1. Amphibians
Section 30.2

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

3. 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

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

5. 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

6. 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

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

9. 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

11. 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

12. 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

13. 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

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

15. 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