Exam 27: The Rise of Animal Diversity

Which of these, if true, would support the claim that the ancestral cnidarians had bilateral symmetry? 1. Cnidarian larvae possess anterior-posterior, left-right, and dorsal-ventral aspects. 2) Cnidarians have fewer Hox genes than bilaterians. 3) All extant cnidarians, including Nematostella, are diploblastic. 4) β-catenin turns out to be essential for gastrulation in all animals in which it occurs. 5) All cnidarians are acoelomate.

There is evidence that ray-finned fishes evolved

An elementary school science teacher decided to liven up the classroom with a saltwater aquarium. Knowing that saltwater aquaria can be quite a hassle, the teacher proceeded stepwise. First, the teacher conditioned the water. Next, the teacher decided to stock the tank with various marine invertebrates, including a polychaete, a siliceous sponge, several bivalves, a shrimp, several sea anemones of different types, a colonial hydra, a few coral species, an ectoproct, a sea star, and several herbivorous gastropod varieties. Last, she added some vertebrates-a parrotfish and a clownfish. She arranged for daily feedings of copepods and feeder fish. -One day, little Tommy (a student in an undersupervised class of 40 fifth graders) got the urge to pet Nemo (the clownfish), who was swimming among the waving petals of a pretty underwater "flower" that had a big hole in the midst of the petals. Tommy giggled upon finding that these petals felt sticky. A few hours later, Tommy was in the nurse's office with nausea and cramps. Microscopic examination of his fingers would probably have revealed the presence of

Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal heterotrophy is that only animals derive their nutrition by

Which shark structure is most analogous to a swim bladder full of gas?

In the traditional phylogeny (A), the phylum Platyhelminthes is depicted as a sister taxon to the rest of the protostome phyla, and as having diverged earlier from the lineage that led to the rest of the protostomes. In the molecular phylogeny (B), Platyhelminthes is depicted as a lophotrochozoan phylum. What probably led to this change?

A new species of aquatic chordate is discovered that closely resembles an ancient form. It has the following characteristics: external armor of bony plates, no paired lateral fins, and a suspension-feeding mode of nutrition. In addition to these, it will probably have which of the following characteristics?

Evidence of which structure or characteristic would be most surprising to find among fossils of the Ediacaran fauna?

Fossil evidence indicates that the following events occurred in what sequence, from earliest to most recent? 1. Protostomes invade terrestrial environments. 2) Cambrian explosion occurs. 3) Deuterostomes invade terrestrial environments. 4) Vertebrates become top predators in the seas.

How many of the following statements about craniates is (are) correct? 1. Craniates are more highly cephalized than are noncraniate chordates. 2) Craniates' genomic evolution includes duplication of clusters of genes that code for transcription factors. 3) The craniate clade is synonymous with the vertebrate clade. 4) Pharyngeal slits that play a major role in gas exchange originated in craniates. 5) The two-chambered heart originated with the early craniates.

Using similarities in embryonic development, body symmetry, and other anatomical features to assign an organism to a clade involves 1. cladistics based on body plan. 2) molecular-based phylogeny. 3) morphology-based phylogeny.

Chordate pharyngeal slits appear to have functioned first as

Which of these, if discovered among cycliophorans, would cause the most confusion concerning our current understanding of cycliophoran taxonomy?

Which of the following could be considered the most recent common ancestor of living tetrapods?

Placozoan evolutionary relationships to other animals are currently unclear, and different phylogenies can be created, depending on the character used to infer relatedness. Sponges have no tissues, but about 20 cell types. Tp (Trichoplax adhaerens) produces a neuropeptide almost identical to one found in cnidarians. The genome of Tp, although the smallest of any known animal, shares many features of complex eumetazoan (even human!) genomes. The next three questions refer to the phylogenetic trees that follow. I. II. III. -Which phylogeny has been created by emphasizing genomic features of placozoans?

At least one of these has been found in all species of eumetazoan animals studied thus far.

Organisms at which of the following trophic levels increased the most because of the movement of animals onto land?

Basing your inferences on information in the previous paragraph, to which clade(s) should cycliophorans belong? 1. Eumetazoa 2) Deuterostomia 3) Bilateria 4) Ecdysozoa 5) Lophotrochozoa

Arthropods invaded land about 100 million years before vertebrates did so. This most clearly implies that

Figure 27.1 -Which of the following factors, when used to label the horizontal axis of the graph in Figure 27.1, would account most directly for the shape of the plot?