ccabiology.weebly.comccabiology.weebly.com/uploads/1/0/0/1/10018860/dissec…  · Web viewce area. Why is this ... Dissecting pan, dissecting kit, screwdriver, lab apron, plastic

Starfish DissectionIntroduction:Echinoderms are radially symmetrical animals that are only found in the sea (there are none on land or in fresh water). Echinoderms mean "spiny skin" in Greek. Many, but not all, echinoderms have spiny skin. There are over 6,000 species. Echinoderms usually have five appendages (arms or rays), but there are some exceptions.Radial symmetry means that the body is a hub, like a bicycle wheel, and tentacles are spokes coming out of it (think of a starfish). As larvae, echinoderms are bilaterally symmetrical. As they mature, they become radially symmetrical. Most adult echinoderms live on the bottom of the ocean floor. Many echinoderms have suckers on the ends of their feet that are used to capture and hold prey, and to hold onto rocks in a swift current.Sea StarsSea stars (group name Stelleroidea) are sometimes called starfish, though they are not real fish (they lack both vertebrae and fins). There are two sub-types of sea stars:

Asteroideas are the true sea stars and sun stars. Ophiuroideas are brittle stars and basket stars.

The differences between the two sub-types lies in how the arms connect to the central disk. Ophiuroids have arms that do not connect with each other. There is a distinct boundary between arm and central disk. Asteroids have arms that are connected to each other. Also, it is harder to tell with asteroids where the central disk ends and the arms begin. The sea star's top surface (or skin) looks spiny if you examine it. If you look very closely you will notice that there are different types of growths on the surface. Some bumps are used to absorb oxygen, they are called dermal branchiae.  Pedicellaria are pincher-like organs used to clean the surface of the skin. Barnacle larvae could land on a sea star and start growing if it were not for these organs.How Do Sea Stars Move?Each sea star had hundreds of tiny feet on the bottom of each ray. These are tube feet, or podia. These tiny feet can be filled with sea water. The vascular system of the sea star is also filled with sea water. By moving water from the vascular system into the tiny feet, the sea star can make a foot move by expanding it. This is how sea stars move around. Muscles within the feet are used to retract them. Each ray of a sea star has a light sensitive organ called an eyespot. Though it can not see nearly as well as we do, sea stars can detect light and its general direction. They have some idea of where they are going.

 Materials:Preserved starfish, dissecting pan, scissors, scalpel, forceps, T-pins, pencil, lab apron, safety glassesFigure 1 -Aboral Surface Procedure (Aboral Surface):1. Obtain a preserved starfish and rinse off any preservative with water.

2. Place the starfish in the dissecting pan with its dorsal or aboral (top) surface upward.3. Observe the starfish and determine  its symmetry.4. Locate the central disc in the center of the starfish. Count and record the number of arms or rays the starfish has.5. Locate the small, round hard plate called the madreporite on top of the central disc. Water enters through this into the water vascular system. Label the central disc, arms, and madreporite on Figure 1.6. Feel the upper surface of the starfish for spines. These spines protect the starfish and are part of their internal skeleton. Label these on figure 1.7. Look at the tip of each arm and find the eyespot. Label this on Figure 1.

Procedure (Oral Surface):Figure 2 - Oral Surface

8. Turn the starfish over to its ventral or oral surface (underside).9. Locate the mouth in the center of the central disc. Find the ring of oral spines surrounding the mouth. Label these  on figure 2.10. Find the groove that extends down the underside of each arm. This is called the ambulacral groove. Label this on figure 2.11. Feel the numerous, soft tube feet inside each groove. these are part of the water vascular system & aid in movement and feeding. Label these on Figure 2.

Procedure (Internal anatomy): Figure 3 - Cuts in Arm12. With the starfish's aboral surface facing you, cut off the tip of a ray. Cut along lines a, b, and c (Figure 3) and then remove this flap of skin.13. Inside each arm, locate two long digestive glands called the pyloric caeca. These make enzymes to digest food in the stomach. Label these in Figure 4.14. Cut a circular flap of skin from the central disc. (You will have to also cut around the madreporite in order to remove this flap.) Observe the stomach under the central disc. Label this on Figure 4.15. Remove the pyloric caeca from the dissected ray. Find the gonads (testes or ovaries) underneath. These may be small if the starfish is NOT in breeding season. Label these on figure 4. Remove these to see the rest of the water vascular system.Figure 4 - Starfish Digestive & Reproductive Systems

