bio chap 31

53) Which of the following is a way that crayfish and grasshoppers are different? A) Crayfish have an exoskeleton, while grasshoppers do not. B) Grasshoppers have compound eyes, while crayfish have a simple eye. C) Grasshoppers have well-developed nervous systems, while crayfish have a ladder network of nerves. D) Grasshoppers have spicules and tracheal tubes that serve as the means of gas exchange, while crayfish have gills. E) Crayfish have an open circulatory system, while grasshoppers have a closed circulatory system.

Answer: D Explanation: It is true that grasshoppers have spicles and traceheal tubes for gas exchange while crayfish use gills. All arthropods have an external exoskeleton, and a body with fused segments, although the number of segments varies. All arthropods also have jointed appendages, some of which are specialized in obtaining food and in bearing sensory systems, including compound eyes. In addition, they have well-developed nervous systems and digestive systems as well as reproductive systems. The circulatory system for all arthropods is an open system where a fluid bathes the tissues and internal structures.

46) Which of the following organisms exhibit complete metamorphosis? A) crayfish B) starfish C) grasshoppers D) butterfly E) lobsters

Answer: D Explanation: Many insects undergo a change in form and physiology as they develop into an adult. In incomplete metamorphosis, the young nymphs resemble the adult but are smaller and do not have wings. In complete metamorphosis, the development involves drastic changes and one stage does not resemble the next. The stages are typically larva, pupa, and adult. The butterfly goes through all of these stages.

28) If you live on a river delta or coastline, you may not be able to eat the local clams because of high levels of toxins present in the water. Why? A) Clams seasonally produce toxic substances. B) Clams regularly consume poisonous red tide organisms. C) Most native clams have been replaced by harmful exotic species. D) Clams are filter-feeders and pollutants in the water become concentrated in their tissues. E) The toxins contained in clams cannot be detoxified in the human digestive tract.

Answer: D Explanation: Shellfish are filter feeders that collect food that is suspended in the water. Food particles become trapped in the mucus on the gills and are then swept toward the mouth by the action of cilia. Toxins found in the detritus upon which they feed would be concentrated in the tissues of the shellfish.

18) Which of the following infections is associated with a flatworm? A) hookworm B) trichinosis C) elephantiasis D) tapeworm E) pinworm

Answer: D Explanation: Tapeworms are a type of flatworm and are classified in phylum Platyhelminthes. All of the other answer choices are infections due roundworms (nematodes).

42) Which group of animals have three pairs of legs, a tympanum for reception of sound waves, and Malpighian tubules for excretion? A) starfish B) lancelets C) crayfish D) grasshoppers E) earthworms

Answer: D Explanation: The excretory system of grasshoppers consists of Malpighian tubules that extend into the hemocoel and collect nitrogenous wastes that are then excreted into the digestive tract. In addition, grasshoppers have a tympanum for the reception of sound waves; grasshoppers use courtship sounds by rubbing body parts (such as legs) together. The tympanum allows the reception of these signals.

21) The head region of a tapeworm is called the A) proglottid. B) cercaria. C) sporocyst. D) scolex. E) glycocalyx.

Answer: D Explanation: The head region of a tapeworm is called the scolex and contains hooks to attach to the intestinal wall and suckers for feeding.

62) The madreporite helps the sea star A) reproduce. B) locate food. C) digest food and distribute it to the arms. D) regulate its vascular system. E) keep its surface clean of algae and barnacles and debris.

Answer: D Explanation: The madreporite, or sieve plate, allows water to flow into or out of the water vascular system of a sea star.

63) The nervous system of a sea star includes A) no actual nerve cells. B) a complex of nerve ganglia in each ray. C) a central nervous system, including a brain. D) a central nerve ring that gives off radial nerves in each arm. E) a dorsal hollow nerve cord.

Answer: D Explanation: The nervous system of a sea star consists of a central nerve ring found in the central disk and radial nerves that extend into each arm. At the end of each arm there is a light-sensitive eyespot.

56) The term deuterostome refers to A) having a spiny skin. B) having three germ layers. C) possessing a notochord. D) the second embryonic opening becoming the mouth. E) the coelom forming by outpocketing of the primitive gut.

