Lab 6 - Echinoderms andChordates


Introduction to Echinoderms

Our closest cousin amongst the invertebrates is a most unlikely taxon,the echinoderms (Phylum Echinodermata, = spiny skin; 6,000 sp )Echinodermsare eucoelomate deuterostomes. They show a superficial fivepart(pentamerous) radial symmetry. The larvae are bilaterallysymmetric,cephalized, and also motile, yet they construct into sessile or sedentaryradiallysymmetric adults.

You are watching: What is the consistency of the madreporite

All echinoderms room marine. They have actually a calcareous endoskeleton,consisting that numerous little plates spanned by a thin epidermis. Theyareprobably the very first animals to have developed an endoskeleton obtained frommesodermal tissue. Numerous little spines job from thesurfaceof the body. Echinoderms have an open circulatory system, andrespirationand excretion occur by method of dermal gills, tiny finger-likeprojections of the skin the stick out near the base of the spines onthesurface. The large coelom likewise functions in circulation and inrespiration.Mixed in with the spines and dermal gills on the surface ar of the animalare numerous small pincers on tiny stalks, structures calledpedicillaria.These can snap close up door on tiny prey, and aid keep the animal"s skin clearof any little settlers (they loss boarders).

Echinoderms relocate by odd tiny hydraulic structures referred to as tubefeet.Each pipe foot has actually a small bulb dubbed an ampulla. The ampullasqueezeswater into the tube foot to stretch it out, v a one method valvekeepingit from return to the radial canals until the ampulla relaxes.Longtitudinalmuscles in the feet contract to shorten them, pulling the animal along.Water enters the pet through a madreporite, a tiny sieveplatethat keeps out piece of debris. Water passes right into a ring canal,out right into a collection of radial canals, and finally into the tubefeet.Tube feet can role in both locomotion and in feeding.

Echinoderms have no brain, or main nervous system, consistentwiththeir go back to a sedentary life v a radially symmetric human body plan.Thenervous system is composed of a simple nerve ring, through fivebranchesto innervate the arms. Their senses room rudimentary, including lightsensitiveeyespotsand sensory tentacles (modified pipe feet) at the tips of thearms,and tiny patches of cells sensitive to chemicals or touch.

They have an unusual form of connective tissue, mutable or catchconnective tissue, i m sorry can change consistency at will, native veryhard to really soft. This is what enables starfish to flex your arms, ordrop an eight if assaulted by predators. Record connective organization alsosolidifiesto lock the spines of urchins right into their protective position. Asexualreproductionoccurs by splitting or fragmentation. Sexes are separate, through externalfertilization. Lock have great regenerative powers; one arm canregeneratean whole starfish!

There are 5 living classes, yet over 20 die out classes ofechinoderms.The genealogical echinoderm was probably an animal like the sea lily,whichresembles an upside-down starfish ~ above a stalk. The pipe feet andwater-vascularsystem originally worked in filter feeding. Some echinodermsreturnedto an "active" existence, detached and also flipped end (mouth next nowdown),with the pipe feet now functioning in locomotion.


Phylum Echinodermata

Class Asteroidea - starfish

Class Echinoidea - sea urchins, sand dollars

Class Ophiuroidea - brittle stars

Class Holothuridea - sea cucumber

Class Crinoidea - sea lilies

Echinoterms pentamerous symmetry endoskeleton spines dermal gills pedicillaria pipe feet ampullae madreporite ring canal radial canal mutable or capture connective tissueTo Do and View

Observe the echinoderms ~ above display. Try to visualize thebasicstarfish body arrangement as friend look at the various classes. Think abouthowthe an easy starfish body has actually been amendment in every class. What are thedifferentfeeding methods of the miscellaneous classes? exactly how do your physicaladaptationsreflect their technique of feeding and also diet?

Tips for Dissection

The starfish has one big advantage over any other pet fordissection.If you screw up among the arms, you obtain four more chances! watch forthefollowing outside features: arms, spines, madreporite,tubefeet, ambulacral groove,ambulacral spines, mouth. Youmight point out the teeny tinyanus at the top center of the disc. Oryou could not....

