Several animal phyla are recognized for their lack of bilateral symmetry, and are thought to have diverged from other animals early in evolution. Among these, the sponges (Porifera) were long thought to have diverged first, representing the oldest animal phylum. They lack the complex organization found in most other phyla. Their cells are differentiated, but in most cases not organized into distinct tissues. Sponges typically feed by drawing in water through pores. However, a series of phylogenomic studies from 2008-2015 have found support for Ctenophora, or comb jellies, as the basal lineage of animals. This result has been controversial, since it would imply that that sponges may not be so primitive, but may instead be secondarily simplified. Other researchers have argued that the placement of Ctenophora as the earliest-diverging animal phylum is a statistical anomaly caused by the high rate of evolution in ctenophore genomes. COUNT 4
QSN1 Animal phyla that are recognized for their lack of bilateral symmetry are thought to have come from where? ANS1 other animals early in evolution QSN2 Which animal represents the oldest animal phyla? ANS2 sponges QSN3 How do sponges typically feed? ANS3 drawing in water through pores QSN4 During what time were a series of phylogenomic studies conducted that found support for comb jellies as the basal lineage of animals? ANS4 2008-2015