Poikelotherms- cold blooded
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It may be defined as a class of those animals which are cold blooded vertebrates amphibious in habit having tetrapodous limbs or pentadactyle pattern and require presence of water for breathing purpose.Amphibia have got an intermediate position between fishes and reptiles. They resemble in general pattern of their body with fishes and to some extent in anatomical pattern of body they are more reptilian. In development they are fish like and exhibit many important fish characters in larval forms.They possess some important characters which are mentioned below-
1)In animal kingdom amphibians are placed between fish and reptiles. They include frogs,toads,salamanders, Gymnophions(Apoda-order limbless amphibians or Ceacelians).They are amphibious in habit i. e. they may live on land as well as in water.They have 2 pairs of pentadactyle limbs.
2)They are cold blooded animals. Their skin is smooth or rough,moist, glandular and naked without any scales except in Gymnophiona.
3)Eyes with movable eyelids.
4)Nostrils paired and connected to mouth cavity.
5)Skull with occipital condyles to articulate with atlas.
6)Teeth present.
7)Heart 3 chambered,RBCs nucleated and oval.
8)Respiration by gills,lungs,skin and by buccal cavity.
9)Aotic arches symmetrical.
10)Kidney mesonephric provided with permanent nephrostoma.
11)Cloaca present which receives duct from reproductive system, excretory system and opening of digestive system.
12)Brain with 10 pairs of cranial nerves.
13)Eggs with gelatinous covering usually laid in water.
14)Larva pass through aquatic stage before metamorphosis.
15)They reveal some parental care.
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