SCIENTIFIC INQUIRY Int e rpr e t th e Data Redraw the bilaterian portion of Figure 32.11

Chapter 32, Problem 6

(choose chapter or problem)

SCIENTIFIC INQUIRY Int e rpr e t th e Data Redraw the bilaterian portion of Figure 32.11 for the nine phyla in the table below. Consider these blastopore fates: protostomy (mouth develops from the blastopore), deuterostomy (anus develops from the blastopore), or neither (the blastopore closes and the mouth develops elsewhere). Depending on the blastopore fate of its members, label each branch that leads to a phylum with P, D, N, or a combination of these letters. What is the ancestral blastopore fate? How many times has blastopore fate changed over the course of evolution? Explain. Blastopore Fate Phyla Protostomy (P) Platyhelminthes, Rotifera, Nematoda; most Mollusca, most Annelida; few Arthropoda Deuterostomy (D) Echinodermata, Chordata; most Arthropoda; few Mollusca, few Annelida Neither (N) Acoela Source: A. Hejnol and M. Martindale, The mouth, the anus, and the blastoporeopen questions about questionable openings. In Animal Evolution: Genomes, Fossils and Trees, eds. D. T. J. Littlewood and M. J. Telford, Oxford University Press, pp. 3340 (2009).