What do sea stars, sea cucumbers, and sea urchins have in common?

A. Long, sharp spines


B. Thick, fleshy tentacles


C. Long, spindly arms


D. A water vascular system with tube feet|||D


Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures.





Tube feet function in locomotion and feeding. The tube feet in a sea star are arranged in grooves along the arms. They operate through hydraulic pressure. They are used to pass food to the oral mouth at the center, and can attach to surfaces. A sea star that is overturned simply turns one arm over and attaches it to a solid surface, and levers itself the right way up.|||D.


Echinoderms are characterized by radial symmetry, several arms (5 or more, mostly grouped 2 left - 1 middle - 2 right) radiating from a central body (= pentamerous). The body actually consists of five equal segments, each containing a duplicate set of various internal organs. They have no heart, brain, nor eyes, but some brittle stars seem to have light sensitive parts on their arms. Their mouth is situated on the underside and their anus on top (except feather stars, sea cucumbers and some urchins).





Echinoderms have tentacle-like structures called tube feet with suction pads situated at their extremities. These tube feet are hydraulically controlled by a remarkable vascular system. This system supplies water through canals of small muscular tubes to the tube feet (= ambulacral feet). As the tube feet press against a moving object, water is withdrawn from them, resulting in a suction effect. When water returns to the canals, suction is released. The resulting locomotion is generally very slow.|||A.





They are all part of Phyllum Echinodermata, meaning spined skin.|||In order to sort out between the different answers you get I would highly recommend to look at images of the various echinoderms you mention. If you know how they look like the answer will be obvious.|||D.|||B|||D is the answer......|||The word 'Sea'!


i choose A - long sharp spines|||they all live in the deep sea


thats my answer and i am sticking tooo it .