Cut across one of the arms, about halfway to the tip. Watch theextensivegonadaltissue lying in the coelomic cavity. The gonads connect to thesidesof the arm near the allude where the arm joins the disc. Even thoughsexesare separate, it is nearly impossible to tell masculine from female withoutmicroscopic examination. The feather gonads lie under the pair ofdigestiveglands that fill much of the arm. Put your starfish dorsal side up,and select an eight to cut. Making use of your scissors, very closely cut along themid dorsal line of the arm until you reach the main disc. Gentlyscrapethe overlying tissue of the eight to expose the top side that ambulacralgroove and the pipe feet. Keep in mind theampullae on optimal of the pipe feet,and the influential radial canal.

Cut roughly the very outer edge of the disc, taking care to cutaroundthe area of the madreporite. Gently remove the epidermis the the disc,withoutdisturbing the madreporite. Look because that thestone canal and ringcanal (very difficult to spot). The tiny intestine in ~ the centerof the bowl (anus) will organize the organization back, for this reason you may need to snipthroughit. The intestine connects to the flat pentagonal pyloric stomach,which sit on height of the bigger cardiac stomach, i m sorry fillsmostof the center of the disc. Try to uncover the pyloric duct thatextendsfrom the pyloric stomach into each the the arms.

Starfish Anatomy arms spines madreporite pipe feet ambulacral groove ambulacral spines mouth anus gonadal tissue digestive glands ampullae radial canal rock canal ring canal intestine pyloric stomach cardiac stomachCharacteristics the Classes

Class Asteroidea - (1,500 sp.), starfish

Starfish are essential marine predators. They room wolves in slowmotion.Most have five arms. Keep in mind that the radial the opposite isonlysuperficial, as result of the existence of the madreporite. Some starfish canactually feed on bivalves by extruding their cardiac stomach.Theycan squeeze through an opened a just 1/10 mm wide, within the naturaltolerance that the irregular edges of bivalve shells.

Class Echinoidea - (950 sp.), sea urchins,sanddollars

Echinoids lack arms, but still display the properties five-partsymmetryof the various other echinoderms. Girlfriend can plainly see the 5 rows of tubefeeton the shells you will see in lab. There space over 5,000 fossil speciesof sea urchins. They space well protected by spicy spines, enclosed totheendoskeletal plates. This spines can obtain to be very long. Sea urchinspinesare movable, and aid the urchins to crawl about. Sand dollars aresedentaryechinoids. Echinoids feeding by scraping birds off the substrate withtheirsharp teeth.

Class Ophiuroidea - (2,000 sp.), brittle stars

Members that this class resemble starfish, however their long arms areextremelybrittle. Pipe feet are modified for filter feeding top top microscopicplankton.

Class Holothuridea - (1,500 sp.), sea cucumbers

Note the five component symmetry presented by the rows of pipe feet.Endodermalplates are greatly decreased to a couple of small and scattered pieces insidetheleathery epidermis. The mouth is surrounded by tentacles,which space actually modified pipe feet. Sea cucumbersfeedby snaring plankton in the mucus coating on their tentacles. Lock bringthe tentacles into the esophagus to wipe castle clean, recoat castle withmucus,and feed some more. YUM! Sea cucumbers are considered a good delicacyin the orient (trepang or bêche-de-mere). They have actually a uniquedefensivemechanism. When threatened, they have the right to evert difficult stinky hair fromtheiranus. Enough said...

Class Crinoidea - sea lilies

Sea lilies are an ancient group, walking back around 530 mya. They werethought to be extinct till they were rediscovered farming on the oceanfloor. In sea lilies, the mouth and anus room both top top the top surfaceon a little disc, through the arms situated along the leaf of the disc.Crinoidtube feet are modified because that filter feeding.

Economic, Ecological, and also Evolutionary Importance

Some starfish (Crown that Thorns) reason extensive damage to coralreefs.

Sea cucumbers are an oriental delicacy, supporting a multi-milliondollarseafood industry.

What walk the shape of the larvae suggest about the at an early stage evolutionof echinoderms?

Consider This

How space each the the class of echinoderms acquired from the basicstarfishbody plan?

How walk the radial the opposite of echinoderms said to their lifestyle?Aren"t all greater animals bilaterally symmetric?

