تنبيه :: عزيزي اذا واجهتك مشكلة في تصفح الموقع , فاننا ننصحك بترقيه متصفحك الى احدث اصدار أو استخدام متصفح فايرفوكس المجاني .. بالضغط هنا .. ثم اضغط على مستطيل الاخضر (تحميل مجاني) .
 
 
النتائج 1 إلى 3 من 3

الموضوع: report about shark

  1. #1

    a-r
    عضو جديد
    الصورة الرمزية a-r
    الحالة : a-r غير متواجد حالياً
    رقم العضوية : 74323
    تاريخ التسجيل : 04-02-11
    الدولة : عراق
    الوظيفة : طالبة
    الجنـس : انثـى
    المشاركات : 4
    التقييم : 10
    Array

    افتراضي report about shark


    لو سمحتوا اريد report about shark بس بسرعة لان حيل محتاجتة










  2. #2
    عضو فضي
    الصورة الرمزية علم الدين
    الحالة : علم الدين غير متواجد حالياً
    رقم العضوية : 3267
    تاريخ التسجيل : 16-02-08
    الجنـس : ذكـر
    المشاركات : 306
    التقييم : 123
    Array

    افتراضي رد: report about shark


    Introduction:
    Sharks (superorder Selachimorpha) are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago.
    Since that time, sharks have diversified into 440 species, ranging in size from the small dwarf lanternshark, Etmopterus perryi, a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark, Rhincodon typus, the largest fish, which reaches approximately 12 metres (39 ft 4 in) and which feeds only on plankton, squid, and small fish by filter feeding. Sharks are found in all seas and are common down to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater, with a few exceptions such as the bull shark and the river shark which can live both in seawater and freshwater. They breathe through five to seven gill slits. Sharks have a covering of dermal denticles that protects their skin from damage and parasites, and improves their fluid dynamics so the shark can move faster. They have several sets of replaceable teeth.
    Well-known species such as the great white shark, tiger shark, and the hammerhead are apex predators, at the top of the underwater food chain. Their extraordinary skills as predators fascinate and frighten humans, even as their survival is under serious threat from fishing and other human activities.
    Subject
    Etymology:
    Until the 16th century, sharks were known to mariners as "sea dogs".According to the OED the name "shark" first came into use after Sir John Hawkins' sailors exhibited one in London in 1569 and used the word to refer to the large sharks of the Caribbean Sea, and later as a general term for all sharks. It has also been suggested to be derived from the Yucatec Maya word for shark, xok, pronounced 'shok'.
    Anatomy:
    Teeth:
    Shark teeth are embedded in the gums rather than directly affixed to the jaw, and are constantly replaced throughout life. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward as in a "conveyor belt"; some sharks lose 30,000 or more teeth in their lifetime. The rate of tooth replacement varies from once every 8–10 days to several months. In most species teeth are replaced one at a time, except in ******cutter sharks the entire row of teeth is replaced simultaneously.
    Tooth shape depends on diet: sharks that feed on mollusks and crustaceans have dense flattened teeth for crushing, those that feed on fish have needle-like teeth for gripping, and those that feed on larger prey such as mammals have pointed lower teeth for gripping and triangular upper teeth with serrated edges for cutting. The teeth of plankton-feeders such as the basking shark are smaller and non-functional.
    Skeleton
    Shark skeletons are very different from those of bony fish and terrestrial vertebrates. Sharks and other cartilaginous fish (skates and rays) have skeletons made of cartilage and connective tissue. Cartilage is flexible and durable, yet has about half the density of bone. This reduces the skeleton’s weight, saving energy. Sharks have no rib cage and therefore on land a shark's own weight can crush it.
    Jaw:
    Like its relatives, rays and skates, the shark's jaw is not attached to the cranium. The jaw's surface, like the shark's vertebrae and gill arches, needs extra support due to its heavy exposure to physical stress and its need for strength. It has a layer of tiny hexagonal plates called "tesserae", which are crystal blocks of calcium salts arranged as a mosaic. This gives these areas much of the same strength found in the bony tissue found in other animals.
    Generally sharks have only one layer of tesserae, but the jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have two to three layers or more, depending on body size. The jaws of a large great white shark may have up to five layers. In the rostrum (snout), the cartilage can be spongy and flexible to absorb the power of impacts.
    Fins:
    Fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hair and feathers. Sharks can only drift away from objects directly in front of them because their fins do not allow them to move in the tail-first direction.
    Dermal denticles:
    Unlike bony fish, sharks have a complex dermal corset made of flexible collagenous fibers and arranged as a helical network surrounding their body. This works as an outer skeleton, providing attachment for their swimming muscles and thus saving energy.[13] In the past, sharkskin has been used as sandpaper. Their dermal teeth give them hydrodynamic advantages as they reduceturbulence when swimming.

