Chapter30 - Amphibians

*Herpetology is the study of reptiles and amphibians

What is an amphibian?

- 4000+ species
- Gave rise to modern land vertebrates
- Amphibian means -double life-
- Larvae start life in H2O with gills , adults are terrestrial with lungs

Evolutionary adaptations for life on land:

1. stronger bones
2. lungs and breathing tubes
3. sternum (breastbone) and ribs to protect internal organs


Carboniferous Period = Age of Amphibians, 360-290 million years ago

Climate changes caused habitats to disappear

3 orders of amphibians survive today;
1. Frogs and Toads
2. Salamanders
3. Caecilians


Form and Function in Amphibians

1. Feeding: larvae = herbivore, adults = mostly carnivore

Digestive tract; mouth > esophagus > stomach > small intestines > large intestine (colon) > cloaca

2. Respiration: larva = skin and gills, adult = lungs and some through skin

Many terrestrial salamanders = no lungs at all, through skin and mouth cavity

3. Circulation: double loop system

3 chamber heart right atrium, left atrium, and ventricle

Compare Single to Double Loop Circulation

Single: Heart --> Gills --> Body

Double: Heart --> Lungs --> Heart --> Body


circulation circulation double

4. Excretion: kidneys filter liquid waste = urine

Kidneys > ureters > small urinary bladder > cloaca

5. Reproduction: females lay eggs in water, male deposits sperm over eggs


Tadpoles - Herbivorous, Aquatic, Single Loop Circulation, Gills

Frogs - Carnivorous, Terrestrial or Aquatic, Double Loop, Lungs

Yolk of egg nourishes developing embryo

Larvae commonly called tadpoles, metamorphosis is the process by which tadpoles become adults

A few species will care for their eggs by incubating their young in their mouth, on their back, or stomach!

6. Response: well developed nervous and sensory system

1. Eyes move in socket and have a protective structure = nictitating membrane is a transparent membrane that covers the eye when the frog is in the water
2. Tympanic membrane = eardrums
3. Lateral Line systems = detect water movement (vibrations)

Amphibian Taxonomy

Kingdom Animalia
....Phylum Chordata
.........Subphylum Vertebrata
..............Class Amphibia

Order Urodela (Salamanders and Newts) long bodies and tails, lives in moist woods

Mud puppy keeps gills and lives in water all their lives

Order Anura (Frogs and Toads) hop/jump with legs, adult has no tail

Order Apoda (Caecilians) legless with fishlike scales


The number of living species is declining; environmental threats such as decreasing habitats, fungal infections, introduced predators, increasing human population

You'll learn more about the anatomy of frogs when we do the frog dissection!

Other Chapter Notes: Chordates & Fish  | Types of Fish