hello bisque 132 this is the beginning of recorded lecture three five uh continuing on with invertebrates we're gonna finish up i promise uh so last time we had started talking about arthropods and we've gotten to the point where we were going through specific subfilers so uh up next is subphylum hexapoda so uh pota means foot we've seen this many times a hexa like a hexagon has six sides hexa means six so six foot these are insects uh and i said that arthropods is the the largest phylum of all animals this is the largest subphylum within arthropoda so obviously there's a lot of stuff here um i want you to be familiar with these if you're not already as insects ants beetles cockroaches butterflies crickets and flies again that's not you know naming all of them just some of the more prominent ones um they're known for having three tag mata we mentioned this in the sort of generic arthropod which turns out to be a hexapod the b head thorax abdomen and uh many of the members have a wings so yeah i didn't see didn't see any uh crustaceans with wings or spiders with wings or centipedes with wings but uh wings are something that we we definitely see in a lot of hexapods and that's part of you know the secret to their success uh being able to to live in all these other different ways that we couldn't see in the other subphyla and another thing that we see a huge diversity among hexapods that allow them to be such a large subphylum has to do with their mouth parts uh don't don't sweat the details down here but what this is you know showing in kind of a color-coded fashion is again the secret to success is taking a a body that is modular and has you know lots of different parts that can be modified to do different things so you know you can take these same basic mouth parts and create a mouth that's good at siphoning up nectar like a bee or grated lapping up you know chewed up grass stuff like a grasshopper or you know with a long um uh maxillae in order to get nectar deeper within a flower or piercing skin to get blood like a mosquito and of course many many others these are all just sort of illustrating the point that within subphylum hexapoda they've got mouth parts that can they can easily be modified for diverse feeding strategies that's a great way to evolutionarily radiate out and speciate out if you can be modified to do a lot of different things another thing that's uh distinctive of this subphylum is metamorphosis so all arthropods have to malt but many of them just molt to grow larger what we see in insects in hexapods is actually changing the form of their body and gaining new abilities or new parts during uh this molting so there are two types the complete metamorphosis is what we see in a butterfly for example where you have a larva form that forms a pupa and then comes out as an adult it looks completely different the other type of metamorphosis called an incomplete metamorphosis is where you have a series of molds where you know it's growing and changing a little bit each way and as an adult it ends up being different from the first form but it wasn't a single dramatic mold that changed things for example the grasshopper here has wings and then the earlier nymphs did not so my summary here many hexapods undergrow undergo metamorphosis as part of their molting in order to not just grow larger but to actually alter their body okay and with that we're done with arthropods and uh this is another you know a major milestone here we're done with protostomes so uh we're we're done with this this clade protostomia uh which means all we have left now are these deuterostomes and yeah if you've forgotten this protostomes where the mouth first deuterostomes were the anus first go back to the last chapter if you want to you know have an explanation of this again but yes we are now moving on to super phylum deuterostomias these two chordates and aquinodermata so much smaller than protostomia but as it turns out this one's going to be bigger than it looks anyway so clay deuterostomia these are called deuterostomes and yes i can safely say this is going to include all further groups that we will talk about let's start with uh the echinoderms uh with uh phylum aquinodermata so clay deuterostomia phylum aquino dramata this is gonna be uh sea stars or starfish if you will uh brittle stars sea urchins sea cucumbers uh yeah all this stuff so sea star citroen sea cucumbers and brittle stars they are and i can you know a lot of times i have to say oh they're mostly there so they're primarily this because it feels like there's an exception all the time but uh you can confidently say every single aquinoderm is not just aquatic but marine all salt water no fresh water echinoderms no terrestrial echinoderms so they've they found their niche um they are celamates uh and what's interesting is you know we've we've been you know breaking down in this table here celamates and pseudocylomates and acelamates and everything uh but what i'm pointing out now is that if you wanted to draw a circle around you know what acelamate is it would be something like this so there are some protostomes that are celamates and some that are not and all deuterostomes incidentally are salinates but the point is uh that the celium within deuterostomia that we find in chordates and any kino dramata it evolved independently of the celine in arthropods which evolved independently of the celium in uh these you know few low fedrochozoans that are celamates so uh selamate is not a clade it's one of those paraphyletic groups uh because it's not an ancestor in all its descendants so uh yeah echinoderms are uh celamates the cell evolved independently of the coelom in any of these other groups selamate is not a clade um okay so go back to this uh yep remember we're doing deuterostomes for the last two uh body cavity celimate uh and you know circulatory system closed we'll get to that