Class Amphibia 17C

Taxonomy Phylum Chordata Subphylum Cephalochordata- amphioxus or lancelet Subphylum Urochordata- tunicates or sea squirts Subphylum Vertebrata Class Agnatha- jawless and cartilaginous, hagfish and lamprey Class Chondrichthyes- cartilaginous, sharks and rays Class Osteichthyes- bony fish Class Amphibia- cecilians, salamanders, frogs, toads Class Reptilia- snakes, lizards, turtles, tortoises, alligators, crocodiles, tuataras Class Aves- birds Class Mammalia- dogs, cats, lions, horses, cows, bears, giraffes, elephants, monkeys, kangaroos, humans, platypus, mice, beavers, seals, sea lions, walruses, whales, dolphins, porpoises, manatees, dugongs, anteaters, armadillos, sloths, bats, shrews, moles, hedgehogs… Fish Cold Blooded (Ectotherm) Warm Blooded (Endotherm)

Class Amphibia Skin Lacks scales Richly supplied with blood vessels Kept moistened by secretions from glands in the skin Some secretions are poisonous to discourage predators Chromatophores- cells that color the skin for camouflage or for warning Functions as respiratory organ; blood vessels bring blood close enough to the environment so direct gas exchange can occur

Class Amphibia Feet No claws on the feet Webbing may be present for those that spend time in water

Three Orders Order Apoda Caecilians Worm or snake-like body No appendages Tropical habitats 160 species What’s the difference between apoda and annelida Apoda have a backbone and jaws Both have closed circulatory system

Three Orders Order Caudata Salamanders Slender body with four identical limbs on trunk Temperate habitats 400 species

Three Orders Order Anura Frogs and toads Large head Tailless Short front limbs and large muscular hind limbs Diverse habitats 3900 species

Class Amphibia “double life” Metamorphosis- drastic change in habits and body structures 2-part life cycle is typical Begins as an unshelled egg laid in or near water After hatching, spends time in a swimming stage using gills for respiration, then develops into a terrestrial adult breathing with lungs

Mostly external fertilization, males discharge milt over eggs Female lays jellylike eggs in the water (toads lay strings of eggs, frogs produce masses of eggs) Mostly external fertilization, males discharge milt over eggs Larval salamander resembles adult but with feathery external gills Larval frog = tadpole Oval body tapering to a slender tail. Flap of skin covers gills. Gills degenerate and lungs develop Limbs appear Tail disappears Digestive system changes from being able to digest mainly algae and plant material to where it can digest insects.

Respiration Gills in the larval stage Lungs in the adult stage of terrestrial amphibians Lining of mouth and throat Skin (90-95% of respiration for certain lungless salamanders, also very important for adult frogs in the water)

Circulation Three chambered heart 2 atria and 1 ventricle Left atrium receives oxygenated blood from the gills, skin, or lungs. Right atrium receives deoxygenated blood from the body Oxygenated and deoxygenated blood mix in the ventricle- not very efficient Fish two chambered heart

Ectotherm Hibernation- period of slow body processes, almost a lifeless state, burrow into the mud of a stream or lake during cold periods Estivation- period of inactivity, escape heat by staying at the bottom of a pond, burrowing into the mud, or hiding in a cool place