Amphibians First Tetrapods on Land Class Amphibia First
Amphibians First Tetrapods on Land
Class: Amphibia • First truly tetrapod vertebrate • Ectothermic • All amphibians have bony skeletons • Most have 4 limbs, except Caecilians (limbless) • Many have webbed feet • Typically the glandular skin is smooth, moist, and lacks scales • Metamorphose from juvenile water breathing to adult air breathing • Ecological indicators
p p p Order Anura (Salientia): Frogs and Toads Order Caudata (Urodela): Salamanders, Newts, Waterdogs, Mudpuppies, Sirens, and Amphiuma Order Gymnophiona (Apoda): Caecilians
Class: Amphibia - Gas exchange occurs through lungs, gills, and/or the skin - - Adults have double circulation - - Some salamanders have no lungs (secondarily lost) Both a pulmonary and a systemic circuit Heart has three chambers - Two atria and one ventricle Some mixing of oxygenated and deoxygenated blood occurs in ventricle
Anamniotic egg http: //epod. usra. edu/archive/images/egg_mass. jpg p Jellylike n p unshelled; must develop in water Small-sized n lack large membranes to nourish embryo and store waste Amphibian egg mass
Amphibian development http: //www. herpnet. net/Iowa-Herpetology/ http: //www. mybitoftheplanet. com/2002/ Newt http: //fwie. fw. vt. edu/VHS/ Controlled by the hormone thyroxin http: //www. herpnet. net/Iowa-Herpetology/
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