hi this is Kim and this is video three on the animals and in this video I'm talking about the cordat which includes the vertebrates which includes us first though I want to go back to something I ended with in video number two we were talking about the difference between protostomes and deuterosomes and remember I used a couple of terms such as blastopore I want to just remind you that egg and sperm to get come together through fertilization to form that first cell called the zygote and that zygote then divides in a very specific pattern that is unique in protostomes and deuterosomes different pattern of cell division at the beginning it's really mitosis but early in development we call that division cleavage because it has a very specific pattern also we talked about the blastopore a blastula is this hollow ball of cells that forms in embryonic development in animals and that Hollow ball of cells then at some point starts to indent and become What's called the gastrula and that indentation is called gastrulation that indent becomes the gut cavity of the animal and that first opening becomes the mouth in proto stems and it becomes the anus in deuterosomes we are a dorone here's another picture of that so in protostomes that blastopore that initial opening becomes the mouth so that would be in analid molus and arthropods then in dutter stems which is the kinod derms and cordat it becomes the anus so phm Cordata has some characteristics that unite the philm even though there are two subo that seem pretty different from us the four cordate characteristics are noord which is seen here in red it's this Red Rod running down the back of this animal that's the not cord a dorsal nerve cord and you see that running down the back of the animal in blue the fairings with Gill slets they're called Fingal Gill slets on this list and then a post anal tail post post anal means behind the anus and here's that tail so even these really primitive chordates the Euro Cordata and the seph cordada which are actually invertebrates have those characteristics at some point in their life so here are the three sub Fila of Euro cordada I'm sorry of cordada the sub Fila of cordada starting with Euro cordada and including including SEO cordada those are the nonvertebrates they also called invertebrates I'm not sure why they wrote nonvertebrates here and then the vertebrata which includes us so this is the vertebrates I want to start with Euro cordada these are some weird animals they can be called SE squirts or tunet they can they're called tunit because they secrete this tunic around the adult body it's actually made of cellulose it's pretty crazy but in these animals the adults only retain one cordate characteristic the fairings otherwise the larvie have the other cordate characteristics a dorsal nerve cord a ferx a noord and right here is the postanal tail the larve are free swimming the adults are sessle which means they don't move and again very primitive cordat the other group which you will see if you go on to take a higher level Majors biology class the amphioxys is in subm SEO cordada they're also called lancelets these look like little fish but they don't have a vertebral column or a skull like fish would they don't really have a a distinguishable head they spend most of their time partially buried and they filter feed so their head is sticking up and they're going to filter feed they do have all the cordate characteristics so here's amphioxys you can see he has a post anal tail he has a not cord a dorsal nerve cord and he has a ferx with gill slits and then finally we get to the vertebrates the vertebrates are unique that they have a vertebral column that encloses the dorsal nerve cord so our spinal cord is enclosed in our vertebral colum they also have the brain encased in a skull and the head is really where all of the sensory information is processed so this shows vertebral column surrounding that dorsal nerve cord I'm going to start with the most primitive vertebrates and actually there's some controversy right now as to whether or not these first guys should even be classified as vertebrates so this first one is a hagfish hagfish do not have Jaws I'm GNA write that on here it's going to be messy but no jaws and the reason a lot of scien are now saying maybe they shouldn't really be classified as vertebrates is because they really don't have vertebrae and they have a very poorly developed skull they produce slime and they're all Marine they feed on invertebrates and Dead Fish they have four rows of teeth where they can bore into a fish and eat a dead or dying fish but due to the fact that they don't have any vertebrae and they have a very poorly velop skull some are saying they shouldn't be classified as vertebrates they used to be in the vertebrate class Agatha a means without and Natha means Jaws so they used to be in the class that means no jaws and they were called the jawless fish so we're going to still consider them really primitive vertebrates another primitive jawless vertebrate are the lam pre and they also used to be classified as agnatha because they don't have Jaws either the lampre though do have a skull and do have Verte they are parasites and you can see that scary mouth where they attached to the side of a fish by suction and those tooth like plates burrow in they have a rasping tongue that can help open the side of the fish and they suck on the blood of the fish so these also used to be Agatha and that classification has changed slightly but we'll still refer to these as the jawless fish okay there's only so big you can get if you don't have Jaws