Transcript Phylum Chordata Subphylum Vertebrata Class Amphibia

Phylum Chordata
Subphylum Vertebrata
Class Amphibia
Amphibians
Amphi – double;
frogs, toads, caecilians,
salamanders
• Thin, moist skin
• 4 legs
• terrestrial, but
closely tied to
water
Amphibians
• both internal and external
fertilization
• eggs lack protective
• membrane and shell –
need water to prevent
dessication.
red eye tree frog eggs
http://nationalzoo.si.edu/Animals/Reptile
sAmphibians/Exhibit/Topics/zoo_breedi
ng.cfm?inc=o
Ectotherms
• body temperature is dependent on
environmental temperature
• become dormant during times of year when
it is too hot or too cold - estivate
Metamorphosis
Metamorphosis in
frogs
Herbivorous tadpoles hatch with internal gills
• increase in mouth and tongue size
• loss of gills / formation of lungs
• growth of legs, resorption of tail
• new visual pigment in eyes
• hemoglobin protein in blood
• insectivorous adult
Metamorphosis in salamanders
• young aquatic salamanders have gills and a
tail fin
• adults do not have gills or fins – breathe
through skin or with lungs
Metamorphosis in salamanders
Some salamanders do not have larval stage,
but hatch as small versions of adults
Circulatory System
• 3-chambered heart
• one chamber gets oxygen rich blood from
lungs
• one chamber gets oxygen poor blood from
body tissues
• blood from both go to third chamber –
blood goes to body tissues and skin
Order Anura
Frogs and Toads
Frogs
• smooth, moist skin
• long legs
Toads
• bumpy, dry skin
• short legs
Both are tailless and insectivorous
Order Anura
Frogs and Toads
• vocal cords capable of producing a wide
range of sounds.
• Vocal cords are sound-producing bands of
tissue in the throat.
Order Caudata
Salamanders
• long, slender body with a neck and tail.
• smooth, moist skin
• lack claws
• a few cm to 1.5 m
• carnivorous
Order Apoda
Caecilians
• burrowing amphibians, have no limbs, and
have a short, or no, tail.
• primarily tropical animals with small eyes
that often are blind.
• eat earthworms and other invertebrates
found in the soil.
• have internal fertilization.
Origins of Amphibians
• Most likely, amphibians arose as their
ability to breathe air through well-developed
lungs evolved.
• The success of inhabiting the land depended
on adaptations that would provide support,
protect membranes involved in respiration,
and provide efficient circulation.
Origins of Amphibians
• Amphibians first appeared about 360
million years ago.
• Amphibians probably evolved
from an aquatic tetrapod around
the middle of the Paleozoic Era.
Challenges to life on land
• Land life for amphibians held many dangers.
• Unlike the temperature of water, which
remains fairly constant, air temperatures
can vary greatly.
• In addition, without the support of water,
the body was clumsy and heavy.
Challenges to life on land
• Able to breathe through their lungs,
gills, or skin, amphibians became, for a
time, the dominant vertebrates on land.