that central cavity is what we call the sponges seal. In addition to that, they have a large opening at the top, which were going to call and oscul intim or sorry inoculum. Whats going to happen here is that youre going to have little pores all over the body of this sponge and its going to draw water in so the water is going to come in through these pores and then eventually its going to flow up and out the Oscul on when it does that we have specialized cells which are lining the inside of this internal cavity, and these specialized cells have a lot of flagella on them. These flagella have a sticky mucus on them, so if theres, any small animals or bacteria plankton in that water, theyre going to trap that and then theyre going to ingest it by phagocytosis, so whats going to happen here is that this is a feeding cell. So this whole cell is what we call the co ana site and if you notice, we have a lot of those cells lining the internal sponges seal there.
For us, we also have an outer layer, so we have an epidermis. We have some other cells in here that have odd shapes that are called amoeba sites, and those amoeba sites in this case can take on a range of functions. They are known as amoeba sites because they do have studios that makes them look similar to amoebas the protists amoebas but theyre responsible for producing what we call spicules and thats the yellow structures that you see here. These can give sponges a very rough shape because those spicules are going to be made up of silica or in some cases, calcium carbonate, and so, when we think of sponges being very rough and sometimes rocks like its because of those spicules that they have inside theres. Also, a gel filled matrix thats, really inside all of this area here and thats what we call the meso high, oh okay. So this is the general structure of the sponge. They are suspension, feeders, so or filter feeders. We could call them as well. The water is going to be drawn into the sponges seal through all of the little pores that line the outside of the sponge. They are going to filter out any food particles using the flagella that are part of the co ana sites, and then the water thats, been filtered is going to exit through the top out the oscul on now. If we talk about the reproduction in sponges, for the most part, these are going to be from Aphrodite.
So when we say that these are hermaphrodites were saying that we have both male and female reproductive structures or we can produce both male and female reproductive structures. Thats generally going to be the case here. Typically, they alternate so one period of time. They will produce female gametes and then later they may produce sperm Gammys. So theyre not going to be doing this at the same time, and the reason for that is that this way they can cross fertilize and that cross fertilization is going to be important for genetic variation. So we have eggs that can be produced and then the sperm are typically going to be modal, so those are going to be transported in the water and they can then fertilize a nearby sponge so that we do get that cross fertilization. In the case of the zygote, once we do get fertilization take place, the zygotes are going to be flagellated and since they are flagellated, they can swim to a new location. They can settle, find a suitable substrate and then they can anchor themselves there and grow into a normal sponge structure. So those are our sponges thats, our simplest of all of the animals. Those are the only ones that do not have true tissues. So we want to make sure that we know that these do not have true tissues. Now, if we go back to our phylogenetic tree, we said that Porifera, those are basal animals because they branch off very early in all of this, the size porifera.
All of the other animal groups, they do fall into this clade called: u Metazoa, u Metazoa means true tissues, so all of the other animals are going to have true tissues, and what we mean by true tissues is that these are specialized cells, theyll, be grouped together And separated by memories – and this is separated from other tissues or other cells by membranes, so all of the other animals are going to fall into this. U Metazoa category were going to look at the first group that branches off or that from that which is this one here, which is called nigeria. So when we say this is a silent sea and the nigeria group is going to be what we typically call jellyfish, we have what we call hydras, which is the one on the very bottom here, and then we also have anemones. So these do have true tissues. Its very simple tissues when were talking about Nigeria. This is a very primitive group. These are, some of them are going to be modal. Some of them are going to be sessile, meaning theyre not going to move around theyre going to be anchored and well have different. Some that actually can do both some that have some stages where theyre modal and other stages, where they are sessile. Now we look at these, they are simple organisms, theyre going to be diplomatic and they also have radial symmetry. So by radial symmetry they have a tops and they have a bottom, but theres not going to be a front or back to them, just the top and the bottom.
