>> Mostly terrestrial, aquatic or amphibious
>> Two pairs of pentadactyl limbs present
>> Lungs are the chief respiratory organs
>> It includes the classes Amphibia, Reptilia, Aves and Mammalia
Class Amphibia:
>> Earliest group of tetrapods and lead dual mode
>> Evolved during devonian period and flourished during carboniferous period
>> Osteolepid fishes are ancestors of amphibians
>> Body divisions are head & trunk
>> Skin soft without exoskeleton
>> Two pairs of pentadactyl limbs without claws present
>> Skull dicondylic
>> Vertebrae procoelous (anurans), amphicoelous(apodans)and opisthocoelous (many urodeles)
>> Sternum developed for the first time in this group
>> Mouth large, teeth are homodont, acrodont, polyphyodont
>> Respiration mostly through skin (cutaneous),buccal cavity(buccal respiration) or lungs (pulmonary respiration)
>> Heart three chambered with sinus venosus on dorsal side and truncus arteriosus on ventral side.
>> Incomplete double circulation
>> Hepatic and renal portal systems are well developed
>> Kidneys mesonephric; ureotelic
>> Brain covered by outer duramater and inner piamater
>> 10 pairs of cranial nerves
>> Middle ear has single ossicle called columella auris which is modified hyomandibular
>> Tympanum, lacrimal and harderian glands appeared for the first time.
>> Eggs are mesolecithal and teloleci thal
>> Development mostly indirect
>> Amphibia includes 3 orders
>> Order Apoda/Gymnophiona-caecilians or blind worms. Eg. Ichthyo phis, Uraeotyphlus, Gegenophis, Typhlonectes
>> Order Urodela/Caudata-Salam and ers and newts, Eg. Salamandra, Nect urus, Mud puppy Tylototriton (Him alayan newt), Ambystoma (tiger salamander), Amphiuma(congoeel), Cryptobranchus
>> Order Anura/Salientia-frogs and to ads Eg.Bufo melanosticus (Indian toad) Rana (frog)Rhacophorus (Flying frog) Hyla(Tree frog) Alytes (Mid wife toad)Ascaphus
FROG
order : Anura
Family : Ranidae
>> Freshwater in habitat
>> Carnivores
>> Poikilothermic anamniotes
>> Frogs exhibit hibernation (winter sleep) and aestivation (summer sleep)
>> Change the skin colour to match their surroundings which is called camouflage Rana tigrina
>> Skin smooth,moist and scaleless
>> Body divided into head and trunk
>> Neck and tail are absent
>> Eyes with immovable upper eyelid and the movable lower eyelid is drawn over the eye ball as nictitating membrane.
>> Tympanum present behind and below each eye
>> Forelimbs with four fingers, hindlimbs with five toes.
>> Webbed feet help in swimming
>> Sexual dimorphism: Male frogs have sound amplifying vocal sacs and a copulatory or
>> amplexusory pad on the first digit of each fore limb.
Digestive system
>> Alimentary canal shorter as frog is carnivorous
>> Mouth opens into large buccopharyngeal cavity
>> Teeth present along the margin of upper jaw only called maxillary teeth
>> Vomerine teeth are present on the roof of buccal cavity.
>> Maxillary teeth are homodont, acrodont and polyphyodont
>> Tongue bifid and useful for capturing the prey
>> Buccopharyngeal cavity opens into oesophagus through gullet.
>> Oesophagus is short and leads into stomach
>> sphincter present between oesophagus and stomach whereas pyloric sphincter present between stomach and dueodenum
>> Dueodenum and ileum are anterior and posterior parts of small intestine.
>> Rectum forms the large intestine which opens into cloacal chamber
>> Cloacal chamber also receives ureters, urinary bladder and opens out by cloacal aperture.
>> Villi in small intestine are foldings of columnar epitherlium which increase the area of absorption.
>> Dueodenum and ileum are anterior posterior parts of small intestine.
>> Rectum forms the large intestine which opens into cloacal chamber
>> Cloacal chamber also receives urete rs and urinary bladder and opens out by cloacal aperture
>> Villi in small intestine are floldings of columnar epithelium which incre ase the area of absorption.
>> Liver bilobed with gall bladder to store the bile juice
>> Bile duct is formed by the union of hepatic ducts and cystic duct
>> Panecreas is an irregular gland present between stomach and dueodenum
>> Pancreatic ducts join the bile duct forming hepatopancreatic duct which opens into dueodenum.
>> Bile helps in emulsifiation of fats and converts the acidic food to alkaline medium
>> Digestion occurs by the action of pancreatic juice and intestinal juice (succus entericus)
Respiratory system:
>> Respiraton occurs by 3 methods.
>> Cutaneous respiration- occurs thro ugh moist, vascular skin and is the most important method of respiration
>> Buccopharyngeal respiration-occurs through moist vascular lining of buccopharyngeal cavity
>> Pulmonary respiration-occurs thro ugh lungs and buccopharyngeal cavity acts as force pump.
>> Floor of the buccal cavity is raised and lowered by the contractions of petrohyal and sternohyal muscles respiration.
>> Glottis opens into laryngotracheal chamber which is connected to lungs by short bronchi
>> Vocalcords are present in laryngotracheal chamber
>> Laryngotracheal chamber is supported by ring like cricoid and two crescentic arytenoid cartilages.
Circulatory system:
>> Heart-3 chambered with two atria and single ventricle and covered by double layer pericardium
>> Sinus venosus opens into right atrium whereas common pulmonary vein opens into left atrium.
>> Atrioventricular aperture is the common opening through which the two atria open into ventricle.
>> Atrioventricular aperture is guarded by 2 pairs of atrioventricular valves.
>> Atrioventricular valves are attached to the wall of ventricle by chordae tendinae.
>> Columnae carneae are the ridges of the thick muscular walls of ventricle.
>> Conus arteriosus arises from the right side of ventricle.
>> Pylangium and synangium are proximal and distal parts of conus arteriosus
>> 2 sets of semilunarvalves are present, one set at the origin of conus arteriosus and second set
>> between pylangium and synangium.
>> Longitudinal spiral valve divides the conus arteriosus into dorsal, left cavum pulmocutaneum and ventral, right cavum aorticum
