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− | <languages /><br />
| + | {{HonorSubpage}} |
− | <noinclude></noinclude>
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− | {{honor_desc/es | |
− | |stage=00
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− | |honorname=Moluscos - Avanzado
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− | |skill=3
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− | |year=1949
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− | |category=Estudio de la naturaleza
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− | |authority=Asociación General
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− | |insignia=Shells_Advanced.png
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− | }} | |
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− | <noinclude></noinclude>
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| <section begin="Body" /> | | <section begin="Body" /> |
| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=1}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=1}} |
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=3}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=3}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | <!-- 3. Learn the classification terms of mollusks, know the distinguishing characteristics of each, and become acquainted with several species under each class. --> | + | <!-- 3. Conocer los términos de la clasificación de los moluscos, conocer las características distintivas de cada uno y familiarizarse con varias especies de cada clase. --> |
− | There are ten classes of molluscs; eight of the classes have living representatives, the other two classes are known only from fossils. More than 250,000 species of mollusc are recognized and named. Snails (Gastropoda) account for about 80% of living mollusc diversity.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4}} |
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− | <!-- 4 Distinguish between univalve and bivalve mollusks from the following considerations: --> | + | <!-- 4 Distinguir entre moluscos unívalvos y bívalvos teniendo en cuenta las siguientes partes: --> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4a}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4a}} |
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− | ;Bivalves: Razor shells (''Ensis spp.'') can dig themselves into the sand with great speed to escape predation. Scallops can swim to escape an enemy, clapping their valves together to create a jet of water. Cockles can use their foot to leap from danger. However these methods can quickly exhaust the animal. In the razor shells the siphons can break off only to grow back later.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4e}} <!--T:17--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4e}} <!--T:17--> |
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− | ;Bivalves: Bivalves are unique among the molluscs for lacking a radula; they feed by siphoning and filtering large particles from water.
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− | ;Univalves: Univalves include some that are herbivores, detritus feeders, predatory carnivores, scavengers, parasites, and also a few ciliary feeders, in which the radula is reduced or absent. The radula of a univalve is usually adapted to the food that a species eats. The simplest univalves are the limpets and abalones, herbivores that use their hard radulas to rasp at seaweeds on rocks. Many marine univalves are burrowers, and have soft siphons or tubes that extend from the mantle. Sometimes the shell has a siphonal canal to accommodate this structure. A siphon enables the animal to draw a small flow of water into their bodies. The siphon is used primarily to "taste" the water, in order to detect prey from a distance. Univalves with siphons tend to be either predators or scavengers.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4f}} <!--T:19--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=4f}} <!--T:19--> |
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− | ;Univalves: When retracted into their shells, many snails with gills (including many marine, some freshwater and some terrestrial species) are able to protect themselves with a door-like anatomical structure called an operculum. Some snails hibernate during the winter (typically October through April in the Northern Hemisphere). They may also estivate in the summer in drought conditions. To stay moist during hibernation, a snail seals its shell opening with a dry layer of mucus called an epiphragm.
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− | ;Bivalves: The radical structure of the bivalves affects their behaviour in several ways. the most significant is the use of the closely-fitting valves as a defence against predation and, in intertidal species such as mussels, drying out. The entire animal can be contained within the shell, which is held shut by the powerful adductor muscles. This defence is difficult to overcome except by specialist predators such as the Starfish and Oystercatcher. The file shells (''Limidae'') can produce a noxious secretion when threatened, and the fan shells of the same family have a unique, acid-producing organ.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | <!-- 5. Identify from shells or drawings and know the meaning of the following concho logical terms: --> | + | <!-- 5. Identificar a partir de conchas o dibujos y saber el significado de los siguientes términos lógicos de caracoles: --> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5a}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5a}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | ''Valve'' is another word for ''shell''. This is the hard covering protecting most molluscs.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5b}} <!--T:22--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5b}} <!--T:22--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | The apex is a word most often used to mean the tip of the spire of the shell of a gastropod. It is the first-formed, and therefore the oldest, part of the shell. To be more precise, the apex would usually be where the tip of the embryonic shell or protoconch is situated, if that is still present in the adult shell.