in just a minute but before that uh let me go back to this point i had already filled this out you know one of the things i said uh way back when we got to this point was that all further groups were going to have bilateral symmetry well all further groups includes chemoterms and if you remember bilateral symmetry is supposed to mean you know one plane down the middle dividing into mirror halves and if you think about it one of the most famous aquinoderms the starfish or the sea star doesn't seem to have that so it has what's called penta radial symmetry so uh what gives what's up with that um yes they are a member of this members of this group bilateria uh because they have bilateral symmetry as larva so okay so here is a young sea star with very obvious you know single plane down the middle bilateral symmetry uh it is as an adult that they develop into this uh this penta radial symmetry so don't have to redo this phylogenetic tree we're off on a technicality and it makes sense so uh some members have bilateral symmetry as larvae but develop penta radial symmetry as adults so we've covered all our bases there in case there was any uh any confusion so uh let's take a look at their anatomy so again we're using a c star as a generic example here but again there are other aquino germs we're just trying to keep things simple here one of the things we see in the sea star is with several of the organ systems they exist in a central ring you know whether it's the nervous system or whether it's the digestive system or whether it's this water vascular system that we'll talk about in just a minute uh that exists in sort of a central ring and radiate out to each of the arms uh so this is it's kind of like those you know segmented worms uh that had a little bit of everything in each one of their segments well the sea star has a little bit of everything in each one of its arms which is why if an arm becomes detached you know ripped off in battle or something like that it can grow into a new individual because it has a little bit of everything it has everything it needs so organ systems radiate out to the arms uh from a central ring um another thing to point out about achino germs is their skeleton we've been talking skeleton in most of these groups they have an endoskeleton so if you see a sea star like this in a beachside gift shop or whatever that's the the stella the skeleton of a sea star some of them you know more gnarly looking than others especially on you know a microscopic level uh this is a skeleton made of primarily of calcium carbonate and again this is an endoskeleton it's the inside as opposed to those exoskeletons that we saw with arthropods which were sort of outer armor okay now the water vascular system so this is something that is you know completely unique to this group and quite frankly kind of weird so the way echinoderms move is through these tube feet and the way these tube feet are powered is hydraulic pressure so uh to go back to this uh anatomy here here is you know the water comes in in the central the central part it radiates out through these arms and with with small muscles they can control how much of this pressurized fluid goes into these tube feet and how much you know stays out of the tube feet in order to extend them and move them around and to crawl around now that's not all in addition to using this water vascular system for you know moving for locomotion for grabbing prey and manipulating them this water vascular system also functions as a circulatory system so this is why i wrote closed it's not a traditional closed circulatory system with with true blood like we see in other animals that have closed circulatory systems but it really it's unique but it's probably more appropriate to call it closed than it would be to call it open if we're trying to keep things simple so here's my summary of all that uh phylum aquino dermata members have a unique water vascular system uh this is formed from the salem so they're using this body cavity to to do this it uses hydraulic pressure to power movement of these tube feet it's used for locomotion and prey manipulation and it also functions as their circulatory system okay well uh that that does it for echinoderms now there's uh there's just one group left uh phylum chordata and so it's actually at this point that we have to transition to the next chapter uh which is entitled vertebrates now it's called vertebrates but we're actually not on vertebrates yet we we actually have to talk about chord dates before we can get to vertebrates so it's kind of a weird way to transition to chapters but it is what it is so okay what is a chordate well core dates have these five features i've highlighted one of them here but and only four of them are drawn uh there are five features that distinguish they're unique to chordates one of these is something called the notochord this is a flexible rod that supports the body that you know in some members can uh you know form a skeleton act as a as a skeleton but in but you know the basic chordate it's just a nerve cord so here we go this is still clay deuterostomia phylum chordata members have five features and this is sort of an important parenthetical point uh they have all chordates have these five features at some point during their development we're gonna see it is very possible and we see this within our own bodies uh for these features to be lost but they're all seen at some point during development even if they're not present in the adult so okay feature number one notochord a flexible rod that supports the body okay in addition to that we have the dorsal hollow nerve cord so this is a also dorsal here along the back this is a nerve cord and you know it relays information this forms the the spinal cord and the brain in you know humans for for example but it doesn't have to be that sophisticated um pharyngeal slits or pharyngeal