General characters• Reptiles means creeping• Limbs are clawed when present• Study of reptiles is called herpetology• Cold- blooded(poikilothermic)• Exoskeleton of horny scales,scutes or bony plates• Skin dry,cornified and non glandular• Skull is monocondylic• T-shaped interclavicle present• Heart with 2 auricle and incompletely divide ventricle(3.5 chambers) except crocodiles whose have 4 chambers• R.B.C. oval and nucleated• 3-chambered Cloaca present• Uricotelic excretion• Metanephric kidney• Cranial nerves 12 pairs (except snakes which have 10 pairs)• Sexual dimorphism present• Fertilisation internal• Eggs are cleidoic(large yolky eggs with calcareous shell)• No larval stage• Amniotes(all 4extra-embryonic membranes present)
Classification of only living reptiles Class-Reptilia subclass- Subclass- Anapsida Diapsida Order-Order-Chelonia Rhynchocephalia Order-Squamata Order-Crocodilia
• Chelone means turtles ORDER-CHELONIA• Anapsid skull• Body enclosed in a dorsal carapace and ventral plastron made of dermal bony plates• Teeth absent jaws with horny beaks• Single nasal opening• Limbs of aquatic forms modified into paddles• Short tail• Single intromittent organ in male• Sternum is absent• Cloacal respiration found• Longest lifespan• marine turtles;freshwater terrapins and terrestrial tortoises• Example- Chelone
ORDER-RHYNCHOCEPHALIA• Single species sphenodon punctatum(tuatara) of new zealand• Skull diapsid• Skin with scales and mid dorsal row of spine• Vestigial pineal eye present in parietal foramen• No copulatory organ in male• Teeth acrodont• Eggs hatches in 13 months• Living fossils
ORDER-CROCODILIA• aquatic reptiles• Sternum present• Skin thick with bony plates and scutes• Limbs are clawed and webbed• Males have one intromittent organ• Teeth thecodont• Heart completely 4 chambered• Examples-gharial, alligator and crocodile• Example- Crocodylus
ORDER-SQUAMATA• Lizards and snakes• Suborder lacertilia/sauria- lizards• Suborder ophidia/serpentina- snakes• Bifid tongue in most• Jacobson organ (gustatory and and olfatory organ) present in the roof of mouth• horny epidermal scales• Teeth acrodont or pleurodont• Male with double copulatory organ(hemipenes)• Example- Calotes (garden lizard)
Difference between lizards and snakesLIZARDS SNAKES1. Limbs present usually Limbs absent usually2. Sternum present Srernum absent3. Eyelids are movable Eyelids are immovable4. Tympanum is present Tympanum is absent5. Both lungs well developed Left lung usually reduced6. Nictitating membrane present Nictitating membrane absent
Dinosaurs• Dino-terrible; saurus-lizard• They were diapsid• Extict reptiles• Thecodont teeth• Clavicle and interclavicle absent• Double headed ribs• Extinct due to meteor attack on earth• Dinosaurs were aquatic,aerial and terrestial• They was present on earth on jurassic epoch of mesozoic era
IDENTIFICATION OF POISONOUS AND NON-POISONOUS SNAKES
POISONOUS SNAKES OF INDIA The common krait.Indian Cobra Russells viper. The saw-scaled viper.
SNAKE VENOM• There are about more than 300 species of snakes in INDIA out of which only 20 % are poisonous and 80 % are non-poisonous.• Fangs are modified maxillary teeth’s• Poison glands are modified parotid salivary glands• Snake venom is modified saliva used by snakes to immobilize and digest prey or to serve as a defence mechanism against a predator• Venom is mixture of enzymes and proteins• It is tasteless, odourless and acidic in nature• It is fatal only when mixed in blood• Haemotoxin affect circulatory system by damaging blood vessels and haemorrhage• Neurotoxin affect nervous system and cause death due to paralysis of respiratory muscles and asphyxia
Medicinal uses of venom•In Drug researches•Have antibacterial applications•To cure Excessive bleeding: some of the enzymes in venomhas been found to clot blood which stop excessive bleeding.•To cure Stroke: Pit Viper venom has potential for breakingblood clots and treating stroke victims.•To cure Neurological diseases :Enzymes from cobra venommay be cures for Parkinsons disease and Alzheimers disease.•To cure Cancer (various types) : An enzyme derived fromcopperhead venom could be used to treatment for breastcancer.•To prevent Aging: some are even used in a commercialwrinkle cream•To cure arthritis•To cure paralysis
Antivenom/Antivenin• Antivenom is a antibody (ig G) for snake venom• It is a protein• It is prepared by hyperimmunising horses against venoms of snake• It neutralises the free, unbound venom & also dissociates the bound toxin• If venom is obtained from a single species, then it is called monovalent antivenom. If the antivenom obtained from two or more species of snakes, then it is called polyvalent.• In India Antivenin is produced at the Haffkin’s Institute at Bombay and Central Research Institute at Himachal Pradesh.
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