Overview of Invertebrates in Marine Biology

Okay, so the word invertebrate means it doesn't have vertebrae, it doesn't have a backbone, which is an interesting qualification because most things in the ocean, most animals, are in fact invertebrates. So this naming is simply out of convenience because we are selfish human beings and are egocentrical and try and categorize everything towards ourselves and we have vertebrae. But it's also very hard to classify because it's so diverse. But this is the cool stuff, right? This is the animals. These are the things that live in the sea. So 97% of animals are invertebrates. And they have all major animal groups represented in the marine community. So we can find so many different things. in the marine environment that a lot of times we can't find in the terrestrial environment. And so a lot of times when people are studying invertebrates, oftentimes they are studying the invertebrates which are in the ocean. Several of these, like I mentioned before, are only found in the marine environment and are not found on land. So let's take a step back and talk about animals in general. Animal is a hard classification to get at, but it's a lot of things and then it's a few things that it's not. So one, they're multicellular organisms. Multicellularity allows us to specialize in organs and tissues and things. They are heterotrophic, meaning we can't make our own food through photosynthesis or chemoautosynthesis. We have to eat other things. All animals do. They have aerobic respiration, which means they have mitochondria. and that allows us to use oxygen for energy rather than anaerobic bacteria which don't. We reproduce sexually, asexually, sometimes both, but generally animals can reproduce sexually, sometimes asexually as well. Most can move during some part of their life cycle or are motile and their embryonic development is similar and unique. All right, so first question, and these questions are gonna pop up throughout this lecture and will be used for your quizzes. One, what are three characteristics of animals? So what you would do is refer back to that list and put in those three characteristics. Or another way you could ask this, which of these characteristics are not found in animals? So one of the ways you can classify organisms is by their body structure. And one of the body structures we use to categorize animals are their symmetry, how they can be split into equal halves essentially, and that relates to their body plan. So you can have a radial, round, circular body plan like a jellyfish or a coral right a coral polyp where you can split it in many different ways and it still be equal halves another one which is similar to that but slightly different it's not listed here is penta radial so you can see these sea stars up in the top right here they have five appendages each of them is equal so you can split it in five different places but it's not equal on every point like it would be in a jellyfish all right bilateral that just means it be split into left and right halves so really only one plane will divide it into two equal halves or you can have no symmetry at all which would be asymmetry and that's what most sponges are you can see there in the bottom right so what are the symmetries of these three organisms we have a c star a sponge and a flatworm all right so we're going to go through the phyla of animal that are most abundant or most present and most obvious in the marine environments the sponges cnidarians flatworms and annelids so we'll start with oops sorry and then we also have the mollusk arthropods echinoderms tunicates and lanceolets so we'll start with the sponges sponges are the simplest type of animals they do not have tissues they have specialized cells but they do not have tissues They are mostly immobile or Cecil and just sit on the substrate they are filter feeders so stuff is pushed through their body through pores and called ostia and it's pushed through there through these flagella that they have they're asymmetrical although the ones here on the right kind of look like they're bilateral but collectively there's no one spot where you can split them into two equal halves And they're regenerative, so you can cut them up into lots of different pieces, and each of those little pieces can become a new sponge. They have some defense mechanisms, because they're just sitting there ready to be eaten. So they've got these little structures called spicules in there that keep them from being so edible. And their major protein found in them is called spongin. Alright, and they can also reproduce sexually, and they have a free-living... larva that would form swims around and then finds a spot. Alright, so here's the life cycle of a sponge. You can see it has all these pores