Exam 27: The Rise of Animal Diversity

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

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. -Had the teacher wanted to point out organisms that belong to the most successful animal phylum, the teacher should have chosen the

Table 27.1. Proposed Number of Hox Genes in Various Extant and Extinct Animals -All things being equal, which of these is the most parsimonious 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?

Which of the following statements concerning animal taxonomy is (are) true? 1. Animals are more closely related to plants than to fungi. 2) All animal clades based on body plan have been found to be incorrect. 3) Kingdom Animalia is monophyletic. 4) Only animals reproduce by sexual means. 5) Animals are thought to have evolved from flagellated protists similar to modern choanoflagellates.

Which statement is most consistent with the hypothesis that the Cambrian explosion was caused by the rise of predator-prey relationships?

Which of the following is true of members of the phylum Cnidaria?

The feeding mode of the extinct conodonts was

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. -In how many of the following ways is Tp unlike the typical animal? 1. Tp is multicellular. 2) Tp lacks muscle and nerve cells. 3) Tp has cilia. 4) Tp has a different place where digestion of food occurs. 5) Tp lacks cell walls.

What do animals as diverse as corals and monkeys have in common?

The most recently discovered phylum in the animal kingdom (1995) is the phylum Cycliophora. It includes three species of tiny organisms that live in large numbers on the outsides of the mouthparts and appendages of lobsters. The feeding stage permanently attaches to the lobster via an adhesive disk, and collects scraps of food from its host's feeding by capturing the scraps in a current created by a ring of cilia. The body is sac-like and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are eucoelomate, do not molt (though their host does), and their embryos undergo spiral cleavage. -Which of these features is least useful in assigning the phylum Cycliophora to a clade of animals?

Which of the following animal groups is entirely aquatic?

The most ancient branch point in animal phylogeny is that between having

Fossil steroid and molecular clock evidence suggests that animals originated

Terry 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 round mouth surrounded by a sucker, and two small eyes. Terry thinks it might be a marine leech, a hagfish, or a lamprey. -Which feature excludes the organism from possibly being a leech?

Cycliophorans have two types of larvae. One type of larva is produced when the digestive system of a female is impregnated by a male. The digestive system then collapses and develops into a larva, which swims away in search of a new host after the surrounding female dies. Which is the embryonic tissue that is apparently most important in forming this type of larva?

As a result of harvesting a higher proportion of older and larger cod and other fish species for food

If a physoclistus fish removes gas from its swim bladder, this fish's density cannot actually change until that gas arrives at the

Whatever its ultimate cause(s), the Cambrian explosion is a prime example of

Match the extant vertebrate group with the description. Internal fertilization, leathery amniotic egg, and skin that resists drying are characteristics of

We should expect the inner wall of the swim bladder to be lined with tissue that is derived from