Internal Anatomy 1. If so directed by your instructor, place a preserved earthwo

Question

Internal Anatomy 1. If so directed by your instructor, place a preserved earthworm on its ventral side in the dissecting parn and follow these directions; otherwise proceed immediately to "Prepared Slide" on page 225. With scalpel or razor blade, make a shallow incision slightly to the side of the blackish median dorsal blood vessel (Fig. 17.9a). Start your incision about 10 segments after the clitellum, and proceed anteriorly to the mouth. If you see black ooze, you have accidentally cut the intestine Identify the thin partitions, the septa, between segments 3. Lay out the body wall, and pin every 10th segment to the wax in your pan. Add water to prevent drying out. While alive, the earthworm body wall is always moist, and this facilitates gas exchange across the body wall. Notice the earthworm has no respiratory organ 4. An earthworm feeds on detritus (organic matter) in the soil. Identify the digestive tract, which begins at 2, and 3 (Fig 17.9a and b). It opens into the swollen. muscular, thick-walled pharynx, which extends from segment 3 to segment 6. The esophagus extends from the pharynx through segment 14 to the crop. Next is the gizzard, which lies in segments 17 through 17. The intestine extends from the gizzard to the anus. Does the digestive system show specialization of partsExplain your answer. 5. Identify the earthworm's circulatory system. The blood is always contained within vessels and never runs free. The dorsal blood vessel is readily seen along the dorsal side of the digestive tract. A series of aortic arches or "hearts" encircles the esophagus between segments 7 and 11, connecting the dorsal blood vessel with the ventral blood vessel. Does the earthworm have an open or closed circulatory system? Explain your answer. 6. Locate the earthworm's nervous system. The two-lobed brain is located on the dorsal surface of the pharynx in segment 3. Two nerves, one on each side of the pharynx, connect the brain to a ganglion that lies below the pharynx in segment 4. The ventral nerve cord then extends along the floor of the body cavity to the last segment. 7. Find the earthworm's excretory system, which consists of a pair of minute, coiled, white tubules, the nephridia, located in every segment except the first three and the last. Each nephridium opens to the outside by means of an excretory pore. Does the excretory system show that the earthworm is segmented? Explain your answer 8. Ildentify the carthworm's reproductive system, including seminal vesicles, light-colored bodies in segments 9 through 12, which house maturing sperm that have been formed in two pairs of testes within them; sperm ducts that pass to openings in segment 15; and seminal receptacles (four small, white special bodies that lie in segments 9 and 10), which store sperm received from another worm. Ovaries are located in segment 13 but are too small to be seern. 9. During mating, earthworms are arranged so that the s perm duct openings of one worm are just about, but quite, opposite the seminal receptacle openings of the other worm. After being released, the spern pass down a pair of seminal grooves on the ventral surface (see Fig. 17.8) and then cross over at the level of the seminal receptacles of the opposite worm. Once the worms into a cocoon secreted by the clitellum. Is the earthworm hermaphroditic? answer separate, eggs and sperm are released Explain your

Explanation / Answer

4.Earth worm digestive system consists mouth, pharynx,esophagus,crop,gizzard and rectum

5. The blood is always circulated in vessels and never runs freely. So it has closed circulatory system

7. It is segmented

9 Earth worms are having seminal vasicles at 9-12 segments, two pairs of testes, sperm duct at segment 15,seminal receptors located at 9&10 segments, ovaries are present in the 13th segment and hence the earth worm is hermaphroditic animal

10 there are no specific respiratory organs are present as long as the animal alive the skin will be in moist condition and gases are exchanged through the skin

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.