here. There are eggs that are produced with on the inside. Sperm are released by another sponge somewhere else. They will go in and fertilize this egg and then it will turn into this larva, find a spot. Settle down and become a full grown sponge Alright, what are the flagellated cells called of sponges question number three you can actually find the answer right here They're also called collar cells. So good luck with that. Alright, no idea. They have radial symmetry and this one actually does not seem to be very radial the picture we have here but there are two body forms generally in their life cycle a cnidarian will have a medusa and a polyp form but one of them will often be dominant so jellyfish the medusa form is dominant in corals the polyp form is dominant they are also characterized by these stinging cells called a cnidocyte which hold within them nematocysts which are have little poison inside of them and will sting and hurt and kill their prey but also it can be a defense mechanism they have a basic nervous system so they do have tissues but their digestive system is very simple and not differentiated between their respiratory system. Alright so again here's the medusa form it's free floating plankton form uh the larva that it creates is called the planula we discussed this in class before it can bud for asexual reproduction so basically a little piece of it might come off and fall over into a different area or they can also go through fission which is where they will split into two equal halves. But polyps and budding is another way in which they can reproduce. All right, what are the two stages of cnidarians? Question number four. All right, we're going to go through the different types of cnidarians, the different classes. So scyphozoa, these are your jellyfish. Generally are medusa in form. They only have a polyp for a short time in the reproductive. life and all of them are marine so there's no fresh water jellyfish and again they are plankton so they can move but they can't fight against the current and they often have very powerful powerful stings on them all right anthozoas corals anemones sea fans and sea pansies so these are polyp dominated and generally create this large colony such as your coral structures and secrete calcium carbonate which forms that hard part of the calcium structure all of them are all serine hydrozoans are also mostly polyp with a reproductive medusa physalia is one of these that has a gas filled float which we talked about before and it would be considered then pluston and there are some freshwater species in hydrazoa as well all right which class do corals belong to question number five all right now we're moving on to something else flatworms also known as platyhelminthes they are can be infectious agents such as flukes and tapeworms some are parasitic but others just live on their own they have a well-developed reproductive system and they have a very basic nervous system and three distinct tissue layers and they are bilaterally symmetrical you can also cut them in a bunch of different ways the planarians which is in the bottom right here are these research animals which are you can do lots of different things with them you cut their head and they'll grow two heads you can cut them in half and it'll grow two new ones and there's other really cool stuff you can do with them. All right, marine flatworms, also called terbolarians, mostly are free-living carnivores, which are very colorful and have a lot of distinct patterns in them. They can detect light and dark with their eye spots, but otherwise they can't see very well, and most of them are really small. Tapeworms are parasitic, and these can be found in freshwater. marine or in yourself right so they have a segmented body each little segment builds off of it as it grows has this head which is different than all the segments with a sucker or a hook which it used to embed itself into the wall of the intestinal lining of its host and then it just absorbs nutrients as they pass through the digestive system so they don't have a digestive system of their own all right what type of flatworms have a scolex for attaching to the inside of intestines i just talked about this all right next segmented words are also known as annelids so that this is one confusing thing the parasitic worms we just talked about look like they're segment well they are segmented but that's generally not a characteristic of platforms whereas all annelids are segmented Some of these live in freshwater or terrestrial environments such as earthworms, but the ones in the marine environment don't really look like earthworms. They have a well-developed nervous system, they have external and internal segments, and a closed circulatory system, so they have some type