OESOPHAGUS STOMACH
ECHINODERMS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Class Holothuroidea, sea cucumbers
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Class Asteroidea, Starfish
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Class Echinodea, sea urchins
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Class Crinoidea, sea lilies and feather stars
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Detailed explanation-1: -sea urchin, any of about 950 living species of spiny marine invertebrate animals (class Echinoidea, phylum Echinodermata) with a globular body and a radial arrangement of organs, shown by five bands of pores running from mouth to anus over the test (internal skeleton).
Detailed explanation-2: -Echinoids are marine animals belonging to the phylum Echinodermata and the class Echinoidea. They have a hard shell (referred to as a test) covered with small knobs (tubercles) to which spines are attached in living echinoids. The test and spines are the parts normally found as fossils.
Detailed explanation-3: -The internal organs are enclosed in a hard shell or test composed of fused plates of calcium carbonate covered by a thin dermis and epidermis. The test is referred to as an endoskeleton rather than exoskeleton even though it encloses almost all of the urchin.