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Zoology Ch. 12 Molluscan Success Molluscs are _________________ and they possess a _____________. Molluscs are _____________. Theories regarding the _____________ of the coelom influence how zoologists interpret evolutionary ______________________ among triplobalstic animals. Molluscs range in size and body form from the giant ____________, measuring _______m in length, to the smallest garden _________, less than _________cm. Characteristics of the phylum Mollusca include: 1. Body of _________ parts, head and _________ 2. _____________ that secretes a calcareous shell and covers the _______________ mass 3. Mantle cavity functions in ______________, gas exchange, elimination of digestive wastes, and release of __________________ products 4. _________________ symmetry. 5. Protostome characteristics, including trocophore larvae, ___________ cleavage, and schizocoelous coelom formation 6. Coelom _______________ to cavities surrounding the ____________, nephridia, and gonads 7. __________ circulatory system in all but one class (Cephalopoda) 8. _____________ usually present and used in scraping food. The body of the mollusk has __________ main regions – the head-foot, the visceral mass, and the ___________. The head-foot is elongate with an _____________ head, containing the ___________ and certain nervous and sensory structures, and an elongate foot, used for _____________________ and __________________. The visceral mass contains the organs of _______________, circulation, reproduction, and ______________ and is positioned ____________ to the headfoot. The mantle usually attaches to the ___________ mass, enfolds most of the body, and may secrete a ____________ that overlies the mantle. The shell of a mollusk is secreted in ____________ layers. The ____________ layer of the shell is called the ________________. Mantle cells at the mantle’s outer margin secrete this ________________ layer. The middle layer of the shell, called the ________________ layer, is the _______________ of the three layers and consists of calcium carbonate. The inner layer of the shell, the _______________ layer, forms from thin sheets of calcium carbonate. Cells along the entire ________________ border of the mantle secrete the nacreous layer. The nacre secretion ____________ the shell. Between the mantle and the foot is a space called the ______________ _______________. The mantle cavity opens to the outside and functions in _________ exchange, excretion, elimination of digestive wastes, and release of ________________ products. The mouth of most mollusks possess a rasping structure called a ______________, which consists of a ______________ belt and rows of posteriorly curved ____________. The radula overlies a fleshy tonguelike structure supported by a cartilaginous __________________. Muscles of the odontophore permit the ____________ to be protruded from the __________, move back and forth, and ___________ is scraped from a substrate and passed to the ______________ tract. Class Gastropoda The class Gastropoda with over ____________ species and includes the __________, limpets, and slugs. Gastropoda is the ___________ and most varied molluscan class with species occupying ___________, freshwater, and terrestrial habitats. One of the most important ________________ of the molluscan body form in the gastropods occurs early in development. _____________ is a ____________, counterclockwise _____________ of the visceral mass, mantle, and mantle cavity. Torsion positions the gills, __________, and openings from the excretory and reproductive systems just behind the ________ and nerve cords, and twists the digestive tract in to a ________ shape. The earliest fossil gastropods had a shell that was ______________ in one plane. This arrangement is not common in __________ fossils, because growth resulted in an increasingly cumbersome __________. Most snail shells are _____________________ coiled into a ____________ form. Nearly all gastropods have a _______________ foot that is often ciliated, covered with ___________ cells, and used to creep across the substrate. Most gastropods feed by ______________ algae or other small, attached organisms from their substrate using their _________. Others are _______________ that feed on larger plants, scavengers, _____________, or predators. The anterior digestive tract is ciliated and contains the ___________. Food is trapped in ____________ strings and is incorporated into a mucoid mass called the ______________, which extends to the _____________ and is rotated by cilia. A digestive gland in the visceral mass releases _____________ and acid into the stomach, and food trapped on the ________________ is freed and digested. Wastes form fecal ___________ in the intestine. Gas exchange always involves the _____________ cavity. Modern gastropods have ___________ gill due to ______________. Some gastrpods have a rolled extension of the mantle called a _______________, that serves as an inhalant tube. Gastropods have an ___________ circulatory system, where ____________ leaves the vessels and directly _____________ cells