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− | The word apex can also be used to refer to a similar part in other molluscan shells, however, the apex of bivalves is more usually known as the umbos, beaks or prodissoconch.
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− | The apex of tusk shells is the small, open posterior end, and the opening itself is usually called the apical aperture.
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− | The phrase apical whorls, or protoconch, means the whorls of the embryonic shell at the apex of the shell, especially when this is clearly distinguishable from the later whorls of the shell, otherwise known as the teleoconch.
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− | The space under the apex of a patellate gastropod is called the apical cavity.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5c}} <!--T:27--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5c}} <!--T:27--> |
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− | [[Image:Semicassis pyrum (base).JPG|thumb|250px|''Semicassis pyrum'', which has a large aperture.]]
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− | The aperture is the main (or only) opening in the shell of a gastropod or snail. It is where the soft parts of the animal emerge. In some prosobranch gastropods, the aperture is able to be closed, and even completely sealed, with a sort of door or operculum.
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− | The aperture of many snail shells is round, rounded, elliptical or oval. This shape corresponds roughly to the cross-section of the body whorl of the shell.
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− | The aperture of a snail shell can have many other forms: semicircular, trilobate or auriculate. In some gastropods, the aperture is narrowed by protruding shell folds or "bacon", which help make the soft parts of the animal less vulnerable to predation.
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− | For convenience of reference, the apertural edge or margin of a gastropod shell is divided into three areas or walls:
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− | * The parietal wall: the area next to the penultimate whorl of the shell
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− | * The columellar wall: the wall next to the columella
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− | * The palatal wall: the outer free wall of the final whorl of the shell
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5d}} <!--T:32--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5d}} <!--T:32--> |
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− | [[Image:Zebra mussel GLERL 1.jpg|left|thumb|byssus threads on ''Dreissena polymorpha'']]
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− | Mussels use byssus to attach to rocks and other surfaces. When a mussel's foot encounters a crevice, it creates a vacuum chamber by forcing out the air and arching up, similar to a plumber's plunger unclogging a drain. The byssus, made of keratin and other proteins, is spewed into this chamber, and bubbles into a sticky foam. By curling its foot into a tube and pumping the foam, the mussel produces sticky threads about the size of a human hair. It varnishes the threads with another protein, resulting in an adhesive.
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− | Byssus is a remarkable adhesive that is neither degraded nor deformed by water as are synthetic adhesives. This has spurred genetic engineers to insert mussel DNA into yeast cells for translating the genes into the appropriate proteins.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5e}} <!--T:34--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5e}} <!--T:34--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | The foot is an organ that can be extended outside the shell, and is used as a means of locomotion. It is most common in univalves.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5f}} <!--T:35--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5f}} <!--T:35--> |
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− | [[Image:Loligo vulgaris.jpg|250px|thumb|European Squid (''Loligo vulgaris''). The mantle is all that is visible behind the head.]]
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− | The mantle is an important part of the anatomy of molluscs. It is the dorsal body wall which covers the visceral mass.
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− | In many, but by no means all, species of molluscs, the epidermis of the mantle secretes calcium carbonate and creates a shell.
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− | The word "mantle" (a old word, meaning cloak) is used for this anatomical structure because in many kinds of molluscs, the edge of the mantle extends beyond the main part of the body, forming flaps or double-folded structures.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5g}} <!--T:38--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5g}} <!--T:38--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | [[Image:Viviparus contectus met operculum2.JPG|right|thumb|Gastropod shell of ''Viviparus contectus'' with operculum]]
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− | The operculum, meaning little lid, (plural: opercula or operculums) is a corneous or calcareous structure which exists in some groups of marine, freshwater, and land snails or gastropods. It is present in most but not all gastropods that have shells and gills. Pulmonate snails do not have opercula, but some terrestrial species are capable of secreting an epiphragm.
