hello bisque 132 this is the beginning of recorded lecture four one uh continuing on with vertebrates so last time we had just got started on this chapter enough to talk about uh fishes uh now we're gonna turn our attention to uh everything else uh and incidentally everything else can be defined by an evolutionary innovation uh that the ancestor to amphibians mammals reptiles and birds had and that is the evolution of four limbs so this uh it's called a super class uh but it's just a clade here this superclass is called tetrapoda and yep that's amphibians uh mammals birds and reptiles all um sharing the common ancestor with four limbs so tetrapoda four feet yeah superclass tetrapoda members have four limbs and this is going to include all further groups in this chapter so among these tetrapods uh let's start down here with class amphibia called amphibians so this is going to include frogs toads salamanders and sicilians we'll get to them soon enough so amphibians are the first land vertebrates uh so before this there were just different groups of fish that lived in aquatic environments these are the first vertebrates that were able to live on land and of course that evolutionary innovation we just talked about the four legs the tetrapoda uh that was you know required to to make it to land limbs that can support weight outside of water and there were definitely some selective pressures that pushed towards this there are some advantages to living on land one is new food sources you know we talked about this in that intro to animals chapter that plants made it to land first uh and so with with plants in these terrestrial environments there are definitely um there's definitely an incentive to to get on land as well and also to escape from predators that are purely aquatic so these are both advantages to life on land for these uh vertebrates so if you're gonna be on land uh the gills that your fish ancestors had are not gonna cut it uh so amphibians had to evolve lungs uh to to extract oxygen exchange gases with air instead of from water but they are kind of kind of bad lungs and we'll talk about this when we get to our circulatory system chapter later on in the course but the circulation of amphibians is not great so their efficiency and breathing is is pretty terrible so to supplement their lungs amphibians have something called cutaneous respiration which is exactly what it sounds like their skin is particularly thin especially to the skin we'll see in other groups of tetrapods and so they are able to exchange gases getting rid of co2 acquiring o2 just straight through their skin through capillaries that are pressed up uh against their skin so um that's called cutaneous respiration getting o2 through the skin and this is done to supplement their lungs which are uh not the best another trait of amphibians is metamorphosis so i'm sure we've all learned about this in elementary school uh you know about frogs but other amphibians do this as well here's the northern crested newt uh going from you know it's egg it's you know newton stages you know uh the tadpole growing these four legs and then you know becoming terrestrial so many undergo metamorphosis they hatch in an aquatic environment with gills and then eventually develop lungs and become terrestrial uh they're going to be some exceptions to this that's why i said many uh but yeah it's something that can be associated with amphibians so again these are the first terrestrial vertebrates but they they still have to be close to water because for a lot of these a substantial amount of their life cycle takes place in water uh another factor that you know causes them to have to stay close to water is the fact that their skin which as we just mentioned is particularly thin to enable cutaneous respiration their skin uh lacks protection it dries out easily and so do their eggs their eggs do not have any sort of shell or really protective barrier around them so both their skin and their eggs can easily dry out so they have to be either in water or in very moist environments so they can they can survive on land but not very well uh not very far from from abundant sources of water or some sort of moisture additionally we can say about amphibians that most are ectotherms we defined this earlier in the chapter when we were talking about fish i said fish are mostly ectotherms as well this is the so-called cold-blooded uh they don't maintain normal body temperature they get their heat from the environment so okay this is class amphibia if we want to talk about more specific groups the domain kingdom file uh class order it would be next so let's talk about some of the orders within class amphibia uh up first is order uh uradella these are salamanders uh and you know i've got a couple examples here of actually some pretty atypical salamanders or atypical amphibians uh this is an oxotol which is kind of a weirdo uh because it never develops lungs it stays at this uh this stage where it has gills uh it's a completely aquatic amphibian it's very it's successful at doing this very beautiful looking kills uh and this is another strange uh i mean not that strange for salamanders but you know strange for amphibians uh this is a salamander that has neither gills nor longs it gets all of its gas exchange through cutaneous respiration and the way it manages that is by being you know rather small we saw this in invertebrates that managed to get away without having any circulatory or respiratory systems at all by being small you can kind of get the sense of this thing based on looking at the leaf that it's uh that it's standing on uh that yeah there are a fair number of salamanders like this that have neither gills nor lungs so order odella salamanders and uh many of them don't have lungs uh either gills only or cutaneous