Amphibians Section 30.2

Animal Classification Sponges Cnidarians Worms Mollusks Arthropods Echinoderms Invertebrates Animals Fishes Amphibians Reptiles Ectotherms (cold-blooded) Amphibians Vertebrates Birds Mammals Endotherms (warm-blooded)

What is an Amphibian? Class Amphibia – means “double life” Starts life in water and changes on land Evolutionary advantages over fishes Thin, moist skin Most amphibians have four legs Lungs

What is an Amphibian? Nearly all amphibians rely on water for reproduction Undergo external fertilization Water is needed to transport sperm

Ectotherms Amphibians become dormant in regions that are too hot or cold for part of the year Many of them burrow into mud and stay there until suitable conditions return

Metamorphosis Tadpoles possess fins, gills, and a two-chambered heart as seen in fish Tadpoles develop legs, lungs, and a three-chambered heart to become adults

Walking Requires More Energy The evolution of the three-chambered heart in amphibians ensured that cells received the proper amount of oxygen

Walking Requires More Energy One chamber receives oxygen-rich blood from the lungs and skin Another chamber receives oxygen-poor blood from the body tissues Blood from both chambers then moves to the third chamber which mixes the two types of blood

Walking Requires More Energy Because the skin of an amphibian must stay moist to exchange gases, most amphibians are limited to life on the water’s edge or other moist areas

Frogs and Toads Frogs and toads belong to the order Anura Frogs have long hind legs and smooth, moist skin Toads have short legs and bumpy, thick, dry skin

Frogs and Toads Frogs and toads also have vocal cords Vocal cords – sound-producing bands of tissue in the throat As air moves over the vocal cords, they vibrate and cause molecules in the air to vibrate

Frogs and Toads Tympanic membrane – amplifies sounds frogs and toads make Throat pouches and tympanic membranes increase the loudness of their calls

Frogs and Toads Frogs and toads are among the first organisms to be exposed to pollutants in the air, on land, or in the water Declining numbers of frogs species sometimes indicate the presence of pollutants in the environment