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Chordates and Vertebrates Lab Essay

Procedures/Methods: For each organism, find and draw a representative image. Each organism may include prepared slides as well as specimens, or students may need to find them on the internet. Provide descriptive notes for each organism and address any questions asked in detail using complete sentences. List all references.

Results:

1. Urochordata –Tunicates
a. Molgula – preserved

i. What is the function of the two knobs/protrusions?

The function of the two knobs/ protrusions are the incurrent and excurrent siphons. These creatures are suspension feeders so the siphons are where water and nutrients are exchanged, and wastes and gametes leave.

2. Cephalochordata
a. (Amphiox) Lancelets – note the pharynx with gill slits, the nerve cord and the notochord

3. Vertebrata

a. Lampreys – most primitive

i. How do adult lampreys feed?

Lampreys lack the typical jaws of other fishes, in both their larval and adult forms. After metamorphosis though, the oral hood present in larval lampreys is replaced by the adult’s concave, circular, sucker-disk mouth, with horny teeth. The feeding behavior is characterized by rhythmic rasping, negative pressure pulses in the sucker, and swallowing of fluid into the gut. Once the lamprey is attached to a host fish, the parasite extracts blood and/or muscle tissue. They prey on fishes in the ocean or lake system with their toothed oral suction like disc and breaking the skin and using a tongue that is covered with keratinized teeth to suction off blood and bits of tissue. They stay attached to their host usually until the resources are no longer available and are known to kill their hosts, but they can detach whenever they so choose.

b. Chondricthyes
i. Rays

ii. Dogfish shark

c. Ray-finned fishes – note bony support structures on fins

i. Perch –

1. Note the swim bladder. What is its purpose?

The swim bladder, also called the air bladder, is a buoyancy organ possessed by the perch as well as most bony fish. The swim bladder is located in the body cavity and is derived from an out-pocketing of the digestive tube. It contains gas (usually oxygen) and functions as a hydrostatic, or ballast, organ, enabling the fish to maintain its depth without floating upward or sinking. It also serves as a resonating chamber to produce or receive sound. In some species the swim bladder contains oil instead of gas. In certain primitive fish it functions as a lung or respiratory aid instead of a hydrostatic organ.

ii. Catfish

iii. Eels

Tetrapods (Within Vertebrata)
1. Amphibia
a. Toads

b. Frogs

2. Reptilia
a. Lizards

b. Snakes

c. What is a distinguishing characteristic between reptiles and amphibians?

Although both species are cold blooded, they are very different in appearance and physical makeup. Reptiles are covered in distinctive scales, and some may even have a rough texture. Amphibians, on the other hand, typically have smooth moist skin. Reptiles also have more diverse body types than amphibians. They may or may not have limbs, and can range in size from very small to substantially larger and heavier than humans. Most adult amphibians have four limbs, and while their size varies, very few grow larger than a man’s arm. The role of water is also an important distinguishing characteristic.

Though many reptiles live in the vicinity of water, this is not essential for them to stay alive and some lizards and snakes are ideally suited to dry areas. By contrast, many amphibians must remain moist in order to breathe, although they do have lungs, they also take in oxygen through their skin. This thin skin means that they lost moisture easily as well, and some will even die if their skin dries completely. Life cycles are different in that when reptile eggs hatch, the young look like miniature adults. An amphibian initially emerges from an egg in the form of an aquatic larva, like a tadpole that breathes through gills until they mature and develop lungs so they may survive without being completely submerged.

3. Aves
a. Roadrunner

b. Barn Owl

4. Mammalia
a. Cottontail rabbit

b. Opossum

c. Which of these organisms is a marsupial?
The opossum also just spelled possum is the marsupial of these two organisms.

d. What is a marsupial?

A marsupial is a mammal of an order whose members are born incompletely developed. At birth, they take a long, arduous journey from the birth canal, driven purely by instinct, grabbing hold of the mother marsupial’s fur which she has cleaned and made easier to traverse with saliva, to reach the pouch. Upon reaching the pouch, they latch onto a teat which swells in their mouth to prevent them from being accidentally dislodged during the mother’s movements. They remain attached for months to continue and complete their development.

Discussion:

Students learned all of the following in the chordates and vertebrates lab. Chordates have four key characteristics. They have notochords, a dorsal, hollow nerve cord, pharyngeal slits or clefts, and a muscular, post anal tail. Two major groupings are Urochordata and Cephalochordata. The urochordata to be observed are the tunicates. Tunicates retain pharyngeal slits, have incurrent and excurrent siphon, and they are suspension feeders. Lancelets are the cephalochordate that will be observed in the lab. The next grouping are the craniates. The craniates have chordate characteristics plus a distinct head. Myxini are craniates, an example of which being the hagfish, but there are no specimen to be observed in the lab. The next major grouping are the vertebrates. These are craniates plus a backbone. The backbone includes vertebrae, they have a more extensive skull, and more elaborate skeletal support.

The Lampreys are basal vertebrates that are jawless with a cartilaginous skeleton, and they retain their notochord. The Gnathostomes are vertebrate characteristics plus a true hinged jaw. Chondrichthyes, sharks and rays have cartilaginous skeletons, are gnathostomes. Another gnathostome is actinopterygii, which are ray-finned fishes. They have bony fin support, and ossified skeleton. The perch is an example of the actinopterygii, which has a swim bladder for buoyancy control which is for air instead of urine. They have a lateral line for vibration sensation, which will be viewed in lab. Catfish and eels will also be observed.

