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| − | {{honor_header|3|1949|Nature|General Conference}}
| + | '''Byssus''', plural "byssi", derives from [[Hebrew language|Hebrew]] ''būṣ'' 'fine linen,' [[Aramaic]] ''bus'', [[Greek language|Greek]] ''βύσσος'' – 'a very fine yellowish [[flax]] and the [[linen]] woven from it', [[Latin]] ''byssus'' – 'fine [[cotton]] or cotton stuff', '[[silk]]' and via [[New Latin]] to '[[sea silk]]'. |
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| − | ==1. Have the Shell Honor. ==
| + | As may be seen above, the word byssus not only refers to the excretions of seashells, as sometimes assumed, but was originally used for various fine threads and cloths. The word is used twice in the text of the [[Rosetta Stone]]. |
| − | {{Ay prerequisite|Nature|Shells}}
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| − | ==2. Define the term "mollusca" or "mollusk." ==
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| − | The word ''mollusc'' is derived from the French ''mollusque'', which originated from the Latin ''molluscus'', meaning thin-shelled, from ''mollis'', soft | |
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| − | The body of a mollusk consists of three sections; a head, with eyes or tentacles; a muscular foot; and a visceral mass housing the organs. | + | # An exceptionally fine and valuable fibre or cloth of ancient times. Originally used for fine flax and linens, its use was later extended to fine cottons, silks, and sea silk. |
| | + | # The long fine silky [[wiktionary:Filament|filament]]s excreted by several [[mollusk]]s (particularly ''[[Pinna (genus)|Pinna nobilis]]'') by which they attach themselves to the [[sea bed]], from which [[sea silk]] is manufactured. They range to 6 [[Centimetre|cm]] in length. |
| | + | # The [[stipe (mycology)|stipe]] (stem) of certain [[fungi]] which are particularly thin and thread-like. |
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| − | ==3. Learn the classification terms of mollusks, know the distinguishing characteristics of each, and become acquainted with several species under each class. == | + | ==In mussels== |
| − | 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.
| + | [[Image:Zebra mussel GLERL 1.jpg|left|thumb|byssus threads on ''[[Dreissena polymorpha]]'']] |
| | + | [[Image: Byssus threads.gif|right|thumbnail|200px|Byssus threads on [[mussel]]s]] |
| | + | 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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| − | <center>
| + | Byssus is a remarkable adhesive that is neither degraded nor deformed by water as are synthetic adhesives. This has spurred [[Genetic engineering|genetic engineers]] to insert mussel [[DNA]] into [[yeast]] cells for translating the genes into the appropriate proteins. |
| − | {| border=1 cellpadding=5
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| − | |width="110" | '''Class'''
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| − | |width="300" | '''Major organisms'''
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| − | |width="120" | '''Extant species'''
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| − | |width="120" | '''Distribution'''
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| − | | Caudofoveata || worm-like organisms || 70 || deep ocean
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| − | | Aplacophora || solenogasters, worm-like organisms || 250 || deep ocean
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| − | | Polyplacophora || chitons || 600 || rocky marine shorelines
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| − | | Monoplacophora || limpet-like organisms || 11 || deep ocean
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| − | | Gastropoda || abalone, limpets, conch, nudibranchs, sea hares, sea butterfly, snails, slugs || 150,000<ref>Ponder, Winston F. and Lindberg, David R. (Eds.) (2008) [http://www.ucpress.edu/books/pages/10802.php ''Phylogeny and Evolution of the Mollusca'']. Berkeley: University of California Press. 481 pp. ISBN 978-0520250925.</ref> || marine, freshwater, land
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| − | |-
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| − | | Cephalopoda || squid, octopus, cuttlefish, nautilus || 786 || marine
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| − | | Bivalvia || clams, oysters, scallops, mussels || 8000 || marine, freshwater
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| − | | Scaphopoda || tusk shells || 350 || marine
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| − | | Rostroconchia † || fossils; probable ancestors of bivalves || extinct || —
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| − | | Helcionelloida † || fossils; snail-like organisms such as ''Latouchella'' || extinct || —
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| − | |}
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| − | </center>
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| − | ==4 Distinguish between univalve and bivalve mollusks from the following considerations: == | + | ==References== |
| − | ===a. Shell ===
| + | * ''The Compact edition of the Oxford English dictionary: complete text reproduced micrographically and Supplement.'' Oxford at the Clarendon Press. 1987 |
| − | The terms ''univalve'' and ''bivalve'' refer to the configuration of the shells of the mollusks. Univalves, such as snails, have shells consisting of one (thus ''uni-'') piece. Bivalves, such as mussels, have shells consisting of two (thus ''bi-'') pieces hinged together.
| + | * ''Webster's Third New International Dictionary (Unabridged)'' 1976. G. & C. Merriam Co. |
| | + | * Ecsedy, Hilda 1975. "Böz – An Exotic Cloth in the Chinese Imperial Court." Hilda Ecsedy. ''Altorientalische Forschungen 3'': pp. 145-153. |
| | + | * Starr, Cecie and Taggart, Ralph. ''Biology: The Unity and Diversity of Life''. Belmont, CA: Thomson Learning, Inc., 2004. |
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| − | ===b. Mollusk body ===
| + | [[Category:Animal anatomy]] |
| − | ;Univalves: Univalve bodies could almost be described as ''folded'' such that the mouth and anus both appear the the shell's opening.
| + | [[Category:Bivalves]] |
| − | ;Bivalves: Bivalves on the other hand, have flattened bodies.