of blood flowing through them, and they are bilaterally symmetrical. The repeating units... have on them sitae, which are bristle-like structures that extend from the sides. So you can see that in the top right picture. There's the bristles or the sitae extending from the peripodium, which is basically paired feet-like structures. And they can help the worm stay in place. okay we've seen these guys before the polychaetes they're the largest group of analytes also most diverse and they were also found in hydrothermal vents they can form these calcareous tubes such as the two tube worms and they are generally carnivorous or deposit feeders waiting for things to fall on top of them which they will eat okay oligachetes these are generally terrestrial so we're gonna mostly ignore them but you their CTA are not as abundant or as obvious as the polychaetes all right which group of aniline's would you more likely find in hydrothermal vents and which would you find in burrowed in shallow waters so you can answer that all right mollusks they mean they're Name literally means soft body. A basic plan with the head and a muscular foot. And they have a mantle. The mantle secretes the shell and is also important for some other physiological functions. And a lot of them have a shell like snails, snails and chitons and clams. But not all of them because octopi and squid don't have. a shell. Some of them have a scraping part in their mouth called a radula and they all have a well-developed nervous system and that's why you have octopi which are so smart. They have an open circulatory system and complete digestion system and they can feed all types. They can be grazers, they can be carnivorous, they just can't make their own. They can be filter feeders, they can be deposit feeders. Alright, here's some chitons. You've probably seen these if you've gone to the ocean, but maybe not recognize what they are. They all have eight plates on their dorsal side and a muscular foot which they use like a suction cup just to stick to rocks and are hard to peel off. And they mostly are just razors. Mollusks include bivalves, so anything with two shells that you see is generally going to be a bivalve such as clams, oyster scallops, and mussels. they don't have a head they don't have a radula they have some muscles which are really strong for pulling their shell together for protection and then a foot that they can extend out from that for burrowing in the bottom or they can actually kind of use it to to swim around as well they may also have a siphon for circulating water if they are filter feeding and gills for breathing and then they also have Threads, some of them to attach to each other called Bissell threads. Alright, here's the body plan. You can see from the side they actually have a pretty cool internal anatomy, although they look pretty simple from the outside, including reproductive structures, circulatory structures, digestive structures, and so on. Alright, gastropods, then these are your snails. There are plenty sea snails as well, and even sea slugs that don't have a... shell on them and they are called nudibranchs they do have a radula which they use to browse for substances and some of them can be highly toxic and poisonous and can kill you so especially if they're brightly colored you should probably leave them alone if you see them in the ocean all right cephalopods as we mentioned can be really smart such as the octopus but also includes the nautilus, cuttlefish, and squid. All of them are marine. They have jet propulsion so they suck in water and then push it out in a specific way. They have a thick mantle that covers their body but no shell, well at least the octopi don't. And then they have these little beak-like jaws which they can use to crush prey and some of them have tentacles which with little suction cups on them and ink for defense all right so question eight is a matching one match the description with our four different groups of mollusks all right arthropods insects belong to arthropods but there's a lot of marine um invertebrates which are also arthropods about one million species known so they're very diverse very successful in class in fact 75 of all the animals on the earth are arthropods mostly because of insects they have this specialized protein called chitin in their exoskeleton they molt you can see a crab molting in the top right there they have jointed appendages which is also allowed them to specialize appendages and and is one reason why they're so diverse and successful they have segmented body parts including head thorax and abdomen and in the one on the bottom here our little shrimp uh it has the head and thorax combined um they also have specialized eye and sense organs gills for respiration and all types of