1. Amphibians

2. Modern Amphibians Skeleton mostly bony Body forms vary greatly
varying numbers of vertebrae; ribs present in some, absent or fused to vertebrae in others
Body forms vary greatly
elongated trunk with distinct head, neck, and tail to a compact, depressed body
Limbs usually four (tetrapod)
Some are limbless
some have forelimbs much smaller than hindlimbs
Some have limbs small and vestigial
Webbed feet often present
no true nails or claws
forelimb usually with four digits but sometimes five and sometimes fewer

3. Modern Amphibians Skin usually smooth and moist with many glands
some of which may be poison glands
pigment cells (chromatophores) common, or considerable variety
no scales - except concealed dermal ones in some
Mouth usually large with small teeth in upper or both jaws
two nostrils open into anterior part of mouth cavity
Respiration by lungs (absent in some salamanders), skin, and gills in some
either separately or on combination
external gills in the larval form and may persist throughout life in some

4. Modern Amphibians Heart Ectotherms Excretory system
sinus venous, two atria one ventricle, a conus arteriosus,
double circulation through the heart
skin abundantly supplied with blood vessels
Ectotherms
Excretory system
paired mesonephric or opisthonephric kidneys
urea main nitrogenous waste
Ten pairs of cranial nerves

5. Modern Amphibians
Many amphibian species make use of both aquatic and terrestrial habitats
either simultaneously or sequentially during different life stages.
A typical life cycle involves semiterrestrial adults that breed and lay eggs in water.
Eggs then develop into aquatic larvae.
the larvae undergo metamorphosis, or transformation, and become semiterrestrial adults.
Metamorphosis is triggered by changes in concentrations of circulating hormones
metamorphosis is most extreme among frogs, where there is a striking difference between the larva (the tadpole) and the adult.

7. Modern Amphibians All amphibians are carnivorous,
exception of larval frogs (tad-poles),
which are primarily herbivorous.
Most amphibians are generalists, and will eat anything they can capture and ingest.
Frogs and salamanders capture prey with their tongues, which are highly developed.
Certain salamander species have specialized projectile tongues that they fire with impressive accuracy to capture prey.

8. Modern Amphibians
Three living amphibian orders comprise more than 5400 species
Order Gymnophiona (Apoda)
caecilians
Order Urodela (Caudata)
Salamanders
Order Anura (Salientia)
Frogs & toads

9. Order Gymnophiona 160 species Elongate, limbless, burrowing creatures
Found in tropical forests of South America, Africa, Southeast Asia
Long, slender body, small scales
Diet consists of worms & small invertebrates
Internal fertilization; eggs deposited in moist ground near water

10. Caecilians – legless amphibians

11. Order Urodela Tailed amphibians
Oura – tail; delos – evident
Tailed amphibians
~500 species of salamanders
Found in almost all northern temperate regions
Most abundant & divers in North America
Also found in tropical areas of Central America & South America
Most are less than 15 cm long
Japanese giant salamander exceeds 1.5 m

12. Order Urodela Breeding behavior Internal fertilization
Female recovers in her vent a packet of sperm (spermatophore)
Deposited by a male
on a leaf or stick
Aquatic lay eggs in
water
Terrestrial lay eggs in
soft moist earth

13. Order Anura Frogs & Toads – more than 4840 species
An – without; orua - tail
Frogs & Toads – more than 4840 species
Occupy a variety of habitats
Aquatic mode of reproduction & water-permeable skin prevents them from wandering too far from water
Ectotherms
four limbs usually of unequal size
hind limbs are elongated and modified for jumping
head and trunk fused, tail in larval form lost as adult
vocalizations are restricted primarily to the male for courtship, establishing territories
most have external fertilization
where eggs and sperm are shed directly into the water
Generalized reproductive pattern males vocalize to attract females
adults predaceous - insectivorous/carnivorous

17. Order Anura Habitats & Distribution Temperate & tropical regions
Except New Zealand
Oceanic islands & southern South America
Live near water
Some in damp forest
Patchy in distribution
Restricted to certain localities (specific stream or pool)

18. Order Anura Reproduction External fertilization
Eggs begin to develop immediately
Tadpoles develop within a few days