Question

Hypothesize an evolutionary relationship among the bipinnaria 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 breed their young generally lack a

bipinnaria stage, with the eggs developing directly into miniature adults.

Tunicates which are large group of marine animals , and their recent common ancestry with tadpoles is reflected in the tadpole-like larvae of most tunicates.They are also called as urochordates.

Fish like chordate,lancelet and amphioxi respire mostly through the skin.The use of gill slits for feeding rather than respiration is characteristic of the lower chordates.

Answer 2

-Not completely understood, share echinoderm and chordate characteristics
-Chordates/them have pharnygeal slits
-Ambulacraria hypothesis unites echinoderms and hemichordates on the basis of a shared diffuse epidermal nervous system
-Shared tripartite coelom in hemichordates/echinoderms
-Buccal diverticulum now believed to be a synapomorphy of hemichordates only
-Early embryogenesis of hemichordates similar to echinoderms
-Tornaria larva almost identical to bipinnaria larva, suggesting that hemichordates/echinoderms are sister groups
-Sequence analysis of the gene encoding the small subunit of rRNA supports a deuterostome clade