Describe the distinguishing features of the animals group below in Chapter 16 Ec

Question

Describe the distinguishing features of the animals group below in Chapter 16

Echinoderms:

16 Echinoderms and Invertebrate Chordates After completing this exercise, you will be able to l endoskeleton, water-vascular system, notochord, pharyngeal gill slits, dorsal hollow 2. describe the natural history of members of phylum Echinodermata and the invertebrate 3. identify some representatives of the echinoderm classes (sea stars, brittle stars, sea urchins, 4. compare and contrast the invertebrate chordates (subphyla Urochordata and 5. identify structures (and indicate associated functions) of the representatives of these phyla merve cord, post-anal tail, invertebrate members of phylum Chordata; and sea cucumbers) Cephalochordata): and subphyla. Introduction The ancestors of echinoderms and chordates, the phylum to which we belong, had a coelom (body cavity) a look quite different, chordates are thought to have evolved from the bilaterally symmetrical larvae of ancestral (first embryonic opening becomes anus). Although the adult forms of these two phyla echinoderms some 600 million years ago. There is an additional small phylum, the Hemichordata, whose members (acorn worms) have echinoderm and chordate characteristics. Acorn worms are long, slender, wormlike animals (Figure 16-1a). Most live in shallow seawater. They obtain food by burrowing in mud and sand or filter feeding. Evidence of their former n on exposed tidal flats where mud or sand that has passed through their bodies is left in activity can be see numerous coiled, ropelike piles (Figure 16-1b). collar proboscis stalk trunk proboscis Figure 16-1 (a) Preserved acorn worm. (b) Ropelike piles of sand formed by burrowing acorn worms. 16.1 Phylum Echinodermata: Echinoderms) (60 min.) aquatic, marine Habitat Body Arrangement radial symmetry (larvae are bilaterally symmetrical), coelomate, no well-defined head, no segmentation, gut (usually complete) 271

Explanation / Answer

The word echinos means spines and derma means skin.
They belong to the kingdom Animalia.
They are triploblastic, coelomate marine animals.
They have organ system level of organization.
They have water vascular system as well as tube feet.
They show external fertilization and reproduce by both asexual and sexual means.
Adults are radially symmetrical and larvae are bilaterally symmetrical.

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