BSsqans-lect19 echino

BSsqans-lect19 echino - BIS 1B (Winter 2008) Study question...

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BIS 1B (Winter 2008) Study question answers: Echinodermata Lecture 19 1. Why would it be difficult for an echinoderm to live in freshwater or terrestrial habitat? Echinoderms lack osmoregulatory organs; thus, they would face major problems with osmoregulation in a freshwater (hypotonic) environment. Echinoderms have cutaneous, gas exchange; thus, they would face major problems with water loss in a terrestrial environment. 2. How does a starfish extend a tube foot from its body and attach it to the substrate? The foot consists of a bulbous ampulla and a tubular podium, which terminates in a suction cup. It has a classic hydrostatic skeleton: it is filled with a fluid (which is incompressible, but capable of changing shape). The ampulla is surrounded by circular muscles, which can squeeze water from the ampulla into the podium, thereby extending the podium. The sucker is pressed against the substrate and held there by mucus (secreted by glands in the sucker) and by suction (tiny muscles pull the center of the suction cup inwards). 3. List four functions are performed by the water vascular system? The water vascular system functions in (i) support and locomotion, (ii) circulation, (iii) gas exchange, and (iv) excretion/osmoregulation. 4. What are some anti-predator adaptations demonstrated by echinoderms? Being active only at night, when predators are less likely to be hunting for prey Presence of a hard calcareous skeleton armed with sharp (and sometimes poisonous) spines Production of copious quantities of sticky mucus Pedicellaria may produce toxins thdt can paralyze some predators (fish), prevent other organisms from settling on the echinoderm, and grasp and hold objects used for camouflage (to hide from predators) In sea cucumbers: evisceration (rupture and spew out the hindgut) and discharge of the Cuvierian tubules Mutualistic associations with other animals that provide protection (e.g., some brittle stars live inside sponges) 5. Why don't many hermaphrodites self-fertilize? Some hermaphrodites do self-fertilize, and this can be advantageous when it is
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This note was uploaded on 04/15/2008 for the course BIS 1b taught by Professor Kimsey during the Spring '08 term at UC Davis.

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BSsqans-lect19 echino - BIS 1B (Winter 2008) Study question...

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