Unit 14 Echinoderms and Chordates

we'll continue our survey of the animal kingdom talking about the phm ionad dermata eadms include lots of different kinds of interesting animals like starfish sea cucumbers feather star or feather stars or sea sea lies and sea urchins and so lots of different kinds of things and this including sand dollars Ean dermata means spiny comes from two Greek words EO which means spiny and Derma which means skin these are relatively slow moving or cile creatures there are some that are sessile the adults exhibit radial symmetry but the larvae exhibit bilateral symmetry so this even though the radial symmetry is something we haven't seen since the narian the bilaterally symmetrical larvae shows that they're not closely related to the Nigerians eadms don't have head they have an oral surface which is the lower surface for most of them and that contains the mouth and then the other side typically contains the anus it's called the aboral side some of them are capable of regeneration of Limbs like you see here in this starfish that has several limbs arms that are shorter than others is because they have been damaged or cut off and they can grow back so that's really unique characteristic that starfish have that that makes them such top predators they have simple digestive system but it's complete digestive they have they have stomach and an intestine and an anus they can actually see stars can actually turn their stomachs inside out they can eest them from the mouth and into the like for instance clam shell and digest the the clam right within the within the shell and absorb the nutrients and then pull the stomach back out back into the body most of the food that they eat is digested except for hard things like shells and exoskeletons and those get ejected they don't have brain but they do have nerve Network that's very sophisticated including eye spots on the ends of arms they don't really see but they can detect light they have an open circulatory system like most invertebrates do and something that's unique only to econ derms which is water vascular system this is network of tubes containing water and it allows for their movement and flexibility they have these little extensions called tube feet that you can see here in the in the picture that allow them to move and exchange gases and they feed with it they smell with it and so forth they're used for lots of different purposes they also have an endoskeleton this is the first group we've talked talked about that has an endoskeleton an internal skeleton under the skin made of calcium carbonate we don't see this too often or don't notice it very often with sea with starfish which is our most common econorm that we think of but if you think about sand dollars that you collect at the beach the the white round sand do dollar that you collect is actually the endoskeleton of the Sand Dollar some examples of eadms there are sea lies these these two over here are sea lies they're SES filter feeders and they their tentacles or arms contain the tube feet that can that allow them to feed on stuff out of the water we have brittle stars that have hard center part as you see here and very flexible long legs they can actually move pretty fast sand dollars which are kind of like sea urgin except they're flat this is these are live sand dollars in the ocean and they eat things like algae and and other kinds of Plankton and things like that on the on the sea floor here's sea typical sea star or sand starfish sea cucumber which are really interesting they kind of graze along the surface of the of the sea floor they're kind of Bottom Feeders and then sea urchins which are really interesting with all these spikes they also have very sharp teeth on their oral surface and these spikes that can really be painful as well as sometimes poisonous and the final FM that will discuss is phm Cordata FM Cordata or phm Cordata is the cordat which includes most of the animals that you think of most of the time as animals like fish amphibians reptiles birds and mammals there are also some invertebrate cordat like the sea squirts here and the lancelet that you see right here but this includes lot of familiar as well as some unfamiliar animals this is wombat which we don't see too often that's native to Florida and here's duck bill platypus cordat have four characteristics that are common to all chordates at some point in their life they have first of all dorsal Hollow nerve cord most of the nerve cords that we've seen in some of the other groups that had that had nervous system arranged like that brain brain and cord had ventral nerve cord on the lower surface but the dorsal cord is on the upper surface they also have Nota cord which is flexible supporting rod in vertebrates this is what becomes the backbone or the vertebral column and it's located between the digestive tract and the nerve cord and may include enclose the nerve cord in vertebrates of course they have Fingal slits that are located in the ferx region just behind the mouth in fish and in young amphibians these become the gills the openings on the side of the of the head that allow for gas exchange in various chordates they become different things from the from the embryonic stage and humans they actually develop into the the three main bones in the middle ear the hammer Anvil and Stirrup that transfer sound waves from the eardrum to the to the auditory complex and the inner ear and they have muscular post anal tail now some some of these things are only obvious during the embryo stage other others are obvious during part of the life cycle at least it just depends on which particular group you're talking about cordat have these structures okay here we have the the just generic diagram of cordate showing you the location of all these things so the Fingal the feren with the Fingal gill slits brain and dorsal Hollow nerve cord there's our notic cord our muscle segments on the post anal tail they generally have complete digestive system and circulatory system with heart and blood vessels most cordat have closed circulatory systems although there are few who have open ones there are two groups of surviving invertebrate chordates they these are chordates that have the cordate characteristics but do not have backbone the first group here is the tunet or sea squirts you see here the adult SE squirt kind of looks more like sponge than anything else it has two siphons it has an incurrent siphon and excurrent siphon and basically it pulls water in filters things out of the water and then squirts the water back out and it doesn't look anything like cordate they're sessile as you saw in the picture