Question

sea cucumbers, like most echinoderms, lack a circulatory system and use coelomic fluid as the primary circulatory medium as well. a single, filamentous gonad is present near the oral end of the body, and gametes are released through a gonopore at the base of the tentacles. unique paired structures, found only in holothurians, are the respiratory trees—highly branched outgrowths of the hindgut (fig. 15.12). typically, two of these structures are present and are connected to the cloaca. seawater is pumped into and out of the respiratory trees by muscular contractions of the anus, and gas exchange occurs across the thin tissues of the respiratory trees as water passes over them. no discussion of sea cucumbers would be complete without mentioning their amazing ability to eviscerate their internal organs. when sufficiently disturbed or provoked, the muscular body wall quickly contracts and some portion of the viscera is forced out through the anus, essentially turning the sea cucumber inside out! in some species this is limited to expulsion of the respiratory trees, but others exhibit true evisceration and the entire contents of the body cavity are expelled. eventually the lost body parts are re - formed, reflecting the astounding regenerative capabilities of echinoderms! check your progress 3.1 what method of food acquisition do sea cucumbers employ? 3.2 because sea cucumbers have lost the sharp spines and hard endoskeleton on which most echinoderms rely for protection, how do they defend themselves? 3.3 what characteristics do sea cucumbers possess that would cause zoologists to group them in the same phylum with other echinoderms? exercise 15 - 6 investigating locomotion in sea stars and sea urchins materials needed - live sea stars and sea urchins - 2 large finger bowls - seawater if living sea stars and sea urchins are available in your laboratory, you can perform some simple exercises to characterize the different methods of locomotion that these two groups use. despite the simple, decentralized nature of the echinoderm nervous system, they clearly are capable of sophisticated, coordinated behaviors and movements. evidence even supports the contention that a limited amount of learning is possible in some echinoderms! procedure 1 first obtain a living sea urchin and place it in a large finger bowl filled with seawater. 2 observe its pattern of locomotion and answer the following questions. are the spines utilized in locomotion? are the tube feet utilized in locomotion?

Explanation:

3.1: The text does not mention the food - acquisition method of sea cucumbers.
3.2: The text only mentions evisceration as a defense mechanism when disturbed, but no other defense methods are stated.
3.3: The text does not list the characteristics that group sea cucumbers with other echinoderms in the same phylum. For the locomotion questions about sea urchins, the text only provides the procedure to observe but no answers.

Answer:

3.1: No information provided in the text.
3.2: Evisceration when disturbed (but other defenses not mentioned).
3.3: No information provided in the text.
Are the spines utilized in locomotion? No answer in text.
Are the tube - feet utilized in locomotion? No answer in text.