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Phylum Echinodermata (star fish, sea urchins etc)
- Calcerous endoskeleton
- preserved well in fossils
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Echinodermata basic characteristics
- slow, sessile and marine
- pentaradial symmetry (5) in adults
- bilateral symmetry in larvae
- thin epidermis covers endoskeleton
- no central brain
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function of madreporite
allows water to flow in and out of system (Echinodermata)
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Function of tube feet in Echinodermata
- locomotion, feeding and gas exchange
- operated by water pressure and adhesion
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Echinodermata reproduction
- usually separate sexes
- engage in broadcast spawning (fertilization occurs in open water)
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Echinodermata- Class Echinoidea
- sea urchins and sand dollars
- no arms
- rows of tube feet
- slow
- spines are used for locomotion and protection
- eat seaweed
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Echinodermata-Class Holothuroidea
- sea cucumbers
- elongated
- secondary bilateral
- 5 rows of tube feet
- tube feet around mouth serve as feeding tentacles
- deposit or suspension feeders
- shoot out internal organs when disturbed
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Phylum Chordata
- 4 synapomorphies (shared derived characteristics)
- have a notochord
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What is a notochord? (chordates)
- flexible rod located dorsally, between digestive tube and nerve cord
- stiff but not rigid
- always present in embryos, not always in adults
- in many vertebrates it is reduced to a bad between vertebrae
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What are the four synapomorphies in chordates?
- 1. Notochord
- 2. Dorsal hollow nerve cord
- 3. Pharyngeal slits/clefts
- 4. Muscular post-anal tail
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Dorsal, hollow nerve cord development
- unique to chordates (solid in other animals)
- develops from plate of ectoderm dorsal to notochord
- plate rolls into tube during embryonic development
- anterior portion develops into brain
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Pharyngeal slits/clefts functions
- connects pharynx to external environment
- allows water that enters mouth to exit before entering digestive system
- used for suspension feeding
- gas exchange, jaw supports and hearing
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Muscular post-anal tail
contains muscle and skeletal elements
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