Chapter 31

1. Chapter 31 Echinoderms and Invertebrate Chordates Section 1: Echinoderms Section 2: Invertebrates Chordates

2. Section 1 Echinoderms Objectives: • Compare the developmental pattern found in protostomes with that found in deuterostomes. • Describe the major characteristics of echinoderms. • Summarize how the sea star's water vascular system functions.

3. Section 1 Echinoderms Animal Development • Protostomes During embryonic development, a protostome’s mouth develops from the blastopore. • Deuterostomes In a deuterostome, the anus forms from the blastopore and the mouth forms later from a different opening. • Echinoderms and Chordates Because echinoderms and chordates are both deuterostomes, scientists believe that both groups were derived from a common ancestor.

4. Section 1 Echinoderms Modern Echinoderms • Body Systems Echinoderms lack a head or brain. Their nervous system consists of a central ring of nerves with branches extending into each of the five parts of its body plan. In many echinoderm species, respiration and waste removal are performed by skin gills. • Shared Traits Echinoderms share four characteristics: an endoskeleton composed of ossicles; five-part radial symmetry; a water-vascular system; and coelomic circulation and respiration.

5. Section 1 Echinoderms Echinoderm Diversity • Sea Stars Sea stars pry open prey using their tube feet. • Brittle Stars Brittle stars are relatives of sea stars. • Sea Lillies and Feather Stars Sea lillies and feather stars are the most ancient and primitive living echinoderms. • Sea Urchins and Sand Dollars Sea urchins and sea dollars lack distinct arms but have the basic five-part body plan.

6. Section 1 Echinoderms Echinoderm Diversity continued • Sea Cucumbers Sea cucumbers are soft-bodied, sluglike animals without arms. • Sea Daisies Sea daisies are strange disk-shaped little animals that are a new class of echinoderms.

7. Section 2 Invertebrate Chordates Objectives: • Describe the characteristics of chordates. • Define the term invertebrate chordate. • Compare tunicates and lancelets.

8. Section 2 Invertebrate Chordates The Chordate Skeleton • Chordates Phylum Chordata includes invertebrate and vertebrate chordates. • Other Chordate Characteristics At some point in their lives, all chordates have a notochord, a dorsal nerve chord, pharyngeal slits, and a postanal tail.

9. Section 2 Invertebrate Chordates Invertebrate Chordates • Invertebrate Chordates Invertebrate chordates do not have a backbone (vertebral column). Two invertebrate subphyla are Urochordata (tunicates) and Cephalochordata (lancelets). • Tunicates Tunicate larvae have a nerve cord, notochord, pharyngeal slits, and a postanal tail. As adults, they lose all of these characteristics except the pharyngeal slits. • Lancelets Lancelets retain their notochord, dorsal nerve cord, pharyngeal slits, and postanal tail into adulthood.