Chapter 32

A graduate student finds an organism in a pond and thinks it is a freshwater sponge. A postdoctoral student thinks it looks more like an aquatic fungus. How can they decide whether it is an animal or a fungus? See Concept 32.1 (Page 672) Figure out whether it is autotrophic or heterotrophic. See if it reproduces sexually. Look for cell walls under a microscope. Determine whether it is unicellular or multicellular. See if it is a eukaryote or prokaryote

All animals can trace their lineage to a common ancestor that lived in the _____. See Concept 32.2 (Page 673) Jurassic Devonian Cenozoic Neoproterozoic era Pliocene

The earliest ancestors of about half of all extant animal phyla can be traced back to the _____ explosion. See Concept 32.2 (Page 675) Devonian Pleistocene Jurassic Carboniferous Cambrian

Which type of symmetry does each of the following animals display? Drag each picture to the appropriate bin.

Animal tissues develop from embryonic germ layers. Triploblastic animals have three germ layers (ectoderm, mesoderm, and endoderm) and three basic body plans related to body cavities (acoelomate, pseudocoelomate, and coelomate). Select the three statements that are true. To review the germ layers and the terminology associated with body cavities, see the Hints. In a coelomate, the tissue lining the inner side of the body cavity arises from the same germ layer as the lining of the digestive tract. A diploblast has no mesoderm. In a coelomate, the tissue lining the inner side of the body cavity arises from the same germ layer as the tissue lining the outer side of the body cavity. A pseudocoelom has the same functions as a true coelom. An acoelomate triploblast has no endoderm. In a pseudocoelomate, the tissue lining the inner side of the body cavity arises from the same germ layer as the muscles. The digestive tract of a coelomate functions as a coelom.

Many animals can be categorized as either protostomes and deuterostomes based on certain features of their embryonic development. Determine whether each of the following terms applies to only protostomes, only deuterostomes, both protostomes and deuterostomes, or neither.

Which of the following is radially symmetrical? See Concept 32.3 (Page 677) a dog an automobile a spoon a submarine sandwich a doughnut

Gastrulation is the process that directly forms the _____. See Concept 32.3 (Page 679) primary germ layers blastula central nervous system organs muscles

Which of the following is NOT a characteristic of all animals? See Concept 32.3 (Page 677) They are all multicellular. They are heterotrophic. They have tissues, organs, and organ systems. They are eukaryotes. They ingest their food.

An important trend in animal evolution was cephalization. An animal is said to show cephalization when it _____. See Concept 32.3 (Page 677) has bilateral symmetry has tissue specialization is large has an aggregation of sensory neurons at the anterior end has a hard, outer covering

Which of the following animals does NOT have a body cavity? See Concept 32.3 (Page 678) earthworm mouse clam flatworm nematode

During embryological development, the anus forms before the mouth in _____. See Concept 32.3 (Page 679) flatworms humans slugs earthworms arthropods

Which of the following statements is correct? See Concept 32.4 (Page 680) Eumetazoans have three embryonic tissue layers. The origin of all extant animal phyla can be traced to the Cambrian explosion. Sponges are diploblastic animals. All animals share a common ancestor. Most animal phyla belong to the clade Radiata.

Select the correct statement about the evolution of animals. The oldest generally accepted fossils of large animals range in age from 565 to 550 million years old. No animal fossils are found in strata formed before the Cambrian explosion. Approximately half the phyla of living organisms are found in Cambrian sediments.

Identify the features that distinguish animals from organisms in other multicellular kingdoms. Select all that apply. Animals are motile. Animals are ingestive heterotrophs. Animals have sensory organs at their anterior end.

Select the correct statement(s) about animal body plans. Select all that apply. Development in all animals is determined by the unique family of Hox genes (or other similar homeobox genes). All triploblastic animals possess a coelom. In both protostomes and deuterostomes, the blastopore develops into the mouth.

The figure shows a cross section of a coelomate showing a coelom and a cross section of a pseudocoelomate showing a pseudocoelom. What is the key difference between a coelom and a pseudocoelom? Pseudocoeloms arose early in animal evolution and evolved into coeloms. Only a coelom is fully lined with mesoderm tissue. A coelom is a true body cavity, whereas a pseudocoelom is a false coelom that is not fully functional.