feeding strategies so they're very diverse have lots of different types some of the types that are marine include the crustaceans there are some terrestrial crustaceans but most of them are marine. They have two pairs of antennae. The head and the thorax are combined into the cephalothorax and then their body is called a carapace. And again they have a large array of different types of appendages such as the lobster claws, to little feet, to moving and feeling and all the other things as well. so this includes copepods barnacles amphipods isopods crabs shrimp lobsters and etc Alright, an arthropod's exoskeleton is made out of a carbohydrate called blank. It must be shed in a process called double blank. Alright, echinoderms, these are sea stars and sea urchins. They have spiny skin, which is literally what echinoderms mean. And their skeleton is on the inside of their body, which means they have an endoskeleton. They also have a water vascular system which you see there bottom right basically a bunch of tubes with water that they can compress and move around and they use and then they can secrete sticky substances so they can use that to stick to things or let go of things. They have gills for respiration. They have penta radial or radial symmetry in adults and their larvae are bilateral. They do not have a central nervous system, so they don't have a brain, and they can regenerate. So if you cut a sea star one of its legs off, it can reproduce that sea star as a whole new sea star as long as it gets the nutrients it needs and has some of the central ring. All right, the sea stars move with two feet. They are a predator for most of their ecosystems they live in. Their central disc, which is that round part in the middle that we saw before, has at least five arms. Sometimes there's more, 10, 15, 20, depending on the species. And their internal organs extend throughout their entire body, which is what allows them to be cut off one little branch and then grow into five different, have five different legs growing off of that segment. The hard part is made out of calcium carbonate, much like corals, which is embedded throughout their skin. And they're, again, mostly carnivorous, go and eat clams, oysters, and things, pry them apart, and eat them. All right, sea dollars, sea urchins, or sorry, sand dollars, sea urchins, sea biscuits. Also, you can see the penta radial symmetry on these. They have a... external structure called a test, so the hard part. And then they have little spines or things which go through little holes in them. Their mouth is on the bottom of the test and their anus is on top. And they feed on algae, dead things, encrusting organisms like algae that may grow. And they can they are grazers so they just scrape whatever they can off of surfaces. All right sea cucumbers are pretty weird. So they also have penta radial symmetry if you look because you can see like the mouth anus of this one in the middle has five segments there. So along the the worm shape it's still penta radial. And, but, however, two of their feet rows are on one side, and that's generally how it's going to stay on the bottom of the ocean. They are deposit feeders, so they're just waiting for things to come down and eat that. And they can also have a defense where they will actually excrete their digestive system if they are in danger. And this just scares predators away and has them go away, which is kind of... Crazy. All right, what does the word echinoderm mean in Latin? Okay, we're almost done. Chordates. This is the one that we belong to. They have these six characteristics. The four that you may have learned in other ones include the notochord, tubular nerve cord, or dorsal hollow nerve cord, gill slits, and the post-anal tail. But they also have a muscular pharynx and a ventral heart and so those those are used to define this. Tunicates are sea squirts. This is one type of chordate and they do have a sessile and free living form and it has this basic siphon which just squirts water through it and filter feeds that way. The outer layer is called the tunic. and they can attach to a lot of different variety of things okay this um very primitive organism is called the lancelet there's a few species they aren't very big and they are filter feeders in shallow waters kind of look like an eel the beginnings of a fish they have segmented muscles similar to fish and they have gills which are used to filter the food but they have all the features of a chordate as an adult whereas the sea squirt only had them as a larvae Alright, so this is the table found in your book with all the characteristics of those major phyla that we just went over. We'll get to look at some of these in class and have some quizzes before you come to class. Alright, that's it.

