IB 104 Lab Quiz 2 - Lab 4 Deuterostomes whose first...

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Lab 4: Deuterostomes Deuterostomes—animals whose first embryonic opening becomes the anus and the oral opening is secondarily derived. Phylum Echinodermata : “hedgehog skin” A body wall containing calcareous ossicles (calcium containing hard plates) Adults are pentaradial…. immature forms are bilaterally symmetrical Structure, Function, and Classifications No head, brain, or excretory organs Unique attributes: Water vascular system—a hydraulic system of locomotion that often included tentacle- like projections called tube feet Calcareous ossicles Pentaradial symmetry in adults In some groups, pincer-like pedicellariae —capture tiny animals and protect skin gills In many, skin gills called dermal branchiae for respiration Echinoderms posses the ability to change the flexibility of the connective tissues in their body walls—stiffen against predators or flex to enter a hiding place, eat, or dislodge a damaged limb All echinoderms live in marine environments Have well developed digestive tract (true coelom), open circulatory system, no excretory organs —remove waste by diffusion through thin body surfaces like tube feet and dermal branchiae There are 6 classes—we look at 4 1. Crinoidea —inhabit deep water, are rarely seen. Includes sea lilies and feather stars. Most have feathery arms branching off of a cuplike body that is attached to the sea floor by a long slender stalk. Mouth on top 2. Echinoidea —armless, globe or disc-shaped with movable spines. Includes sea urchins, sand dollars, and sea biscuits. Distinguished by a hardened test , a one-piece skeletal covering produced by fusion of their skeletal ossicles. Not only pentaradial but do show it in body structure 3. Holothuroidea —armless, lack spines but have microscopic ossicles. Sea Cucumbers. They forcibly spit out their internal organs which can be regenerated due to the elasticity of the connective tissues in their bodies. 4. Asteroidea —Mouth on bottom. Star shaped, central disc w/ 5 arms (rays) Starfish dissection: Aboral side—right side up, where the anus is located 5 rays and a central disck (pentaradial) Epidermis has spines or projections of skeletal ossicles Fingerlike bulges are the skin gills or dermal branchiae
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Pedicellariae —tiny two-jawed pincers on the epidermis used for capturing small prey Sieve plate or medreporite —round brownish disc between two arms though which sea water
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IB 104 Lab Quiz 2 - Lab 4 Deuterostomes whose first...

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