Introduction to Chordates

We now turn come the last phylum that animals, one the dominates thedeuterostomesas thoroughly as arthropods dominate the protostomes, the PhylumChordata(42,500 sp.). Chordates room eucoelomate deuterostomes, andprobablyshare a usual ancestor v echinoderms. 3 importantcharacteristicsunite the Phylum Chordata. At some allude in their life cycle, allchordateshave a notochord, a dorsal hollow nerve cord, and also pharyngealgill slits. A notochord is a flexible supporting rod the cartilage,although in many adult chordates the notochord is replaced by a vertebralcolumn. The dorsal hole nerve cord eventually forms the spinalcordand the brain.

The pharyngeal gill slits appear in every chordate embryos, an echo ofour remote origin in the sea, yet are usually shed in the earlydevelopmentof the organism. Primitive chordates evolved small slits opening intothepharynx. By contracting the pharynx, the animal could attract water intoitsbody and also over the gill slits. This slits originally worked inaidingrespiration and also capturing food by filter feeding. Smaller, moreprimitivevertebrates might rely top top diffusion because that gas exchange, yet larger andmoreactive develops required more surface area to permit rapid exchange ofgases.Chordates developed gills, sheets of very folded organization in thespacesbetween the gill slits, tissues v a very rich blood supply toexchangegases. Gill arcs were reinforced v cartilage to aid hold themopen.Over time, the area between the gills, or the gill arches, becameossified(turned harder) and migrated slightly front to form the firstprimitivevertebrate jaw. Vertebrates could now bite and also chew your prey,and were no longer minimal to filter feeding as a method of life.


Phylum Chaetognatha - arrow worms

Phylum Hemichordata - acorn worms

Phylum Chordata

Subphylum Urochordata - tunicates

Subphylum Cephalochordata - lancelets (Amphioxus)

Subphylum Vertebrata - vertebrates

Superclass Pisces

class Agnatha -lampreys

class Chondrichthyes -sharks, rays

class Osteichthyes -bony fishes

Superclass Tetrapoda

course Amphibia -frogs,toads, salamanders

class Reptilia -snakes,turtles, crocodilians

course Aves -birds(dinosaurs)

class Mammalia -placental(humans), marsupial (kangaroo), monotremes (egg layers - platypus)

Terms notochord dorsal hole nerve cord pharyngeal gill slits gills tetrodotoxin evolutionary constraint jaw dipleurula larvae neoteny vertebrae vertebral obelisk backboneTwo that the "lesser phyla" deserve special mention, due to the fact that theyshowmany of the functions we combine with modern vertebrates.

Phylum Chaetognatha - (100 sp., fr Gr. Khaite = hair, gnathos= jaws), arrowhead worms, Sagitta

I doubt if anyone below has ever before noticed among these worms whileswimmingin the ocean. This tiny small predators are just 6-7 cm. Long, andarecompletely transparent. However they are extremely abundant. They space themost numerous carnivore in the ocean. They are the tiger sharks that theplankton. The small moveable hooks that surround the mouth, and also givethesecreatures their name, are offered to record prey. Prey space injected witha small jolt oftetrodotoxin, the exact same paralytic poison discovered insome Japanese puffer fish. They lack circulatory, respiratory andexcretoryorgans, relying completely on diffusion. They are living fossils, goingbackessentially unchanged for about 500 my. They stand for a an extremely earlybranchon the chordate tree.

Phylum Hemichordata (90 sp.), acorn worms

These naval worms space another old group, evolving around 450mya.They might be the first deuterostomes ~ above Earth. They range in size from 2cm to 1.5 meters. Lock share few of the basic characteristics ofthe chordates, which we"ll review later, such as a dorsal hole nervecord and also gill slits. We provided to think they additionally had a notochord,anotherchordate trademark, yet closer research revealed this hypothesis to bewishfulthinking. They live in U-shaped burrows in the ocean floor. Notice theslits in the next of the pharynx. This pharyngeal gill slitsareused for gas exchange and also feeding. This obscure small structure willeventuallygive increase to the vertebrate jaw, a marvelous example of evolutionaryconstraint - evolution is constrained to operation in particular channels.Allsubsequent advancement has to begin with what"s already there. Lock sharea usual ancestor through echinoderms, a fact we deduce from your similarlarval develops (dipleurula larvae) and also other developmentalsimilarities.This larval form, incidentally watch strikingly similar to thetrochophorelarvae the annelids and also molluscs.

