27 3 Annelids Segmented Worms Slide 1 of

27 -3 Annelids. Segmented Worms Slide 1 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids What Is an Annelid? I. What Is an Annelid? A. Annelids are worms with segmented bodies. They have a true coelom that is lined with tissue derived from mesoderm. Slide 2 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids What Is an Annelid? II. Three Germ Layers of an Annelid Slide 3 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids What Is an Annelid? A. The body of an annelid is divided into segments. B. Each segment is separated by septum, which are internal walls between each segment. Slide 4 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids What Is an Annelid? A. Body segments may carry eyes, antennae, other sense organs, or be specialized for functions such as respiration. B. Bristles called setae may be attached to each segment. C. Annelids have a tube-within-a-tube digestive tract that food passes through from the mouth to the anus. Slide 5 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids III. Form and Function in Annelids A. Annelids have complex organ systems. B. Many of these systems are unique because of the segmented body plan of this group. Slide 6 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids A. In earthworms, the pharynx pumps food and soil into the esophagus. B. The food then moves through the crop, where it can be stored. C. It then moves through the gizzard, where it is ground into smaller pieces. D. The food is absorbed farther along in the digestive tract in the intestine. Slide 7 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids IV. Circulation A. Annelids typically have a closed circulatory system, in which blood is contained within a network of blood vessels. Slide 8 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids B. Blood in the dorsal (top) vessel moves toward the head of the worm. C. The dorsal blood vessel functions like a heart because it contracts rhythmically and helps pump blood. Dorsal blood vessel Slide 9 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids A. Blood in the ventral (bottom) vessel runs from head to tail. Ventral blood vessel Slide 10 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids D. In each body segment, a pair of smaller blood vessels connect the dorsal and ventral blood vessels and supply blood to the internal organs. Slide 11 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids V. Respiration A. Land-dwelling annelids take in oxygen and give off carbon dioxide through their moist skin. Slide 12 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids VI. Excretion A. Digestive waste passes out through the anus. Slide 13 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Form and Function in Annelids VII. Response A. Most annelids have a well-developed nervous system consisting of a brain and several nerve cords. Brain Ganglia Copyright Pearson Prentice Hall Slide 14 of 36 End Show

27 -3 Annelids Form and Function in Annelids VIII. reproduction A. When eggs are ready for fertilization, a clitellum secretes a mucus ring into which eggs and sperm are released. B. A clitellum is a band of thickened, specialized segments. C. After eggs are fertilized in the ring, the ring slips off the worm's body and forms a protective cocoon. D. Young worms hatch weeks later. Slide 15 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Groups of Annelids IX. Oligochaetes A. Oligochaetes contains earthworms and their relatives. B. Oligochaetes typically have streamlined bodies and relatively few setae compared to polychaetes. Most oligochaetes live in soil or fresh water. Slide 16 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Ecology of Annelids X. Ecology of Annelids A. Earthworms and many other annelids spend their lives burrowing through soil, aerating and mixing it. B. Earthworms help plant matter decompose. C. Earthworm castings are rich in nitrogen, phosphorus, potassium, micronutrients, and beneficial bacteria. Slide 17 of 36 Copyright Pearson Prentice Hall End Show

27 -3 Annelids Slide 18 of 36 Copyright Pearson Prentice Hall End Show