Chapter 28.3 – Class: AMPHIBIA

I. CharacteristicsA. Thin, moist skin for

breathing thru it: cutaneous respiration

B. Most have 4 legsC. Most live on land – but water is

required due to external fertilization:1. water is needed as a medium to

transport sperm2. eggs lack protective membranes

& a shell – they would dry out on land

D. Ectotherm – an animal that has a variable temperature; heat is from its environment

1. Body reactions require specific temperatures, so amphibians are dormant in very hot & cold seasons

E. Metamorphosis1. Aquatic larvae have gills, tail

fin, & a 2-chambered heart

2. Adults breathe thru skin, have poorly

developed lungs, & a 3-chambered heart

F. 3 chambered heart – this heart provides enough O2 to the body’s cells, since walking on land requires more energy and O2 than swimming

1. 1st chamber receives O2-rich blood from the lungs & skin

skin must be moist to exchange O2

2. 2nd chamber receives O2-poor blood from the body tissues

3. 3rd chamber pumps O2-rich blood to body tissues & O2-poor blood to lungs & skin

II. Diversity of AmphibiansA. Order ANURA: frogs & toads w/ no

tails

1. Predators that eat insects & worms

2. Vocal cords produce sounds to attract a mate

3. Low #s of frogs or frogs w/ deformities may signal

pollutants

Frogs ToadsLong legs Short legs

Poorly developed lungs Well developed lungs

Smooth, moist skin Bumpy, dry skin

Found in water/moist areas

Found on land/loose soil

No spades on hind legs Spades for digging in soil

Few are poisonous (dart frogs)

Many are poisonous

B. Order CAUDATA: salamanders & newts

1. long, slender body w/ neck & tail

2. resemble lizards, but they lack claws & their skin is smooth & moist

Central Newt – toxic!

Red-backed Salamander

Tiger Salamander

4-toedSalamander

C. Order APODA: caecilians1. limbless w/ a short or no tail2. found in the tropics & are

often blind3. internal fertilization