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Material Type: Notes; Professor: Moodie; Class: General Biology II; Subject: Biology; University: Central Oregon Community College; Term: Winter 2009;
Typology: Study notes
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Lab day and time: ____________ Name ________________________
Recognize the characteristics that all vertebrates share Understand the diversification of the vertebrates Learn the four major groups of fishes and their characteristics Be able to describe the major adaptations of fishes Understand the theory for the water-land transition of vertebrates Describe the diversity of amphibians
Vertebrates are a group of animals that share characteristics with other chordates: notochord, dorsal hollow nerve cord, pharyngeal slits and a post-anal muscular tail. All four chordate features are usually not present in the adult stage of the vertebrates, but are found in the embryonic stages. Vertebrates, however, have a major innovation not shown at any stage in other chordates (the Urochordata and Cephalochordata), the brain case or cranium. This structure encloses a brain in cartilage or bone. While the group is named for the vertebral column enclosing the nerve cord, some vertebrates do not show this trait (e.g. hagfish and lampreys). In addition to an endoskeleton of cartilage or bone which provides structural support, vertebrates also have various sensory organs at the head end, a muscular pharynx for pumping water (in fishes), and a closed circulatory system with a pumping organ, the heart , which has two to four chambers. The classes of Vertebrates are: Myxini (hagfishes), Petromyzoniformes (lampreys; these two classes make up the superclass Agnatha), Chondrichthyes (cartilaginous fishes), Osteichthyes (boney fishes), Amphibia (frogs & salamanders), Reptilia (turtles, lizards, snakes & crocodilians), Aves (birds), Mammalia (mammals). We will look at the fishes and amphibians today.
Shape of Life: Bones, Brawn and Brains What adaptations did fish evolve to become dominant in the seas? What feature allowed fish brains to become larger?
Planet of Life: Ancient Oceans What problem would a sea-living fish have if it moved into freshwater? According to scientists, how did some fish solve this problem? What are some hypotheses for why some fish species would prefer freshwater habitats? Explain how fish could have evolved bony skeletons over cartilaginous ones. Under what conditions are gills AND lungs thought to be an advantage to fish like the lung fish?
Class Myxini Observe the preserved specimen on the front table. Unfortunately, we do not have a dissected specimen to study, but you can note the external features of hagfish. Does it have paired appendages? What type of tail? How do you think the tail would be used for locomotion (in what direction would it move (side to side or up and down)? Does it have gill coverings like a trout? Are there any sensory appendages on the head? If yes, describe them. Does it have a hinged jaw?
Osteichthyes The Osteichthyes are represented by the bony fishes such as trout, sturgeon, bass, etc. The bony fishes are quite diverse in form. Compare external and skeletal features of the two types of jawed fishes. How are the position of the jaws different between Chondrichthyes and Osteichthyes? Have the positioning of the girdles (skeletal structures holding the paired fins in place) changed from Chondrichthyes to Osteichthyes? How so? What other differences can you detect between the Chondrichthyes and Osteichthyes? Sketch representatives of the two classes and point out features that they share and features that appear different (more room on next page). Amphibia
This class includes the frogs, toads, salamanders & caecilians (legless salamanders). Amphibians show characteristics for living in aquatic and terrestrial environments. While frogs and toads have become quite specialized in their structure, salamanders show the generalized body of vertebrates making the transition from water to land. Frog Dissection