Answer: D Explanation: The term deuterostome is from the Greek, "deuteros," meaning "second" and "stoma," meaning "mouth"; so the term refers to the formation of the mouth from the second opening. A deuterostome is a developmental stage where the second embryonic opening becomes the mouth and an outpocketing by the primitive gut becomes the coelom.

25) Larval Trichinella worms live in the A) liver. B) lungs. C) lymph glands. D) skeletal muscle of pork. E) water.

Answer: D Explanation: Trichinosis is caused by a roundworm. Trichinosis can be contracted by consuming undercooked pork.

30) Which of the following is a characteristic of earthworms? A) segmentation B) expanded dorsal surface of the intestine called a typhlosole C) hermaphroditic D) paired nephridia in each segment E) All of the answer choices are characteristics of earthworms.

Answer: E Explanation: All of the answer choices are characteristics of earthworms.

6) Which of the following statements is/are true about deuterostomes? A) The second opening during embryonic development becomes the mouth. B) Echinoderms are deuterostomes. C) Deuterostomes have a coelom. D) Deuterostomes have radial cleavage. E) All of the answer choices are true statements about deuterstomes.

Answer: E Explanation: All of the answer choices are true statements about deuterostomes.

13) Which of the following statements is correct about the flatworms? A) Flatworms have three complete tissue layers. B) Flatworms may be either free living or parasitic. C) Flatworms have a sac body plan, with only a mouth and no anus. D) Most planaria are found in marine environments, but some dwell in freshwater and moist terrestrial environments. E) All of the answer choices describe flatworms.

Answer: E Explanation: All of the answer choices are true statements about flatworms.

2) Which statement is true about invertebrate animals? A) The vast majority of animal species are invertebrates. B) Many invertebrate species live in a marine environment. C) Most animal phyla are invertebrates. D) All major invertebrate groups arose from protistan ancestors. E) All of the answer choices are true statements about invertebrates.

Answer: E Explanation: All of the answer choices are true statements about invertebrates.

23) Which of the following statements is/are correct about the roundworms? A) There are three layers of tissues in the body. B) Roundworms have a tube-within-a-tube body plan. C) There is an internal body cavity called a pseudocoelom. D) Roundworms have a smooth, unsegmented outside body wall. E) All the answer choices are true statements about roundworms.

Answer: E Explanation: All of the answer choices are true statements about roundworms.

1) Which of the following is a characteristic of all animals? A) They ingest food that is digested in a central cavity. B) Usually undergo sexual reproduction. C) They produce an embryo that undergoes development in stages. D) The adult form is diploid. E) All of the answer choices describe characteristics of animals.

Answer: E Explanation: All of the answer choices describe characteristics of animals.

59) Which of the following is a characteristic of echinoderms? A) radial symmetry in adults B) endoskeleton of spiny, calcium-rich plates C) bilateral symmetry in larva D) both sexual and asexual reproduction E) All of the answer choices describe characteristics of echinoderms.

Answer: E Explanation: All of the answer choices describe characteristics of echinoderms.

51) The life cycle of animals A) demonstrates alternation of generations, where the zygote is haploid and the adult is diploid. B) does not demonstrate alternation of generations. Both the zygote and the adult are haploid. C) demonstrates alternation of generations, where the zygote is diploid and the adult is haploid. D) does not demonstrate alternation of generations because only the spores are haploid. E) does not demonstrate alternation of generations; gametes are haploid and the organism is diploid.

Answer: E Explanation: Alternation of generations is seen in plants and describes a life cycle where both the haploid and diploid phases are multicellular. In animals, only the diploid organism is multicellular.

37) A major characteristic of the arthropods is the presence of A) flame cells. B) radial symmetry. C) a soft exoskeleton. D) a closed circulatory system. E) jointed appendages.

Answer: E Explanation: Arthropods have a rigid exoskeleton that completely covers the organism. They also have segments that each have a pair of jointed appendages attached.

27) Which of these is a bivalve? A) slug B) octopus C) earthworm D) snail E) oyster

Answer: E Explanation: Bivalves have shells that come in two parts that are connected by a hinge; the one organism listed that has two shells is the oyster.

