1. What Phylum Do Frogs Belong In? Why?

Name: Frog Dissection

1. What phylum do frogs belong in? Why?

2. What class do frogs belong in? Why?

3. Obtain a preserved frog. Observe its external features carefully. What is the exterior covering of the frog like?

4. Notice the circular tympanic membrane. The tympanic membrane functions as an external ear drum. Draw your frog in the space below. Label the tympanic membrane. Write its function.

5. Compare the colors on the dorsal and ventral sides of the frog. How does each of these colors help the frog survive? (Hint: Think about the frog on land and in the water.)

6. How is the positioning of the frog’s eyes an adaptive advantage (help it survive)?

Open the mouth of your frog by cutting the jaws with your scissors. Locate the maxillary teeth around the edge of the jaw. They help hold food, but are not used for chewing. Notice the 2 openings in the throat. The larger opening is to the esophagus and the smaller is called the glottis and leads to the respiratory system. Notice how the tongue is attached and its shape. Locate the openings of the Eustachian tubes on the sides. These lead to the tympanic membrane and are used to equalize pressure in the ear.

7. Where is the tongue attached? How is this helpful to the frog? 2

Place your frog with the ventral surface up. Cut through the frog’s skin and muscle lengthwise from the chin to the anus and across at the bottom and top to make 2 flaps. If your frog is female, she may contain many black eggs. Remove these carefully before continuing.

Digestive system Locate the esophagus in the throat and trace it down to the stomach. Note the constriction at the base of the stomach, the pyloric sphincter, which regulates the movement of food into the intestine. Cut open the stomach and observe its contents. You might use a probe to locate the esophagus if that was difficult before. Follow the digestive tract to the coiled small intestine. The first part that usually runs parallel to the stomach is the duodenum. Follow the small intestine to where it widens, the large intestine or colon. The colon ends in the rectum which in turn ends in the cloaca. The digestive, reproductive and excretory systems all open into the cloaca. The cloaca opens to the outside of the frog. Note the large, brown liver. Lift up the liver to locate the greenish gallbladder on its underside. Locate the pancreas, a soft irregular pinkish organ which lies on a membrane between the stomach and small intestine.

8. How many lobes are in a frog’s liver?

9. Draw the digestive organs of your frog in the space below. Write the name of each organ highlighted above. Write the function of each structure next to its name.

Respiratory system Locate the pinkish-grey or brown lungs. They are hidden underneath and beside the liver, high up in the body cavity.

10. How does the shape of the tongue help the frog with breathing?

11. Are the lungs all in one piece or do they have lobes like the liver? 3

12. What other body part is used for respiration besides the lungs?

13. What must this part of the body be like to be able to function in respiration?

Circulatory system Locate the heart between the lungs. The pointed ventricle is lighter in color than the atria. 12. How many chambers does the frog’s heart have?

Lift the stomach and find the round, red spleen. The spleen filters the blood and removes red blood cells that no longer function correctly.

13. Draw the respiratory and circulatory organs (lungs, heart – with atria and ventricle, spleen) Label each organ Write the function of each organ next to its name.

Excretory system Locate the kidneys, bean-shaped organs that lie against the back body wall. Notice the yellow stripe which is the adrenal body that secretes hormones. The urine is transported to the cloaca and excreted out of the anus with other wastes.

14. What is the function of the kidney?

Reproductive system A female frog has 2 lobed, grayish ovaries that lie close the kidneys. In a mature female, the ovaries may be filled with black and white eggs. A male frog has white testes close to the kidneys. Locate the yellow, fingerlike fat bodies attached near the kidneys. The fat bodies provide nourishment for the gametes. 4

16. Draw the organs of the excretory and reproductive systems described above. Write the name of each organ Write the function of each organ next to its name.

The Nervous system Turn the frog over so the dorsal side is up. Insert the point of the scissors through the skin at the base of the skull and remove the skin from the head. Use the bone cutters to open the skull and locate the brain. Try to find the white spinal cord within the vertebrae of the neck.