#1
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CSS Specific Book
Can someone tell me is there any book in the market for zoology published specifically for css syllabus ?
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#2
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Yes, dear there are many books of it. Try to find out in urdu Bazar..
Thanks |
#3
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i have seen a book of caravan which is compiled for css exam but it is not that much authentic as foreign books are. And as far as topics are concerned, these are dispersed in these books and you have to go through all the books i-e miller & harley, raven & john, reece & campbell, integrated principles of zoology, verma & agarwal, etc.
I ,too, have solved 15 years papers and have my own notes. |
#4
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can yoy share the notes here ... specially some topics like biting mechanism of snake which are not there in the recommended books
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#5
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BITING MECHANISM OF SNAKES
The mechanism of biting is a complicated process and it can be describes in the following steps: i) Opening of the mouth: By the contraction of the digastric muscles the mouth is opened. ii) Rotation of maxilla: As the mouth opens the lower jaw moves forward and a rotation of the squamosal, quadrate, and mandible in relation to each other occurs. Now the sphenopterygoid muscles contract. This contraction results in the forward movement of the pterygoid and up-pushing of the ectopterygoid. The upward movement of the ectopterygoid brings a rotation of maxilla on its own axis round the lachrymal and as a result the fang is raised and becomes directed forward. The fang is nearly horizontal in position when the mouth remain closed, but during the opening of the mouth to bite, the fang assumes almost vertical position. iii) Closing of the mouth: The closing of the mouth is brought about by the contraction of the temporalis and sphenopterygoid muscles. The point of fang is directed backward w hile the mouth is closed. It takes longer time to open the mouth thanto close it. iv) Transference of veno m: During the contraction of the digastric muscles theposterior ligament is relaxed ad during the rotation of the squamosal bone the fan-shaped ligaments are stretched to squeeze the wall of the poison gland. This makes the poison to come out of the poison gland through the poison duct and the fang. Conclusion: Vipers (family Viperidae) possess hollow fangs on the maxillary bone at the anterior margin of the upper jaw. These fangs connect to venom glands that inject venom when the viper bites. The maxillary bone (upper jaw bone) of vipers is hinged so that when the snake‟s mouth is closed, the fangs fold back and lie along the upper jaw. When the mouth opens, the maxillary bonerotates and causes the fangs to swing down. Because the fangs project outward from the mouth, vipers may strike at objects of any size. Some cobras can “spit” venom at their prey; if not washed from the eyes, the venom may cause blindness. Venom glands are modified salivary glands. Most snake venoms are mixtures of neurotoxins and hemotoxins. The venoms of coral snakes, cobras, and sea snakes are primarily neurotoxins that attack nerve centers and cause respiratory paralysis. The venoms of vipers are primarily hemotoxins. They break up blood cells and attack blood |
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