16. Cut off the tip of a ray to observe the parts of the tube feet. Find the zipper-like ridge that extends the length of the ray. The tube feet are attached to these.17. Locate the bulb-like top of a tube foot called the ampulla. This sac works like the top of an eyedropper to create suction. The bottom of the tube foot is a sucker. Label these in Figure 4.18. Embedded in the soft body wall are skeletal plates called ossicles. Locate these and label them in Figure 4.19. Running down the center of each arm is a lateral canal to which tube feet are attached. Label this in Figure 5.In the central disc the five lateral canals connect to a circular canal called the ring canal. Find this canal & label it on figure 5.

A short, canal called the stone canal leads from the ring canal to the madreporite where water enters. Find this canal & label the stone canal & madreporite on Figure 5.Draw an arrow on Figure 5 tracing the path that water takes when it enters & moves through the starfish.

Figure 5 - Water Vascular System

Questions:1. What type of symmetry did your starfish have?2. What is the upper surface of the starfish called?3. What is the lower surface of the starfish called?4. On which surface are these parts of a starfish visible:    a. Mouth -    b. Madreporite -    c. Suckers -    d. Oral spines -    e.  Eyespots -    d. Ambulcaral groove - 5. What type of skeleton, endoskeleton or exoskeleton, does the starfish have?6. What is the function of the pyloric caeca?7. Where is the stomach of a starfish located? What can the starfish do with its stomach when feeding on clams & oysters?

8. Name the kingdom, phylum, and class for the starfish you dissected. 

Crayfish Dissection

Objectives:• Describe the appearance of various organs found in a crayfish.• Name the organs that make up systems of the crayfish.Materials: • safety goggles, gloves, magnifying glass, a lab apron, plastic ziplock bag preserved crayfish,  pen, dissecting tray, paper towels, scissors, forceps, dissecting needle, and dissecting pins.Purpose: In this lab, you will observe the external structures of a crayfish and dissect it to study its internal structures and systems.

Background:Like all crustaceans, a crayfish has a fairly hard exoskeleton that covers its body. As shown in the diagram on the next page, its body is divided into two main parts, the cephalothorax and the abdomen. The cephalothorax consists of the cephalic (or head) region and the thoracic region. The part of the exoskeleton that covers the cephalothorax is called the carapace. The abdomen is located behind the cephalothorax and consists of six clearly divided segments. The cephalothorax consists of 13 segments. Each segment of both the cephalothorax and the abdomen contains a pair of appendages. The head (or cephalic) region has five pairs of appendages. The antennules are organs of balance, touch, and taste. Long antennae are organs for touch, taste, and smell. The mandibles, or jaws, crush food by moving from side to side. Two pairs of maxillae hold solid food, tear it, and pass it to the mouth. The second pair of maxillae also helps to draw water over the gills. Of the eight pairs of appendages on the cephalothorax, the first three are maxillipeds, which hold food during eating. The chelipeds are the large claws that the crayfish uses for defense and to capture prey. Each of the four remaining segments contains a pair of walking legs. In the abdomen, the first five segments each have a pair of swimmerets, which create water currents and function in reproduction. The sixth segment contains a modified pair of uropods. In the middle of the uropods is a structure called thetelson, which bears the anus. The uropod and telson together make up the tail fan. The crayfish moves backward by forcing water forward with its  tail fan.

Procedure Part 1—External Anatomy of a Crayfish1. Put on safety goggles, gloves, and a lab apron.2. Place a crayfish on its dorsal side in a dissection tray. Use the diagram below to locate the cephalothorax and the abdomen. The carapace, a shield of chitin, covers the dorsal surface of the cephalothorax. On the carapace, observe an indentation, the cervical groove, that extends across the midregion and separates the head and thoracic regions. On the thoracic region, locate the prominent suture or indentation on the cephalothorax that defines a central area separate from the sides. Note the individual segments of the abdomen.

What is the main difference between the cephalothorax and abdomen?___________________________________________________________3. Turn the crayfish on its side, and locate the rostrum, which is the pointed extension of the carapace at the head of the animal shown in the diagram above. Beneath the rostrum locate the two eyes. Notice that each eye is at the end of a stalk.

4. Locate the five pairs of appendages on the head region. First locate the antennules in the most anterior segment. Behind them observe the much longer pair of antennae.Why is it useful to turn the specimen on its side for this part of your study?