Phylum Chordata

Subphylum Urochordata - (1,250 sp.), tunicates

Tunicates are sessile, marine organisms. They are covered v acellulosecloak, or tunic, which offers this team its name. Lock exchange gasesandfilter feeding by method of your pharyngeal gill slits. They count on twoprominentsiphons, one incurrent and also excurrent siphon, to traction water v theirbodies. The pharynx is lined v cilia, which attract water in. Thesuspendedorganic corpuscle stick come a great of rubber in the pharynx, and also arelatereaten. These siphons room convergent with mollusc siphons. Tunicateslooka little like molluscs, and also a little bit like a transparent sponge, and may evenfunction prefer these organisms, but these similarities are entirelysuperficial,and the three groups are not directly related. Although these curiousanimalsdon"t specifically look prefer us, lock are an extremely derived native theirpresumablybilateral and also motile ancestors. The larvae of tunicates looks very muchlike a tiny tadpole. One of the the strongest theories that vertebrateoriginssuggests that vertebrates occurred from tunicate larvae by a processcalledneoteny.In neoteny, the juvenile form becomes capable of sexual reproduction,andthe adult stage is completely bypassed.

Subphylum Cephalochordata - lancelets, Amphioxus (laterrenamedBranchiostoma).

Lancelets are an extremely common in shallow water. They room usually hard tosee since they bury themselves in the sand, with just the head endstickingout, therefore they deserve to filter feed by method of the gill slits in theirpharynx.As you could expect the a sedentary filter feeder, your cephalizationisgreatly reduced. Note the segmented musculature in the body.Segmentationevolved individually in the vertebrate line, maybe as one adaptationfor burrowing.

Subphylum Vertebrata

Vertebrates all have a vertebral shaft or backbone. Thelinearseries of vertebrae, or backbones, shows the underlyingsegmentationof the mesodermal tissues. Vertebrate embryos display this segmentationclearlyin the muscles the line the back of the embryo. Cephalization is verypronounced, vertebrates space generally energetic animals. Vertebrates haveextremely well occurred sensory organs, and also a complex central nervoussystem v a mind encased in a security skull. Vertebrates have aclosedcirculatory system, and the sexes room separate. Over there are seven livingclasses the vertebrates.

To Do and View

Observe the skeletons and live chordates top top display. Payparticularattention come the way in i m sorry the critters move, and also how the movementis reflected in their skeletal structure. Contrast and compare fish,amphibians,reptiles, and also mammals with respect to their technique of movement, and thestructure that the jaw and mouth. Exactly how do these differences relate totheirhabitat and also ecological duty (niche)?

Tips because that Dissection

Turn your frog over so that the ventral surface ar is up. Closely cutthrough the abdominal wall surface from in between the behind legs to the lower jaw.Cut through the skeletal of the pectoral girdle as you with the area ofthefront foot (try her scissors - they are very sharp!). Peel backtheskin over the abdomen. Keep in mind the thin peritoneal membrane thatenclosesthe large coelom i m sorry holds the interior organs. If you have actually afemale frog, lot of the coelomic room may be filled through eggs.Carefullyremove many of the egg to disclose the interior organs.

Note the large heart, flanked on each side through a prominentlobeof the liver. Lift increase the heart to reveal the lungs thatlie beneath. Lift increase the heart, liver, and also lungs to expose the esophagusand the height of the stomach. Note just how the esophagus leader upintothe pharynx and also the mouth. Follow the stomach under to find the smallintestine and also the large intestine, which leader to the cloacaand the anus. An alert how the intestines are highly coiled toincreasesurface area because that digestion. Reduced through one lung to watch itsinternalstructure. What execute the architecture of the lung and also intestine have actually incommon?

Cut v the stomach and lower intestine, and also carefully removethedigestive system to expose the urogenital system. Look for the oval kidneys,lying close come the inner surface of the dorsal human body wall. You could seelight stripes down the size of every kidney. These space the adrenalglands. Depending on the season in which the frogs to be killed, youmight additionally find star-shaped yellow fat bodies, used for fatstorage.In i beg your pardon season would these fat body be largest? Why? If her frog isa male, girlfriend will uncover two tiny ovoid testes lied on peak ofthekidneys. If her frog is a female, you will discover two big ovariesin the exact same position. In both sexes, you will observe a very coiled oviductrunning follow me the external edge of every kidney. In the male frog, thisoviductis a vestigial organ.