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| − | ===c. Reproduction===
| + | [[de:Byssus]] |
| − | ;Univalves: All land snails are hermaphrodites, producing both spermatozoa and ova. In other words, each individual is both male and female. Some freshwater snails, such as Apple Snails, and marine species, such as periwinkles, have separate sexes; they are male and female. Most snails can mate when they are around 1 year old.
| + | [[es:Biso]] |
| − | | + | [[eo:Bisino]] |
| − | :Prior to reproduction, most land snails perform a ritual courtship before mating. This may last anywhere between two and twelve hours. Prolific breeders, pulmonate land snails inseminate each other in pairs to internally fertilize their ova. Each brood may consist of up to 100 eggs. | + | [[fr:Byssus]] |
| − | | + | [[it:Bisso]] |
| − | :Pulmonate land snails and slugs have a reproductive opening on one side of the body, near the front, through which the outer reproductive organs are extruded so that exchange of sperm can take place. After this, fertilization occurs and the eggs develop. | + | [[lb:Byssus]] |
| − | | + | [[nl:Byssus]] |
| − | :Garden snails bury their eggs in shallow topsoil primarily while the weather is warm and damp, usually 5 to 10 cm down, digging with their foot. Egg sizes differ between species, from a 3 mm diameter in the grove snail to a 6 cm diameter in the Giant African Land Snail. After 2 to 4 weeks of favorable weather, these eggs hatch and the young emerge. Snails may lay eggs as often as once a month. | + | [[pl:Bisior]] |
| − | | + | [[zh:Byssus]] |
| − | ;Bivalves: In bivalves, the sexes are usually separate, but some hermaphroditism is known. Bivalves practice external fertilization. External fertilization is a form of fertilization in which a zilo cell is united with an egg cell external to the body of the female. Thus, the fertilization is said to occur "externally". This is distinct from internal fertilization where the union of the egg and sperm occur inside the female after insemination through copulation.
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| − | :In sexual reproduction, there must be some way of getting the sperm to the egg. Since sperm are designed to be mobile in a watery environment, aquatic mollusks can make use of the water in which they live. Eggs and sperm are simultaneously shed into the water, and the sperm swim through the water to fertilize the egg in a process known as broadcast fertilization.
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| − | ===d. Movements===
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| − | [[Image:Snail climbing grass SMC 07.jpg|thumb|250px|right|Snail climbing a blade of grass]] | |
| − | ;Univalves: Most snails move by gliding along on their muscular foot, which is lubricated with mucus. This motion is powered by succeeding waves of muscular contraction which move down the undersurface of the foot. This muscular action is clearly visible when a snail is crawling on the glass of a window or aquarium. Snails move at a proverbially low speed (1 mm/s is a typical speed for adult ''Helix lucorum''). They produce mucus in order to aid locomotion by reducing friction, and the mucus also helps reduce the snail's risk of mechanical injury from sharp objects. This means that they can 'walk' over sharp objects like razors without being injured.
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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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| − | {{clear}}
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| − | ===e. Securing food===
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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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| − | ===f. Self-preservation===
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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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| − | ==5. Identify from shells or drawings and know the meaning of the following concho logical terms: ==
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| − | ===a. Valve ===
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| − | ===b. Apex ===
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| − | ===c. Aperture ===
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| − | ===d. Byssus ===
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| − | ===e. Foot ===
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| − | ===f. Mantel ===
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| − | ===g. Operculum===
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| − | ===h. Mother of pearl===
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| − | ===i. Epidermis===
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| − | ===j. Ribs===
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| − | ===k. Teeth===
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| − | ===l. Concentric lines===
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| − | ===m. Canal===
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| − | ===n. Spines===
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| − | ===o. Whorls===
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| − | ===p. Lips===
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| − | ==6. Explain the development of a shell. How long do mollusks live?==
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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. ==
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| − | ==8. Explain the activities of the shipworm. ==
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| − | {{:Adventist Youth Honors Answer Book/Nature/Shipworm}}
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| − | ==9. What accounts for the distribution of mollusks.==
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| − | ==10. Name two mollusks that have no shells. ==
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| − | <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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| − | ==11. Find answers for the following interesting questions: ==
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| − | ===a. How are bivalve and univalve animals fastened to their shells? ===
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| − | ===b. How is shell color controlled? ===
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| − | ===c. What mollusk has four gills? ===
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| − | ===d. From what sea animal was India ink formerly made? ===
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| − | ===e. What mollusk spins a silken thread? ===
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| − | ===f. What shells were used for money by ancient tribes? ===
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| − | ===g. What shell is considered sacred by the Tibetans? ===
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| − | ===h. Purple dye of ancient times came from the secretion of what mollusk? ===
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| − | ===i. What is the source of pearls? How are they formed? ===
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| − | ==12. Name six commercial uses for shells. ==
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| − | ==13. Do one of the following: ==
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| − | ===a. Personally find and collect 40 species of shells representing the five classifications. List each shell as to the place and date it was found, common name, scientific name, and class. ===
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| − | ===b. Make a collection of 50 species of shells you have found, received, or purchased representing the five classifications. 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.===
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| − | ==References==
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| − | [[Category:Adventist Youth Honors Answer Book|{{SUBPAGENAME}}]] | |