______________________________________________________________5. Locate the mouth. Then observe the mandibles, or true jaws, behind the antennae. Now locate the two pairs of maxillae, which are the last appendages in the cephalic region. Which appendages in the cephalic region are related to the eating of food? ___________________________6. On the thoracic portion of the cephalothorax, observe the three pointed maxillipeds.How are the maxillipeds related to eating?________________________________________________

7. Next observe the largest prominent pair of appendages, the chelipeds, or claws. Behind the chelipeds locate the four pairs of walking legs, one pair on each segment.8. Now use the walking legs to determine the sex of your specimen. Locate the base  segment of each pair of walking legs. The base segment is where the leg attaches to the body. Use a magnifying glass to study the inside surface of the base segment of the third pair of walking legs. If you observe a crescent-shaped slit, you have located a genital pore of a female. In a male, the sperm duct openings are on the base segment of the fourth pair of walking legs. Use a magnifying glass to observe the opening of a  genital pore.Is your specimen a male or a female? _________________________________Exchange your specimen with a nearby classmate who has a crayfish of the opposite sex. Then study its genital pores.

9. On the abdomen, observe the six distinct segments. On each of the first five segments, observe a pair of swimmerets.10. On the last abdominal segment, observe a pair of pointed appendages modified into a pair of uropods. In the middle of the uropods, locate the triangular-shaped telson.11. Now turn the crayfish ventral side up. Observe the location of each pair of appendages from the ventral side.From which view, dorsal or ventral, can you see the location of the appendages on the segments more clearly?_________________________________12. Remove all jointed appendages of the crayfish so that you can dissect easily.13. Next you will study the internal anatomy of a crayfishPart 2—Internal Anatomy of a Crayfish

14. Using one hand to hold the crayfish dorsal side up in the dissecting tray, use scissors to carefully cut through the back of the carapace along dissection cut line 1,  as shown in the diagram below. Cut along the indentations that separate the thoracic portion of the carapace into three regions. Start the cut at the posterior edges of the carapace, and extend it along both sides in the cephalic region.15. Use forceps to carefully lift away the carapace. Be

careful not to pull the carapace away too quickly. Such action would disturb or tear the underlying structures. 16. Place the specimen on its side, with the head facing left, as shown in the diagram below. Using scissors, start cutting at the base of cut line 1. Cut along the side of the crayfish, as illustrated by cut line 2. Extend the cut line forward toward the rostrum (at the top of the head).19. Use forceps to carefully lift away the remaining parts of the carapace, exposing the underlying gills and other organs. 20. Use the diagram to the left to locate and identify the organs of the digestive system. Locate the maxillae that pass the pieces of food into the mouth. The food travels down the short esophagus into the stomach. Locate the digestive gland, which produces digestive substances and from which the absorption of nutrients occurs. Undigested material passes into the intestine. Observe that the intestine is attached to the lobed stomach. The undigested material is eliminated from the anus. Rows of chitinous teeth line

the stomach. Predict their function.________________________________21. Use the diagram to the side to locate and identify the organs of the respiratory system. Locate the gills, which are featherlike structures found underneath the carapace and attached to the chelipeds and walking legs. A constant flow of blood to the gills releases carbon dioxide and picks up oxygen. The feathery nature of the gills gives them a very large surface area. Why is this important?_____________________________________22. Use the diagram of the internal anatomy of the crayfish to locate and identify the organs of the circulatory system. Locate the dorsal tubular heart and several arteries. The crayfish has an open circulatory system in which the blood flows from arteries into sinuses, or spaces, in tissues. The blood flows over the gills before returning to the heart.23. Use the same diagram to locate and identify the organs of the nervous system. Find the ventral nerve cord. Locate a ganglion, one of the enlargements of the ventral nerve cord. Locate the dorsal brain, which is located just behind the compound eyes. Note the two large nerves that lead from the brain, around the esophagus, and join the ventral nerve cord.Many nerves leave from each ganglion. Where do you think these nerves go?_________________________24. Use the same diagram to locate and identify the organs of the excretory system. The blood carries cellular wastes to the disk-like green glands. Locate these organs just in front of the stomach. The green glands excrete waste through pores at the base of each antenna.What organs in your body carry out

the same function as the green glands____________25. If time allows: Use the diagram once again to locate and identify the organs of the reproductive system. The animal shown in the diagram is a male crayfish. If your specimen is a male, locate the testis. The testis is the long, white organ under the heart and a bit forward. The sperm ducts that carry sperm from the testis open at the fifth walking leg. If your specimen is a female, locate the bi-lobed ovary. It is in the same relative position as the testis, but the ovary appears as a large, reddish mass under the heart. Then locate the short oviducts that extend from near the center of each side of the ovary and open at the third walking leg. Exchange your specimen with a nearby classmate who has a crayfish of the opposite sex. Then study its reproductive system.