These are the things that live in the sea. So 97% of animals are invertebrates. And they have all major animal groups represented in the marine community. So we can find so many different things. in the marine environment that a lot of times we can't find in the terrestrial environment.

And so a lot of times when people are studying invertebrates, oftentimes they are studying the invertebrates which are in the ocean. Several of these, like I mentioned before, are only found in the marine environment and are not found on land. So let's take a step back and talk about animals in general. Animal is a hard classification to get at, but it's a lot of things and then it's a few things that it's not.

So one, they're multicellular organisms. Multicellularity allows us to specialize in organs and tissues and things. They are heterotrophic, meaning we can't make our own food through photosynthesis or chemoautosynthesis.

We have to eat other things. All animals do. They have aerobic respiration, which means they have mitochondria. and that allows us to use oxygen for energy rather than anaerobic bacteria which don't. We reproduce sexually, asexually, sometimes both, but generally animals can reproduce sexually, sometimes asexually as well.

Most can move during some part of their life cycle or are motile and their embryonic development is similar and unique. All right, so first question, and these questions are gonna pop up throughout this lecture and will be used for your quizzes. One, what are three characteristics of animals? So what you would do is refer back to that list and put in those three characteristics. Or another way you could ask this, which of these characteristics are not found in animals?

So one of the ways you can classify organisms is by their body structure. And one of the body structures we use to categorize animals are their symmetry, how they can be split into equal halves essentially, and that relates to their body plan. So you can have a radial, round, circular body plan like a jellyfish or a coral right a coral polyp where you can split it in many different ways and it still be equal halves another one which is similar to that but slightly different it's not listed here is penta radial so you can see these sea stars up in the top right here they have five appendages each of them is equal so you can split it in five different places but it's not equal on every point like it would be in a jellyfish all right bilateral that just means it be split into left and right halves so really only one plane will divide it into two equal halves or you can have no symmetry at all which would be asymmetry and that's what most sponges are you can see there in the bottom right so what are the symmetries of these three organisms we have a c star a sponge and a flatworm all right so we're going to go through the phyla of animal that are most abundant or most present and most obvious in the marine environments the sponges cnidarians flatworms and annelids so we'll start with oops sorry and then we also have the mollusk arthropods echinoderms tunicates and lanceolets so we'll start with the sponges sponges are the simplest type of animals they do not have tissues they have specialized cells but they do not have tissues They are mostly immobile or Cecil and just sit on the substrate they are filter feeders so stuff is pushed through their body through pores and called ostia and it's pushed through there through these flagella that they have they're asymmetrical although the ones here on the right kind of look like they're bilateral but collectively there's no one spot where you can split them into two equal halves And they're regenerative, so you can cut them up into lots of different pieces, and each of those little pieces can become a new sponge.

They have some defense mechanisms, because they're just sitting there ready to be eaten. So they've got these little structures called spicules in there that keep them from being so edible. And their major protein found in them is called spongin. Alright, and they can also reproduce sexually, and they have a free-living...

larva that would form swims around and then finds a spot. Alright, so here's the life cycle of a sponge. You can see it has all these pores here. There are eggs that are produced with on the inside.

Sperm are released by another sponge somewhere else. They will go in and fertilize this egg and then it will turn into this larva, find a spot. Settle down and become a full grown sponge Alright, what are the flagellated cells called of sponges question number three you can actually find the answer right here They're also called collar cells. So good luck with that.

Alright, no idea. They have radial symmetry and this one actually does not seem to be very radial the picture we have here but there are two body forms generally in their life cycle a cnidarian will have a medusa and a polyp form but one of them will often be dominant so jellyfish the medusa form is dominant in corals the polyp form is dominant they are also characterized by these stinging cells called a cnidocyte which hold within them nematocysts which are have little poison inside of them and will sting and hurt and kill their prey but also it can be a defense mechanism they have a basic nervous system so they do have tissues but their digestive system is very simple and not differentiated between their respiratory system. Alright so again here's the medusa form it's free floating plankton form uh the larva that it creates is called the planula we discussed this in class before it can bud for asexual reproduction so basically a little piece of it might come off and fall over into a different area or they can also go through fission which is where they will split into two equal halves. But polyps and budding is another way in which they can reproduce. All right, what are the two stages of cnidarians?

Question number four. All right, we're going to go through the different types of cnidarians, the different classes. So scyphozoa, these are your jellyfish. Generally are medusa in form. They only have a polyp for a short time in the reproductive.

life and all of them are marine so there's no fresh water jellyfish and again they are plankton so they can move but they can't fight against the current and they often have very powerful powerful stings on them all right anthozoas corals anemones sea fans and sea pansies so these are polyp dominated and generally create this large colony such as your coral structures and secrete calcium carbonate which forms that hard part of the calcium structure all of them are all serine hydrozoans are also mostly polyp with a reproductive medusa physalia is one of these that has a gas filled float which we talked about before and it would be considered then pluston and there are some freshwater species in hydrazoa as well all right which class do corals belong to question number five all right now we're moving on to something else flatworms also known as platyhelminthes they are can be infectious agents such as flukes and tapeworms some are parasitic but others just live on their own they have a well-developed reproductive system and they have a very basic nervous system and three distinct tissue layers and they are bilaterally symmetrical you can also cut them in a bunch of different ways the planarians which is in the bottom right here are these research animals which are you can do lots of different things with them you cut their head and they'll grow two heads you can cut them in half and it'll grow two new ones and there's other really cool stuff you can do with them. All right, marine flatworms, also called terbolarians, mostly are free-living carnivores, which are very colorful and have a lot of distinct patterns in them. They can detect light and dark with their eye spots, but otherwise they can't see very well, and most of them are really small.