pouches are located near the mouth and these are used to to help in filter feeding this is definitely one of those features that has been lost or you know certainly reduced in function uh it is not used for filter feeding in humans but you know if you look at an embryology if you look at human embryos this is present at certain very very early stages because yeah just to let you know humans are going to be coordinates of course because we haven't come to ourselves yet so pharyngeal slits uh openings behind the mouth can be used to filter feed and uh finally the fifth feature which you know wasn't labeled in this original figure but i sort of drew a picture around it here uh something called the endostyle this is a mucus-producing tissue that also aids in filter feeding and it's another thing that humans you know don't have a parent uh oh sorry turns out i can't count this was only number four number five is the post anal tail uh a tail that extends past the anus so uh this is another thing that humans have lost uh but we have during our during our embryonic development this postanal tail tail extending extending uh beyond the anus so we can also say if we want to finally finish this table here uh that coordinates our and we have a closed circulatory system so that lets us finally finish out this table and again it seems like a phenomenal amount of information but you know for most of these things they're all bilateral except for a couple they're all triploblasts except for a couple you know the protostome deuterostome is easy enough and and then and then it turns out to not be that much information about remembering which ones are acylimate pseudocelimates salimates uh and the circulatory systems of each of these groups so this does not have any new information everything on here i've mentioned uh throughout you know last chapter and this one on you know these slides that have text but you know this is just a convenient way if you want to screenshot this or whatever uh or draw this out yourself um to just organize all of this information so now that we know what it means to be a chordate onto onto the vertebrates right i mean that's what the chapter is called vertebrates well actually we can't get there yet the as it turns out uh all all vertebrates uh are going to be chordates and you know have these chordate features but there are actually two groups of animals that are chordates they are members of this phylum chordata but they are not vertebrates they don't have a skull or a spine or things like that so we don't want to call these invertebrates because in invertebrates typically refers to you know all of this other stuff all the phyla that are that are not chordates but we can't call them vertebrates either so these two weirdo groups that are chordates but not vertebrates are referred to as non-vertebrates sorry if that's confusing terminology but i don't make this stuff up so what are these weird non-vertebrates well one of these is subphylum and yes it's a subphylum because this is underneath phylum chordata subphylum cephalochordata members are called lancelets because i guess they kind of look like a little lance whatever these look like fish but if you examine them more closely they're definitely not fish they don't have any bones they don't have a skull they don't really have a well-defined head you know they certainly don't have eyes or or teeth or any of that stuff they definitely have all the apparent chordate features they got the pharyngeal slits the postanal tail they you know they have the dorsal nerve cord and noda cord uh and the endostyle they got all this you know chordate stuff uh but you know they are definitely not vertebrates uh these are filter feeders that bury themselves in you know sand or rock and you know filter particles out of the water so not much to say about them subphylum cephalochordata lancelets filter feeders and these are one of those two non-verti the other group of non-vertebrates is subphylum urochordata members here are called tunicates and man these things are weird looking so this include bluebell tunicates and this looks like a heart uh at the bottom of the ocean uh this this sea squirt um these are really weird because this thing doesn't look like it has any of those chordate features certainly not things like the dorsal nerve cord it doesn't look like uh it has you know a mouth and an anus this sort of tube-shaped body well that is because uh it has lost these features during its development so if you look at you know one of these tunicates in its larval form uh okay you can see all this you can see the pharyngeal slits here you can see the anus uh you can see the notochord and the dorsal nerve cord it's as an adult that it takes on a very different shape and loses a lot of these features uh but you know has the the body plan that it has as an adult and again is a filter feeder so but the larvae have chordate features most are lost in adulthood they're filter feeders most of them are sessile you know attached to rocks or something and filter feeding but they're actually some really cool uh salps is what they're called uh might be confused for a jellyfish a sea jelly but this is a chain of colonial tunicates that you know exist within the ocean floating around and being a filter feeder but either way uh some grow in long chain colonies but at the end of the day they're still filter feeders so okay those two sub phyla or what we call non-vertebrates now we're on to actual vertebrates this is a subphylum underneath phylum chordata subphylum vertebrata also known as craniata and so you know it's one of those terms that's sort of embedded you know in our collective consciousness that these are vertebrates we should call them the vertebrates it's vertebrata but as we're going to see the the cranium actually came first so craniata might be a better name for this but right now they're kind