at the beginning of the of the slides for this part they're they sometimes appear in little clusters but if you look at the larvae form of the SE squirt you see the very definite cordate characteristics with the postanal tail and the dorsal nerve cord Nota cord and the Fingal slits the other group is the lancelets lancelets are little fish-like organisms they're about an inch to 2 inches long they look very much like that original diagram that we saw of the of the generic cordate these live in the in the ocean they burrow down into the sand with just their mouth sticking out like you see here the mouth has tentacles that filter things out of the water and they have again they have all the characteristics of cordat these are probably most closely related to vertebrates the all the vertebrate groups that we'll talk about next much more so than the than the sea squirts or tunicas the next group that we'll talk about is the fish and actually there are three groups of fish we have the Agatha which are the jwst fish including the lampy which is blood sucker parasite of large fish and whales and things like that and the hag fish which is bottom feeder just really gross liing slimy creatures here they are sometimes called eels but they're not true eels because Tre eels are actually bony fish and have the same kinds of fins that other bony fish have the second group is the cartilagenous fish the condres this includes the shark skates and Rays they have cartilage skeleton they don't have swimbladder like the bony fish do they have sharks in particular have to keep moving periodically so that the so that water continues flowing across their gills for the exchange of of gases so sharks skates and Rays this is nice picture of of hammerhead shark here and then the third group The oste these is the bony fish they have bony skeleton they have swimbladder swimbladder is an inflatable structure inside the fish that allows it to adjust its buoyancy to swim at different depths some fish actually have lungs they're called lung fish this is the most diverse group of fish 95% of all fish species including most of the ones that you would normally think of as fish the fish that you would have in an aquarium they're ones you would go catch if you went fishing and so forth all fish are ectotherms that means they can't regulate their body temperature their body temperature depends on their outside environment the next group is the amphibians and the reptiles next two groups actually the amphibians have instead of soft shell eggs they actually have eggs without shells they larvae are completely Aquatic and then they change through metamorphic process into the the adults they have gills as larvae and tail and as adults part frogs in particular lose their gills and lose their tail there are they live in water environments they have to have water in order to reproduce because their eggs will dry out otherwise and so they can't really live anywhere that doesn't have some water at least they have porous skin and they dehydrate very easily so this includes frogs toads NES salamanders and things like that reptiles on the other hand have an egg with shell sometimes the shells are hard more like you would think of with chicken egg and others are more leathery feeling they this is group that had great explosion of of diversity back in the Mesozoic Era because they were able to move away from water they didn't have to live by water all the time since they had developed this amniotic egg with shells they have crus or scaly skin keratin is actually the structure the the the protein that the scales are made of and it's the same Protein that's found in your in your hair and nails so things like alligators crocodiles snakes lizards tur Turtles tortoises Etc are members of the reptiles the next group is the birds and actually birds are probably an offshoot they're very often considered nowadays an offshoot of the of the reptiles birds have feathers they have wings but not all birds fly as you know they have beak they can lay eggs and they have skeleton made up of hollow bones most birds are endotherms they can regulate their body heat like mammals can but reptiles amphibians and fish cannot those are exotherms and the ectotherms and the birds and mammals are endotherms they are considered descendants of reptiles because they're very very similar to reptiles in lot of ways they have scaly clawed feet and actually feathers are type of modified scale here you see some examples of birds this is the largest bir pre which is an Indian Condor and of course the ostrich is the largest bird the males can grow up to 9 ft or over 9t tall and over 300 lb in weight there smallest bird it be hummingbird about 2 to 2 and half inches long and then this one shown here at the bottom is coapo which is which is rare flatless nocturnal parrot that's it's very endangered estimated to only have about 125 individuals left in population anywhere the last group is the mammals and mammals are three have three different groups of mammals the monotes the marsupials and the placental mammals monotes are the egg laying mammals they're kind of transitional between reptiles and mammals there are three species of monot that they're two species of species of aidas or spiny ante eaters and then also the Platypus they're really interesting they have they have mamory glands without nipples they and the babies have to lick the milk off their mother's belly they the male platypuses have poisonous spur on their feet that can actually kill you they're just really interesting kind of combination of characteristics between reptiles and amphibians reptiles reptiles birds and and mammals I'm sorry the second group is the marsupial marsupial are born in very immature state they're basically an embryo with with arms and mouth and they they're born very very early and crawl from the birth canal into the mother's pouch where they latch onto nipple and finish their development in the pouch all of the mammals that are native to Australia are marsupial and this includes dingos and koalas and Kangaroos and things like that and then also the posum the opossum which is found also in North and South America is also marsupial it's the only New World marsupial and the only marsupial found outside of Australia in the immediate surrounding islands and the FI and the final group of of of mammals is the placental mammals these young are born at relatively Advanced stage Nour in while in the womb by placenta which is developed inside the the uterus during the pregnancy and are also fed with milk all mammals have hair and feed their young with milk milk mamory glands give the mammals their name