25. Rinse your specimen with water, dispose in the trash, and rinse your instruments. Leave instruments and tray neatly at your station. Wipe your lab counter if necessary. Wash your hands.

Clam DissectionIntroductionThe phylum Mollusca includes snails, clams, chitons, slugs, limpets, octopi, and squid. As mollusks develop from a fertilized egg to an adult, most pass through a larval stage called the trocophore. The trocophore is a ciliated, free-swimming stage. Mollusks also have a radula or file-like organ for

feeding, a mantle that may secrete a shell, and a muscular foot for locomotion. Clams are marine mollusks with two valves or shells. Like all mollusks, a clam has a mantle which surrounds its soft body. It also has a muscular foot which enables the clam to burrow itself in mud or sand. The soft tissue above the foot is called the visceral mass and contains the clam's body organs.

TaxonomyKingdom - AnimaliaPhylum - MolluscaClass - Bivalvia or Pelecypoda

ObjectiveTo study the internal and external anatomy of a bivalve mollusk.MaterialsDissecting pan, dissecting kit, screwdriver, lab apron, plastic gloves, safety glasses, preserved clamProcedure1. Put on your lab apron, safety glasses, and plastic gloves.2. Place a clam in a dissecting tray and identify the anterior and posterior ends of the clam as well as the dorsal, ventral, & lateral surfaces. Figure 1

3. Locate the umbo, the bump at the anterior end of the valve. This is the oldest part of the clam shell. Find the hinge ligament which hinges the valves together and observe the growth rings.

4. Turn the calm with its dorsal side down and insert your closed scissors between the ventral edges of the valves. Carefully work the tip of the scissors between the valves so you do not jab your hand.5. Turn the scissors so that the valves are about a centimeter apart. Leave the tip between the valves and place the clam in the pan with the left valve up. Locate the adductor muscles. With your blade pointing toward the dorsal edge, slide your scalpel between the upper valve & the top tissue layer.

Cut down through the anterior adductor muscle, cutting as close to the shell as possible.6. Repeat step 6 in cutting the posterior adductor muscle.Bend the left valve back so it lies flat in the tray. Run your fingers along the outside and the inside of the left valve and compare the texture of the two surfaces.

7. Examine the inner dorsal edges of both valves near the umbo and locate the toothlike projections. Close the valves & notice how the toothlike projections interlock.

8. Locate the muscle "scars" on the inner surface of the left valve. The adductor muscles were attached here to hold the clam closed.

9. Identify the mantle, the tissue that lines both valves & covers the soft body of the clam. Find the mantle cavity, the space inside the mantle.

10. Locate two openings on the posterior end of the clam. The more ventral opening is the incurrent siphon that carries water into the clam and the more dorsal opening is the excurrent siphon where wastes & water leave.11. With scissors, carefully cut away the half of the mantle

that lined the left valve. After removing this part  of the mantle, you can see the gills, respiratory structures.12. Observe the muscular foot of the clam, which is ventral to the gills. Note the hatchet shape of the foot used to burrow into mud or sand.13. Locate the palps, flaplike structures that surround & guide food into the clam's mouth. The palps are anterior to the gills & ventral to the anterior adductor muscle. Beneath the palps, find the mouth.14. With scissors, cut off the ventral portion of the foot. Use the scalpel to carefully cut the muscle at the top of the foot into right and left halves. Carefully peel away the muscle layer to view the internal organs.15. Locate the spongy, yellowish reproductive organs.16. Ventral to the umbo, find the digestive gland, a greenish structure that surrounds the stomach.17. Locate the long, coiled intestine extending from the stomach. Follow the intestine through the clam. Find the area near the dorsal surface  that the intestine passes through called the pericardial area. Find the clam's heart in this area.

18. Continue following the intestine toward the posterior end of the clam. Find the anus just behind the posterior adductor muscle. Use your probe to trace the path of food & wastes from the incurrent siphon through the clam to the excurrent siphon.

