Question

Hypothesize an evolutionary relationship among the bipinnarial larva of echinoderms, larval and adult tunicates, and lancelets.

Answer 1

The first stage in the larval development of most of the starfish is bipinnarial. It is usually followed by abrachiolaria stage. Its movement and feeding is accomplished by the bands of cilia. Starfish that brood their young generally lack a bipinnaria stage, with the eggs developing directly into miniature adults.
Tunicates, large group of marine animals whose recent common ancestry with vertebrates is reflected in the tadpole-like larvae of most tunicates. They are aalso called as urochordates.

Fish like chordate, Lancelets or amphioxi respire mostly through the skin. The use of the gill slits for feeding rather than respiration is characteristic of the lower chordates. They having a dorsal notochord, or stiffening rod, extending from tip to tail, that gives it its characteristic pointed