Amphibians
Amphibians
 Vertebrate (backbone)
 Ectothermic (coldblooded)
 Must absorb heat from
external sources
 When environment
becomes too hot or too
cold, many amphibians
become dormant (inactive
or at rest) by burrowing in
the mud.
Amphibians: Metamorphosis
 All amphibians begin life in water
 Most amphibian eggs are fertilized externally
 Eggs do not have shells (moist; must lay in water)
Amphibians: Metamorphosis
 Fertilized eggs hatched
into tadpoles (larval
stage)
 Tadpoles have fins, gills,
and a 2-chambered heart
 Tadpoles develop into
adults
 Develop legs, lungs, and a
3-chambered heart
Amphibians: Respiration
 Tadpoles obtain
oxygen from water
that passes over gills
 Adults have lungs so
that they can
exchange gases with
the air
 Adults also exchange
gases through their
thin, moist skin
Salamander
tadpole with
feathery gills
extended
Amphibians: Circulation
 Tadpole – 2chambered heart and
a single loop of
vessels
 Adult – 3-chambered
heart and two loops
of vessels (needed
for life on land)
Types of Amphibians:
 Order Anura – frogs & toads
 Do not have tails; feed on insects and worms; have
jaws and teeth; frogs have long legs and smooth
skin; toads have bumpy skin and short legs
Types of Amphibians:
 Order Caudata – salamanders
 Long, slender body with neck and tail; smooth,
moist skin and no claws; some live in water, others
in damp places; hatch from eggs, adults are
carnivorous
Types of Amphibians
 Order Gymnophiona – caecilians
 Burrow into the ground; no limbs; short or no tail;
live in warm, tropical climates; usually blind; eat
earthworms; internal fertilization
Comparison of Hearts