Phylum Echinodermata


 
 
Concept Explanation
 

Phylum Echinodermata

Phylum Echinodermata: Echinoderms are spiny-skinned marine animals. They have an exoskeleton of calcareous plates from which the spines arise.

  • The adults are radially symmetrical, while the larvae are bilaterally symmetrical.
  • Most echinoderms are sessile. Some live in groups, while others are solitary.
  • A unique feature of echinoderms is the water vascular system. It is a complex system of water-containing tubes and bladders which pass through pores in the skeleton.
  • On the outside, these tubes look like feet. These tube feet are used for locomotion, exchange of gases and feeding. In most echinoderms the mouth is on the lower surface and the anus is on the upper surface.
  • Echinoderms reproduce sexually and the sexes are separate.
  • Some echinoderms like starfish (Asterias) and brittle stars (e.g., Ophiura) have arms arising from a central disc. Some, like sea urchins (Echinus), heart urchins (Echinocardium) and sea cucumbers (Holothuria) do not have arms. Sea cucumbers have tentacles near the mouth. Feather stars (Antedon) look like cups and have a branched anus.
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    Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    Which of the following are correct :

    (a) Echinoderms reproduce sexually and the sexes are separate.

    (b) Echinoderms reproduce asexually and they are hermeprodite.

    (c)  Echinoderms as adults are radially symmetrical.

    Right Option : C
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    Explanation
    Question : 2

    Radial symmetry is best seen in ________________

    Right Option : D
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    Explanation
    Question : 3

    Spiny skin is a characteristic feature of _________________

    Right Option : A
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    Explanation
     
     
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