Exam 33: An Introduction to Invertebrates

Imagine that you are a research chemist who wishes to develop a chemical adhesive that will work under water. Which of the following organisms might give you a clue about where to start?

The heartworms that can accumulate within the hearts of dogs and other mammals have a pseudocoelom, an alimentary canal, and an outer covering that is occasionally shed. To which phylum does the heartworm belong?

Without genetic variation, evolution cannot occur. Sexual reproduction leads to increased genetic variation, but male bdelloid rotifers have never been observed. Which of the following are correct statements with regard to evolution in bdelloid rotifers?

You find what you believe is a new species of animal. Which of the following characteristics would enable you to argue that it is more closely related to a flatworm than it is to a roundworm?

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

In a rock pool, a student encounters an organism with a hard outer covering that contains much calcium carbonate, an open circulatory system, and gills. The organism could potentially be a crab, a shrimp, a barnacle, or a bivalve. The presence of which of the following structures would allow for the most certain identification of the organism?

Which one of these mollusc groups can be classified as "suspension feeders"?

A primary 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. The bivalves started to die one-by-one; only the undamaged shells remained. To keep the remaining bivalves alive, the teacher would most likely need to remove the ________.

Imagine that you are a graduate student seeking an idea for a research project that will help us understand the evolution of a parasitic lifestyle from a free-living lifestyle. Which of the following outcomes would you expect if you compare the genes of parasitic species to relatives that are free-living?

In the figure, assume that the two medusae shown at step 4 were produced by one polyp colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to evaluate whether the following sentence is true or false; if false, select the answer that provides the correct reason. Although the two medusae are genetically identical, a sperm produced by one will differ genetically from an egg produced by the other.

Sponges ________.

A primary 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. -One day, Tommy, a student in an under-supervised class of 40 Year 5 students, got the urge to pet Nemo (the clown fish), 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 ________.

What would be the most direct effect of removing or damaging an insect's antennae? The insect would have trouble ________.

The crown-of-thorns sea star, Acanthaster planci, preys on the flesh of live coral. If coral animals are attacked by these sea stars, then what actually provides nutrition to the sea star, and which chemical (besides the toxin within their nematocysts) do the corals rely on for protection?

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 hypothesise that their translucent bodies make them hard to spot by predators. How could you directly test this hypothesis?

A primary 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. -The teacher and class were especially saddened when the colonial hydrozoan died. They had watched it carefully, and the unfortunate creature never even got to produce offspring by budding. Yet, everyone was elated when one of the students noticed a small colonial hydrozoan growing in a part of the tank far from the location of the original colony. The teacher was apparently unaware that these hydrozoans exhibit ________.

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 defenceless morsels for predators. In fact, sea slugs have multiple defences. 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 coloured sea slugs are often highly toxic, others are nontoxic and mimic the colouration of the toxic species. Their colours are mostly derived from pigments in their prey. There are also sea slugs that use their colouration 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 ________.

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. (C. J. Klok, R. D. Mercer, and S. L. Chown. 2002. Discontinuous gas-exchange in centipedes and its convergent evolution in tracheated arthropods. Journal of Experimental Biology 205:1019-29.) Copyright 2002 The Company of Biologists and the Journal of Experimental Biology. Look at the graph for Scutigerina weberi (note the scale of the y-axis) in the figure. -How would a terrestrial centipede most likely benefit from the ability to close its spiracles? Closing spiracles would ________.

The sea slug Pteraeolidia ianthina can harbour living dinoflagellates (photosynthetic protists) in its skin. These endosymbiotic dinoflagellates reproduce quickly enough to maintain their populations. Low populations do not affect the sea slugs very much, but high populations (> 5 × 105 cells/mg of sea slug protein) can promote sea slug survival. Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates. According to the graph, during which season(s) of the year is the relationship between the sea slug and its dinoflagellates closest to being commensal?

Large animals need specialised organs for gas exchange because ________.