Tapeworms are parasitic, and these can be found in freshwater. marine or in yourself right so they have a segmented body each little segment builds off of it as it grows has this head which is different than all the segments with a sucker or a hook which it used to embed itself into the wall of the intestinal lining of its host and then it just absorbs nutrients as they pass through the digestive system so they don't have a digestive system of their own all right what type of flatworms have a scolex for attaching to the inside of intestines i just talked about this all right next segmented words are also known as annelids so that this is one confusing thing the parasitic worms we just talked about look like they're segment well they are segmented but that's generally not a characteristic of platforms whereas all annelids are segmented Some of these live in freshwater or terrestrial environments such as earthworms, but the ones in the marine environment don't really look like earthworms. They have a well-developed nervous system, they have external and internal segments, and a closed circulatory system, so they have some type of blood flowing through them, and they are bilaterally symmetrical. The repeating units... have on them sitae, which are bristle-like structures that extend from the sides.

So you can see that in the top right picture. There's the bristles or the sitae extending from the peripodium, which is basically paired feet-like structures. And they can help the worm stay in place.

okay we've seen these guys before the polychaetes they're the largest group of analytes also most diverse and they were also found in hydrothermal vents they can form these calcareous tubes such as the two tube worms and they are generally carnivorous or deposit feeders waiting for things to fall on top of them which they will eat okay oligachetes these are generally terrestrial so we're gonna mostly ignore them but you their CTA are not as abundant or as obvious as the polychaetes all right which group of aniline's would you more likely find in hydrothermal vents and which would you find in burrowed in shallow waters so you can answer that all right mollusks they mean they're Name literally means soft body. A basic plan with the head and a muscular foot. And they have a mantle.

The mantle secretes the shell and is also important for some other physiological functions. And a lot of them have a shell like snails, snails and chitons and clams. But not all of them because octopi and squid don't have. a shell.

Some of them have a scraping part in their mouth called a radula and they all have a well-developed nervous system and that's why you have octopi which are so smart. They have an open circulatory system and complete digestion system and they can feed all types. They can be grazers, they can be carnivorous, they just can't make their own.

They can be filter feeders, they can be deposit feeders. Alright, here's some chitons. You've probably seen these if you've gone to the ocean, but maybe not recognize what they are.

They all have eight plates on their dorsal side and a muscular foot which they use like a suction cup just to stick to rocks and are hard to peel off. And they mostly are just razors. Mollusks include bivalves, so anything with two shells that you see is generally going to be a bivalve such as clams, oyster scallops, and mussels. they don't have a head they don't have a radula they have some muscles which are really strong for pulling their shell together for protection and then a foot that they can extend out from that for burrowing in the bottom or they can actually kind of use it to to swim around as well they may also have a siphon for circulating water if they are filter feeding and gills for breathing and then they also have Threads, some of them to attach to each other called Bissell threads. Alright, here's the body plan.

You can see from the side they actually have a pretty cool internal anatomy, although they look pretty simple from the outside, including reproductive structures, circulatory structures, digestive structures, and so on. Alright, gastropods, then these are your snails. There are plenty sea snails as well, and even sea slugs that don't have a... shell on them and they are called nudibranchs they do have a radula which they use to browse for substances and some of them can be highly toxic and poisonous and can kill you so especially if they're brightly colored you should probably leave them alone if you see them in the ocean all right cephalopods as we mentioned can be really smart such as the octopus but also includes the nautilus, cuttlefish, and squid.

All of them are marine. They have jet propulsion so they suck in water and then push it out in a specific way. They have a thick mantle that covers their body but no shell, well at least the octopi don't. And then they have these little beak-like jaws which they can use to crush prey and some of them have tentacles which with little suction cups on them and ink for defense all right so question eight is a matching one match the description with our four different groups of mollusks all right arthropods insects belong to arthropods but there's a lot of marine um invertebrates which are also arthropods about one million species known so they're very diverse very successful in class in fact 75 of all the animals on the earth are arthropods mostly because of insects they have this specialized protein called chitin in their exoskeleton they molt you can see a crab molting in the top right there they have jointed appendages which is also allowed them to specialize appendages and and is one reason why they're so diverse and successful they have segmented body parts including head thorax and abdomen and in the one on the bottom here our little shrimp uh it has the head and thorax combined um they also have specialized eye and sense organs gills for respiration and all types of feeding strategies so they're very diverse have lots of different types some of the types that are marine include the crustaceans there are some terrestrial crustaceans but most of them are marine.

