Chapter 33 HW:

Select the correct statement(s) describing nematodes.

- Nematodes lack a circulatory system and circular body wall muscles. - Some nematodes play important roles in nutrient cycling.

Select the correct statement(s) about invertebrate taxa.

- Tapeworms lack a mouth and gastrovascular cavity. - Ectoprocts lack a distinct head. - Rotifers are smaller than many protists.

Some invertebrates combine morphological simplicity with features of great structural or biochemical complexity. Select all correct examples of this statement.

- Trematodes are acoelomates that have effective defenses against attack by their hosts' immune system. - Cnidarians are diploblasts that produce complex, capsule-like organelles.

Read this The Guardian article and then answer the questions. 'The Smell Will Knock You Off Your Feet': Mass Mussel Die-Offs Baffle Scientists (The Guardian, 10/14/2019) Subscription to The Guardian provides instant access to breaking news with theguardian.com. Visit https://support.theguardian.com to subscribe.

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Which of the following statements about bilaterian animals is false?

Most bilaterians have tissues but some do not. - Bilaterian animals form an enormous clade whose members all have tissues (unlike sponges) as well as a two-sided or bilaterally symmetric form (unlike sponges and cnidarians). All bilaterally symmetric animals also are triploblastic. Bilaterians include both invertebrate and vertebrate animals.

You work for the Iowa Department of Natural Resources and are inventorying mussels in the Cedar River. You find similar results to those in this research. Which of the following is true?

Mussel populations are declining.

Your friend is studying a mass die-off of warblers in Canada. Which of the following is most likely to lead your friend to believe a pathogen is the cause?

Only warblers are affected.

The animal phylum most like the protists that gave rise to the animal kingdom is _____. See Concept 33.1 (Page 688)

Porifera - Evidence that supports this includes the lack of true tissue in sponges and the close similarity between choanocytes and choanoflagellates.

Based on the phylogenetic tree shown here, identify the basal taxon of metazoans (animals).

Porifera - The term basal taxon refers to a lineage that diverges from all other members of its group early in the history of the group. Hence, a basal taxon lies on a branch that originates near the common ancestor of the group. In this phylogenetic tree, Porifera is shown as the first group of metazoans (animals) to have diverged from all other metazoans, and so Porifera is the basal taxon of metazoans.

In order to restore mussel populations in U.S. rivers, which of the following would likely be best?

Restore rivers to their former natural state.

What evidence suggests that vertebrates are more closely related to echinoderms than are any other invertebrate phyla?

Shared DNA sequences - The clade Deuterostomia comprising chordates (including vertebrates) and echinoderms is defined primarily by DNA similarities. Read about deuterostomes. Return to Assignment

Your environmental science class visits a local stream to look for mussels. Where are you most likely to find some?

Sitting on the bottom of the stream.

Scientists have concluded that bdelloid rotifers have likely been asexual for 100 million years. What evidence supports this conclusion?

The comparison of the DNA of bdelloids and that of sexually reproducing rotifer species - Comparisons of the DNA of sexual and bdelloid rotifers indicate that the common ancestor to modern bdelloid rotifers lived about 100 million years ago. That suggests that this group has been asexual for this long. Read about bdelloid rotifers.

Which of the following is characteristic of the phylum Platyhelminthes? See Concept 33.3 (Page 692)

They are dorsoventrally flattened. - This is why they are also called flatworms

Which of the following is true of annelids? See Concept 33.3 (Page 701)

They perform gas exchange across their skin. - Cutaneous respiration occurs across their skins. Polychaetes have lateral extensions, called parapodia, which provide even more surface area for cutaneous respiration.

A marine biologist dredges up a small animal from the bottom of the ocean. It is uniformly segmented, with short, stiff appendages and soft, flexible skin. It has a complete digestive system and a closed circulatory system, plus multiple true coeloms. Based on this, you determine that the animal must be a(n) _____. See Concept 33.3 (Page 701)

annelid - The description matches the characteristics of annelids.

Members of the phylum Mollusca _____. See Concept 33.3 (Page 697)

are soft-bodied and often covered by a shell - Members of the phylum Mollusca are soft-bodied and are often covered by a shell.

What structure is responsible for gas exchange in most spiders? See Concept 33.4 (Page 704)

book lungs - The extensive surface area of book lungs is a structural adaptation that enhances the exchange of O2 and CO2 between the hemolymph and air.

A pseudocoelomate refers to an animal with a

functional body cavity lined by tissues derived from mesoderm and endoderm. - Most bilaterian animals have a body cavity, a fluid- or air-filled space located between the digestive tract and the outer body wall; this body cavity is also called a coelom. A so-called "true" coelom forms from tissue derived from mesoderm, and the animals with a true coelom are known as coelomates. Some bilaterian animals have a body cavity that is formed from both mesoderm and endoderm. Such a cavity is called a "pseudocoelom," and the animals with a pseudocoelom are called pseudocoelomates. Despite its name, however, a pseudocoelom is not false; it is a fully functional body cavity.

Which of the following is a characteristic of cnidarians? See Concept 33.2 (Page 689)

gastrovascular cavity - The gastrovascular cavity, characterized by a single opening, is the digestive compartment of cnidarians

Ectoprocts and brachiopods are collectively referred to as __________. See Concept 33.3 (Page 696)

lophophorates - The lophophore is a structure common to these two phyla that bear ciliated tentacles.

Some species of rotifers consist solely of females. Their method of reproduction is described as _____. See Concept 33.3 (Page 695)

parthenogenesis - The females lay unfertilized eggs that develop into females.

Which of the following are thought to be most closely related to humans? See Concept 33.5(Page 711)

sea stars - Humans and sea stars are deuterostomes.

If trends in mussel populations continue, which of the following is most impacted in fresh waters?

water filtration Submit