Which feature of deuterostome development explains the formation of identical human twins? Deuterostomes have indeterminate development. In deuterostomes, the blastopore becomes the anus. Deuterostomes have radial cleavage.

Which of the following is (are) unique to animals? nervous system signal conduction and muscular movement flagellated gametes heterotrophy the structural carbohydrate, chitin

As you are on the way to Tahiti for a vacation, your plane crash lands on a previously undiscovered island. You soon find that the island is teeming with unfamiliar organisms, and you, as a student of biology, decide to survey them (with the aid of the Insta-Lab Portable Laboratory you brought along in your suitcase). You select four organisms and observe them in detail, making the notations found in the figure. Which organism would you classify as an animal? organism A organism B organism C organism D

Both animals and fungi are heterotrophic. What distinguishes animal heterotrophy from fungal heterotrophy is that most animals derive their nutrition by ________. preying on animals consuming living, rather than dead, prey ingesting materials using enzymes to digest their food

One hypothesis suggests that the Cambrian explosion was caused by the rise of predator-prey relationships. This hypothesis is best supported by an increased incidence of which of the following fossil traces? worm burrows hard parts organic material larger animals

While looking at some seawater through your microscope, you spot the egg of an unknown animal. Which of the following tests could you use to determine whether the developing organism is a protostome or a deuterostome? See whether the embryo _____. develops an archenteron exhibits spiral cleavage or radial cleavage develops a blastopore develops germ layers

Among protostomes, which morphological trait has shown the most variation? type of symmetry (bilateral versus radial versus none) type of development (protostome versus deuterostome) type of body cavity (coelom versus pseudocoelom versus no coelom) number of embryonic tissue types (diploblasty versus triploblasty)

What was an early selective advantage of a coelom in animals? A coelom _____. allowed asexual and sexual reproduction contributed to a hydrostatic skeleton, allowing greater range of motion was a more efficient digestive system allowed cephalization and the formation of a cerebral ganglion

Which of these statements, if accurate, would support the claim that the ancestral cnidarians had bilateral symmetry? Cnidarians have fewer Hox genes than bilaterians. All cnidarians are acoelomate. Cnidarian larvae possess anterior-posterior, left-right, and dorsal-ventral aspects. The presence of collar cells.

Use the information to answer the question. Trichoplax adhaerens 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 are nerve or muscle cells, and none of which have cell walls. Individual animals move using cilia, and any "edge" can lead. T. adhaerens 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. T. adhaerens sperm cells have never been observed, nor have embryos past the 64-cell (blastula) stage. T. adhaerens' body symmetry seems to be most like that of ________. worms most sponges tetrapods cnidarians

What is the probable sequence in which the following animal clades originated, from earliest to most recent? deuterostomes, bilaterians, amniotes, vertebrates, tetrapods deuterostomes, bilaterians, vertebrates, tetrapods, amniotes bilaterians, deuterostomes, vertebrates, tetrapods, amniotes bilaterians, deuterostomes, amniotes, vertebrates, tetrapods

The most ancient branch point in animal phylogeny is the characteristic of having _____. a body cavity or no body cavity radial or bilateral symmetry true tissues or no tissues diploblastic or triploblastic embryos

In the traditional phylogeny (A), the phylum Platyhelminthes is depicted as a sister taxon to the rest of the protostome phyla and as having diverged earlier from the lineage that led to the rest of the protostomes. In the molecular phylogeny (B), Platyhelminthes is depicted as a Lophotrochozoan phylum. What probably led to this change? The removal of the acoel flatworms (Acoela) from the Platyhelminthes allowed the remaining flatworms to be a monophyletic clade clearly tied to the Lophotrochozoa. Platyhelminthes' close genetic ties to the arthropods became clear as their Hox gene sequences were studied. Platyhelminthes ceased to be recognized as true protostomes. All Platyhelminthes must have a well-developed lophophore as their feeding apparatus.