of used interchangeably members of this subphylum are called vertebrates uh and again the first evolutionary innovation was the head and the skull which protects the brain we definitely don't see that uh in in tunicates or or lancelets here and vertebrates this subphylum is going to include all further groups so at this point i want to introduce a new phylogenetic tree i made this myself uh it does not include everything but it includes you know a fair amount of stuff there's a chordate ancestor here working up in a stepwise fashion so let's start by talking about fish well okay where are fish well there's bony fish but these are some libraries these are also fish fish is a paraphyletic group fish the things that we call fish that is not a single clade it is not an ancestor in all of its descendants it's several clades that we sort of lump together we exclude all the other vertebrates to to create this group so fish is not a clade it's a paraphyletic group but you can't not have fish it's it's a term that still exists uh even if it's even if it's not a clade so most fish are uh ectotherms so this is a new term at this point it's uh defined within the key terms sometimes colloquially called cold-blooded the formal definition of ectotherm is an animal incapable of maintaining a relatively constant internal body temperature so they they rely on their environment for their body temperature and we'll see this again in other groups but yeah i'm just introducing this because it's the first time we've seen this okay so the the simplest the simplest of fishes uh is a group called hagfish these are limbless uh kind of look like an eel but eels are gonna be very different uh these are limbless scavengers and here's a picture that maybe shows this a little bit better um they'd have a skull uh but no vertebrae so again the skull evolved first so these are the uh most ancient living fish uh because they're at this primitive stage where they have a skull but not any vertebrae yet these are sort of eel like just you know referring to their limblessness uh scavengers okay um our next evolutionary innovation after the skull is the the vertebral column the spine so uh we see this in the next uh group of fish called lampreys uh here's a cartoon of a lamprey here's some other drawings of lampreys here are some terrifying photographs of lampreys or actually that's a fish there's the lamprey uh attached to it um and yeah they do have a skull they do have vertebrae uh they don't have a jaw uh so they they have these teeth that you know they use to attach themselves to their hosts these are all either filter feeders or parasites so without a jaw they can't really be hunters or carnivores but they can definitely be parasites and filter feeders so lampreys have a skull and a vertebral column uh and yeah noting that these vertebrae that's a replacement for the nodochord uh again the job of this is to protect that spinal cord doing the bone here doing a much better job of that than the notochord sort of an extension or growth of that and again no jaw we'll see that's it enough lampreys are parasites or filter feeders okay so they don't have a jaw you can probably guess what the next major evolutionary innovation is a jaw and so uh the the clade that we're in now uh is called natto stomata and this is a clade that can be called jawed vertebrates so notice it's not jawed fish it's jawed vertebrates so the the evolution of the jaw is something that happened in an early fish but it's something that's passed on from fish to you know all of all of their descendants onto amphibians mammals reptiles birds so this this clade of natto stomata john vertebrates this includes everything to come we are jawed vertebrates obviously with our jaw so they have a skull a vertebral column and a jaw and again this is a this is a big deal uh the jaw enables for additional modes of feeding you could chew up food you can hunt prey more effectively yeah this this is big there's a reason why uh virtually all uh vertebrates alive today have a jaw in one form or another okay so uh our next group again we're under this umbrella of jawed vertebrates is a class called class chondrichthyes this includes sharks rays uh and skates uh these are sometimes called cartilaginous fishes uh because i mean you can't really tell by just looking at this skeleton but it's made out of cartilage we have cartilage you know in our earlobes and in our nose instead of having a heavy bone skeleton they have a more lightweight flexible cartilage skeleton so uh chondrichthyes cartilaginous fishes uh sharks and rays uh so yeah they're called cartilaginous because they have a cartilaginous skeleton not made out of bone uh it's lightweight but it's not as strong as bone so there there are going to be some upsides and some downsides to this and there's going to be there are some reasons for this a lot of these need to move to not sink that means they don't have a good physiological solution uh to you know affect their buoyancy so so the way to not sink to the bottom is to to keep moving and in fact a lot of these have to keep moving to keep breathing these sharks called obligate ram ventilators so they need to constantly be on the move uh and if you have a really heavy skeleton that's burning a lot of energy if you have to constantly be moving to either breathe or to not sink so that's the reason for the the lightweight cartilaginous skeleton because again it's definitely not as strong as bone but it cuts down on the amount of energy you have to spend to move around and yeah a lot of them definitely have to move around to avoid sinking or drowning essentially if they don't get new water on their gills so the light skeleton reduces energy spent in movement there are some features here that uh we don't want to discount uh paired fins uh doesn't seem like a big deal but you know this is definitely an upgrade over