The next group are Tetrapods, which have all the characteristics of gnathostome plus limbs. They have five key characteristics. Four limbs and feet with digits, neck for head movement, pelvic girdle that is fused to back bone, no gills, and ears for sound detection. Amphibia are early life aquatic adult life. Examples of these are toads, frogs, salamanders, and caecilians (a legless lizard which even though he doesn’t have legs, he has all the other characteristics). The next group is the amniote, which has tetrapod characteristics plus terrestrially adapted egg. The amniotic egg membranes incled the amnion, chorion, yolk sac, and allantois. Examples are reptilian and aves (birds). The reptilian include tuataras, turtles, crocodilians, birds, snakes, lizards. The scales are waterproof and the lab has specimens of snakes and lizards.

The aves have three characteristics, adaptation for flight (most), keratin-containing feathers, and they lack urinary bladder, and no teeth. There are roadrunner (just the foot) and barn owl (just the wing) specimens to observe in the lab. The last big group are the mammals. They have the same characteristics as the amniotes plus hair and milk production. There are five key characteristics. Mammals have mammary glands, hair, high metabolic rate (endothermic), larger brains, and differentiated teeth (specialized for specific purposes). Under phylum mammalia, there are monotremes (platypus and echnida (only mammals that lay eggs), marsupials (pouched mammals-kangaroo, koala, possum), and eutherians (placental mammals).

Conclusion:

Students successfully completed this lab and learned the differences and characteristics for each organism. When viewing the Urochordata (Tunicates), the lab showed molgula. Students learned that the function of the two knobs/protrusions are the incurrent and excurrent siphons. Organisms with these incurrent and excurrent siphons are suspension feeders, so the siphons are where water and nutrients are exchanged and wastes and gametes leave. Then the Cephalochordata were viewed in the form of Lancelets, where students saw the pharynx with gill slits, the nerve chord and the notochord. Next, students observed the vertebrata. The lampreys were the most primitive, and from them it was learned that they lack the typical jaws of other fishes both in their larval and adult forms. The Lamprey’s feeding behavior is characterized by rhythmic rasping, negative pressure pulses in the sucker, and swallowing of fluid into the gut.

Then the students viewed the chondricthyes in the forms of rays and dogfish. Next the ray-finned fishes were observed, including the perch, catfish, and the eels. The students saw the bony support structures on the fins and also learned about the purpose of the swim bladder. The swim bladder, also called the air bladder, is a buoyancy organ possessed by the perch as well as most bony fish. The swim bladder is located in the body cavity and is derived from an out-pocketing of the digestive tube. It contains gas (usually oxygen) and functions as a hydrostatic, or ballast, organ, enabling the fish to maintain its depth without floating upward or sinking. It also serves as a resonating chamber to produce or receive sound. After the ray-finned fishes, the tetrapods were observed. The amphibians, reptilians, aves, and mammals were all observed. Students viewed toads, frogs, lizards and snakes for amphibians and reptialians respectively.

Students also learned the differences between the amphibians and reptiles. Reptiles are covered in distinctive scales, and some may even have a rough texture. Amphibians, on the other hand, typically have smooth moist skin. Reptiles also have more diverse body types than amphibians. They may or may not have limbs, and can range in size from very small to substantially larger and heavier than humans. Most adult amphibians have four limbs, and while their size varies, very few grow larger than a man’s arm. The role of water is also an important distinguishing characteristic. Though many reptiles live in the vicinity of water, this is not essential for them to stay alive and some lizards and snakes are ideally suited to dry areas. By contrast, many amphibians must remain moist in order to breathe, although they do have lungs, they also take in oxygen through their skin.

This thin skin means that they lost moisture easily as well, and some will even die if their skin dries completely. Life cycles are different in that when reptile eggs hatch, the young look like miniature adults. An amphibian initially emerges from an egg in the form of an aquatic larva, like a tadpole that breathes through gills until they mature and develop lungs so they may survive without being completely submerged. Roadrunners and barn owls were observed for aves.

For mammals, cottontail rabbits and opossums were observed. Students also learned what marsupials are. A marsupial is a mammal of an order whose members are born incompletely developed. At birth, they take a long, arduous journey from the birth canal, driven purely by instinct, grabbing hold of the mother marsupial’s fur which she has cleaned and made easier to traverse with saliva, to reach the pouch. Upon reaching the pouch, they latch onto a teat which swells in their mouth to prevent them from being accidentally dislodged during the mother’s movements. They remain attached for months to continue and complete their development. The lab successful familiarized students with all the different types of vertebrates/chordates.

References:
List all references used in APA format.

Carol, R. L. “The Origin of Reptiles.” In Origins of the Higher Groups of Tetrapods” Controversy and Consensus, edited by H. P. Schultze and L. Trueb. Ithaca, NY: Comstock, 1991. “Morphology of the Vertebrates”. University of
California Museum of Paleontology. Retrieved 2008-09-23 Nelson, J. S. (2006). Fishes of the World (4th ed.). New York: John Wiley and Sons, Inc. pp. 601 pp. ISBN 0-471-25031-7. Personal Communication. Dr. Bledsoe. November 5, 2014.

Rychel, A.L., Smith, S.E., Shimamoto, H.T., and Swalla, B.J. (2006). “Evolution and Development of the Chordates: Collagen and Pharyngeal Cartilage”. Molecular Biology and Evolution 23 (3): 541–549. Shu, D-G., Conway Morris, S., and Han, J (January 2003). “Head and backbone of the Early Cambrian vertebrate Haikouichthys”. Nature 421 (6922): 526–529. swim bladder. (2014). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/577044/swim-bladder tunicate. (2014). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/609172/tunicate/49484/External-features


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