52) In which way are crayfish and grasshoppers similar? A) Both have tympanum for use in mating rituals. B) Both have Malpighian tubules that function in the extraction of nitrogenous waste. C) Both have spicules and a tracheal system for respiration. D) Both have bodies that are composed of a cephalothorax and abdomen. E) Both have antennae that have a sensory function.

Answer: E Explanation: Both grasshoppers and crayfish have antennae. Only grasshoppers have tympanum and Malpighian tubules, while green glands are specific to crayfish. The body of a crayfish is fused into two sections, while the grasshopper is divided into three sections. Crayfish use gills to exchange gasses, while the grasshopper uses spicules and tracheal tubes.

58) Which of the following would be classified in a phylum other than Echinodermata? A) sea star B) sea urchin C) sea cucumber D) sand dollar E) crayfish

Answer: E Explanation: Crayfish are classified in phylum Arthropoda because of their jointed appendages and exoskeleton.

41) An arachnid differs from a crustacean because A) arachnids have book gills. B) arachnids are mostly aquatic and crustaceans are mostly terrestrial. C) only arachnids shed their exoskeletons. D) arachnids have two major body segments, the cephalothorax and abdomen, while crustaceans have three body segments. E) arachnids have four pairs of walking legs.

Answer: E Explanation: Crustaceans are named for their hard shells; their exoskeleton is calcified to a greater extent than other arthropods. In crustaceans, such as the crayfish, the thorax has five sets of walking legs and the first set is a pinching claw. Arachnids have a cephalothorax that bears six pairs of appendages: the chelicerae and the pedipalps, and four pairs of walking legs. The cephalothorax is followed by an abdomen that contains internal organs.

11) One of the many interesting features of flatworms are flame cells. What are flame cells used for? A) light detection B) storing sperm C) digestion of food D) generating body heat E) excretion of excess water

Answer: E Explanation: Flame cells are ciliated cells found in flatworms and function to pull fluid through pores to the outside, helping to maintain osmotic balance with the outside environment.

16) Which of the following is characteristic of flukes? A) Flukes are ectoparasites of invertebrates. B) Most flukes have separate sexes. C) Flukes are covered by a ciliated integument. D) Flukes possess an oral sucker that is surrounded by a nonsensory papilla. E) Flukes have a well-developed alimentary canal.

Answer: E Explanation: Flukes are endoparasites that have a tough nonciliated integument. The anterior end has an oral sucker that is surrounded by sensory papilla. Most flukes are hermaphroditic, containing both male and female reproductive structures. While the digestive system is less developed than free-living flatworms, the alimentary canal is well developed.

8) Which of the following organisms has a true coelom? A) sponges B) hydras C) flatworms D) roundworms E) earthworms

Answer: E Explanation: Of all the animals listed, only earthworms have a true coelom. Sponges lack true tissue. Hydras have two layers of tissue in the embryos. Flatworms are acoelomates with a digestive cavity. Roundworms are pseudocoelomates.

40) Which of the following is a feature of arthropods? A) a solid ventral nerve cord B) a variety of respiratory organs C) a well-developed nervous system D) jointed appendages and a segmented body E) All of the answer choices describe features of arthropods.

Answer: E Explanation: Once the exoskeleton has been formed, it is hard and will not expand; in order to grow, it is necessary for arthropods to shed the existing exoskeleton and produce a new, larger one.

24) Which of these parasitic worms is a fluke? A) Ascaris B) Trichinella C) the worm that causes elephantiasis D) hookworm E) the worm that causes schistosomiasis

Answer: E Explanation: Schistosomiasis mansoni is a type of blood fluke which is found in the phylum Platyhelminthes. All of the remaining answers are examples of nematodes.

20) An adaptation exhibited by the tapeworm for survival in a host's intestine is A) proglottids coated with calcium carbonate. B) alkaline secretions from the scolex. C) a protective lining of chitin. D) releasing eggs before the proglottids reach the intestinal tract. E) a tough integument resistant to the digestive fluids of the host.

Answer: E Explanation: Tapeworms have a tough integument, a specialized body covering resistant to the digestive juices of the host.