these guys also don't have scales and they don't have fin okay so no Jaws obviously but they also don't have any fins so it's pretty hard to move efficiently if you don't have fins sorry I don't have my um apple pencil right now so I'm going to do my best with the mouse so really the most primitive vertebrates that are truee vertebrates are the class cond dries so condro this means cartilage and iches means fish these are the cartilage fish it includes the Rays the skates and the Sharks what were the advancements in this group well you can see right away Jaws I think that was a movie these are the First with jaws and they also have paired fins which means they can move very efficiently not as efficiently as the bony fish that we'll see in a little while but more efficiently than a lamb pre or a hag fish for sure if you have Jaws you can be a predator which means you can get larger so being able to move with these paired fins is going to make them a good predator and also having Jaws is going to make them a good predator and both of these things allow these animals to get bigger okay there's only so big a Lampe or a hagfish can get because they can't eat bigger food they can't be effective Predators so they can't get as large as these do they're called the cartilage fish because they don't have any bone their skull and vertebral column are made of cartilage believe it or not though they were around at the same time as the bony fish the bony fish didn't come after the cartilage fish it's just a different approach okay it's just a different kind of skeleton in the Cartage fish one thing that's interesting about these guys is they don't have a swim bladder so they can't be buoyant in the water column and so when they're not swimming they sink to the bottom you'll see in a minute that the swim bladder in the bony fish is what's going to keep them floating in the water column if you don't have a swim bladder and you're going to sink to the bottom when you're not swimming you need an asymmetrical tail look at this tail it's bigger on the top than it is on the bottom this should remind you very much of the tail on an airplane it produces lift so when this animal moves its tail side to side the asymmetrical shape of this tail is going to cause this animal to be lifted off from the bottom of the ocean you'll also notice this guy has really wide based attachment for his fin so the fins don't rotate so while they have paired fins no rotation of the fins because they have this wide based attachment so they can't really be as agile if you've ever gone to SeaWorld or some other aquarium where you see sharks swimming you can see that they'll swim right up to the glass and then they have to quickly jerk their whole body sideways to turn you'll also see that in the shark videos on Discovery Channel where they're attacking their prey and they come right up to it and then they have to make a sharp turn to move away from whatever they're going for so they're not really as agile as the bony fish are for that reason but I think sharks are pretty incredible here's the development of Jaws it actually happened from Gill arches that move forward so you can see in this jawless fish at the top there are these Gill arches and as those move forward we start getting more development of Jaws here's another picture of that the Gill Arch is moving forward to develop the Jaws here's that asymmetrical tail it's called heteros seral hetero means different these are it's two different sizes and shapes the top of versus the bottom so it provides lift for the fish that don't have an air bladder but again they do have reduced maneuverability this is is just a picture of a shark egg baby shark developing inside there that's pretty crazy sharks if you've ever touched one they're pretty sharp and that's because they have these remnants of the dermal armor that the prehistoric fish had which is pretty crazy that's under the microscope so sharks are pretty cool please don't eat sharks they're becoming less and less abundant in our oceans they're very overfished people hunt them and kill them for no good reason so please don't eat them eat sustainable fish okay the next class are the bony fish osto means bone so ostes this means bony fish they evolved about the same time as sharks about 400 million years ago but they adopted a heavy internal skeleton made of bone so this is the first animal we're looking at that has true bone so the jalous fish didn't have it and the Sharks didn't have it they are the most um abundant number of species of all the vertebrates so the most species Rich group of all vertebrates are the bony fish over 30,000 living species what were the advancements a swimbladder to help them be buoyant in the water column a symmetrical tail along with Point attachment of fins and these fins can rotate so these guys are very agile if you've ever had the pleasure of going to an aquarium or snorkeling and you can watch these fish in a coral reef and how they can turn sideways and get into tiny little cracks and the fins are all really specialized for their lifestyle they also have a gill covering that they can move to bring water water across their gills so they can actually be more active because they can meet the higher oxygen demand of being active because of that gill covering so this is the air bladder it can release gas or fill with gas to change where the fish is in the water column if you bring that fish up to the surface too quickly from a pretty deep depth you've probably seen how that swimbladder just pushes all of its organs out through it mouth because you're not giving