Stop!! Take a deep breath...You"re doing simply fine, thoughmaybejust a tad grossed out. However hold ~ above to her chair (or her labpartner),it"s about to acquire a lot worse because...we"re walking to try to exposethebrain!!Turn her frog over, and remove the skin indigenous the top of the head.(Wait!It gets better!!) now use her surgical scissors to reduced through thebonesof the skull, beginning near the nares (nostrils), simply in front of theeyes (ewww...). You will need to really carefully cut and removethetop the the skull in tiny small pieces. It"s tough to do this withoutdisturbingthe vulnerable tissues beneath, yet give the your best shot....Once thebrainis in view, identify the olfactory lobe (smell brain), the cerebrum(thinking brain), and the optic lobe (seeing brain). Noticethatthe optic lobes are the largest part of the frog"s brain? Why? Whatpartof the mind would you mean to be largest in a rat? In a human? How"syour brain feeling appropriate now?

Frog Anatomy peritoneal membrane coelom love liver lung esophagus stomach pharynx small intestine big intestine cloaca anus kidney adrenal glands fat body testes ovaries oviduct mind olfactory lobe cerebrum optic lobeCharacteristics the Classes

Superclass Pisces

Class Agnatha - jawless fish (hagfish, lamprey); 63 sp. (fr.Gr. A = lacking, gnathos = jaw)

These primitive jawless fishes were the very first vertebrates. Forabout 100 million years, hagfish were the just vertebrates! Theirskeletonsare created of cartilage rather of bone. Lock lack pairedfins.All modern-day agnathans are parasites or scavengers, yet their ancestorswerefilter feeders, more than likely very comparable to the lancelets.

Class Chondrichthyes - sharks, skates, rays; 850 sp. (fr.Gr.chondros = cartilage, ichthys = fish),

Like the agnathans, this primitive fish have cartilaginousskeletons.But this group shows several an essential evolutionary advancements, such as jawsto manipulate food. They likewise have a primitive sensory system dubbed alateralline, which castle share with bony fishes. The lateral heat sensorscandetect tiny pressure tide in water, such as those produced bystrugglingprey. Lateral lines space the fish tantamount of hearing. Their skin iscoveredwith tooth-like structures called denticles.

Shark skin, dubbed shagreen, to be once used for sandpaper.Sharkswere once critical fishery, and also were sought, in the job beforesyntheticvitamins, for your vitamin-enriched liver (they don"t acquire cancer!).Sharkslack a swim bladder, so once they stop swimming they start tosink.Many sharks will certainly drown unless they room in constant motion, because theycan only respire by swimming constantly to pressure water v thegills.They propel themselves v the water v their an effective tails. Thepelvic and also pectoral fins are supplied as horizontal stabilizersor rudders. This paired fins space the humble evolutionary beginning of thepaired limbs of higher vertebrates.

Class Osteichthyes - bony fishes; 18,000 sp. (fr. Gr. Ostion= bone, ichthys = fish)

Bony fishes own a true bony skeleton, well developedbonyjaws, a swim bladder v which they can regulate theirbuoyancy,and protective scale (note: fish scales space not homologouswiththe scales of reptiles).

Superclass Tetrapoda

Class Amphibia - frogs, toads, salamanders; 4,200 sp. (fr.Gr.amphi = both, bios = life)

Amphibians were the an initial animals to arise onto land, and also gave riseto all higher vertebrates. This class dates back about 300 mya, andprobablyevolved native the lobe-finned fishes prefer the coelacanth. Theirreinforcedskeletons allow them to usage their pelvic and also pectoral bones as limbstowalk about on land. In a an extremely real sense, lock never completely leftthewater. The name amphibian mean amphi=both, bios=life. Amphibiansliterallythey live ~ above both sides of life (land and water).

Amphibians depend on external fertilization in the water. Your eggsarelaid straight in the water, to keep them from dry up, and the larvaedevelop in the water, returning to land together adults. Their lungs, whichevolvedfrom the swim bladders of the bony fishes, space relativelyweak;they supplement their lungs by breathing through their skin. Theamphibians"skin must be preserved moist, so terrestrial amphibians are restricted tomoisthabitats. It additionally makes them an extremely vulnerable to mountain rain, ultravioletradiation and other elements of industrial air pollution. Amphibians arevanishing everywhere the people at a dreadful rate.