64) Sea stars reproduce A) by budding. B) by binary fission. C) asexually by fragmentation. D) by sexual processes only. E) by sexual means and also by asexual fragmentation.

Answer: E Explanation: The reproductive system of sea stars consists of gonads and produces either eggs or sperm. They can also reproduce asexually by fragmentation; any fragment can produce a new sea star as long as it contains part of the central disk.

15) Tapeworms are ectoparasites od various vertebrates, including humans.

Answer: FALSE Explanation: Tapeworms are endoparasites (internal parasites) of various vertebrates, including humans.

14) What part of a tapeworm contains both male and female sex organs and becomes filled with developing embryos? A) proglottids B) scolex C) cyst D) gastrovascular cavity E) nematocyst

Answer: A Explanation: A tapeworm contains long series of units called proglottids which contain both male and female sex organs. They fertilize their own eggs. These fertilized units break off and are excreted in the host's feces.

3) Animals that have no particular symmetry exhibit A) asymmetry. B) radial symmetry. C) bilateral symmetry. D) trilateral symmetry. E) spherical symmetry.

Answer: A Explanation: Animals that have no discernable symmetry are asymmetric and include sponges. Radial symmetry is found in jellyfish and shows a circular organization radiating out from a central point. Bilateral symmetry is found in humans and shows organization into two halves (right and left) and tend to have cephalization.

34) Earthworms are A) annelids. B) molluscs. C) echinoderms. D) platyhelminthes. E) arthropods.

Answer: A Explanation: Annelida include earthworms and are segmented with a hydrostatic skeleton and a closed circulatory system. Molluscs include clams, snails, and squids and all have a foot, mantle, and visceral mass. Echinoderms include star fish and are characterized by a water vascular system and a thin epidermis covering an endoskeleton of calcareous plates. Platyhelminthes are flatworms like tapeworms and flukes. Arthropoda includes crustaceans, insects, and spiders and are characterized by an exoskeleton, an open circulatory system, and well-developed sensory organs.

67) Which description best fits the lophotrochozoa? A) As embryos, they have three germ layers that will develop into the organ level of organization as adults. B) As embryos, they have two germ layers that will develop into the tissue level of organization as adults. C) Lophotrochozoa are deuterostomes. D) Lophotrochozoa are primarily a terrestrial group. E) The lophophore, a flagellated appendage, is used to define members of this group.

Answer: A Explanation: As embryos, they have three germ layers that will develop into the organ level of organization as adults. Lophotrochozoa are protostomes. Lophotrochozoa are primarily an aquatic group. The lophophore is a ciliated tentacle-like feeding apparatus that is used to define members of this group.

19) A tapeworm infection could result from A) eating insufficiently cooked pork. B) being bitten by a mosquito. C) ingesting eggs in contaminated water. D) eating freshly peeled fruit. E) wading in contaminated water.

Answer: A Explanation: Larvae in the secondary host, a pig, burrow through the intestinal wall and travel in the bloodstream to finally encyst and lodge in the muscle. These cysts can be passed to a new host if the meat is not heated sufficiently to kill the larvae.

66) Which type of animal symmetry produces mirror images no matter how the animal is sliced longitudinally? A) radial symmetry B) asymmetrical symmetry C) bilateral symmetry D) asymmetrical symmetry and bilateral symmetry E) None of the answer choices is correct.

Answer: A Explanation: Radial symmetry means that the animal is organized circularly, so that no matter how the animal is sliced longitudinally it produces mirror images. Asymmetrical symmetry means that they have no particular symmetry. Bilateral symmetry means that the animal has definite right and left halves. The only cut that produces a mirror image is down the center of the animal.

48) Which pair exhibits the closest phylogenetic relationship? A) spider—tick B) housefly—mite C) earthworm—grasshopper D) crayfish—planarian E) scorpion—clam

Answer: A Explanation: Spiders and ticks are both arachnids and share many of the same traits. Houseflies are insects, while mites are arachnids. Earthworms and grasshoppers are in different phyla; Annelida and Arthropoda, respectively. Crayfish and planaria are in different phyla; Arthropoda and Platyhelminthes, respectively. Scorpions and clams are in different phyla; Arthropoda and Mollusca, respectively.

