1. 30.2 Amphibians

2. What is an Amphibian?
The class Amphibia transitions from a completely aquatic larva to an air-breathing , semi terrestrial adult
Includes three orders
Caudata: salamanders and newts
Anura: frogs and toads
Apoda: legless caecilians

3. Characteristics: Thin, moist skin Four legs No claws on toes
External fertilization

4. Amphibians are ectotherms
An ectotherm is an animal in which the body temperature changes with the temperature of its surroundings
Become dormant in regions that are too hot or cold for part of the year

5. Amphibians undergo metamorphosis
Fertilized eggs hatch into tadpoles
Possess fins gills, and two-chambered heart
Develop legs, lungs, and three-chambered heart as they grow into adults

6. Walking requires more energy
In the three chambered heart:
One chamber receives oxygen-rich blood from the lungs and skin
Another chamber receives oxygen-poor blood from the body tissue
Blood from both chambers moves into the third chamber
Pumps oxygen-rich blood to body tissues
Pumps oxygen-poor blood back to lungs and skin
Results in some mixing
Skin is an important means of exchanging gases
Must stay moist

7. Diversity of Amphibians
Frogs and toads belong to the order Anura
No tails
Frogs:
long hind legs
smooth moist skin
Toads:
Short legs
Bumpy dry skin

8. Many secrete chemicals through skin as a defense Have vocal chords
Both:
Have jaws and teeth
Eat insects
Many secrete chemicals through skin as a defense
Have vocal chords
Sound producing bands of tissue in the throat
As air moves over it, they vibrate

9. Salamanders belong to the order Caudata
Long slender body with a neck and tail
Resemble lizards but have smooth moist skin and lack claws
Newts are salamanders that live entirely in water

10. Caecilians are limbless amphibians
Have no limbs
Short, or no tail
Primarily tropical animals with small eyes
Eat invertebrates in the soil

11. Origins of Amphibians Challenges of life on land
Air temperatures vary greatly
Without the support of water the body was clumsy and heavy
Amphibians probably evolved from an aquatic tetrapod around the middle of the Paleozoic Era
Survived and dominated because of ability to breathe through their lungs, gills, or skin