that swimbladder time to slowly release that gas this next one shows you their tail you can see that it is symmetrical another term for the tail is the coddle fin coddle means tail oops sorry I thought I thought I had my highlighter there the coddle fin is another name for the tail dorsal means back so that's the dorsal fin here's that gill covering the operculum pectoral fins pelvic fin anal fin these fins again can rotate they have this point attachment of the fins very narrow attachment very agile there are actually two major groups of the Bony fishes what are called the rayin fishes which you just saw here you can see the Rays in these fins and then there are lob fin fishes the major difference is there are no muscles within the fins of the ray fin fishes but the L fin fishes actually have bones and muscles in their fins some of them even kind of walk I'm doing the little quotes the air quotes right now that you can't see they actually walk on the bottom of the ocean with these bone supported fins so those are most likely the amphibian ancestors those little fin fishes you can see here muscle and bone supporting that fin that's pretty crazy okay versus just a fin used for swimming no walking not all LF fishes actually walk on the bottom just some do in fact that one right there is called the Cela camp and I'll show you him in a minute but I just want to show you some of the diversity in the bony fish so beautiful so many different shapes of their bodies and their fins based on their lifestyle lion fish seahorse Sea Dragon these guys are amazing here's the sea Camp these are very very primitive fish they were thought to be extinct and then in the 1930s a fisherman um in Africa saw this come in on a fishing boat and that's when we found out that they weren't actually extinct they walked on the bottom with four limbs very much like an amphibian would they live up to 2,300 feet in depth so very very deep water they can get really big and they almost move like a Trotting Horse which is pretty crazy okay the next group we have are the amphibians and these were the first vertebrates to come on to land they are the Dre descendants of fish fish like the camp think about this you're an aquatic organism and suddenly you're going to come on to land there are going to be some major challenges that you're going to face the amphibians tried to solve these problems but didn't perfectly do it the reptiles did a a much better job than the amphibians the amphibians are still very tied to the water this includes the frogs toads salamanders noes and the legless amphibians called the Sicilians I thought I had a picture of those guys here here we go so here are the legless apota means no feet this guy is beautiful they're all beautiful look at this salamander and here of course is a frog here are some pictures of early amphibians and you can see the similarity in bone structure between this lob finin fish with the Bony and muscular support and that just really became even more developed so you can look at the pelvis and the T you know you can look at the tibia the femur and the fibula and see how those all relate and how that develops in those early amphibians we do have fossils of these I'm going to skip those slides though with the details about those okay so let's look at the challenges that these amphibians faced on land and they're actually more than this but this is kind of the short list support and movement obviously moving on land under the pressure of gravity is very different from swimming in water you're going to need light legs and you're going to need vertebral changes to support those legs and I'm going to show you those on a picture in a minute respiration breathing on land very different from breathing in the water where oxygen just moves across your gills versus having to actively take in that oxygen from the atmosphere desiccation means dry out if you're bathed in water very different from being on land where water is not as plentiful reproduction if you're in the water you can just release eggs and sperm and those will swim together move together sperm will swim to the egg and fertilization will just happen that's going to be much tougher to do on land also you need to have a way to protect your egg from dry out Vision in here ing very different on land than in the water if you've ever opened your eyes underwater or tried to hear underwater you know that it's very different and then temperature change water is a pretty constant environment in terms of temperature very little change from day to night and season to season the move on to land had very dramatic temperature changes from day to night in season to season so these are the challenges the amphibians had to deal with they solved some of these problems but not completely so let's start with support and movement so this is the skeleton of a fish it's very basic there's this coddle fin also known as the tail and then the vertebral column is pretty similar all the way down okay they can't move their head side to side no reason to right you're in water you can just shift your body body side to side look left or right you can just move your whole body um you don't have a real rib cage you have some rib processes here um vertebral processes but really the whole skeleton is pretty similar to each other all the vertebrae are similar to each other I should say as amphibians moved on to land Locomotion in support for the first time we have a pelvis and shoulder blades the scapula why because they needed to support legs so legs are going to help this organism walk on land versus swimming and then those