    Conclusion
    Sharks are often killed for shark fin soup. Fishermen capture live sharks, fin them, and dump the finless animal back into the water. Finning involves removing the fin with a hot ****l blade.
    Sharks generally reach sexual maturity only after many years and produce few offspring in comparison to other harvested fish. Harvesting sharks before they reproduce severely impacts future populations.
    Shark fin has become a major trade within black markets all over the world. Fins sell for about $300/lb in 2009

    References:
    1. Martin, R. Aidan. "Geologic Time". ReefQuest. Retrieved 2006-09-09.
    2. Allen, Thomas B. (1999). The Shark Almanac. New York: The Lyons Press
    3. Jones, Tom. "The Xoc, the Sharke, and the Sea Dogs: An Historical Encounter". Retrieved 2009-07-11.








    التعديل الأخير تم بواسطة علم الدين ; 11-02-12 الساعة 10:40 PM
    لا تقل أصلي وفصلي دائبا***إن أصل الفتى ما قد حصل
    لا تقل ذهـــــبت أيــامـــه ***كل من سار على الدرب وصل

    للاطلاع على الجديد النافع الممتع ،مواضيع شيقة وممتعة ومفيدة :
    مدونة العلم والمعرفة للجميع

    http://alelmwalmarefa.blogspot.com/

  3. #3
    مشرفه اللغه الانجليزيه
    المرحله الثانويه
    الصورة الرمزية تاكي
    الحالة : تاكي غير متواجد حالياً
    رقم العضوية : 3452
    تاريخ التسجيل : 17-02-08
    الدولة : N my lovely country UAE ..~
    الوظيفة : خريجة بكالوريوس
    الجنـس : انثـى
    المشاركات : 1,472
    التقييم : 244
    Array
    MY SMS:

    Everything is okay in the end. If it's not okay, then it's not the end

    افتراضي رد: report about shark


    well done اخوي علم الدين

    الله يوفقك واستمر في مشاركاتك المفيدة ^^






معلومات الموضوع

الأعضاء الذين يشاهدون هذا الموضوع

الذين يشاهدون الموضوع الآن: 1 (0 من الأعضاء و 1 زائر)

المواضيع المتشابهه

  1. موضوع عن سمك القرش , shark
    بواسطة esraa2001 في المنتدى اللغة الانكليزية
    مشاركات: 6
    آخر مشاركة: 13-04-23, 07:49 PM
  2. تقرير / بحث : shark للصف العااشر E
    بواسطة العاشق الصغير في المنتدى اللغة الانكليزية
    مشاركات: 4
    آخر مشاركة: 11-10-28, 09:58 PM
  3. search about The Great White Shark بحث عن اسماك القرش البيضاء الضخمة
    بواسطة المعshoootمري في المنتدى اللغة الانكليزية
    مشاركات: 2
    آخر مشاركة: 11-05-23, 05:15 PM
  4. English report
    بواسطة Prince Evil في المنتدى اللغة الانكليزية
    مشاركات: 3
    آخر مشاركة: 10-01-05, 05:52 PM
  5. English report , Report about stress , stress
    بواسطة شهماوي 4ever في المنتدى اللغة الانكليزية English
    مشاركات: 2
    آخر مشاركة: 08-11-08, 04:06 PM

الكلمات الدلالية لهذا الموضوع

المفضلات

المفضلات

ضوابط المشاركة

  • لا تستطيع إضافة مواضيع جديدة
  • لا تستطيع الرد على المواضيع
  • لا تستطيع إرفاق ملفات
  • لا تستطيع تعديل مشاركاتك
  •