dissection of frog, perch, worm lab.pdf

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Ms. KiriakopoulosSNC2Dtools, and dissection pan. Rinse your specimen with water and pat dry.2. Using the hand lens, examine the external structure of the earthworm so that you can identifythe prostomium, clitellum, setae, and anus. The prostomium is in front of the mouth. The clitellumlooks like a saddle and is on the dorsal side of the earthworm. The setae are tiny bristles found onthe ventral side. The anus is found on the ventral side of the last segment of the worm.3. Hold the earthworm in your hand so that the dorsal side is facing up. Using your scissors, make ashallow cut on the dorsal side from the clitellum to the prostomium.4. Separate the tissue and use dissecting pins to pin the body wall down to the tray. You may need tocut through the tissue that holds the body wall.5. Locate the mouth, esophagus, crop, gizzard, intestine, and anus using Figure 2.30.6. Clean up your work area. Make sure to follow your teacher’s directions for safe disposal ofmaterials. Wash your hands thoroughly.Part 2 — Digestive System of the Perch7. Complete a diagram of the perch digestive system based on Figure 2.31. When you are finishedwith your diagram, complete a virtual dissection of a perch or obtain a preserved specimen of aperch, dissection tools, and dissection pan. Rinse your specimen with water and pat dry.8. Observe the external structure of the perch. Note the position and number of fins. Find thelateral line, and locate the gill cover and anal opening.9. Examine the mouth of the perch.10.Create a flap through the muscle wall.Make an incision from the bottom of the gillcover along the ventral side to the analopening. Continue the incision up from theanal opening to the lateral line and thenalong that line to the head of the fish. Finishyour flap by extending your incision back tothe base of the gill cover.Figure 2.31 The external and internal anatomy of the perch
Ms. KiriakopoulosSNC2D11.Lift the flap of muscle wall to look at the organs of the perch. If you have a female perch, the areamay be filled with eggs. If this is the case, you should remove the mass of eggs before proceeding.If the perch is male, the testes will be smaller and lighter in colour. Locate the liver (light brown),gall bladder (olive colour), esophagus, stomach, pyloric caeca, and intestines.12.Clean up your work area. Make sure to follow your teacher’s directions for safe disposal of materials.Wash your hands thoroughly.Part 3 — Digestive System of the FrogMale or Female?1. Place a frog on a dissection tray. To determine thefrog’s sex, look at the hand digits, or fingers, on itsforelegs. A male frog usually has thick pads on its"thumbs," which is one external difference betweenthe sexes, as shown in the diagram below. Male frogsare also usually smaller than female frogs. Observeseveral frogs to see the difference between malesand females.What is the sex of your frog? _________Anatomy of the Frog’s MouthProcedure: Pry the frog’s mouth open and use scissors tocut the angles of the frog’s jaws open. Cut deeply enoughso that the frog’s mouth opens wide enough to view thestructures inside.1. Locate the tongue.2. In the center of the mouth, toward the back is a singleround opening. This is the esophagus. This tube leads tothe stomach. Use a probe to poke into the esophagus.3. Close to the angles of the jaw are two openings, one oneach side. These are the Eustachian tubes. They are used to equalize pressure in the inner ear whilethe frog is swimming. Find the Eustachian tubes.4. Just behind the tongue, and before you reach the esophagus is a slit like opening. (You may need touse your probe to get it to open up). This slit is the glottis, and it is the opening to the lungs. The frogbreathes and vocalizes with the glottis. Find the glottis.5. The frog has two sets of teeth. The vomarine teeth are found on the roof of the mouth. Themaxillary teeth are found around the edge of the mouth. Both are used for holding prey, frogs swallowtheir meals whole and do NOT chew. Locate both sets of teeth.6. On the roof of the mouth, you will find two tiny openings, if you put your probe into those openings,you will find they exit on the outside of the frog. These are the nostrils.
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