Earthworm DissectionThe following is a classification of a species in the earthworm family Lumbricidae. This common species is Lumbricus terrestris also known as the night crawler or dew worm.

Phylum -Class -

Family -Genus -

Species -

AnnelidaOligochaetaLumbricidaeLumbricusterrestris

Objectives:• Describe the appearance of various organs found in the earthworm.• Name the organs that make up various systems of the earthworm.

Materials:Safety goggles, dissecting pins, gloves, forceps, lab apron, scissors, paper towel, scalpel, water, dissecting probe, preserved earthworm, hand lens, dissection tray.

Purpose:In this lab, you will dissect an earthworm in order to observe the external and internal structures of earthworm anatomy.

Background: Among the most familiar invertebrate animals are the earthworms, members of the phylum Annelida. The word annelida means "ringed" and refers to a series of rings or segments that make up the bodies of the members of this phylum. Internally, septa, or dividing walls, are located between the segments. External segments are called metameres. There may be more than 100 segments in an adult worm. The clitellum is a swelling of the body found in sexually mature worms and is active in the formation of an egg capsule, or cocoon. Eggs are produced in the ovaries and pass out of the body through female genital pores. Sperm are produced in the testes and pass out through tiny male genital pores. During mating, sperm from one worm travel along the sperm grooves to the seminal receptacles of another worm. Fertilization of the eggs takes place outside the body as the cocoon moves forward over the body, picking up the eggs of one worm and the sperm of its mate. The pumping organs of the circulatory system are five aortic arches. Circulatory fluids travel from the arches through the ventral blood vessel to capillary beds in the body. The fluids then collect in the dorsal blood vessel and reenter the aortic arches. The earthworm takes in a mixture of soil and organic matter through its mouth, which is the beginning of the digestive tract. The mixture enters the pharynx, which is located in segments 1–6. The esophagus, in segments 6–13, acts as a passageway between the pharynx and the crop. The crop stores food temporarily. The mixture that the earthworm ingests is ground up in the gizzard. In the intestine, which extends over two-thirds of the body length, digestion and absorption take place. Soil particles and undigested organic matter pass out of the worm through the rectum and anus. The nervous system consists of the ventral nerve cord, which travels the length of the worm on the ventral side, and a series of ganglia, which are masses of tissue containing many nerve cells. The nerve collar surrounds the pharynx and consists of ganglia above and below the pharynx. Nervous impulses are responsible for movement and responses to stimuli. Each segment contains an enlargement, or ganglion, along the ventral nerve cord. Excretory functions are carried on by nephridia, which are found in pairs in each body segment. They appear as tiny white fibers on the dorsal body wall. The earthworm has no gills or lungs. Gases are exchanged between the circulatory system and the environment through the moist skin.

Procedure:External Anatomy1. Put on safety goggles, gloves, and a lab apron.

2. Place  earthworm in the dissecting tray & rinse off the excess preservative. Identify the dorsal side, which is the worm’s rounded top, and the ventral side, which is its flattened bottom. Turn the worm ventral side up, as shown in the diagram below.

3. Use a hand lens as you observe all parts of the worm, externally and internally. Locate the conspicuous clitellum, a saddle-like swelling on the dorsal surface.  The clitellum produces a mucus sheath used to surround the worms during mating and is responsible for making the cocoon within which fertilized eggs are deposited.  The anterior of the animal is more cylindrical than the flattened posterior and is the closest to the clitellum.  The ventral surface of the earthworm is usually a lighter colour than the dorsal surface.  The mouth is located on the ventral surface of the first segment while the anus is found at the end of the last segment. Find the anterior end by locating the prostomium (lip), which is a fleshy lobe that extends over the mouth. The other end of the worm’s body is the posterior end, where the anus is located.

4. Locate the clitellum, which extends from segment 33 to segment 37. Look for the worm’s setae, which are the minute bristle-like spines located on every segment except the first and last one. Run your fingers over the ventral surface of the earthworm’s body.  You should be able to feel bristle-like setae used for locomotion

5. Refer again to the diagram of the ventral view of the worm to locate and identify the external parts of its reproductive system. Find the pair of sperm grooves that extend from the clitellum to about segment 15, where one pair of male genital pores is located. Look also for one pair of female genital pores on segment 14. There is another pair of male genital pores on about segment 26. Try to find the two pairs of openings of the seminal receptacles on segment 10.   Note: These openings are not easy to see.