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− | In its most typical condition, an operculum serves to close the opening or aperture of the shell when the soft parts of the animal are withdrawn into the shell.
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− | An operculum can vary in shape greatly from one family of gastropods to another, but an operculum is fairly often circular, or more or less oval in shape. In species where the operculum fits snugly, its outline corresponds exactly to the shape of the aperture of the shell.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5h}} <!--T:41--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5h}} <!--T:41--> |
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− | [[Image:NautilusCutawayLogarithmicSpiral.jpg|thumb|left|200px|The iridescent nacre inside a Nautilus shell ]]
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− | Nacre, also known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer. It is exceptionally strong, resilient, and iridescent. Nacre is found in some bivalves, some gastropods and some cephalopods. The inner shell layer in most molluscs however is merely porcellaneous, in other words shiny like a china plate, not iridescent.
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− | Pearls and the inside layer of the pearl oyster shells and the freshwater pearl mussel shells are made of nacre. Many other families of molluscs also have an inner shell layer which is nacreous, including gastropods such as the Haliotidae, the Trochidae and the Turbinidae.
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| {{clear}} | | {{clear}} |
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5i}} <!--T:43--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5i}} <!--T:43--> |
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− | The epidermis is the outermost layer of the mantle. In many, but by no means all, species of molluscs, the epidermis of the mantle secretes calcium carbonate and creates a shell.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5j}} <!--T:44--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5j}} <!--T:44--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | Ribs are strong, well-defined ridges on the surface of the shell.
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| <noinclude></noinclude> | | <noinclude></noinclude> |
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5k}} <!--T:45--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5k}} <!--T:45--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | The radula is a toothed chitinous ribbon which is present in the mouth of most but not all classes of molluscs. It does not exist in any phyla other than the Mollusca.
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− | The radula is usually used for scraping, cutting and chewing food before it enters the esophagus. It is present in all classes of molluscs except the bivalves.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5l}} <!--T:47--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5l}} <!--T:47--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | Concentric lines are circular growth rings on the outside of a shell. Concentric rings are circles of different diameters having a common center. Characteristics of the concentric lines (spacing, definition, etc.) can be used as an aid to identifying a mollusc.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5m}} <!--T:48--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5m}} <!--T:48--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | [[Image:Penion cuvieranus cuvieranus.JPG|thumb|250px|''Penion cuvieranus cuvieranus'', showing its '''siphonal canal''' to the left.]]
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− | In some sea snails, (marine gastropod molluscs in the infraorder Neogastropoda), the animal has an anterior extension of the mantle called a siphon, through which water is drawn into the mantle and over the gill. This siphon is a soft fleshy tube which also serves to "smell" or "taste" the water in order to locate a possible source of food.
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− | In many (but not all) neogastropods where the siphon is particularly long, the structure of the shell has been modified in order to house and protect the soft structure of the siphon. Thus the siphonal canal is a semitubular extension of the aperture of the shells of some marine gastropods, through which the siphon is extended when the animal is active.
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| {{clear}} | | {{clear}} |
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5n}} <!--T:50--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5n}} <!--T:50--> |
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− | [[Image:Haeckel Murex pectens.jpg|thumb|130px|Venus Comb Murex, ''Murex pectens''. From Ernst Haeckel's ''Kunstformen der Natur'', 1904.]]
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− | Spines are sharply pointed spurs protruding from a mollusc's shell. Murexes and conches have prominent spines.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5o}} <!--T:51--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5o}} <!--T:51--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | A whorl is a single, complete 360° turn in the spiral growth of a mollusc shell. A mollusc shell is basically a long tube, usually coiled in a spiral for strength and compactness. The number of whorls in the shell depend on various factors in the geometric growth.
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− | The number of whorls differs in various groups, with the family ''Turritellidae'' having very high spired shells with a large number of whorls and hence a relatively small aperture.
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− | * Apical whorls—those whorls near the apex or tip of the shell.
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− | * Body whorl—The most recently formed whorl of a spiral shell.
