Exam 27: The Rise of Animal Diversity

Which of the following functions as both a mouth and an anus in members of the phylum Cnidaria?

If a multicellular animal lacks true tissues, then it can properly be included among the

Which of the following characteristics distinguishes modern humans from other modern apes? 1) Humans walk upright. 2) Humans walk on two legs. 3) Humans use simple tools. 4) Humans are capable of symbolic thought.

Which of the following genetic processes may be most helpful in accounting for the Cambrian explosion?

What is a primary, common evolutionary feature of all reptiles, mammals, and birds?

Which of the following statements would be least acceptable to most zoologists?

Which of the following are the only extant animals that descended directly from dinosaurs?

A new, sixth global mass-extinction event appears to be occurring on Earth today. The most likely explanation for the dramatic loss of species is

Please use the following information to answer the question(s) below. Trichoplax adhaerens (Tp) is the only living species in the phylum Placozoa. Individuals are about 1 mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about 2,000 cells, which are diploid (2n = 12). There are four types of cells, none of which is a nerve or muscle cell, and none of which has a cell wall. They move using cilia, and any "edge" can lead. Tp feeds on marine microbes, mostly unicellular green algae, by crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted onto the algae, and the resulting nutrients are absorbed. Tp sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage. -On the basis of the information in the previous paragraph, which of these should be able to be observed in Tp?

Table 27.1. Proposed Number of Hox Genes in Various Extant and Extinct Animals -All things being equal, which of these is the simplest explanation for the change in the number of Hox genes from the last common ancestor of insects and vertebrates to ancestral vertebrates, as shown in Table 27.1?

Fossil steroid and molecular clock evidence suggests that animals originated

Which of the following was probably the least important factor in bringing about the Cambrian explosion?

Which of the following clades contains the greatest number of animal species?

A student catches a ray-finned fish from the ocean and notices that attached to its flank is an equally long, snakelike organism. The attached organism has no external segmentation, no scales, a slimy substance on its surface, a round mouth surrounded by a sucker, a tongue, and two small eyes. The student thinks it might be a marine hagfish or a lamprey. Which feature excludes the organism from possibly being a lamprey?

Jaws first occurred in which extant group of fishes?

Please use the following information to answer the question(s) below. Figure 27.2 Fishes that have swim bladders can regulate their density and thus their buoyancy. There are two types of swim bladder: physostomous and physoclistous. The ancestral version is the physostomous version, in which the swim bladder is connected to the esophagus via a short tube (Figure 27.2). The fish fills this version by swimming to the surface, taking gulps of air, and directing them into the swim bladder. Air is removed from this version by "belching." The physoclistous version is more derived and has lost its connection to the esophagus. Instead, gas enters and leaves the swim bladder via special circulatory mechanisms within the wall of the swim bladder. -If a physoclistous fish removes gas from its swim bladder, this fish's density cannot actually change until that gas arrives at the

Which group's members have had both lungs and gills during their adult lives?

Please use the following information to answer the question(s) below. Placozoan evolutionary relationships to other animals are currently unclear, and different phylogenies can be created, depending on the characters used to infer relatedness. Placozoans are multicellular invertebrates with a simple structure of only two tissue layers and only four cell types. They have the smallest amount of DNA measured in any animal. In comparison, sponges have no tissues but about 20 cell types. One species of placozoans, 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. In the trees, the outgroup is a taxon that is outside the group of interest; members of the group of interest are more closely related to one another than to the outgroup. -Which tree(s) has (have) been created by emphasizing genomic features of placozoans?

What do all craniates have that earlier chordates did not have?

What is the probable sequence in which the following clades of animals originated, from earliest to most recent? 1) tetrapods 2) vertebrates 3) deuterostomes 4) amniotes 5) bilaterians