57) Which statement about echinoderms is inaccurate? A) The exoskeleton is made up of bony tissue. B) Gas exchange occurs through gills on the skin. C) Larvae are free-swimming and bilaterally symmetrical. D) A water vascular system allows the tube feet to produce suction. E) Symmetry is radial in the adult, usually with parts in fives or multiples of five.

Answer: A Explanation: The endoskeleton of echinoderms is made of spine-bearing calcium-rich plates, not bony tissue.

22) The segments of a tapeworm consisting primarily of eggs, which are located behind the head, are called A) proglottids. B) cercariae. C) sporocysts. D) scolexes. E) glycocalyxes.

Answer: A Explanation: The proglottids are segments that contain the male and female reproductive structures of the tapeworm. They are located in a long chain behind the scolex.

45) The insect organ most equivalent to the human lung in function is the A) tracheae. B) midgut. C) crop. D) gizzard. E) Malpighian tubule.

Answer: A Explanation: The respiratory system of insects consists of openings in the exoskeleton called spiracles. Air is actively pumped into the spiracles by the alternate contraction and expansion of the body wall. Once inside, the air moves into the trachea, small multibranched tubes that are the actual sites of gas exchange. The trachea is most closely equivalent to the human lung since these are also sites of gas exchange.

61) If the water vascular system of the echinoderm was damaged, which echinoderm function would be impaired? A) locomotion B) respiration C) circulation D) digestion E) sensing the environment

Answer: A Explanation: The water vascular system is used to operate the tube feet of the organism, allowing it to move slowly along. Echinoderms don't have a respiratory, excretory, or circulatory system. Fluids within the coelomic cavity and the water vascular system carry out many of these

60) Sea stars and sea urchins operate their tube feet by A) a hydraulic system that regulates water pressure. B) cilia transporting hemolymph from chamber to chamber. C) sticky threads leading from the mouth. D) actin and myosin fibers that slide and give muscle actions to the five arms or "rays." E) an extensive net of nerve and muscle cells.

Answer: A Explanation: Tube feet work by means of forcing water into the ampulla and a podium (foot portion). The ampulla squeezes water into the podium, causing it to expand. When the foot comes into contact with a surface, the center withdraws giving the foot suction and causes it to adhere to the surface. The organism can move along slowly by expanding and contracting the tube feet. The water enters the system by madreporite, or sieve plate, and passes into the ring canal and then into the radial canal from which the tube feet branch out.

54) Echinoderms and cnidarians A) are both radially symmetrical. B) both have three germ layers. C) both have the sac body plan. D) are both deuterostomes. E) are both found in freshwater.

Answer: A Explanation: While echinoderms are closely related to chordates, they often have radial symmetry in their adult form. Cnidarians also have radial symmetry.

9) Filter feeders are A) active predators. B) sessile or relatively inactive. C) always herbivorous. D) classified as cnidarians. E) classified as gastropods.

Answer: B Explanation: Filter feeders, like sponges, are usually sessile, allowing the food carried in the water to flow through a straining device.

7) Which of the following correctly matches the common name with a phylum name? A) planarian—Nematoda B) fluke—Platyhelminthes C) coral—Porifera D) roundworm—Cnidaria E) sponge—Arthropoda

Answer: B Explanation: Flukes are a type of flatworm and therefore belong in the phylum Platyhelminthes. Planarians are also flatworms and therefore in the phylum Platyhelminthes. Coral are in the phylum Cnidaria. Roundworms are in the phylum Nematoda and sponges are in the phylum Porifera.

31) Earthworms differ from most of the marine annelids in that earthworms A) lack setae that marine annelids have. B) lack paddle-like parapodia that marine annelids have. C) have segments, while marine annelids do not. D) develop from a larval form, while marine annelids do not. E) have well-developed brains and sensory organs in the head region, while marine annelids do not.

Answer: B Explanation: Marine annelids, which are classified as polychaetes, are predatory and have a well-developed head and each segment usually has parapoda and many setae. Earthworms, which are classified as oligochaetes, are not predatory and lack the well-developed head and parapoda of the polychaetes.

