Among the characteristics unique to animals is :
2. Open Ended
The distinction between sponges and other animal phyla is based mainly on the absence versus the presence of
-a body cavity.
- a complete digestive tract.
-a circulatory system.
- true tissues.
3. Open Ended
Which of these is a point of conflict between the phylogenetic analyses presented in Figures 32.10 and 32.11?
-the monophyly of the animal kingdom
- the relationship of taxa of segmented animals to taxa of nonsegmented animals
- that sponges are basal animals
- that chordates are deuterostomes
- the monophyly of the bilaterians
4. Open Ended
Acoelomates are characterized by
- the absence of a brain.
- the absence of mesoderm.
- deuterostome development.
-a coelom that is not completely lined with mesoderm.
- a solid body without a cavity surrounding internal organs.
5. Open Ended
Which of the following was probably the least important factor in bringing about the Cambrian explosion?
- the emergence of predator-prey relationships among animals
- the accumulation of diverse adaptations, such as shells and different modes of locomotion
- the movement of animals onto
- the evolution of Hox genes that controlled development
- the accumulation of sufficient atmospheric oxygen to support the more active metabolism of mobile animals
6. Open Ended
What is the main basis for placing the arthropods and nematodes in Ecdysozoa in one hypothesis of animal phylogeny?
-Animals in both groups are segmented.
- Animals in both groups undergo ecdysis.
-They both have radial, determinate cleavage, and their embryonic development is similar.
-Fossils reveal a common ancestor of the two phyla.
-Analysis of genes shows that their sequences are quite similar, and these sequences differ from those of the lophotrochozoans and deuterostomes.