Chapter 27, Problem 32A

Summary Introduction

To write:The larvae of organisms help scientists classify and determine the phylogeny of animals

Introduction:Chordates are species belonging to the phylum Chordata that at some stage during their development have four distinctive characteristics-a dorsal tubular nerve cord, pharyngeal pouches, a notochord and a postanal tail.

Explanation of Solution

The fishlike lancelets are closely related to saclike, sea squirts because of their dorsal tubular nerve cords, pharyngeal gill slits, notochords, and postanal tails, even if sea squirts have all these features only in their larvae. The notochord that flexible tough rod, provided support for the animal, and it also provided a place for muscles to attach. With this arrangement, chordates could swing their backs from side to side and swim through the water, a key development in the evolution of chordates.

Conclusion

Thus, it concludes thatwith this arrangement, chordates could swing their backs from side to side and swim through the water, a key development in the evolution of chordates.