Introduction to the Chordates Lab

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					                                     Introduction to the Chordates Lab

I.   The objectives of this lab is
     A. To be able to give the four major characteristics of all Chordates.
     B. To introduce the three subphyla of the phylum Chordata and the classes of the subphylum Vertebrata
     C. To be able to distinguish the three subphyla and know major characteristics of each.
     D. To be able to distinguish the classes of the subphylum Vertebrata with major features of each.

II. Methods
    A. Show and tell survey of the different examples of the Chordates. Students will have opportunity to
       examine on limited basis different representative organisms. Less than 5 percent of animals are
       chordates. There are three subphyla of chordates.
       1. Subphylum Urochordata - sea squirts or tunicates. What approximate chordate characters do the
           larval chordates display? What chordate characters do the adults display? Why are they
           considered the ancestral organism for the phylum?

         2. Subphylum Cephalochordata - the lancets (Amphioxus) - Which characteristics of Chordates do
            these adults display? These organisms were once considered the ancestral stock. Why has this

         3. Subphylum Vertebrata - The animals with “backbones” although sometimes it is made of
            a. Superclass Agnatha. What does the word Agnatha mean?
            Class Myxina- hagfish
            Class Cephalaspidmorphi – the parasitic lampreys

                 Lampreys are referred to as the Cyclostomes. What does this word mean?
                 Why is the term cyclostome appropriate for this organism?
                 Why are they economically important?
                 Examine an example of the marine lamprey Petromyzon murinus making sure you can
                 distinguish the head, nostril, buccal papillae, horny teeth, eye, gill slits, Anterior dorsal fin,
                 Posterior dorsal fin, caudal fin, notochord, and dorsal nerve cord.

             b. Class Chondrichthyes - the cartilaginous fishes. What kind of skeleton do these organisms
                have? Study the external anatomy of the dog fish shark.
                Some other words to remember about the Chondrichthyes include: Take note of the
                significance of each of these terms.
                Ovoviviparous - sharks have internal fertilization. What is significant about this?

                 placoid scale
                 heterocercal tail

                Do an examination of the external anatomy of the Dogfish shark Squalus acanthias
                Be sure you can identify the following: Anterior and posterior dorsal fins, caudal fin, pelvic
                fin, pectoral fin, gill slits, lateral line.
             c. Class Osteichthyes - the bony fish. The Campbell text does not use this as a class but refers
                to it as a clade. I tried to find out if it has been elevated to super class or what. In the past,
     Actinopterygii (ray-finned fishes) and Sarcopterygii (lobe-finned fishes) have been given the
     classification of subclasses but your text has elevated them to classes. For this class, let us
     simplify this and place the boney fish in the class Osteichthyes. Their skeleton is comprised
     of bone. This points out that classification is man made and always subject to change.

     Examine the external anatomy of a perch making sure you can identify the following
     structures: Dorsal fins, caudal fin, anal fin, pelvic fin, pectoral fin (not shown on figure but
     in same location as on dogfish shark, Operculum (not shown but the hard plate covering the
     gills), gills, and lateral line.

     What is the significance of each of the following for the Osteichthyes
     Swim bladder
     Gill cover (operculum)
     What was Latimeria? Check it out in your notes and book.

d. Class Amphibia – salamanders, toads, and frogs We will begin to study the frog next week
   in lab. Transition from water to land.
   What are some features that Amphibians have that are important in the transition from water
   to land?

What does the word Amphibia mean? Is this appropriate for these organisms and if so, why

What keeps the Amphibia tied to the water?

e. Class Reptilia - snakes, lizards, turtles Made transition to land although some do well in
   water. What characteristics do they possess that enables them to live on land?

Why is internal fertilization important?
What is the importance of the amniotic egg?
Why are strong skeletons important?

f.   Class Aves - now this class really is for the birds. What is the distinguishing feature?

What does the term homeothermic or endothermic mean?

Are these terms appropriate for birds?

What term regarding (temperature regulation) would be appropriate to describe the Reptiles or

Examine a contour feather. Make a simple sketch of it.

Examine differences among beaks of different birds? Of what importance is this?
           Do you see any other feature that differs among the birds that are displayed? Why would these
              be important?

           g. Class Mammalia - the mammals. . What are unique characteristics of mammals?

           What are some characteristics that mammals and Aves share in common?

           What are the Monotremes?     Give some examples.

           What are Marsupials? Give some examples.

           What are Placental mammals? Give some examples.

           How do these three terms relate to the above groups of mammals?
              1) Oviparous - egg layers. Monotremes are egg layers. Until they hatch, young are
                  nourished by yolk sac.
              2) Viviparous – give live birth in placenta, young nourished by umbilical cord. Marsupials
                  give very premature birth young crawl to mammary gland and remain attached in pouch
                  for much longer period of time. In true placental organisms there is a much longer
                  gestation period and the organism is more fully developed when born.

               3) ovoviviparous – this term does not apply to mammals but does apply to dogfish sharks
               where young are retained within mothers body but are nourished by yolk sac.

Adult tunicate Ciona intestinalis
Lancet Amphioxus Latimera - “Living fossil” Lamprey feeding on
fish Lamprey mouth -

 Gill slits
                 Lateral line

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