respiration only okay that's all i got to say about this order again we're moving fast when we get to the order level uh another order is order a neura a means without and neura means tail no tail yep that's frogs and toads um traditionally toads have rougher skin and live in drier environments and frogs have smoother skin and live in in you know more more aquatic of lifestyles that's not strictly true whether these are clades or not is in question so uh don't worry about that at all just know order a neuro means frogs and toads so okay next is order apota again a means without pota for the millionth time pota means foot so without foot uh yeah this is what it looks like to be without foot uh this thing is called a sicilian it's uh spelled like this uh but it's pronounced like you know someone who's from the island of sicily the sicilian and yeah these are these are weird they live in tropical environments throughout the world they're about the size of an earthworm uh but they're they're amphibians these are not snakes these are not worms uh they're vertebrates and curiously they're still tetrapods so even though they don't have four limbs when when we when we name these clades i mean these these clades exist uh regardless of what we want to call them and you know we choose a name you know trying to describe everything within this and you know our language is just never perfect uh so the the ancestors two uh all tetrapods had four limbs that was a defining feature of the ancestors to all this stuff but and we'll see this again when we get to birds you can always lose features even if it's you know part of the defining feature of your group so these are not exceptions to this all amphibians are in this this clade of tetrapoda uh and and so are sicilians despite lacking limbs they're evolutionarily members of tetrapoda so anyway uh i i wish i could tell you more about them uh but they there's not very much known about their diet and their their lifestyle so uh just know that apota means sicilians these things are poorly understood and limbless burrowing amphibians and so not much else to say about them so next up uh where we talk about reptiles uh but actually before we get to reptiles there is another clade that emerges here so tetrapoda included amphibians mammals reptiles and birds now we have an evolutionary innovation that is shared by mammals reptiles and birds this evolutionary innovation is a structure called the amnion so members of this clade mammals reptiles birds are called amniotes so what is the amnion well remember how i told you amphibian eggs had this you know tendency to dry out and so they had to be laid in water or in very moist environments well the amnion is a solution to that problem uh so here's a an embryo developing and then here is the amnion so the amnion is a structure that surrounds the embryo and is filled the amniotic cavity is filled with amniotic fluid and this keeps the embryo from drying out so uh instead of having to lay the egg in the water uh you surround the embryo with water in a membrane and put that in a shell or sometimes put that in a shell and and then your embryo will not dry out uh now curiously you know this is a shelled egg so this is a this is a reptile or a bird embryo we're looking at here but remember this amniote's clade includes reptiles birds and mammals as well so we don't have shelled eggs but we do have an amnion so here is you know a human uh embryo and yeah there's the amniotic fluid and there's the amnion so it's something all these groups share um if uh you've ever heard of or seen a woman going into labor and her water breaks uh that is the the amniotic sac uh breaking and this amniotic fluid coming out because that baby's about to be born it doesn't need this anymore and and so that that water coming out is is amniotic fluid so okay how do i summarize all this uh clade amniotic uh members called amniotes uh the embryo is surrounded by amniotic fluid encased in an amniotic sac this cushions and hydrates the growing embryo so again this is a major step forward eggs no longer need to be laid in water or moist environment so this opens up a lot of new uh you know drier territory for these vertebrates to colonize uh and this uh amniote uh amnion can be encased within a shell or within the mother's body as as we see with uh virtually all mammals so this clad amniota includes all further groups so okay now we're ready to go to reptiles right well no uh there are actually three clades within amniota based on skull strip based on a particular skull structure called the temporal fenestra so what's going on with this well these are the three ways to have a temporal fenestra anapsids are vertebrates that don't have any temporal finesse at all a temporal fenestra is defined in the key terms uh here we go it's defined in the key terms as a non-orbital opening in the skull that may allow muscles to expand and lengthen so non-orbital means not the eye and so here's what this looks like another opening here so anapsids don't have this extra opening uh so you know a means without uh so anapsids don't have uh temporal fenestra no temporal for nestra uh they're all extinct so this is this absolute unit uh of uh of uh an extinct anapsid here uh not gonna make a a play trying to pronounce this uh yeah these these are these are all extinct but it is a lineage that exists within amniotes if you do have one temporal fenestra that puts you in a group called synapsids synapsids have one temporal fenestra this includes mammals uh and proto-mammals i mentioned these before they reigned in the in the permian period before the permian extinction event so that's why i said these things were more closely related to mammals than they are to to reptiles or dinosaurs they're synapsids just like we are and finally it's possible to have two temporal fenestrae that's how you pluralize that if you have two temporal fenestrae you are a diopsid uh and these this includes reptiles and birds uh so reptiles and birds closely related to one another because they're members of this clade uh diopsides so okay with with that out of the way now it is finally time uh to start talking about reptiles so this uh this is what reptiles are this is what it looks like if you were to try to draw a circle around what we call a reptile and of course this is an ancestor and not all of its descendants uh this is of course to bring up this for the millionth time this is a paraphyletic group actually hey the example we've been using this entire quarter has been reptiles as a paraphyletic group uh lizards and turtles and crocodiles but we're not including birds here birds are not reptiles and so yeah it's excluding this group it's it's paraphyletic now uh i've been using this phylogenetic tree so far through you know fishes and amphibians uh but at this point i actually want to switch over and use something that is a little bit more detailed okay take a second orient yourselves here this is a phylogenetic tree of just amniotes so we're not showing amphibians or fish here ancestral amniote this one goes from the left to the right and yeah you can see those three clades that i mentioned a minute ago synapsida anapsita and diapsita so synapsids yep that's going to lead to mammals anapsid they're all extinct and then diacids reptiles and birds so again just to illustrate the paraphyletic nature of this uh within the clade diapsita you have to exclude birds if you want to define what a reptile is so paraphyletic group you get it reptiles class reptilia paraphyletic group they are if you wanted to try to describe them synapses that are not birds that's that's what uh that's what a reptile is so uh what are some of their features you know we're familiar with these things uh alligators crocodiles uh turtles lizards well uh these uh reptiles have scaly skin uh so this prevents water loss so you know alongside with the the amnion that surrounds their their embryo this again allows them to live in drier climates uh the downside to having tough thick scaly skin is you can't breathe you can't breathe through it anymore and we will see this when we get to our chapter on the circulatory system later on but reptiles experience an upgrade in their circulatory system that makes them more efficient and so they can they can do without cutaneous respiration but it's worth noting that this this is gone uh with this scaly skin most reptiles are ectotherms again this is the third time i've used this term and they have a propensity for using the environment to heat their body so you know this kind of basking or sunning behavior using you know sunlight to warm themselves up because they're not you know constantly burning a lot of energy to keep themselves at a normal hot temperature so i i do want to go into this in a little bit more detail now just because i i think it's interesting um the advantage to this ectotherm lifestyle is that you have reduced caloric needs uh animals that are endotherms like i'll define that soon enough but that means you know warm-blooded uh burn a lot of calories keeping keeping themselves warm so allowing yourself to fluctuate in body temperature and getting free heat from the sun instead of you know burning it yourself you save a lot of calories and in fact uh this can vary a little bit depending on on the you know endotherm versus ectotherm but uh reptiles ectotherms can survive on about a tenth of the calories used by similarly sized endotherms so yeah it allows you to survive at the 10th of the amount of food as someone who's warm blood that's a definite advantage um but the disadvantage is uh if the temperature is cold if you're not able to sun like this yep you're going to be sluggish you're not going to move you know very quickly your muscles aren't going to work well uh yeah so that's a that is a disadvantage to saving all of this energy okay uh let's go through some specific groups let's start well let's start let's start with the cool one let's start where we all want to start let's start with uh with dinosaurs so this is going to include hadrosaurs and stegosauruses triceratops uh and birds i mentioned this in an earlier lecture birds are dinosaurs uh when we talk about birds we're going to see their ancestor was a dinosaur so go to to this uh they evolved from this specific group of dinosaurs uh and so if we define dinosauria as a clade that means it is an ancestor and all of its descendants so of course that gets us our our t-rex and our triceratops uh but it gets us you know our ducks and chickens here as well uh they're part of this clay dinosauria birds are dinosaurs so clay dinosauria we call them dinosaurs uh it's a diverse group uh again i mentioned this couple chapters ago they were the dominant vertebrates until about 65 million years ago cretaceous paleogene extinction event uh wiped out all of them except for the avian dinosaurs except for birds all you know so all these are extinct except for birds and birds are avian dinosaurs you can distinguish these from the rest by calling the others non-avian dinosaurs kind of been through this already but i'm bringing it up again okay uh continuing on uh with this phylogenetic tree so that's all i all i really wanted to say about dinosaurs i know there's a lot more to say but you know in the interest of time we gotta go through all this stuff uh let's talk about pterosaurs so uh contrary to popular opinion these are not dinosaurs they lived amongst the dinosaurs they are also reptiles uh but they're not within that clade dinosauria so they uh they're called flying reptiles uh and it it's it would be