Phylum
Chordata
Class Amphibia
History
›  “Amphibian”
comes from the Greek word
meaning “both life”
›  Amphibians can live in water and on land
History
›  True
“tetrapods” (four legs)
›  Developed supportive skeleton for life on
land
HIstory
›  Girdles
= skeletal bones connecting the
central skeleton to the bones of the
appendages
›  Other
skeletal strengthening: rib cage and
cranium
Characteristics of
Amphibians
Ectothermic
›  Amphibians
are cold-blooded which
means their blood temperature rises and
falls with that of the surrounding
environment.
Respiration
›  They
use gills, lungs, skin, and mouth
cavity during respiration.
Skin and Feet
›  They
have moist, smooth, thin skin with no
scales. Feet are webbed and the toes
lack claws.
Dependent on Water
› 
› 
› 
› 
Respiration through skin requires it to be
thin and moist
Lose lots of water through skin and must
keep it continually moist to prevent lethal
dehydration
Must reproduce in the water since eggs
would dry up on land
Aquatic larval stage more closely related
to fish than terrestrial animals
Metamorphosis
›  Amphibians
have many prominent
characteristics that are adaptations to a
life spent both on land and in water:
›  They
change from an aquatic larval stage
to a terrestrial adult
form. This transformation is called
metamorphosis
Eggs
›  Eggs
lack multicellular membranes or
shells. They are usually laid in water or in a
moist environment and fertilized
externally.
Torpor
›  Amphibians
enter a state of dormancy or
torpor when conditions are unfavorable.
They often bury themselves in mud or
leaves, emerging when conditions are
better.
Torpor
›  Such
states of inactivity are known as:
›  Hibernation
(winter)
›  Estivation (summer)
Classification of
Amphibians
4 Main Groups of Amphibians
›  Anura—frogs
and toads
›  Urodela—salamanders
›  Trachystoma—mud eels
›  Apoda—caecillians
Order Anura
›  Means
“without a tail”
›  Frogs and toads
Order Anura
›  ~3,500
species of frogs
›  ~300 species of toads
›  The most diverse group of amphibians.
›  Jumping locomotion allowed exploitation
of new terrestrial niches
›  Live in almost any climate (except high
latitudes in Arctic,
Antarctic, some oceanic
islands, some extremely
dry deserts)
Order Anura
›  Adaptations
jumping
locomotion
›  Hind
for
limbs much
longer than
forelimbs
›  Short trunk
›  Tail lost
›  Flattened head
›  Large eyes
Order Anura
› Many
deposit
eggs in water;
get freeswimming
tadpoles
› Others lay
terrestrial eggs
› Some carry their
eggs with
them
Order Anura
› Some
types
spend their
entire life in or
near water, but
others live
mainly on land
and come to
the water only
to mate
Order Anura
› Some
frogs and
toads are
climbers that
dwell in trees or
burrowers that
live
underground.
Frog vs. Toad
›  Toads
and frogs have many similarities in
the way they look.
›  Some basic differences between them
are: toads have dry, warty skin, while frogs
have smooth, wet skin
Frog vs. Toad
Frog
Toad
Frog vs. Toad
Frog
Toad
Order Anura
›  Both
frogs and toads return to water to
reproduce. In nearly all species eggs are
fertilized externally. The fertilized eggs
hatch into swimming larval forms called
tadpoles
Order Urodela
›  Means
“visible tail”
›  Salamanders
Order Urodela
›  Long
bodies, moist skin
›  Long tails, 2 pairs of limbs of
approximately the same size
›  Primarily live in Northern Hemisphere
(abundant in cool, moist forests, only 1
type tropical)
Order Urodela
›  Salamander
lay their eggs in water and
like anurans they hatch into swimming
larva
Order Urodela
›  Other
species can reproduce in damp
land environments. Eggs laid on land
hatch into miniature adult salamanders
Order Trachystoma
›  Means
“rough mouth”
›  Mud eels a.k.a. sirens
›  Sirens live in the eastern United States and
north-eastern Mexico.
Order Trachystoma
Order Trachystoma
Order Apoda
›  Means
“no legs”
›  Caecilians
›  Tropical burrowing
amphibians
Order Apoda
o 
o 
o 
These legless wormlike creatures average
30 cm long, but they can be up to 1.3m
long.
They have very small eyes and are often
blind.
They eat worms and other invertebrates
Order Apoda
›  Reproduction
›  The
caecilian male deposits sperm directly
into the female, and the female bears live
young