Internal AnatomyHint: Position your preserved earthworm dorsal side up and pin it down through the first segment and then again further back behind the clitellum.  Cut a slit in the dorsal surface near the posterior pin.  Using fine scissors extend the cut forward to the first segment.  Be careful not to cut too deep.  Starting at the first segment, cut the septa (thin membranes) that internally divide the segments, so the skin can be laid flat.  Use additional pins to hold the integument open and expose the organs.  Continue to lay the skin back until you have uncovered a centimeter or so of the intestine.6. Turn the worm dorsal side up. Using a scalpel and scissors, make a shallow incision in the dorsal side of the clitellum at segment 33.CAUTION: Scalpels and scissors are very sharp. Report any cuts to your teacher. Using the forceps and scalpel, spread the incision open, little by little. Separate each septum from the central tube using a dissecting needle, and pin down each loosened bit of skin. Continue the incision forward to segment 1.

7. Use the diagram below to locate and identify the five pairs of aortic arches, or hearts. Then find the dorsal blood vessel. Look for smaller blood vessels that branch from the dorsal blood vessel. Digestive SystemThe earthworm is an example of a foraging herbivorous annelid, obtaining food by eating its way through the soil and extracting nutrients from the soil as it passes through the digestive

tract.Hint: Starting at the anterior end, locate the muscular pharynx (food ingestion).  This is followed by a tube-like esophagus which terminates in a crop (the wider organ) which serves as a storage stomach.  Posterior to the crop you will find the gizzard.  Gently press on the crop and gizzard to test their firmness.  While the crop is soft and thin, the gizzard is muscular (soil is ground up and churned within the gizzard).  The gizzard is followed by a long intestine in which both digestion and absorption occur.  Undigested material is voided through the anus.

8. Locate the digestive tract, which lies below the dorsal blood vessel. Refer to the diagram above to locate the pharynx, esophagus, crop, gizzard, and intestine.

9. To find organs of the nervous system, push aside the digestive and circulatory system organs. Use the diagram below to locate the ventral nerve cord. Trace the nerve cord forward to the nerve collar, which circles the pharynx. Find one pair of ganglia under the pharynx and another pair of ganglia above the pharynx. The ganglia above the pharynx serve as the brain of the earthworm.

10. The worm’s excretory organs are tiny nephridia. There are two in every segment. Use the preceding diagram to locate some nephridia.

11. Use the diagrams below to locate and identify a pair of ovaries in segment 13. Look for two pairs of tiny testes in segments 10 and 11. To find these organs, you will again have to push

aside some parts already dissected.

12. Dispose of your materials according to the directions from your teacher.

13. Clean up your work area and wash your hands before leaving the lab.

Frog DissectionPictures:  Modern Biology, Holt

Background:As members of the class Amphibia, frogs may live some of their adult lives on land, but they must return to water to reproduce. Eggs are laid and fertilized in water. On the outside of the frog’s head are two external nares, or nostrils; two tympani, or eardrums; and two eyes, each of which has three lids. The third lid, called the nictitating membrane, is transparent. Inside the mouth are two internal nares, or openings into the nostrils; twovomerine teeth in the middle of the roof of the mouth; and two maxillary teeth at the sides of the mouth. Also inside the mouth behind the tongue is the pharynx, or throat. 