easy to conclude that birds evolved from these pterosaurs uh they they both have the ability to to fly uh that's one that could be considered one of those the synapomorphies those shared features they both fly because they have a common ancestor but that's not the case this is yet another example of convergent evolution uh pterosaurs evolved the ability to fly completely independently of birds which also evolved the ability to fly so convergent evolution explains them you know both having the same ability not a close shared ancestor so order pterosauria pterosaurs they're flying yep they're all extinct and yeah not closely related to birds flight is converge and evolution and again these are not uh dinosaurs they're flying reptiles okay uh moving up here crocodilia okay this one's pretty obvious based on the name these are crocodiles these are alligators these are dario's caimans uh i'm just gonna say crocodiles and alligators here and yeah we know and love these things they're primarily aquatic carnivores so yeah that's all you need to know about crocodiles if you didn't know that already uh let's move to something that you may not know a lot about so uh let's move on to to these two which uh you know are sort of lumped together in what's called ordo rincocephalia so okay this is lizards right this thing looks like a lizard we must be talking about lizards now right no so uh despite how much this looks like a lizard this is a distinct branch in uh in in reptiles members of order rinco cephalia and by members i mean there's only one member still alive today uh it's called a tuatara it only lives in new zealand and man it's weird uh so it's it's upper jaw well this is only showing its upper jaw the teeth on both its upper jaw and its lower jaw are actually just extensions of the skull they're just sharpened to bone they're not actually separate teeth like we're used to having and the reason why i'm showing just the upper jaw here the upper jaw here at the back actually has two rows of teeth uh so you can imagine the lower jaw sort of which has a single row fitting in between these two rows of teeth creating some some pretty gnarly shearing action here as these teeth fit into one another that's a type of of dentation a tooth pattern that you don't see at all in in other reptiles and and not in lizards and you know uh perhaps the even freakier thing uh is the third eye that they have on the top of their heads so this is uh you know not as you know highly developed as the other two eyes uh it's not it doesn't have a lens or capable focusing light in the same way but it is a light sensing organ and it's it's poorly understood but it's thought to play some role in its sleep regulation day night cycle sort of stuff so yeah maybe you hadn't heard of these before i hope not now you do uh order rinco cephalia they're all extinct except for one member of the tuatara in new zealand uh double row of upper teeth part of the jawbone again that's weird uh and a poorly understood third eye so yeah superficially looks a lot like a lizard but it is evolutionarily very different um if we do want to talk lizards though we have to go down to order squamata which is actually not just lizards but snakes as well if you want to distinguish between lizards and snakes you have to get more specific but at the order level it includes all of this stuff snakes are once again like you know sicilians these are tetrapods that have lost their limbs for the sake of you know having this close to the ground slithering lifestyle uh there is selective pressure to to live in this way and you know it's always easier to lose a feature than it is to gain it uh and so yep you have you know more limbless vertebrates here um and yeah we're pretty familiar with these orders squamatas snakes and lizards uh incidentally this is the largest order of reptiles that are live today at least and yes snakes are members of tetrapoda clay they've lost their limbs as part of their evolution we still consider them uh to be tetrapods okay moving along uh order test two ditties a little bit of a question exactly how it fits in here but we don't need to worry about this in our course i'm i'm never going to ask a test question where i ask how how closely related any of these groups are to any of these other groups or whatever so don't worry about this uh test two denny's is turtles and tortoises so uh again these are animals that we're all pretty familiar with they've got a protective shell of bone and actually it is made of bone so they can't come out of their shell they are their shell this their their vertebrae and ribs are fused to this carapace it's uh it's a it's a part of their part of their body um interestingly here is their skull and if you look at this closely and you remember a few minutes ago hopefully you're a little confused about things here's the orbit you know it's the eye here's where it attaches to the to the vertebrae um and there's nothing else here this is an a napsid skull but wait a second i i said anapsids i can't look at this thing without chuckling a little bit i said anapsids were all extinct uh and i had said that reptiles were members of this uh this diapsid group they're supposed to be two temporal fenestrae well maybe you can guess where i'm going with this uh just like snakes losing the ability to you know the four limbs of their tetrapod ancestors for reasons that are not understood uh more members of order testudines have lost both of their temporal fenestraes so they're still in this synapsid clade the question mark is only you know where they fit in it it's it or not i'm sorry not synapsid diopside i misspoke i apologize they're still in this diapsid clade the question is only exactly where they fit in they've lost these temporal finesse tray as part of their