*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

History:
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

Feeding: larvae = herbivore, adults = mostly carnivore

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

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

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

Circulation: double loop system ( See figure 30-24 )
3 chamber heart right atrium, left atrium, and ventricle

Compare Single to Double Loop Circulation Single Heart --> Gills --> Body Double Heart --> Lungs --> Heart --> Body

Excretion: kidneys filter liquid waste = urine
Kidneys > ureters > small urinary bladder > cloaca

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

Yolk of egg nourishes developing embryo

Larvae commonly called tadpoles

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

Metamorphosis see figure 30-25

Response: well developed nervous and sensory system ( See figure 30-26)

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)

Groups of amphibians (see figure 30-27)

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

Ecology

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

Frog Stuff

Frogs are carnivorous and feed on insects and worms. Larger frogs even prey on birds and small mammals. Some frogs eat other frogs. See a frog eating a mouse. Frogs always swallow prey whole - they do not chew.

Poison Dart frogs have bright coloration to warn predators that they are poisonous.
[ Strawberry Poison Dart Frog ]

Frogs vs. Toads - Frogs tend to have slimy skin and live in water. Toads have dry bumpy skin. See the frog gallery to compare the two.

If you're interested in different species of frogs check out this animal site: Frogs & Toads

Frogs are called bioindicator species - since water and oxygen goes across their skin, pollution in the environment causes deformities and other problems. Scientists measure the health of an environment by looking at the health of the frogs. See deformed frog. Another deformed frog.

Surinam frogs have a spongey layer of skin on their back, tadpoles develop within
The Darwin Frog carries its young in its mouth

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