in tissue spaces called _______________. Molluscs have a ______________ consisting of a _________, muscular _____________, and _________ auricles. Most gastropods have ___________ one member of the pair of auricles because of coiling, so they have a __________ auricle and a __________ ventricle. In addition to transporting nutrients, _____________, and gases, the blood of the mollusks acts as a hydraulic skeleton. A hydraulic skeleton consists of fluid under _________________ that may be confined to tissue spaces to _________ body structures and to ____________ the body. Molluscs ___________ muscles to force fluid into a structure to push it forward. The nervous system of primitive mollusks is characterized by ________ ganglia located on the ______-_________ and visceral mass, which was twisted by the torsion. The evolution of the gastropod nervous system has resulted in the _________________ of the nerves and the concentration of nervous tissues into fewer, ____________ ganglia, especially in the head. Gastropods have __________-______________ sensory structures. Eyes may be at the base or at the end of _______________. They may be ____________ pits of photoreceptor cells or they may consist of a _________ and cornea. They have ______________ in the foot and ____________________ chemical receptors for detecting prey. Primitive gastropods had __________ nephridia, but the modern species, the ____________ nephridia has disappeared due to shell coiling. The nephridia consists of a ________ with highly folded walls and connects to the reduced _____________, the pericardial cavity. Excretory wastes are derived from fluids filtered and secreted into the ______________ from the ________. Many marine snails are _____________________. Gonads lie in ______________ in the visceral mass and ducts discharge ______________ into the sea for external fertilization. Many other snails are ________________, and internal cross fertilization is dominant. In most marine gastropods, _____________ cleavage results in free-swimming _________________ Larva that develops into another free-swimming larva with foot, ____________, tentacles, and shell called a ______________ larva. _______________ occurs during the veliger stage, followed by settling and metamorphosis to the ______________. Class Bivalvia There are around _____________ species of the class Bivalvia. This is the ____________ largest class of mollusks which includes the __________, oysters, mussels, and scallops. A sheetlike mantle and a shell consisting of ________________ valves cover the animals. Many bivalves are _______________, and some form ____________. Most bivalves are __________ _______________, and are valuable in removing ______________ from polluted water. The two convex halves of the shell are called _______________. Along the ______________ side of the shell is a _____________ ligament and a series of tongue and groove modifications of the shell called _______________, that prevent the valves from twisting. The ___________ part of the shell is the ________________, a big hump area near the shell’s anterior side. The elastic hinged-ligament is made of protein and allows the valves to _______________ when certain muscles relax. ______________ muscles at either end of the dorsal half of the shell ____________ the shell for protection from _____________. The bivalve _____________ attaches to the shell around the adductor muscles near the shel1 margin. If a ____________ grain or a parasite lodges between the shell and the mantle, the mantle secretes _____________ around the irritant, gradually forming a ____________. Bivalve adaptations to sedentary, _____________-_________________ lifestyles include the ____________ of the head and radula and except for a few bivalves the expansion of _________-covered gills. ___________ form folded sheets with one end attached to the ___________ and the other end attached to the _______________. The mantle cavity ____________ to the gills is the inhalant region, and the cavity ______________ to the gills is the exhalant region. __________ move water into the mantle cavity through a ____________ opening of the mantle, which is at the end of the ______________, which is an extension of the mantle. A bivalve buried in the substrate can extend its ______________ to the surface and still ____________ and exchange gases. The ____________ trap food particles brought into the mantle cavity, ____________ move the particles to the _____________, then move the food toward the __________. Cilia covering leaflike ____________ ____________ on either side of the mouth also sort filtered food particles. The rejected materials are moved to the _____________ and water rushing out when valves are forcefully _____________ washes the waste from the mantle cavity. The ____________ tract of bivalves is similar to that of other mollusks. Food entering the _______________ entangles in a mucoid food string, which extends to the ______________ and is rotated by cilia lining the digestive tract. _______________ function in digestion and partially digested food from the _____________ enters the digestive gland for _______________ digestion. Cilia carry undigested wastes in the digestive gland back to the _________________ and then to the _________________. The intestine empties through the __________ near the ______________ opening, and excurrent ________ carries feces away. Bivalves have an ___________ circulatory system. Blood flows from the ___________ to tissue sinuses, nephridia, ___________, and back to the heart. The ______________ system consists of _____________ pairs of interconnected ganglia associated with the esophagus, the foot, and the _______________ adductor muscle. Most bivalves are ______________, with a few being _________________. _____________ are in the visceral mass, where they surround the looped ____________. Most bivalves exhibit ______________ fertilization. _____________ exit through the suprabranchial chamber of the mantle cavity and the exhalant opening. Development proceeds through _________________ and veliger stages. When the ____________ settles to the substrate it assumes the ___________ form. Most ________________ bivalves ____________ their young Fertilization occurs in the mantle cavity by ______________ brought in with inhalant water. Some brood their young in _____________ gills trough reduced trocophore and veliger stages. Young clams are __________ from the gills. Bivalves are in nearly all ______________ habitats. They may completely or partially ____________ themselves in sand or mud, attach to solid substrates, or bore into submerged wood, coral, or limestone. Class Cephalopoda The class Cephalopoda includes the octopuses, ___________, cuttlefish, and nautiluses. They are the most ______________ mollusks. The anterior portion of their ___________ has been modified into a circle of ____________ or arms used to capture prey, attachment, ___________________, and copulation. The foot is also incorporated into a funnel associated with the mantle cavity and is used for _______________ propulsion. The molluscan body plan is further modified in that the cephalopod ___________ is in line with the _____________ mass. Cephalopods have a highly _______________ mantle that encloses all of the ___________ except the head and tentacles. The mantle acts as a _____________ to bring large quantities of ______________ into the mantle cavity. Ancestral cephalopods probably had a conical ____________, and the only living cephalopod to possess an external coiled shell is the _____________. As the nautilus grows, it moves forward, ____________ new shell around itself and leaving behind the old septum. Only the __________ chamber is occupied and when formed the chambers are ____________-_____________. The amount of _____________ in the chambers is regulated to alter the _____________________ of the animal. In all other cephalopods the shell is reduced or ____________. In cuttlefish the shell is _____________ and laid down in ______________ layers, leaving small gas-filled spaces to increase _________________. The shell of the squid is reduced to an ______________, chitinuos structure called the __________. Squid also have cartilaginous ____________ in the mantle wall, neck, and head that ________________ the mantle and _____________ the brain. The shell is __________ in octopuses. As _______________, cephalopods depend on their ability to move quickly using a ________-______________ system. The mantle of the cephalopod contains ____________ and ____________ muscles. Circular muscles __________, ______________ the volume of the mantle cavity and ____________ the collarlike valves to prevent water from moving _________ of the mantle cavity between the head and mantle wall. Water is forced _______ of a narrow funnel where muscles attach to the funnel and control the direction of the animal’s _________________. ___________ muscles _____________ water into the mantle cavity by ______________ he cavity’s volume. Posterior __________ act as stabilizers in squid and aid in propulsion and ______________ in cuttlefish. Most cephalopods locate their prey by _________ and capture prey with ___________ that have adhesive cups. All cephalopods have ____________ and a radula. The jaws are powerful beaklike structures for ____________ food, and the radula rasps food, ____________ it into the mouth cavity. Cuttlefish and nautiluses feed on small _______________ on the ocean floor. Octopuses are _______________ hunters and feed on snails, ___________ and crustaceans. Octopuses have salivary glands that inject ____________ into prey. Squid feed on fish and shrimp, which they kill by biting across the back of the __________. The ___________ tract of cephalopods is ________________ and peristalsis replaces ciliary action in moving food. Most digestion occurs in a ____________ and a large cecum. Digestion is primarily ______________ with large digestive glands supplying _______________. An intestine ends at the ________, near the funnel, and exhalant water carries wastes out of the mantle cavity. Cephalopods, unlike other mollusks have ______________ circulatory systems. Blood is ___________ to vessels throughout its circuit around the body. Capillary beds connect _____________ and ________, and exchanges of gases, nutrients, and metabolic wastes occur across capillary walls. They have a heart with __________ auricles and ___________ ventricle. Cephalopods exhibit ____________ excretory efficiency due to the closed circulatory system. A closed association of blood vessels with nephridia allows wastes to filet and secrete directly from the ____________ into the excretory system. The cephalopods have a ___________ nervous system with a _____________ brain. The brain forms by ___________ of ganglia. Large areas are devoted to controlling muscle contractions, ____________ perception, and functions such as ______________ and decision making. Cephalopods have pigment cells called _______________________. When tiny muscles attached to these pigment cells contract, the chromatophores quickly expand and ____________ the ____________ of the animal. Color changes, in combination with ______ discharge function in alarm responses. All cephalopods possess an ________ gland that opens just behind the ______. Ink is ________ or ___________ fluid containing melanin and other chemicals. Discharged ink __________ a predator, allowing the cephalopod to escape. Cephalopods are _______________ with __________ in the dorsal portion of the visceral mass. The __________ reproductive tract consists of ____________ and structures for encasing sperm in packets called ________________________. The ____________ reproductive tract produces large, yolky __________ and is modified with glands that secret gel-like cases around eggs. One tentacle of the __________ is called the _________________ and is modified for spermatophore transfer. Cephalopods develop in the confines of the __________ membranes, and the hatchlings are miniature adults. Young are ___________ cared for after hatching. Class Polyplacophora The class Polyplacophora contains the ____________, which are common inhabitants of hard substrates in shallow _________ water. Chitons have a reduced __________, a flattened __________, and a shell that divides into ___________ articulating dorsal valves. A muscular mantle that extends beyond the margins of the ______________ and foot covers the broad foot. The mantle cavity is restricted to the space between the margin of the mantle and the __________. Chitons ___________ over their substrate in a manner similar to gastropods, by attaching their foot to the substrate with a tight ___________. A linear series of _________ is in the mantle cavity on each side of the foot. Cilia on the gills create __________ _______________ that enter below the anterior mantle margins and and ____________ posteriorly. The digestive, ______________, and reproductive tracts open near the exhalant area of the mantle cavity, and _____________ water carries products of these systems away. Most chitons feed on attached ______________. A ________________ extends from the mouth to detect food that the radula rasps. Mucus ___________ the food, enters the _____________, extracellular digestion and absorption occur in the ___________, and wastes move on to the intestine. The ______________ system is ladderlike with ___________ anteroposterior nerve cords and numerous tranverse nerves. A __________ __________ encircles the esophagus. Sexes are _____________ in chitons. _____________ fertilization and development result in a swimming trochophore that settles and metamorphoses into an ____________ without passing through a ______________ stage. Class Scaphopoda Members of the class Scaphopoda are called __________ shells or _________________ shells. The over _________ species are all __________________ ___________ animals that inhabit moderate depths. Their most distinctive characteristic is a ________________ shell that is _____________ at both ends. The head and foot project from the ____________ end of the shell, and the rest of the body, including the mantle is greatly elongate and extends the ______________ of the shell. ______________ and _________________ water enters and leaves the mantle cavity through the opening at the ___________ of the shell. Functional ___________ are absent, and gas exchange occurs across mantle folds. They have a __________ and ________________, which they use to feed on foraminiferans Sexes are ____________, and trochophore and veliger larvae are produced. Class Monoplacophora Members of the class Monoplacophora have an ____________________. Arched shell, a broad ____________ foot, and repeated pairs of ____________ and foot-retractor _______________. They are __________________. This group of mollusks is only known from ______________ until 1952, when one was dredged up from the coast of Costa Rica. Class Aplacophora Members of the class Aplacophora are divided into __________ subclasses, Neomeniomorpha called solengasters and Chaetodermomorpha (Caudofoveata), that are wormlike. Solengaster mollusks are ____________________, lack a _________ and crawl on their _____________ surface. The later Caudofoveata are very small and have scalelike spicules on the body wall and lack the typical mollusk characteristics: ____________, crystalline style, statocysts, ___________, and nephridia.