12) Planaria feed by A) attaching to a food item with a sucker and extracting fluids. B) tearing and sucking food particles via a muscular pharynx. C) externally digesting food items and then ingesting the liquified food. D) diffusing in nutrients from the environment through its thin epidermal surface. E) filtering the water.

Answer: B Explanation: Planaria extend a muscular pharynx to a prey item and tear and suck small particles off of the item; the resulting small pieces of food are sucked into the pharynx and then into the gastrovascular cavity where digestion is completed.

10) Which of the following is classified as a flatworm? A) corals B) planaria C) sea anemones D) hydrozoa E) Portuguese man-of-war

Answer: B Explanation: Planarians are flatworms and classified in the phylum Platyhelminthes. All of the other organisms listed are classified as cnidarians.

5) Protostomes are distinguised from deuterostomes based on A) the presence or absence of a nervous system. B) the pattern of embryonic development. C) the presence or absence of a circulatory system. D) the presence of absence of cephalization. E) feeding behaviors.

Answer: B Explanation: Protostomes and deuterostomes are distinguished based on their pattern of embryonic development. During the embryonic development of protostomes, the mouth develops from the blastopore and in deuterostomes the anus develops from the blastopore.

33) Fertilization in the earthworm is accomplished by the use of the A) nephridia. B) clitellum. C) flame cells. D) trachea. E) typhlosole.

Answer: B Explanation: The clitellum of an oligochaete secretes mucus that prevents sperm from drying out as they pass between two mating worms. After the worms separate, the clitellum produces a slime tube which slides along the worm and picks up the sperm and eggs and deposits them in the soil.

49) Respiratory structures in insects are A) commonly termed book lungs. B) spiracles and tracheae. C) hemolymphic. D) lamellae. E) lungs.

Answer: B Explanation: The respiratory system of insects consists of openings in the exoskeleton called spiracles. Air is actively pumped into the spiracles by the alternate contraction and expansion of the body wall. Once inside, the air moves into the trachea, small multibranched tubes that are the actual sites of gas exchange.

65) The most likely ancestors of the chordates are considered to be echinoderms because A) both groups reproduce sexually and asexually. B) both groups exhibit similar predatory behaviors. C) embryos of echinoderms and chordates are deuterostomes. D) adult echinoderms and adult chordates display similar characteristics. E) the nervous system of echinoderms is similar to that of chordates.

Answer: C Explanation: A deuterostome is a developmental stage where the second embryonic opening becomes the mouth and an outpocketing by the primitive gut becomes the coelom. The fact that this is a developmental process shared by these two phyla and not shared by others demonstrates relatedness between them.

44) An insect circulatory system is best described as A) totally closed like ours, with arteries and veins. B) similar to ours, with general closed vessels but no distinct arteries and veins. C) an open system that mostly washes hemolymph "blood" through the hemocoel. D) totally absent; each body cell manages on its own to gain food and gets rid of wastes. E) containing five pairs of "hearts."

Answer: C Explanation: An insect's circulatory system is an open system. The heart lies against the dorsal wall of the abdomen and pumps hemolymph, the fluid used for circulation, into a short artery where it is then sent into the hemocoel, or sinuses surrounding the tissues and organs. It then collects and returns to the heart where the process begins again.

47) Which statement about arachnids is inaccurate? A) Ticks and mites are often parasitic. B) Spiders and scorpions are predators. C) Spiders have trachea for respiration. D) Spiders have a pair of fangs which release poison. E) The body parts include a cephalothorax and an abdomen.

Answer: C Explanation: Arachnids have book lungs that function to carry out gas exchange. The folded lamella that make up the "pages" are invaginations of the body wall.

39) Which type of organism is characterized by having jointed appendages, ability to molt, and three sets of fused segments? A) molluscs B) echinoderms C) arthropods D) annelids E) chordates

Answer: C Explanation: Arthropods are covered in a rigid exoskeleton and must molt to increase in size. They have fused segments with a pair of jointed legs for every segment.

32) The bristles that earthworms use to anchor themselves in the earth and pull themselves along are A) aortic arches. B) lateral ventricles. C) setae. D) parapodia. E) nephridia.