Class Reptilia - snakes, lizards, turtles, crocodilians,dinosaurs;6,000 sp. (fr. L. Repere = come creep)

Class Reptilia might be an man-made grouping, and also different groupsofreptiles may have actually independently developed from different ancestralspecies.Reptiles are the very first fully terrestrial animals, evolving about 280mya.Unlike amphibians, your limbs host their bodies off the ground, makingfor more efficient motion on land. This reliable movement is alsoaidedby much better lungs. Rather than sucking air in through their mouths, asamphibiansdo, reptiles expand and also contract the ribs to draw large amounts of airinto the lungs, as perform birds and mammals. They are covered through scalesderivedfrom the epidermis (fish scales build from the dermis). Scale helpkeepreptiles from dry out, and also are for this reason an adaptation come terrestriallife.Unlike amphibians, reptiles rely on interior fertilization, anotheradaptationto life top top land. Reptiles possess yet an additional marvelous terrestrialadaptation,the amniotic egg. The amnion is a safety membranewhichforms approximately the egg complying with fertilization. Because the developingyoungare sealed right into a covering filled v nutritive fluids, the young candevelopentirely on land. This evolutionary creation is analogous to theseedsof greater plants.

Class Aves - birds; 9,000 sp.

Birds have forearms modified because that flight. Your bones arelightweight,and fused with each other to guard against the stresses and strains that poweredflight. The limbs are covered with feathers, frameworks evolvedfrom scales. Feathers carry out insulation and help in flight. Birds, likemammals, are warm-blooded or endothermic. Birds advanced fromtheropoddinosaurs in the mid to late Jurassic.

See more: Where Did The Saying Pork Chops And Applesauce Come From, Pork Chops And Applesauce

Class Mammalia - lions and also tigers and also bears (andbiologists);4,500 sp. (fr. L. Mamma = breast)

Mammals evolved about 200 mya, and underwent a major radiationduringthe Cretaceous, accurate in the shadows the the dinosaurs. Once thedinosaursvanished, mammals were poised to take their place. Mammals nourishtheiryoung with milk from unique mammary glands. Back allmammalshave nipples, not all mammals have navels. Placentalmammalsnourish the fetus with in the mother"s human body by means of a placentaattachedto the fetus through a lengthy cord (navels). However many mammals room marsupials,nourishing their young in an exterior pouch. A few, choose theduck-billedplatypus and also the echidna, room monotremes, mammals that lay eggslike your reptilian ancestors. Prefer birds, mammals areendothermic.Their body are covered with hair, i m sorry is a uniqueevolutionaryinvention, not regarded scales or feathers. Keratin, the sameprotein the helps form mammalian hair, additionally forms fingernails, claws,horns, and hooves, in various species of mammals.

Terms indigenous lecture cartilage paired fin pelvic fin pectoral fin lateral heat shagreen swim bladder bony skeleton scale amniotic egg amnion feather endotherm milk nipple navel placental mammal marsupial monotreme hair keratinEconomic, Ecological, and Evolutionary Importance

Use her imagination! There are literally dozens of means in whichthevarious groups of chordates are economically important...Think the alltheuses of fur and also hair and also hides (leather). Think about all the chordatesthat it is provided food for humans (hamburgers, eggs, fish etc...). What otherindustries do chordates support or supply?

Why is the evolution of the amniotic egg such an essential step? Howis it analogous to the advancement of the seed in greater plants?

How does the development of segmentation differ in annelids andchordates?Is the ultimate adaptive duty of segmentation the very same for theancestorsof both groups?

Consider This

Why room fish bones therefore lightweight and tiny? Why space the skeleton ofmammalsso relatively heavy? Why room bird skeletons the lightest of all?

Why do we take into consideration the swim bladder and lateral fins of primitivefishesto it is in preadaptations? What evolutionary developments do lock anticipate?

Links come Explore


As always, a great place to start is: an easy info and a prodigious list of echinoderm links, shot theCaliforniaAcademy of sciences echinoderm page: urchins come right into their own at: complying with sites are simply a tiny sample that a very bigquadrant ofcyberspace:

Life is for the bird at:

Herps space us at:

And don"t forget the dinosaurs: