Contemporary Biological Problems Lab Anatomy of the Earthworm Earthworms are seg

Question

Contemporary Biological Problems Lab Anatomy of the Earthworm Earthworms are segmented in that the body has a series of ringlike segments, Earthworms have no head, and they burrow in the soil by alternately expanding and contracting segments along the length of the body Earthworms are scavengers that feed on decaying organic matter in the soil. They have a well-developed coelomic cavity, providing room for a well-developed digestive tract and both sets of reproductive organs. Observation: Anatomy of the Earthworm External Anatomy 1. Examine a live or preserved specimen of an earthworm. Locate the small projection that sticks out over the mouth. Has cephalization occurred?Explain your answer. 2. Count the total number of segments, beginning at the anterior end. The sperm duct openings are on segment 15 (somite XV) (Fig. 17.8). The enlarged section around a short length of the body is the clitellum. The clitellum secretes mucus that holds the worms together during mating. It also functions as a cocoon, in which fertilized eggs hatch and young worms develop. The anus is located on the worm's terminal segment. 3. Lightly pass your fingers over the earthworm's ventral and lateral sides. Do you feel the setae? Earthworms insert these slender bristles into the soil. Setae, along with circular and longitudinal muscles, enable the worm to locomote. Explain the action. Figure 17.8 External anatomy of an earthworm. In this drawing, the segments are numbered 5 105 20 25 30 Ventral seminal groove

Explanation / Answer

1. Yes, cephalization have occurred. Cephalization is the development of organism, so that important organs found near the house and. Earthworm have cepalization because head I formed at anterior end of the body.

3. Yes, I feel setae. These are bristles like structure which help the earthworm to be grip the soil during their locomotion and inhibit backsliding during their peristalatic movement. In this way setae play an important role in their movement in soil

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