OESOPHAGUS STOMACH
ECHINODERMS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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True
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False
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Either A or B
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None of the above
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Detailed explanation-1: -Diversity. There are about 7, 000 extant species of echinoderm as well as about 13, 000 extinct species.
Detailed explanation-2: -Echinodermata is a phylum of about 7000 living species distributed among five classes: Echinoidea (sea urchins and sand dollars), Holothuroidea (sea cucumbers), Ophiuroidea (brittle stars), Asteroidea (sea stars), and Crinoidea (feather stars and sea lilies).
Detailed explanation-3: -The correct answer is (b). Echinoderms do not have gills.
Detailed explanation-4: -The Ophiuroids or brittle stars are probably the most common extant echinoderms. They occur in large numbers in all parts of the oceans, from the shallowest coastal waters to the deep sea trenches. Blastoids persisted until their extinction at the end of Permian, some 250 million years ago.