NAME__________________________________________BIO______DATE___________________

EXTERNAL FROG DISSECTION

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 lab apron preserved frog dissecting pins (610) dissecting tray scissors

probe forceps plastic storage bag and twist tieProcedure:

(Put on safety goggles and a lab apron.

(Place the frog on the dissection tray DORSAL SIDE UP. Examine the arrangement of the spots and the coloration of the frog.

(Turn the frog over in the dissection tray ventral side up.

1. Are there any spots on this side?

2. Why would the frog need to have spots on the dorsal side and not the ventral?

(Examine the forelegs and hind legs of the frog on both the dorsal and ventral sides.

3. How do they differ from each other?

(Examine the forefeet and hind feet.

4. How many toes are present on the forefoot? Are the toes webbed? How many toes are present on the hind foot? Are the toes webbed?(To determine the frogs sex, look at the ventral side hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its "thumbs," which is 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.

5. What is the sex of your frog?

HEAD OF THE FROG

(Use the diagram below to locate and identify the external features of the head.

(Notice the size and position of the eyes.6. How do the position of the eyes and the external nares give an advantage to the frog while it is in the water?

(Using your forceps, examine the thin nictitating membrane.

7. Explain two ways that this third eyelid would benefit the frog.

(Examine the tympanum.

8. How is this different from your ear?

INTERNAL MOUTH STRUCTURES OF THE FROG

(Using the diagram below and your scissors cut the edges of the mouth at each hinge.

The hinge is a bone so you will have to cut through it!

(Open the mouth wide so that you can examine the internal mouth structures.

9. Describe the attachment of the tongue to the lower jaw.

10. Why is the point of attachment of the frogs tongue considered an

advantageous adaptation?11. How is the attachment point different in your tongue?

12. Describe the texture of the tongue.

13. Is this different or similar to your tongue? Explain.(Notice that the frog tongue is forked at the end

14. Explain a possible reason for the forked tongue.(Use the diagram below and the probe locate and identify the structures inside the mouth.

1. groove of the maxilla2. maxillary teeth

3. internal nare

4. bottom of the eyeball

5. eustachian tube opening

6. jawridge

7. underside of tongue

8. glottis

9. cut muscle & bone

a. opening to the esophagus(GULLET)

b. vomerine teeth(Run your index finger along the edge of the upper jaw. You will feel the small

maxillary teeth.

(There is still another set of teeth. Run your index finger along the roof of the

mouth. You will feel 2 sharp vomerine teeth.

15. What do the site and placement of the teeth tell you about the their function during feeding?(Holes at the back sides of the mouth in the upper jaw are openings for the Eustachian tubes. Insert the probe into the Eustachian tubes.

16. Where do the Eustachian tubes lead and what is their function?

(Insert the probe into the internal nares.

17. Where do the internal nares lead?

(Locate the side opening in the center back of the mouth. This is the esophagus opening or the gullet.

18. Account for the extreme width of the gullet?(Locate the glottis, a small vertical slit-like opening below the esophagus (gullet).

19. Where does it lead?NAME______________________________________________BIO______DATE__________

EXTERNAL FROG DISSECTION ANSWER SHEET

ALL QUESTIONS ARE WORTH 5 PTS EACH. NO COMPLETE SENTENCE NO CREDIT.

1. Are there any spots on this side?

2. Why would the frog need to have spots on the dorsal side and not the ventral?

3. How do the forelegs and hind legs differ from each other?

4. How many toes are present on the forefoot? Are the toes webbed?

How many toes are present on the hind foot? Are the toes webbed?

5. What is the sex of your frog?

6. How do the position of the eyes and the external nares give an advantage to the

frog while it is in the water?

7. Explain two ways that this third eyelid would benefit the frog.

8. How this different from your ear?

9. Describe the attachment of the frog tongue to the lower jaw.

10. Why is the point of attachment of the frogs tongue considered an

advantageous adaptation?

