Exam 33: An Introduction to Invertebrates

Toilets are a modern convenience that people often take for granted. In fact, they are helpful in preventing spread of disease because ________.

In terms of food capture, which sponge cell is most similar to the cnidocyte of a cnidarian?

The sharp, inch-long thorns of the crown-of-thorns sea star are its spines. These spines, unlike those of most other sea stars, contain a potent toxin. If it were discovered that crown-of-thorns sea stars do not make this toxin themselves, then the most likely alternative would be that this toxin is ________.

A terrestrial animal species is discovered with the following larval characteristics: exoskeleton, system of tubes for gas exchange, and modified segmentation. A knowledgeable zoologist should predict that the adults of this species would also feature ________.

Use the information to answer the following question. The nontaxonomic term sea slug encompasses a wide variety of marine gastropods. One feature they share as adults is the lack of a shell. One might think, therefore, that they represent defenseless morsels for predators. In fact, sea slugs have multiple defenses. Some sea slugs prey on sponges and concentrate sponge toxins in their tissues. Others feed on cnidarians, digesting everything except the nematocysts, which they then transfer to their own skins. Whereas the most brightly colored sea slugs are often highly toxic, others are nontoxic and mimic the coloration of the toxic species. Their colors are mostly derived from pigments in their prey. There are also sea slugs that use their coloration to blend into their environments. This nudibranch, a type of sea slug, has many reddish cerata on its dorsal surface, as well as two white-tipped rhinophores located on the head. The nematocysts most likely reach the skin of sea slugs through branches of the ________.

Which of the following combinations correctly matches a phylum to its description?

Use the following information and figures to answer the question. Many terrestrial arthropods exchange gases with their environments by using tracheae, tubes that lead from openings (called spiracles)in the animal's exoskeleton or cuticle directly to the animal's tissues. Some arthropods can control whether their spiracles are opened or closed; opening the spiracles allows the carbon dioxide produced in the tissues to travel down the tracheae and be released outside the animal. Klok et al. measured the carbon dioxide emitted over time (represented by ⱽCO₂)by several species of centipedes. The figures present graphs of their results for two species, Cormocephalus morsitans and Scutigerina weberi. Compare the graphs in the figure of carbon dioxide (CO₂)emission for Cormocephalus morsitans and Scutigerina weberi. What hypothesis can you make about each centipede's habitat?

Whiteflies are common pest insects found on cotton, tomato, poinsettia, and many other plants. Nymphs are translucent and mostly sessile, feeding on their host plant's phloem (sap)from the undersides of leaves. They undergo incomplete metamorphosis into winged adults. Because whitefly nymphs cannot escape predation by moving, you hypothesize that their translucent bodies make them hard to spot by predators. How could you directly test this hypothesis?

Which characteristic is shared by cnidarians and flatworms?

Molecular studies have changed many of the phylogenetic relationships previously identified by morphological studies. These changes indicate that ________.

The sea slug Elysia chorotica has no nematocysts or dinoflagellates but, rather, has "naked" chloroplasts in its skin. The chloroplasts are all that remain of the seaweed (Vaucheria sp.)that Elysia feeds upon. The chloroplasts are transferred to the skin; consequently, this slug is green. It spends most of its time basking in shallow water on the surface of seaweeds. How should we expect its chloroplasts to benefit the Elysia sea slug?

Use the following information to answer the question. 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. Lastly, she added some vertebrates-a parrot fish and a clown fish. She arranged for daily feedings of copepods and feeder fish. Normally, the clown fish readily swims among the tentacles of the sea anemones; the parrot fish avoids them. One hypothesis for the clown fish's apparent immunity is that they slowly build a tolerance to the sea anemone's toxin. A second hypothesis is that a chemical in the mucus that coats the clown fish prevents the nematocysts from being triggered. Which of the following graphs supports the second, but not the first, of these hypotheses?

Use the following information to answer the question. The phylum Cycliophora was discovered in 1995. They are 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 saclike and has a U-shaped intestine that brings the anus close to the mouth. Cycliophorans are coelomates, 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?

What would be the best anatomical feature to look for to distinguish a gastropod from a chiton?

The presence of a lophophore in a newly discovered species would suggest that the species ________.

Molecular studies have changed many of the phylogenetic relationships previously identified by morphological studies. An example of such a change is ________.

Which of the following statements is correct with respect to the evolutionary relationship between chordates and invertebrates?

Which of the following animal groups is entirely aquatic?

Which of the following is most likely to be aquatic?

Use the following information and figures to answer the question. Many terrestrial arthropods exchange gases with their environments by using tracheae, tubes that lead from openings (called spiracles)in the animal's exoskeleton or cuticle directly to the animal's tissues. Some arthropods can control whether their spiracles are opened or closed; opening the spiracles allows the carbon dioxide produced in the tissues to travel down the tracheae and be released outside the animal. Klok et al. measured the carbon dioxide emitted over time (represented by ⱽCO₂)by several species of centipedes. The figures present graphs of their results for two species, Cormocephalus morsitans and Scutigerina weberi. Look at the graph for Scutigerina weberi (note the scale of the y-axis)in the figure. What is the best interpretation of these results?