legs are going to need support so for the first time there's this well-developed scapula and there's a pelvis also you see differentiation in this vertebral column you see the start of some neck vertebrae here some cervical vertebrae although they can't rotate their head there is this one cervical vertebrae holding the head up that's a little bit different than the otherss I didn't really mean to draw on this second one but you can see this first one actually doesn't have ribs the one that's now highlighted y yellow it's holding the head up and it doesn't have rib processes there does doesn't have vertebral processes you see Thora thoracic vertebrae here and then you see coddle vertebrae so we're starting to get a little bit of differentiation of the vertebral column you'll see on the lizard coming up that the reptiles really do a very good job with this so legs changes to the vertebral column the addition of some other bones to support walking on land those were all necessary obviously the Frog skeleton looks really different than this is a salamander you've all seen frogs jump and they they have hind legs that look really different from this okay so that's how they self supported movement respiration how did they solve the respiration Pro problem well amphibians are the First with lungs on land there are some lung fish that have some primitive lungs but these are full-blown lungs some retain gills but most amphibians have some type of lungs they don't breathe very efficiently though they use muscles in their throat to bring air in not very efficient so they can't get very big because pretty large oxygen demand also connected with respiration you have to be able to move those gases around through your body you need to get oxygen to your tissues and they have a pretty um different heart than birds mammals and reptiles do they have what's called a three chambered heart now that was an upgrade from the heart of the fish but I'll show you that heart in a few minutes so you can see how that works circulation and respiration are very closely tied together because the circulatory system is what's going to move that oxygen to the tissues drawing out amphibians have not done a very good job of this the skin must stay moist where it will dry out so they're very tight to the water for this or they can use waxes lots of frogs and spread waxes onto their skin to keep them from drying out but the eggs are jelly likee so the eggs can definitely dry out and they really must be laid in the water so they're really tied to the water toads can live um Underground so they can um behaviorally prevent drawing out but frogs salamander Sicilians really tied to the water they have to keep their skin moist and obviously the juveniles the tadpoles if you think about it they're 100% relyant on the water so that leads us to reproduction they must lay eggs in the water or have some other strategy such as laying them on the back of the other frog so sometimes the female lays the eggs on the back of the male and they get covered with skin sometimes the male pushes the fertilized eggs up onto the back of the female and they get covered in skin they are frogs that actually swallow their eggs and they keep them in a pouch in their throat and they develop in in in the throat but they must all hatch out over the water so they haven't really solved this problem they're still really tied to the water on this one too on reproduction vision and hearing for the first time we have animals that can see color on land you have a lot more color that you need to see than in the water so color vision was an advancement in the amphibians not as clear though as the the reptile color vision hearing for the first time we have the start of um an eardrum and some other structures to be able to sense vibration on land so this was an advancement for hearing on land in the amphibians temperature change they didn't really solve this very well um amphibians really can't be active in the winter okay you don't see frogs in the snow right um frogs are active at night when it's cooler and moiser because they don't want to dry out but also speaking of which obviously you know that frogs must be able to hear pretty well because they have those extreme vocalizations they call to each other they wouldn't be calling to each other if they didn't have really good hearing I love this the sound of frogs at night it's so amazing but temperature change they didn't do such a great job with that they're really only able to be active certain seasons of the year they have to hibernate or they lay their eggs and the eggs don't hatch out until it's warmer so those were some of the challenges that amphibians faced on land and some of the ways that they tried to solve those the reptiles are going to be the ones who really solve the problem I wanted to show you these frog eggs on the back pretty crazy those babies are going to hatch out and the Tad pules burrow out here's a beautiful frog and then of course the salamanders and the legless Sicilians okay class reptilia the reptiles they dominated the Earth for 250 million years so they were doing something right they're over 7,000 living species still and they really solved the problems of of living on land so going back to our original list of problems on land um let's start with Locomotion and support let's go to the vertebral column of the reptiles to show you how they did this so now we're going to get even more differentiation of the vertebral column in the reptile so this is a lizard and you see even more vertebrae here you see real defined cervical vertebrae in the neck more