They have two pairs of antennae. The head and the thorax are combined into the cephalothorax and then their body is called a carapace. And again they have a large array of different types of appendages such as the lobster claws, to little feet, to moving and feeling and all the other things as well.

so this includes copepods barnacles amphipods isopods crabs shrimp lobsters and etc Alright, an arthropod's exoskeleton is made out of a carbohydrate called blank. It must be shed in a process called double blank. Alright, echinoderms, these are sea stars and sea urchins. They have spiny skin, which is literally what echinoderms mean.

And their skeleton is on the inside of their body, which means they have an endoskeleton. They also have a water vascular system which you see there bottom right basically a bunch of tubes with water that they can compress and move around and they use and then they can secrete sticky substances so they can use that to stick to things or let go of things. They have gills for respiration. They have penta radial or radial symmetry in adults and their larvae are bilateral. They do not have a central nervous system, so they don't have a brain, and they can regenerate.

So if you cut a sea star one of its legs off, it can reproduce that sea star as a whole new sea star as long as it gets the nutrients it needs and has some of the central ring. All right, the sea stars move with two feet. They are a predator for most of their ecosystems they live in.

Their central disc, which is that round part in the middle that we saw before, has at least five arms. Sometimes there's more, 10, 15, 20, depending on the species. And their internal organs extend throughout their entire body, which is what allows them to be cut off one little branch and then grow into five different, have five different legs growing off of that segment.

The hard part is made out of calcium carbonate, much like corals, which is embedded throughout their skin. And they're, again, mostly carnivorous, go and eat clams, oysters, and things, pry them apart, and eat them. All right, sea dollars, sea urchins, or sorry, sand dollars, sea urchins, sea biscuits.

Also, you can see the penta radial symmetry on these. They have a... external structure called a test, so the hard part. And then they have little spines or things which go through little holes in them. Their mouth is on the bottom of the test and their anus is on top.

And they feed on algae, dead things, encrusting organisms like algae that may grow. And they can they are grazers so they just scrape whatever they can off of surfaces. All right sea cucumbers are pretty weird. So they also have penta radial symmetry if you look because you can see like the mouth anus of this one in the middle has five segments there.

So along the the worm shape it's still penta radial. And, but, however, two of their feet rows are on one side, and that's generally how it's going to stay on the bottom of the ocean. They are deposit feeders, so they're just waiting for things to come down and eat that.

And they can also have a defense where they will actually excrete their digestive system if they are in danger. And this just scares predators away and has them go away, which is kind of... Crazy. All right, what does the word echinoderm mean in Latin?

Okay, we're almost done. Chordates. This is the one that we belong to. They have these six characteristics.

The four that you may have learned in other ones include the notochord, tubular nerve cord, or dorsal hollow nerve cord, gill slits, and the post-anal tail. But they also have a muscular pharynx and a ventral heart and so those those are used to define this. Tunicates are sea squirts. This is one type of chordate and they do have a sessile and free living form and it has this basic siphon which just squirts water through it and filter feeds that way.

The outer layer is called the tunic. and they can attach to a lot of different variety of things okay this um very primitive organism is called the lancelet there's a few species they aren't very big and they are filter feeders in shallow waters kind of look like an eel the beginnings of a fish they have segmented muscles similar to fish and they have gills which are used to filter the food but they have all the features of a chordate as an adult whereas the sea squirt only had them as a larvae Alright, so this is the table found in your book with all the characteristics of those major phyla that we just went over. We'll get to look at some of these in class and have some quizzes before you come to class. Alright, that's it.

Transcript for:Overview of Invertebrates in Marine Biology

Transcript for:
Overview of Invertebrates in Marine Biology