Amphibians Section 33.3

Modern Amphibians – Key Characteristics Legs Lungs Double-loop circulation Partially divided heart Cutaneous respiration

Respiration Larval amphibians have gills but most adults have lungs Amphibian lungs do not have very much surface area Therefore, the lungs are not very efficient Most amphibians also rely on cutaneous respiration through their thin, moist skin

Circulation Double-loop in amphibians allows more oxygen to travel to tissues: heart  lungs  heart  body This is possible because of the pulmonary veins, which carry oxygen rich blood from the lungs to the heart The amphibian heart is 3-chambered: Right & left atrium – separated by the septum One ventricle – where high O2 blood and low O2 blood will mix

Frogs & Toads Go through metamorphosis from tadpole to adult Not only a change in form, but internal changes as well: tadpoles eat plants, adults are carnivores Frogs have moist, smooth skin Toads have drier, bumpy skin

Salamanders, Newts, & Caecilians Long and skinny with legs (except caecilians) Most live on land – many lay their eggs in moist areas Caecilians have no legs – burrow underground; mostly tropical