than one so now they can move their head side to side you see a well-developed rib cage on these trunk vertebrae this rib cage is going to have muscles attached and that's actually going to help them solve the respiration problem as well so for respiration rather than just flexing muscles in their throat they're now going to use rib cage muscles to bring in more oxygen they don't have a diaphragm like mammals do but they are ve able to contract those rib muscles and really bring in a lot more oxygen which means they can get bigger and they can be more active because they can bring in the oxygen that that higher level of activity requires you can see sacral vertebrae for the first time over the pelvis so now we have this well fused pelvis really supporting these legs legs can move up under the body a little bit more rather than being completely spay out to the side welldeveloped scapula to support the front legs so those are the vertebral changes that occurred to offer more support and better Locomotion on land okay the next problem respiration I just talked about briefly so bringing in more oxygen with those rib cage muscles drawing out rep reptiles have scales and watertight skin that keeps them from drawing out on land and they also have a watertight egg it's called the amniote egg the amniote egg also called the amniotic egg was a huge advancement in animals so now this can be laid on land without drawing out reptiles birds and mammals are all considered amniotes so some primitive mammals still lay eggs such as the AK kidna and the Platypus and we'll talk about that when we get to mammals birds of course lay eggs most biologists consider Birds to be reptiles but we're going to talk about them as a separate group but the amniotic egg has chambers that really we see in the placenta of mammals as well so this egg was a big advancement so really that's kind of two things together it's the desiccation problem so the skin of the reptile is not going to going to dry out due to the scales and the watertight skin but the egg is not going to dry out either remember the amphibians had the jelly coat egg now we have a hard shelled egg if you have a hard shell egg you have to have internal fertilization so this is the first time that animals are going to have internal fertilization which means male genital male genitalia to carry out that internal Fertilization in fact some snakes have two penises and if you have a snake you might have seen that before sorry I'm TR trying to write internal fertilization with my mouse I really wish I could just type on this slide but it's not letting me okay internal fertiliz for the first time because it's a hard shell egg it has to get fertilized before it's laid okay same for Birds other problems living on land going back to our list so we just talked about really reproduction and desiccation kind of together vision and hearing are also improved in reptiles reptiles can see more colors and have better hearing temperature change reptiles have behavioral mechanisms for regulating their body temperature both amphibians and reptiles are what are called ectotherms meaning that they can't internally regulate their body temperature they really are the same temperature as their environment so they have to behaviorally modify their body temperature and you've all seen this reptiles out in the sun they can't be active when their body isn't up to a certain temperature so in theory you could walk up to a cold rattlesnake and pick it up and it couldn't do anything to you wouldn't recommend it but that's why they come out in the morning and they lay in the sun until they can get enough heat that their enzymes start working their muscles start working and they can be active because they are ectotherms meaning their therm their temperature is the same as the outside unless they do something to behaviorally change that their heart is more advanced and now I'm going to show you a picture of the reptile heart so here you see on the right is the fish Atrium and ventricle not really separated pretty primitive heart the reptiles have almost full division of the heart into four chambers it's what's called a three and a half chamber heart what this means is you can pump with more Force out to the body than you can to the lungs let's think about this fish don't have that separation so when the when the heart contracts when that heart muscle contracts it's sending Blood Out to the body at at the same Force as it is to the gills if there's too much force it's going to blow out those Gill capillaries in amphibians they don't have the separation so when this heart muscle contracts again the heart the heart is sending blood to the little tiny capillaries of the lungs at the same pressure as it is T to the body you can't blow out the lungs so what that means is the body can only get so big otherwise the blood isn't going to get throughout all the tissues there's not enough pressure there's not enough force of that blood coming out so now in reptiles with this slight division here it means they can pump to the lungs at a lower pressure than to the body so you can see when this heart contracts this blood is going to the lung capillaries okay and then this blood is going out to the body and it can do that at two different forces you're going to see in mammals and birds this is completely divided so now there can really be a difference in pressure think about this I mean your lungs are right next to your heart you don't need much pressure to get the blood to your lungs but you definitely need a lot of pressure to get it to your entire head and body so