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Echinoderms
Phylum Echinodermata
Echinoderms belong to the phylum Echinodermata, which contains marine animals living at all ocean depths. It consists of about 7,000 living species, the largest phylum without freshwater or terrestrial members. Also, few other groups are so abundant in the deep ocean as well as the shallower seas.
As mentioned earlier, echinoderms are radially symmetric. In spite of their appearance, they do not have an external skeleton. Instead, a thin outermost skin covers an internal endoskeleton made of tiny calcified plates and spines, contained within tissues of the organism, and which forms a rigid support. Some groups, such as the sea urchins, have calcareous spines, referred to earlier, which protect the organism from predation and colonization by encrusting (covering or coating) organisms. The sea cucumbers also use these spines for locomotion.
Echinoderms have a unique water vascular system, a network of fluid-filled canals, which function in gas exchange, feeding, and also in locomotion. This system allows them to function without gill slits found in other organisms. Echinoderms possess a very simple digestive system, often leading directly from mouth to anus. They also possess an open and reduced circulatory system, but no heart. Their nervous system consists of a modified nerve net (interconnected neurons with no central brain).
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Instructions - complete the following
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Watch the following
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Class Crinoidea - Feather Stars & Sea Lillies
Class Holothuroidea - the Sea Cucumber
Class Holothuroidea - how to eat a Sea Cucumber
Brittle Star Loses Arm - Regeneration
Sea Stars - detrivores of the Deep
Sea Stars Fight over a Scallop
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