evolution so it's weird but interesting so uh order testudines turtles and tortoises protective shell bone anapsid morphology they're not members of the anapsid clade they have an absent morphology uh and you know their temporal fenestrae uh have been lost okay uh and so that does it for uh i mean not talking about pleasures or ichthyosaurus i'm skipping a couple of these things uh that that does it for reptiles so moving on uh we're gonna kind of leave mammals to the side for now so moving on next up we're going to talk about birds so back to this amniot phylogenetic tree here we go there's where birds fit in again i mentioned before they evolved from a group of dinosaurs thankfully this is a simple straightforward monophyletic group now so class avs also known as birds monophyletic group and uh here's the diagram showing some of the evolutionary steps here uh their dinosaur ancestors had birds but weren't really capable or sorry had feathers uh but were not really capable of flight uh a key evolutionary innovation from you know feathers to just sort of insulate feathers that allow for flight is the asymmetrical nature of these feathers and so yep you've got various dinosaurs on the path to birds there's the archaeopteryx the first uh the first thing that we consider to be a true bird and then you know modern birds of today so birds evolved from non-avian dinosaurs and flight was a key feature in their evolution uh flight was a driving force in their evolution and a lot of the features that they have relate directly or indirectly uh to the ability to fly so many bird traits relate to flight one of these is endothermic so i referenced this earlier but now i brought it up for real it's in the key terms endothermy also known as being warm-blooded uh means a capable an animal capable of maintaining a relatively constant internal body temperature so they are constantly burning a lot of calories to keep their body temperature warm even when it's cold around them uh hottie this is related to flight because a higher body temperature makes chemical reactions go faster which makes muscles perform better flying is really hard and so having you know better muscle performance and a warmer body it does relate in a way to their ability to fly uh the downside as we mentioned before we were talking about ectothermy is relatively high caloric needs so sort of related to this in a way another bird trait is feathers i said they were asymmetrical compared to some symmetrical feathers that we see in their dinosaur ancestors and so i just mean that on either side of this vein in the middle they're not symmetrical those are the feathers that allow them to fly but this relates to the endothermy because feathers are also useful for insulation so if you're burning a lot of energy a lot of calories keeping yourself warm all the time having feathers and down feathers that can insulate you and bottle in some of that heat and avoid losing it to the environment that's really helpful so they're involved in flight but also in reducing calorie loss from endothermic uh another feature related to flight is they're sometimes called hollow bones they're not completely hollow but they're a lot more hollow than the bones of other vertebrates and yeah this is a this is a weight reduction thing uh these air filled bones uh reduce the amount of weight that the bird has makes it easier to fly another thing is kind of see this here the the movement from a jaw with teeth and we see some of the very early birds did have a jaw with teeth to the beaks of the birds that we know and love today this is another weight reduction thing so air filled bones and a beak are other features that again indirectly relate to flight because they reduce body weight and finally we have structures called air sacs um this it gets kind of complicated uh but the the short version is when you breathe in air comes into your lungs when you breathe out air exits your lungs so when you're breathing in you know you can you can run and jump and perform really well but it's hard for you to to do that kind of work when you're on on the exhale birds have these structures called air sacs so when they breathe in some air comes to the lungs but some of that air goes to these air sacs where it's not actually doing gas exchange when they exhale you know breathing out this air that's had its oxygen extracted some of that air from the air sacs moves into the lungs so they are getting fresh air even when they are exhaling so okay i'm not not going to write all that down you should just know that there is specialized air flow in the lungs of birds and that is definitely a trait that aids them in their ability to fly okay now if we want to talk about uh specific orders of birds oh we are gonna get bogged down really really really quickly because there are dozens of different orders of birds and you know to be quite honest most of these are things that we're familiar with i i and you know i would only be doing a in an intro biology class only be doing a rough go through of any of these so we know flamingos and owls and peacocks and puffins and hummingbirds so i'm i'm not going to go through at this level at all i'm just going to say uh class 80s has over 30 orders uh and they're highly diverse you know different food sources different living strategies again going back to this birds evolved you know to fly but plenty of these have lost the ability to fly to live in aquatic environments instead or have lost the ability to fly uh to you know conquer terrestrial environments instead so yeah 30 orders highly diverse that's that's all there is to birds okay up next is mammals uh but this is typically where i run out of time in uh the recorded lecture four one so we'll pick up mammals in the next one this is the end of lecture four one