these limbless lampreys and the the limbless hag fish so having you know paired fins one on either side of the body is is a is a big thing that we're going to see in pretty much all further groups as well most can drink these are marine and as we know most of these are carnivores so there are so this is a this is a class uh if we want to talk about the the rest of fish that's actually not one class there are several different classes of what we collectively call bony fishes so this is a i'm not going to break things down to the class level although the classes certainly exist i'm going to lump together all the fish with bones into a clade called clayed osteocthese so these are called the bony fishes and yep they're named appropriately they have a skeleton that's not made of cartilage but is made out of bone uh and again it's the exact opposite of cartilage which was lightweight but weaker the bone skeleton is heavier but stronger so this is accompanied by a couple of evolutionary innovations that help them you know not sink uh the weight of this heavy bone skeleton is offset by air in a structure called a swim bladder condrick qadricthes do not have this only bony fishes have this the swim bladder is an organ that is attached to the circulatory system gases can be put into the swim bladder or taken out of the swim bladder allowing the fish to to regulate its its buoyancy and so it can stay at a certain level in the water and not sink even though it has a heavy bone skeleton so uh this again this sort of goes together with the bone skeleton the swim bladder allowing it to maintain its desired buoyancy uh another feature that kind of goes with this heavy skeleton is a structure structure called the operculum or gill cover so one of the things that we saw in sharks were you know their fin or their gills you can't see them very well here uh their gills are just sort of exposed to the surrounding water uh many of these like this shark uh have to keep moving to expose their gills to new water and of course that takes a lot of energy to keep moving and if you have a heavy bone skeleton you want to avoid having to move constantly the operculum or the gill cover is a cartilaginous flap that not only protects the gills but has muscles attached to it so it can flap back and forth uh you know circulating water over the gills allowing this fish to to breathe to have new water exposed to its gills without having to swim around constantly so this is also sort of related to the heavy bone skeleton offsetting the weight of that by not having to move all the time so uh members of claydos deithes have no curriculum or a gill cover that protects the gills and helps pass water through the gills now there are sorry i think i said a minute ago i wasn't going to get into the classes i lied uh i'm not getting into all of the classes because of uh several of them are extinct there are two extant classes meaning not extinct that are members of this clade of bony fishes the the biggest one by far is class actinopteryg it's quite a mouthful actin up turkey eye uh these are called yeah these include uh virtually all bony fish that you could possibly try to think of it's gonna be easier to remember the like two bony fish that exists today that are not members of this class members of class acted act up turkey eye are called ray thinned fishes again this is within clayed osteothese class actinoptergei ray finned fishes uh this includes almost all bony fish alive today uh and they're called rey finned because their fins are webs of skin with thin spines so here's a cartoon of this yep there's one of the fins and yeah there's some bone here uh but most of the actual appendage is just this flat thin ray it's it's not a very uh robust appendage uh it works just fine for them they're you know extremely successful uh throughout the planet but yeah their their fins are are pretty simple in contrast the other class of living bony fishes is class sarcopte turkey eye and this only has a couple of members a few species of lungfish and the coelacanth these are known as lobe-finned fishes very few living members and you know obviously the difference here there is in their fins uh instead of being thin rays these lobe-finned fishes have uh much more robust fins filled with bones filled with their own muscles uh the fins and ray finn fishes are attached to the shoulder basically and then they use shoulder muscles to move back and forth here there are muscles within the the appendage within the the fin itself so this is worth uh pointing out and this is worth uh you know uh bringing up these muscular bony fins uh possessed by class sarcoptery because what we're going to see is these are the precursor to the weight-bearing limbs of all further vertebrates so these are the the ancestors to uh what would become amphibians and then mammals and then reptiles and then birds and again you can track these synapomorphies to go back to that term from the very first lecture in the quarter uh the bones uh in these these um lobe affinity fishes correspond to bones of living land vertebrates and other you know extinct links between them and the land vertebrates that exist today again evolution is all all about taking something that already exists and modifying it and so if you have a limb that's filled with muscles and bones that can be modified to form a limb that can bear weight on land and that is what the evidence points to so uh the fins of these sarcoptery evolved into the limbs of all further vertebrates and we'll talk about all further vertebrates uh in the next lecture so this is typically my cut off at the end of fishes before we get into the rest of vertebrates this is the end of recorded lecture three five uh this is also a cut off for exam number three so we'll get into amphibians birds and mammals and all that fun stuff uh for the fourth exam this is the end of exam three stuff