Answer: C Explanation: Each segment of oligochaetes has four pairs of setae or bristles that help them to move through the soil.

55) "Derm" means "skin," so the name Echinodermata literally means A) soft skin. B) hairy skin. C) spiny skin. D) skinless. E) three layers of skin.

Answer: C Explanation: Echinoderm comes from the Greek "echin," meaning "spiny," and "derm," meaning "skin"; so the name literally means spiny skin.

4) Which of the following is true about deuterostomes? A) Deuterostomes have two tissue layers. B) Cleavage is spiral. C) The first opening during embryonic development becomes the anus. D) The mesoderm arises from cells located near the embryonic blastopore. E) Deuterostomes include the ecdysozoa and the spiralia

Answer: C Explanation: In deuterostomes, the first opening during embryonic development becomes the anus. All of the other answer choices describe characteristics of protostomes.

43) The major insect body parts are A) head, cephalothorax, and abdomen. B) cephalothorax, midsection, and abdomen. C) head, thorax, and abdomen. D) head, pyothorax, and metathorax. E) head, cephalothorax, and genitalia.

Answer: C Explanation: Insects have bodies that are divided into three segments: the head, thorax, and abdomen. The head usually bears sensory antennae, eyes, and mouth parts. The thorax bears three pairs of legs and wings, if present. The abdomen contains the internal organs.

38) The largest animal group, both in number of species and number of individuals, is the A) annelids. B) crustacea. C) insects. D) reptiles. E) fishes.

Answer: C Explanation: Insects likely have over one million species and are extremely diverse. They are more species-rich and diverse than all other types of life.

26) Which of the following is an arthropod? A) clams B) squids C) lobsters D) nautiluses E) snails

Answer: C Explanation: Lobsters are members of phylum Arthropoda and have the characteristic hard exoskeleton found in that phylum. All of the remaining answers are organisms classified in phylum Mollusca.

50) Which of the following organisms is lacking one of the five characteristics typically found in animals? A) sponges, which have no true tissues but have two layers of cells that perform different functions B) planaria, who have an incomplete digestive tract but do have muscles and excretory and reproductive systems C) trypanosome, a single-celled organism that causes sleeping sickness in humans D) leeches, segmented worms that are predatory on other animals E) tapeworms, flatworms that infest the intestines of humans

Answer: C Explanation: One of the characteristics that define animals is that they are multicellular. As a single-celled organism, a trypanosome is not an animal.

17) Ascaris is considered to be a(n) A) flatworm. B) earthworm. C) roundworm. D) cnidarian. E) arthropod.

Answer: C Explanation: Roundworms, phylum Nematoda, can be either free-living or parasitic. Ascaris is parasitic and infects humans and pigs.

36) When an earthworm secretes a slime layer to receive eggs and sperm and form a ''cocoon,'' this secretion is produced by the A) annulations. B) peritoneum. C) clitellum. D) nephridium. E) prostomium.

Answer: C Explanation: The clitellum of an oligochaete secretes mucus that prevents sperm from drying out as they pass between two mating worms. After the worms separate, the clitellum produces a slime tube which slides along the worm and picks up the sperm and eggs and deposits them in the soil.

35) Earthworms possess both male and female organs on separate segments; thus, mating consists of "parallel parking" in opposite directions and cross-fertilizing. Given this, which of the following is true? A) This is evidence of a primitive state that is generally less efficient than separate sexes. B) This is primarily to allow them to self-fertilize if no other worm is in their sector of the soil. C) This is an advantage since they can mate with any other earthworm of the same species that they encounter. D) Maintaining any system not clearly male or female is disadvantageous; the earthworm is trapped in an evolutionary dead end. E) This demonstrates how ineffective self-fertilization is as a means of reproduction.

Answer: C Explanation: Unlike organisms that have individuals that are one sex, male or female, any other earthworm is a potential mate.

29) A closed circulatory system is found in A) insects. B) snails. C) clams. D) earthworms. E) scorpions.

Answer: D Explanation: Arthropods, insects, and scorpions have an open circulatory system as do most molluscs, snails, and clams. Earthworms are annelids and have a closed circulatory system.