that's how the reptiles have really taken off to be so successful on land this really talks about being an ectotherm so reptiles are ectothermic they have to obtain heat from external sources and they regulate their body temperature by moving in and out of the sun okay compare that to endothermic animals that generate their own heat internally that is mammals and birds so birds are the first endotherms they can physiologically Thermo regulate that's a huge energy requirement so most of the food we eat as mammals is to keep us warm we produce metabolic Heat as we break down our food and that keeps us at 98.6 degrees F so there's a cost associated with being able to physiologically Thermo regulate right so you have to eat more food but what it means is if you're endothermic it means you can be active day and night and you can be active season to season and you can be living in different types of environments you don't see reptiles in the winter in the snow but you see lots of mammals in the winter in the snow you also see lots of birds so if you can physiologically Thermo regulate it means you need a lot more food intake but you can produce your own heat so that going to be an advancement coming up in the birds so birds are considered to be reptiles but they do have some features that are very very different from reptiles and endothermy is one of them okay there are four surviving orders of reptiles so living reptiles includes the turtles and tortoises um a very rare group called The tatras lizards and snakes are grouped together so snakes are just legless lizards really of sorts they're a little bit different there are legless lizards that aren't aren't snakes also which gets confusing it all has to of their skull and some other features and then crocodiles and alligators about 7,000 species of living reptiles here we go turtles are in the water tortoises are terrestrial no teeth here's the tatra he's only found on islands near New Zealand very rare has a parietal eye right on his forehead um oops lizards and snakes actually more lizard species than Snake species and then crocodiles and alligators there are actually only two species of alligator on Earth so most of what we call alligators are mostly crocodiles 25 different species of crocodile here's a better picture of the heart situation as we're moving into birds and mammals birds and mammals are much more active than any of the other groups so they have a a higher oxygen demand they need a very efficient respiratory and circulatory system again those go together so if you look birds and mammals completely divided left and right so they can pump it very low pressure to the lungs and high pressure out to the body because of that division so when your heart contracts both sides contract at the same time it's just a difference in wall thick and because of this division there's no mixing of the oxygenated and unoxygenated blood if you look at amphibians you can see unoxygenated or low oxygen blood is blue and high oxygen blood is red and you can see they mix there's really not a clear division here so they're pumping at the same pressure to the lungs as they are out to the body and then the same for the fish the fish are pumping at the same pressure to the gills as they are out to the body so that was a big advancement in the birds birds obviously very specialized for their food and their lifestyle they have specialized feet specialized beaks specialized shape to their wings so the big advancement in Birds there's a big change was flight and birds really have a lot of reptile traits okay they have an amnot egg they have scales on their legs and their feathers are actually modif ified scales they're made of keratin and there are intermediate fossils that show lizards starting to get little feathers and then more and more into full feathers they don't have teeth so they have a beak why do they not have teeth teeth are heavy and if you're going to fly you need to do things to reduce your weight and I'm going to talk about those adaptations for flight in a second so what are some other characteristics of birds obviously they have adaptations for flight that we're going to talk about they have wings feathers and some other things they are the first endothermic animals which means they have the ability to maintain a constant body temperature huge energy demand for that they have to eat a lot they have a high metabolic rate in other words they burn a lot of calories flight requires a lot of energy their whole vertebral column is modified for flight they have air sacs in their l their bones and their bones are Hollow they lay an amniote egg they breathe with very efficient lungs and again their legs are covered in Scales here are some of the adaptations for flight there are more than this but besides wings and Feathers they don't have a urinary bladder okay so when a bird um goes potty on your car or your head or whatever the case might be that's really poop and really concentrate ated pee Al together okay they don't have a big bladder that stays full of liquid that would be really heavy to fly around with they've lost some some bones they have hollow bones they have fused bones no teeth I don't know how that got scrunched in there um they have really efficient respiration and circulation and I won't go into the details of that but just know it's highly efficient including the fact that they have air sacs in their bones um and they have a heel just like a boat Keel on their sternum and this is where those really strong flight muscles attach when you eat a chicken breast you are eating the flight muscles of