bio-echino-chord

bio-echino-chord - Deuterostomes: Echinoderms, Chordates...

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Deuterostomes: Echinoderms, Chordates This chapter covers the following animals. Phylum: Echinodermata Class: Asteroidea (Sea Stars) Class: Echinoidea (Sea Urchins, Sand Dollars) Class Ophiuroidea (Brittle Stars) Class Holothuroidea (Sea Cucumbers) Class Crinoidea (Sea Lilies) Phylum: Chordata Subphylum: Cephalochordata (Lancelets) Subphylum: Urochordata (Tunicates or Sea Squirts) Subphylum: Vertebrata (Vertebrates) Class: Cephalaspidomorphi (Lampreys) Class: Chondrichthyes (Cartilaginous fishes- Sharks, Rays) Class: Actinopterygii (Ray-finned fishes) Class: Actinistia (Coelacanths) Class: Dipnoi (Lungfishes) Class: Amphibia (Amphibians) Class: Reptilia (Reptiles) Class: Aves (Birds) Class: Mammalia (Mammals) (Monotremes - Platypus, Echidnas) (Marsupials) (Eutherians or Placental mammals) Phylum Echinodermata Echinoderms are coelomate, and deuterostomes. Echinoderms include sea stars (starfishes), sea urchins, sand dollars, sea cucumbers, and
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sea lilies. There are 6,000 species of echinoderms; they are all marine . Although echinoderm adults have radial symmetry , they evolved from ancestors that were bilaterally symmetrical. They have free-swimming, bilateral larvae that metamorphose (change as they mature) into adults with radial symmetry. Below: Bilateral symmetry can be seen in the sea star larvae (center of photograph). The adult body usually has five-part organization. They possess an internal skeleton ( endoskeleton ) composed of calcium carbonate plates just beneath the surface of the skin. The plates often bear spines that protrude through the skin. Echinoderms have numerous tube feet underneath each arm. The tube feet are connected to a system of pipes referred to as the water vascular system . Water enters the system by a sieve plate on the aboral surface. Each tube foot has a fleshy bulb or ampulla attached so that the entire structure looks like an medicine dropper or pipette. When muscles surrounding the ampulla contract, fluid inside the bulb moves down into the tube foot, extending it. Large digestive glands produce enzymes necessary for digestion . Sexes are separate and gametes are shed into the water. The gonads are large due to the necessity of releasing large numbers of gametes into the marine environment. Coelomic fluid circulates substances and carries amoeboid cells that clean up particulate wastes. Gas exchange is done with numerous tiny gills that extend from the surface of the skin. The nervous system consists of a central nerve ring with nerve branches extending into the
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arms. They do not have a brain . Sea stars (Starfish, Class: Asteroidea) Sea stars and their relatives are composed of a central disk, usually with five or a multiple of five arms (rays) extending outward. They feed on
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bio-echino-chord - Deuterostomes: Echinoderms, Chordates...

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