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− | * Nuclear whorl(s)—small, generally smooth whorls formed within the egg and constituting the apex of the shell.
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− | * Protoconch—a larval shell of a mollusc; also refers to protoconch whorls of an adult shell.
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− | * Teleoconch—all the whorls of a shell after the protoconch whorls.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5p}} <!--T:54--> | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=5p}} <!--T:54--> |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | Lips are the curled section of shell surrounding the aperture. Lips can curl outward, as with the conch, or inward, as with the cowrie.
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− | {{clear}}
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=6}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=6}} |
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− | <!-- 6. Explain the development of a shell. How long do mollusks live? --> | + | <!-- 6. Explicar el desarrollo de una concha. ¿Cuánto tiempo viven los moluscos? --> |
− | <gallery perrow=3 widths=200>
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− | Image:Cypraea chinensis with partially extended mantle.jpg|The marine gastropod ''Cypraea chinensis'', the Chinese Cowry, showing partially extended mantle
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− | Image:Giant_clam_or_Tridacna_gigas.jpg|The giant clam (''Tridacna gigas'') is the largest extant bivalve
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− | Image:A fossil shell with calcite.jpg|Fossil shell covered in calcite crystals
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− | </gallery>
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− | In those molluscs which have a shell, the shell grows gradually over the lifetime of the mollusc by the addition of calcium carbonate to the leading edge or opening, and thus the shell gradually becomes longer and wider, in an increasing spiral shape, to better accommodate the growing animal inside. The animal also thickens the shell as it grows, so that the shell stays proportionately strong for its size.
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− | A mollusc shell is formed, repaired and maintained by a part of the anatomy called the mantle. Any injuries to or abnormal conditions of the mantle are usually reflected in the shape and form and even color of the shell. When the animal encounters harsh conditions which limit its food supply, or otherwise cause it to become dormant for a while, the mantle often ceases to produce the shell substance. When conditions improve again and the mantle resumes its task, a "growth line" which extends the entire length of the shell is produced, and the pattern and even the colors on the shell after these dormant periods are sometimes quite different from previous colors and patterns.
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− | Interestingly, within some species of mollusc there is often a surprising degree of variation in the exact shape, pattern, ornamentation, and color of the shell.
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− | The longest lived mollusc is the ''Arctica islandica'' (Ocean Quahog). Animals of this species close to 400 years old are not uncommon.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=7}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=7}} |
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− | <!-- 7. Give some facts about the life of a ''Strombus pugilis'' (fighting conch) and explain why this shell is so named. --> | + | <!-- 7. Dar algunos datos sobre la vida de un caracol Strombus pugilis (conchas luchadora) y explicar la razón por la que éste molusco es llamado así. --> |
− | The West Indian Fighting Conch is an aggressive sea snail with a nasty sting which it uses to defend itself against marine predators. These shells are best collected when the tide goes out, as great numbers of them suddenly emerge from the sand and retreat to the surf. If one is flipped over, it can right itself using its sharp operculum.
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=8}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=8}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | <!-- 8. Explain the activities of the shipworm. --> | + | <!-- 8. Explicar las actividades del molusco broma. --> |
− | {{:Adventist Youth Honors Answer Book/Nature/Shipworm}} | + | {{:AY Honors/Shipworm/es}} |
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=9}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=9}} |
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− | <!-- 9. What accounts for the distribution of mollusks. --> | + | <!-- 9. ¿Cómo se explica la distribución de los moluscos? --> |
− | molluscs have few requirements in order for them to thrive. They need moisture, but if they find themselves in a dry environment, they are able to seal themselves (and their moisture) inside their shells until external moisture becomes available again. Thus, molluscs can be found in nearly every habitat on Earth - even deserts!