So if we go through and we talk about their general structure, their general structure is that they have a cavity. So this central cavity inside sound with one opening, and these are going to be carnivores. So the last group that we looked at the poor ephra those were filter feeders. These are going to be carnivores, theyre, consuming and trapping actually small animals and protists. If we take a look at the body structures that we have for this group, this is the first one here, and this is whats known as the polyp. The polyp is the sessile form. So this is the form thats going to be anchored to some type of substrates, so its not going to be moving around notice that with this one, we have all of these little tentacles at the top and what those tentacles are going to do is theyre. Going to wave around in the sea and if prey comes along theyre, going to trap that prey if they trap the prey, then that prey can be kind of forced down into this internal gastrovascular cavity. So we do call this a gastrovascular cavity and what happens in this cavity is that there are going to be digestive enzymes that are secreted from the cells that are all around the outside here. So these enzymes are going to be secreted into the internal gastrovascular cavity. They will digest whatever organisms have been forced down there into that cavity, and then any leftover, waste and water can exit back up through the top and the nutrients will go back and be absorbed into the wall of this.
So since thats one opening at the top that one opening that single opening is going to serve as the mouth and its also going to be the anus, so this is where the food comes in is also where the waste are going to exit from now. Group is going to the groups that have the polyps a lot of them are called hydras and also the anemone. The other structure that we have looks like an inverted polyp. This is what we call a Medusa. The Medusa is the modal form, so these are ones that actually move around in the water and notice that they also have a single cavity inside thats, their gastrovascular cavity. They have one opening at the bottom. This is going to be again both the mouth and the anus, so food will come in and it the waste will exit from this seam opening and they have a lot of tentacles that are going to wave down around the bottom as well, and the purpose of Those is to trap prey and then force it into that gastrovascular cavity. Now these jellies can move around because they can use basically the water that goes into the gastrovascular cavity. They can contract that and then they can open it back up and thats going to cause them to have some movement, its not a real good directive movement, but it is going to move them around, so we say their modal but its more drifting than anything else.
The name of this group, Nigeria, comes from the specialized cells which are called cnidocytes. Then we see that right down here on the bottom. These specialized cells contain this organelle called animat assist and that pneumatic cyst is able to shoot out of the cell and sting some prey. In many cases it contains a poison or toxin that may paralyze that prey. So this is something thats very important for feeding. Now. Im, not all Nigeria are going to have this, and not all Medusas are going to have this, but it is fairly common for them to have it. The Nigeria are going to have some simple nerves. These simple nerves are going to form a network that really extends around the body. These do have radial symmetry and those nerves are going to be dispersed all around the body, so this is going to Abell them to respond equally to any sensory input that they get from any direction. So again, theyre not going to be organisms that have a front and a back to them. They can respond equally on all sides. Now, if we start talking about the individual, clades or groups of the nigeria, the first one is the hydras Owen, so the hydras Owens are going to be a group thats going to alternate between polyps and medusa forms. So if we take a look at the general lifecycle of hydras Owens or what we kind of commonly call hydras, these will have a colony of polyps, so theyre going to live together and those polyps are going to have two different types.
We have feeding ones which have the normal polyp structure to them. They have the tentacles at the top that are going to capture prey, and then we also have reproductive polyps. Those reproductive polyps are going to separate off from that colony of polyps and when they do that, they form a Medusa that contains the either of the female gonads or the male gon na those will reproduce the egg in the sperm and then the agonist verb. If we get fertilization take place, those are going to form a zygote that zygote is going to develop into a larva, which we call an Newell. Now this larva is going to have a lot of cilia on the outside, so this is going to enable it to move around a little bit and since it can move around a little bit its going to make its way to some type of anxious, anchors, substrate And once it gets there, then it can develop and grow into that colony of polyps that we started with so thats the general life cycle of the hydras Owen, so hikers Owen, that was the first group or the first clade that we have those are going to Have both a polyp form and a Medusa form? The next group is going to be what we call the anthozoa or ants as Owen and the anthozoa is. These are characterized by what you see on this slide, which is the in that picture, which is the anemones.
This is also going to be the coral. These many of them have symbiotic relationships with algae. These are a very important part of the coral reefs. The next group is what we call the sky, pessoa or the Skype is Owens. These are what we typically think of when we think of jellyfish or Medusas. So these are the jellies predominantly Medusas, not every single one of them is, but most of them are so these are going to be modal species and then the last one is the Cuba zoas or the Cuba zones, and these have a box like shape to their Medusa, so the Medusa is going to look a little bit different from the other groups that weve seen. Some of these are highly toxic. The sea wasp is a good example of these. These you dont, tend to see washed up on the shore as much as you do. The jellyfish, which come from the Skype, is Owen. Okay, so thats the look at the nigerias.