that bird even though they don't fly anymore but if you really dissected out that chicken you would see that sternum has a keel on it for increased surface area for attachment of flight muscles feathers are pretty amazing they have these Hooks and barbs that hold them together almost like velcro if you ever find a a feather you know walking around hiking and you were pick it up and really run your hand along the feather this direction and you'll have those barbs all separate from each other and then if you run your hand the other direction they all hook back together again like magical velcro and that's really what a bird is doing with its beak when it's ping its feathers it's getting all those barbs back in place so it has that perfect air foil surface for for flying you see they asymmetrical just like in the sharks that asymmetrical shape is going to produce lift for the bird this is the first known bird very reptile like had teeth had a long reptilian tail had feathers on his wings and tail most likely was what called scansorial which means he really climbed from Branch to branch and lived up in the trees but didn't actually store or fly like birds do today modern Birds lots of diversity there beautiful animals okay and finally we have the mammals lot of diversity in the mammals if you think of this little shrew versus is an elephant crazy the reason that animals I'm sorry mammals the reason that mammals became successful was because of the extinction of the dinosaurs so mammals were around at the same time as the dinosaurs but they were little tiny nocturnal mammals didn't want to get eaten by dinosaur dinosaurs could only be active during the day mammals were endothermic but they couldn't be active during the day because that's when the big predators were there big predators got wiped out by an asteroid and suddenly the mammals took off and as you know some of the mammals returned to the Sea that's how we have whales and seals and walruses and sea lions and dolphins crazy diversity of mammals what do all mammals have in common they all have hair at some point in their life their name comes from mamory gland that are used to feed their babies milk that's a huge Advantage if you can provide nourishment to your baby you're going to increase the chances of that baby being um surviving for the first year of Life specialized teeth depending on their diet we have carnivore teeth we have herbivore teeth we have omnivore teeth mammals have oil and sweat glands they have a very efficient four chambered heart three bones in the middle ear so really efficient hearing especially in Predators diaphragm really brings in a lot of oxygen single lower Jawbone don't worry about that one you'd have to look at all the other skeletons to really get that one and they're endothermic obviously endothermy is not unique to mamals though birds are also endothermic other notable features um is that they have a high metabolic rate okay so they have to have a really efficient heart and respiration and that's because we keep our body temperature constant there's a huge energy requirement for that most mambl have a placenta but there are other types of reproduction in mammals that we'll talk about in a second I want to show you the specialized teeth so if you have an herbivore diet you have these big broad grinding teeth okay versus if you have a carnivore diet you have these pointy meat shredding teeth so you have really the you know best of both well not really the best of both we're like the Jack of all master of none our te they're kind of intermediate okay so we can't walk up to a zebra carcass and rip meat off the bone with our front teeth but we can process the meat when we chew it so omnivore teeth carnivore teeth herbivore teeth specialized teeth is unique to mammals reptiles have teeth but they're all exactly the same all across their tooth Row three modes of reproduction the monotes lay eggs leathery eggs the akid and the Platypus by the way the safari park has two platypus now that you should go see they're pretty cool and there are two surviving species of a kidna so these are really primitive mammals they still lay eggs the next most primitive are the marsupial so they give birth to a very very tiny tiny immature baby it crawls into the pouch of the mom it hooks itself to a nipple and it continues to develop there and then of course they keep trying to get back in mom's pouch long after they should be moving out of the pouch that might sound familiar too possums as we call them but they're actually called opossums are the only North American marsupial most of these crazy animals live in Australia okay so the monotes live in Australia and most of these crazy marsupial live in Australia Australia was like this Arc of strange animals that broke away out into the ocean and took all the strange animals with it okay finally the placent mammals this is a pretty cool option your baby is fully developed when it's born and in all but the primates when these babies are born they can get up and walk for the most part and you know if you watch like a baby gazelle obviously prey in Africa versus a Predator those little babies are born ready to run they immediately go suckle for Mom and they can immediately Walk and Run if they need to well not immediately but within just a couple of hours of being born versus a couple of years for humans I just wanted to quickly show you the diversity of mammals you don't need to know any of these orders but obviously huge diversity if you think about bats which can fly primates marine mammals it's pretty crazy so those are the Cates thank you