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=10}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=10}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | <!-- 10. Name two mollusks that have no shells. --> | + | <!-- 10. Nombrar dos moluscos que no tienen conchas. --> |
− | <gallery>
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− | Image:Unknown slug on rhubarb.jpg|<center>Slug</center>
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− | Image:Octopus in sea life Helsinki.jpg|<center>Octopus</center>
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− | Image:Cuttlefish.jpg|<center>Cuttlefish</center>
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− | Image:Mastigoteuthis flammea.jpg|<center>Squid</center>
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− | </gallery>
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| <noinclude></noinclude> | | <noinclude></noinclude> |
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| {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=11}} | | {{ansreq|page={{#titleparts:{{PAGENAME}}|2|1}}|num=11}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
− | <!-- 11. Find answers for the following interesting questions: --> | + | <!-- 11. Encontrar respuestas a las siguientes preguntas interesantes: --> |
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− | The muscles of both types of molluscs attach directly to the shell. These animals (including snails) cannot leave their shells and return any more than a turtle can leave its shell. The shell serves as the animal's skeleton.
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− | The outer edge of a mollusc's mantle contains glands that secrete color pigments during shell formation. These pigments control the colors on the ''outside'' of the shell. The iridescence on the inside of the shell is caused by alternating layers of calcite and aragonite refracting different wavelengths of light by different amounts depending on the viewing angle.
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− | [[Image:Nautilus profile.jpg|thumb|300px|The Nautilus, a mollusc with four gills]]
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− | The '''Nautilus'' has two pairs of gills (that's four!).
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− | Cuttlefish have ink, like squid and octopuses. This ink was formerly an important dye, called sepia. Today artificial dyes have replaced natural sepia.
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− | Several molluscs spin a ''byssus'' which is used to anchor them to a substrate. These include mussels in the family ''Mytilidae'' and the zebra mussel (''Dreissena polymorpha''). However, the mollusc with perhaps the most extensive byssus is the '''rigid pen shell''' (''Atrina rigida''). Like most pen shells, ''A. rigida'' lives in soft bottoms, with the majority of the shell buried, point down, leaving only a few inches exposed, held in place by an extensive net of byssal threads.
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− | Many people find the very rounded, shiny, porcelain-like shells of '''cowries''' pleasing to look at and to handle. Shells of certain species have historically been used as currency in several parts of the world, as well as being used, in the past and present, very extensively in jewelry, and for other decorative and ceremonial purposes.
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− | Tibetan Buddhists make use of a particular set of eight auspicious symbols, ''ashtamangala'', in household and public art. The '''chank shell''' or '''conch''' is one of these eight symbols:
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− | # Conch
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− | # Knot
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− | # Fish
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− | # Banner
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− | # Lotus
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− | # Parasol
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− | # Urn
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− | # Wheel
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− | ''Hexaplex trunculus'' (also known as ''Murex trunculus'' or the '''banded dye-murex''') is a medium-sized species of sea snail.
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− | This species of sea snail is important historically because its hypobranchial gland secretes a mucus that the ancient Canaanites/Phoenicians used as a distinctive purple-blue indigo dye. One of the dye's main chemical ingredients is indigotin, and if left in the sun for a few minutes before becoming fast, its color turns to a blue indigo (like blue jeans).
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− | Nacre, also known as mother of pearl, is an important part of the shell structure in many gastropod and bivalve molluscs especially the more ancient families such as top shells and pearl oysters. Like the other calcareous layers of the shell, the nacre is created by the epithelial cells (formed by the germ layer ectoderm) of the mantle tissue. mollusc blood is rich in dissolved calcium, and during shell deposition, the calcium is concentrated out from the blood and crystallized as calcium carbonate. Nacre is continually deposited onto the inner surface of the animal's shell (the iridescent nacreous layer or mother of pearl). This is done both as a means to thicken, strengthen and smooth the inner surface of the shell itself and as a defense against parasitic organisms and damaging detritus.
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− | When a mollusc is invaded by a parasite or is irritated by a foreign object that the animal cannot eject, a process known as encystation entombs the offending entity in successive, concentric layers of inner shell material, which in some cases is nacre. This process eventually forms what we call pearls and continues for as long as the mollusc lives. Almost any species of bivalve or gastropod is capable of producing "pearls", even molluscs which have no inner nacreous layer. However, only a few species, such as the famous pearl oysters, can create pearls which are highly prized.