11. How is the attachment point different in your tongue?

12. Describe the texture of the frog tongue.

13. Is this different or similar to your tongue?

14. Explain a possible reason for the frogs forked tongue.

15. Since a frog does not chew its food, what do the site and placement of the

teeth tell you about their function during feeding?

16. Where do the Eustachian tubes lead and what is their function?

17. Where do the internal nares lead?

18. Account for the extreme width of the gullet?19. Where does the glottis lead?KEY KEY KEY KEY KEY

EXTERNAL FROG DISSECTION ANSWER SHEET

ALL QUESTIONS ARE WORTH 5 PTS EACH. NO COMPLETE SENTENCE NO CREDIT.

1. THERE ARE NO SPOTS ON THE VENTRAL SIDE.

2. THE FROG HAS SPOTS ON THE DORSAL SIDE TO HELP WITH CAMOUFLAGE.****BULLFROGS: SPOTS ARE BECAUSE OF ENEVEN LIGHTING IN BULLFROB HABITAT.

3. THE HIND LEGS ARE LONGER AND MORE MUSCULAR THAN THE FORELEGS.4. THERE ARE FOUR TOES ON THE UNWEBBED FORELEG. THERE ARE FIVE TOES ON THE WEBBED HINDLEG.5. YOUR ANSWER SHOULD BE EITHER MALE OR FEMALE.6. BY HAVING JUST THE NOSTRILS AND THE EYES OUT OF THE WATER, THE FROG CAN

STAY HIDDEN WHILE KEEPING AN EYE OUT FOR PREDATORS.7. THE THIRD-EYELIDE WOULD BENEFIT THE FROG BY KEEPING ITS EYE MOIST IN A

DRY ENVIRONMENT BY RETAINING MOISTURE. THE EYELID COULD ALSO KEEP FOREIGN MATERIALS THAT ARE IN THE WATER FROM DAMAGING THE FROGS EYE. IT WOULD BE LIKE ITS OWN PAIR OF GOGGLES.8. YOUR EAR HAS EXTERNAL CARTILAGE THAT HELPS TO DIRECT SOUND INTO THE INNER EAR. THE FROG DOES NOT HAVE THESE EXTERNAL STRUCTURES. YOUR EAR

HAS A HOLE IN IT TO HELP SOUND TRAVEL INTO THE INNER EAR. THE FROG HAS NO

SUCH HOLE IN ITS EAR.9. THE FROGS TONGUE IS ATTACHED TO THE FRONT OF ITS MOUTH.

10. THE FROGS TONGUE ATTACHMENT IS AN ADVANTAGE TO IT BECAUSE IT WILL

ALLOW THE FROG TO FLIP ITS TONGUE OUT MUCH FARTHER. THE FARTHER IT CAN

FLIP ITS TONGUE THE MORE PREY IT WILL CATCH.11. THE HUMAN TONGUE IS ATTACHED TO THE BACK OF THE MOUTH.12. THE ANSWER SHOULD INCLUDE ADJECTIVES----ROUGH, SMOOTH, BUMPY13. THE FROGS TONGUE TEXTURE IS SIMILAR TO OURS IN THAT IT IS SMOOTH. LOOK BACK AT QUESTION #12 AND SEE HOW THEY DESCRIBED THE TONGUE. IT SHOULD RELATE TO OURS IN THE SAME WAY.14. THE FROGS TONUE IS FORKED TO AIDE IT IN CATCHING FOOD.15. THE TEETH IN THE FROG ARE THERE ONLY TO CATCH AND KEEP HOLD OF THE CAPTURED PREY.16. THE EUSTACHIAN TUBES LEAD TO THE TYMPANIC MEMBRANEAND IT HELPS WITH

EQUALIZING AIR PRESSURE AND PICKING UP SOUND VIBRATIONS.17. THE INTERNAL NARES LEAD TO THE EXTERNAL NARES OR NOSTRILS.18. THE FROG SWALLOWS ITS FOOD WHOLE SO THE GULLET HAS TO BE LARGE IN ORDER

TO ACCOMMODATE THE SIZE OF THE PREY.19. THE GLOTTIS LEADS TO THE LUNGS.MALE