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Echinoderms and Invertebrate Chordates Ch 29. Echinodermata Endoskeleton, radial symmetry, simple nervous system, varied nutrition, water vascular system.

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Presentation on theme: "Echinoderms and Invertebrate Chordates Ch 29. Echinodermata Endoskeleton, radial symmetry, simple nervous system, varied nutrition, water vascular system."— Presentation transcript:

1 Echinoderms and Invertebrate Chordates Ch 29

2 Echinodermata Endoskeleton, radial symmetry, simple nervous system, varied nutrition, water vascular system – Water vascular system—hydraulic system that operates under water pressure, enables animal to move, exchange gases, capture food, excrete wastes Move along surfaces and pry open food with tube feet – Water enters and leaves through madreporite, a sievelike, disk-shaped opening on the upper surface of body Bilaterally symmetrical, ciliated larvae Deuterostomes (mouth forms 2 nd )

3 Diversity of Echinoderms ~6000 species exist today, 6 classes – Asteroidea: sea stars (25% of phylum) most species have 5 rays, but some can have more than 40! – Ophiuroidea: brittle stars Extremely fragile, rays can break off (helps survive predator attacks), propel themselves by slithering, tube feet for feeding – Echinoidea: sea urchins and sand dollars Globe-/disk-shaped, covered with spines, no rays, tube feet for eating and modified as gills for respiration – Holothuroidea: sea cucumbers Vegetable-like appearance, moves along ocean floor, expels tangled sticky mass of tubes through anus or ruptures and loses organs, which regenerate in a few weeks (evasion of predators) – Crinoidea: sea lilies and feather stars Resemble plants, sea lilies only sessile echinoderms, feather stars sessile in larval form; use feathery arms to swim around – Concentricycloidea: sea daisies Two species discovered in New Zealand, tube feet around edge of disk

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5 Invertebrate Chordates All chordates have a notochord—a long, semirigid, rodlike structure between digestive system and dorsal hollow nerve cord – Made up of large, fluid-filled cells held within stiff fibrous tissue Invertebrates: may retain notochord to adulthood Vertebrates: notochord replaced with backbone All chordates have dorsal hollow nerve cord – Develops from a plate of ectoderm that rolls into a hollow tube Composed of cells surrounding fluid-filled canal above the notochord

6 Embryonic invagination of the notochord and neural tube Anterior region with early central nervous system

7 Commonalities in Chordates All chordates have a notochord All chordates have pharyngeal pouches – Paired openings in pharynx behind mouth All chordates have a postanal tail – At some point in development Development controlled by homeotic genes

8 Diversity of Invertebrate Chordates Tunicates (sea squirts): chordate features visible in larval stages Lancelets (similar to fish): spend most of their time buried in sand with only heads out to filter food from water

9 Origins Fossil record is limited because of soft bodies Possibly arose from sessile animals that fed by tentacles (larval stages may be similar)


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