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− | <!-- 12. Name six commercial uses for shells. --> | + | <!-- 12. Nombrar seis usos comerciales de las conchas (moluscos). --> |
− | ;Musical Instruments: Key touches and various decorations on musical instruments such as saxophones, trumpets, violins, banjos, tamburitzas and guitars are sometimes made of mother of pearl. It is used as inlays on many guitar fretboards.
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− | ;Clothing: Mother of pearl buttons can be found on a variety of clothing such as shirts, skirts and coats.
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− | ;Decorative Inlays: Nacre is also used as a decorative feature of watch faces, knives, guns and jewelry.
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− | ;Building Material: Instead of using a marble or tile base, the mother of pearl tesserae can be glued to a fiberglass mesh. The result is a lightweight material that offers a seamless installation, and there is no limit to the sheet size. Mother of pearl sheets may be used on interior floors, exterior and interior walls, countertops, doors and ceilings. Insertion into architectural elements, such as columns or furniture is easily accomplished. Conch shells are occasionally used as a building material, either in place of bricks or as bulk for landfill.
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− | ;Jewelry: Pearls are highly prized jewelry components.
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− | ;Souvenirs: In some countries, cleaned Queen Conch (''Strombus gigas'') shells or polished fragments are sold, mainly to tourists, as souvenirs or in jewelry. Without a permit, however, export is a breach of CITES regulations and may lead to arrest. This is most likely to occur on return to the tourist's home country while clearing customs. In the UK conch shells are the ninth most seized import.
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− | ;Pets: Snails are often kept in aquariums along with fish.
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− | <!-- 13. Do one of the following: <br>a. Personally find and collect 40 species of shells. List each shell as to the place and date it was found, common name, scientific name, and class. <br>b. Make a collection of 50 species of shells you have found, received, or purchased. List each shell collected as follows: if personally found, give the information called for under letter "a" above; if received or purchased, give the name of the person from whom the shell was received, the habitat of the shell, the date of its acquisition, and its common name, scientific name, and class. --> | + | <!-- 13. Realizar una de las siguientes actividades:<br>a. Personalmente encontrar y recolectar 40 especies de conchas que representan a las cinco clasificaciones. Hacer una lista de cada molusco con el lugar y la fecha en que fue encontrado, nombre común, nombre científico y la clase.<br>b. Hacer una colección de 50 especies de conchas que ha encontrado, recibido o comprado que representen las cinco clasificaciones. Hacer una lista de cada concha recogida de la siguiente manera: si la encontró personalmente, dar la información solicitada en el punto «a»; si la recibió o compró, dar el nombre de la persona de quien recibió la concha, el hábitat de la concha, la fecha de su adquisición, su nombre común, nombre científico y la clase. --> |
− | The best approach here is to get a good field guide and then try to identify the shells you have found.
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− | The five classifications of seashells are:
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− | ;Gastropoda: (snails, conches, etc.)
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− | ;Cephalapoda: Such as ''Spirula spirula''. Although the whole animal is rarely seen, the internal shell is very light and commonly floats ashore on beaches. The internal shell of this animal is known as the "ram's horn shell".
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− | ;Bivalvia: (clams, mussels, etc.)
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− | ;Polyplacophora: (chitons)
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− | ;Scaphopoda: (tusk shells)
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− | If you opt to purchase your collection, one possibility is to start with a kit containing specimens from all five of these classes. [http://www.seashells.com Seashells.com] carries a such a kit, reasonably-priced.
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− | ==References== | + | ==Referencias== |
− | * http://depts.washington.edu/natmap/mollusks/glossary.html
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− | * http://www.informaworld.com/smpp/content~content=a793157051~db=all~jumptype=rss
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− | * http://seachestsecret.questacon.edu.au/assets/Delve_Deep_-_Pearl_Oysters.pdf
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− | [[Category:Adventist Youth Honors Answer Book|{{SUBPAGENAME}}]]
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− | <section end="Body" />
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