In the pharynx, there are several openings: one into the esophagus, the tube into which food is swallowed; one into the glottis, through which air enters the larynx, or voice box; and two into the Eustachian tubes, which connect the pharynx to the ear. The digestive system consists of the organs of thedigestive tract, or food tube, and the digestive glands. From the esophagus, swallowed food moves into the stomach and then into the small intestine. Bile is a digestive juice made by the liver and stored in the gallbladder. Bile flows into a tube called the common bile duct, into whichpancreatic juice, a digestive juice from the pancreas, also flows. The contents of the common bile duct flow into the small intestine, where most of the digestion and absorption of food into the bloodstream takes place.Indigestible materials pass through the large intestine and then into the cloaca, the common exit chamber of the digestive, excretory, and reproductive systems. The respiratory system consists of the nostrils and the larynx, which opens into two lungs, hollow sacs with thin walls. The walls of the lungs are filled with capillaries, which are microscopic blood vessels through which materials pass into and out of the blood. The circulatory system consists of the heart, blood vessels, and blood. The heart has two receiving chambers, or atria, and one sending chamber, or ventricle. Blood is carried to the heart in vessels called veins. Veins from different parts of the body enter the right and left atria. Blood from both atria goes into the ventricle and then is pumped into the arteries, which are blood vessels that carry blood away from the heart. The urinary system consists of the frog’s kidneys, ureters, bladder, and cloaca. The kidneys are organs that excrete urine. Connected to each kidney is a ureter, a tube through which urine passes into the urinary bladder, a sac that stores urine until it passes out of the body through the cloaca. The organs of the male reproductive system are the testes, sperm ducts, and cloaca. Those of the female system are the ovaries, oviducts, uteri, and cloaca. The testes produce sperm, or male sex cells, which move through sperm ducts, tubes that carry sperm into the cloaca, from which the sperm move outside the body. The ovaries produce eggs, or female sex cells, which move through oviducts into the uteri, then through the cloaca outside the body.The central nervous system of the frog consists of  the brain, which is enclosed in the skull, and the spinal cord, which is enclosed in the backbone.Nerves branch out from the spinal cord. The frog’s skeletal and muscular systems consist of its framework of bones and joints, to which nearly all thevoluntary muscles of the body  are attached. Voluntary muscles, which are those over which the frog has control, occur in pairs of flexors and extensors. When a flexor of a leg or other body part contracts, that  part is bent. When the extensor of that body part contracts, the part straightens. 

Objectives:• Describe the appearance of various organs found in the frog.• Name the organs that make up various systems of the frog.Purpose:In this lab, you will dissect a frog in order to observe the external and internal structures of frog anatomy.

Materials:• safety goggles, gloves, and a lab apron• forceps, preserved frog, dissecting pins, dissecting tray, scissors, dissecting needle

Procedure: 1. Put on safety goggles, gloves, and a lab apron.      

2. Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its "thumbs," which is one external difference between the sexes, as shown in the diagram below. Male frogs are also usually smaller than female frogs. Observe several frogs to see the difference between males and females.

3. Use the diagram below to locate and identify the external features of the head. Find the mouth, external nares, tympani, eyes, and nictitating membranes.

4. Turn the frog on its back and pin down the legs. Cut the hinges of the mouth and open it wide. Use the diagram below to locate and identify the structures inside the mouth. Use a probe to help find each part: the vomerine teeth, the maxillary teeth, the internal nares, the tongue, the openings to the Eustachian tubes, the esophagus, the pharynx, and the slit-like glottis.

5. Look for the opening to the frog’s cloaca, located between the hind legs. Use forceps to lift the skin and use scissors to cut along the center of the body from the cloaca to the lip. Turn back the skin, cut toward the side at each leg, and pin the skin flat. The diagram above shows how to make these cuts

6. Lift and cut through the muscles and breast bone to open up the body cavity. If your frog is a female, the abdominal cavity may be filled with dark-colored eggs. If so, remove the eggs on one side so you can see the organs underlying them. Use the diagrams below to locate and identify the organs of the digestive system: esophagus, stomach, small intestine, large intestine, cloaca, liver, gallbladder, and pancreas.

7. Again refer to the diagrams to identify the parts of the circulatory and respiratory systems that are in the chest cavity. Find the left atrium, right atrium, and ventricle of the heart. Find an artery attached to the heart and another artery near the backbone. Find a vein near one of the shoulders. Find the two lungs.

8. Use a probe and scissors to lift and remove the intestines and liver. Use the diagram on the next page to identify the parts of the urinary and reproductive systems. Remove the peritoneal membrane, which is connective tissue that lies on top of the red kidneys. Observe the yellow fatbodies that are attached to the kidneys. Find the ureters; the urinary bladder; the testes and sperm ducts in the male; and the ovaries, oviducts, and uteri in the female.

9. Remove the kidneys and look for threadlike spinal nerves that extend from the spinal cord. Dissect a thigh, and trace one nerve into a leg muscle. Note the size and texture of the leg muscles.10. Dispose of your materials according to the directions from your teacher.

Clean up your work area and wash your hands before leaving the lab.

Perch Dissection

Introduction:The fish in the class Osteichthyes have

bony skeletons. There are three groups of the bony fish --- ray-finned fish, lobe-finned fish, and the lung fish. The perch is an example of a ray-finned fish. Its fins have spiny rays of cartilage &/or bone to support them. Fins help the perch to move quickly through the water  and steer without rolling. The perch also has a streamline body shape that makes it well adapted for movement in the water. All ray-finned fish have a swim bladder that gives the fish buoyancy allowing them to sink or rise in the water. The swim bladder also regulates the concentration of gases in the blood of the fish. Perch have powerful jaws and strong teeth for catching and eating prey. Yellow perch are primarily bottom feeders with a slow deliberate bite. They eat almost anything, but prefer minnows, insect larvae, plankton, and worms.  Perch move about in schools, often numbering in the hundreds.The scientific name for the yellow perch, most often used in dissection, is Perca flavescens (Perca means "dusky"; flavescens means "becoming gold colored"). The sides of the yellow perch are golden yellow to brassy green with six to eight dark vertical

saddles and a white to yellow belly. Yellow perch have many small teeth, but no large canines. Yellow perch spawn from mid-April to early May by depositing their eggs over vegetation or the water bottom, with no care given. The eggs are laid in large gelatinous adhesive masses.Materials:Preserved perch, dissecting pan, scalpel, scissors, forceps, magnifying glass, dissecting pins, apron, gloves, eye cover, tape measure

Procedure (External Anatomy):1. Obtain a perch & rinse off the excess preservative. Place the perch in your dissecting pan.2. Label the anterior, posterior, dorsal, and ventral sides of the perch on Figure 1.3. Locate the 3 body regions of the perch --- head, trunk, and tail. Label these on Figure 1.4. Open the perch's mouth and observe its bony jaws. Locate and label the upper jaw or maxilla and the lower jaw or mandible.5. Feel the inside of the mouth for the teeth. Open the mouth wider and use a probe to reach back to the gill chamber.6. Locate the nostrils and label on Figure 1.7. Locate and note the location of the eyes. Label on Figure 1.

8. Find the bony covering on each side of the fish's head called the operculum. The opercula cover & protect the gills. Label these on Figure 1. Use a probe to lift the operculum and observe the gills. Note their color.9. Use a scissors to cut away one operculum to view the gills. Find the gill slits or spaces between the gills.Use your scalpel to carefully cut out one gill. Find the cartilage support called the gill arch and the soft gill filaments that make up each gill. Label the parts of the gill in Figure 2.

Figure 2 - Gill Structure

10. Observe the different fins on the perch. Locate the pectoral, dorsal, pelvic, anal, and caudal fins.

Note whether the fin has spines. Label these on Figure 1 and complete Table 2 on fins on your own sheet. DO NOT FILL IN THIS TABLE.

Table 2 - FinsName of Fin Spines

(yes or no)Number of

Fins Location Function

11. Locate the anus on the perch anterior to the anal fin. In the female, the anus is in front of the genital pore, and the urinary pore is located behind the genital pore. The male has only one pore (urogenital pore) behind the anus. Determine the sex of your perch.12. Find the lateral line on the side of your perch. Label this line on Figure 1.13. Use forceps to remove a few scales from your fish. Observe the scales under the magnifying glass. Sketch a scale on Figure 3.

Figure 3 - Structure of a Scale

14. Count the growth rings on your scale to tell the age of your fish. (Hint: each ring represents one year's growth.)

Procedure (Internal Anatomy):15. Use dissecting pins to secure the fish to the dissecting pan. Use scissors to make the cuts through skin and muscle shown in Figure 4.

Figure 4 - Cut Lines for Internal dissection

16. After making the cuts, carefully lift off the flap of skin and muscle to expose the internal organs in the body cavity. Locate the cream colored liver in the front of the body cavity. Also locate the gall bladder between the lobes of the liver. Remove the gall bladder & liver to observe the short esophagus attached to the stomach. 17. At the posterior end of the stomach are the coiled intestines. Locate these. 18. Find the small reddish brown spleen near the stomach. 19. Below the operculum, are the bony gill rakers. Locate these & them label them on Figure 5.In front of the liver & behind the gill rakers is the pericardial cavity containing the heart. The heart of a fish only has 2 chambers --- an atrium & and a ventricle. Locate the heart.20. In the upper part of the body below the lateral line is the swim bladder. This sac has a thin wall and gives the fish buoyancy. Identify the swim bladder.21. Below the swim bladder are the gonads, testes or ovaries. In a female, these may be filled with eggs. 22. Find the 2 long, dark kidneys in the posterior end of the perch. These filter wastes from the blood. Wastes exit the body through the vent located on the ventral side of the perch.

Figure 5 - Internal Perch Anatomy