Amphibians
HERPETOLOGY =
the study of reptiles and amphibians
Class Amphibia
What is an amphibian?
❏ 4000+ species
❏ AMPHIBIAN = GREEK
FOR AMPHIBIOS WHICH
MEANS “DOUBLE LIFE”
Amphibians
 VERTEBRATES
 Metamorphosis
 HIBERNATE OR ESTIVATE DEPENDING
ON CLIMATE
 Scientist infer that amphibians evolved
from lobe-finned fishes called
crossopterygians.
Amphibian Characteristics
1st true tetrapod vertebrates
Bony skeletons with four limbs
Exceptions: Caecilians (limbless) and Sirens
(forelimbs only)
Feet are webbed and the toes lack claws.
They have moist, smooth, thin skin with no scales.
Amphibians are ectotherms, which
means their blood temperature rises
and falls with that of the surrounding
environment
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Respiration
●Larva (tadpoles) breathe with gills
●Adult frogs have lungs
Some
amphibians
keep gills all
their life,
mudpuppy
Respiration
 Lungs are internal - allows exchange
of oxygen and carbon dioxide between
blood and air
 Greater the surface area the greater
the amount of oxygen can be
absorbed
 Lungs are not as efficient as gills, but
there is more oxygen in air than in
water so lungs do not have to be
Respiration
 Cutaneous respiration- “Skin
breathing”
 Supplement oxygen intake w/ moist
skin
 Limited by body size
 Many terrestrial salamanders have
no lungs at all  breathe through
skin and mouth cavity
Circulation
Heart is a double loop, with 3 chambers  2
atria and a ventricle that is partly divided
Double Loop
Circulation
 Due to moving to land and requiring
more oxygen for their muscles,
amphibians developed a double
loop in their circulatory system
 Amphibians have pulmonary veins
that deliver oxygen rich blood back
to the heart and then to the
remainder of the body
Larvae have two-chambered hearts;
adults have three-chambered hearts
and well-developed circulation.
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CLOACA
sperm, egg, solid wastes, and urine leave the body through this
opening
Feeding
●Larva (tadpoles) are usually herbivores
●Adults are usually carnivores
●Digestive tract
● Mouth  esophagus  stomach  small
intestine  colon (large intestine)
cloaca
Excretion
Kidneys filter cellular (liquid)
waste = urine
Kidneys  ureters  small
urinary bladder  cloaca
Response
 Well developed nerves and nervous system –
complex brain with cerebrum, cerebellum,
medulla oblongata
 Eyes move in socket and are protected by
nictitating membrane – transparent
membrane that covers the eye when
amphibian is in the water
 Tympanic membrane = eardrums
 Lateral line systems = detect water vibrations
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.
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Amphibian
Reproduction
Require water because eggs lack
shells to prevent water loss
Yolk of egg nourishes developing
embryo
External Fertilization - female
releases eggs and male fertilizes
externally-called amplexus
Reproduction
Larvae commonly called tadpoles, process by
which tadpoles become adults - metamorphosis
A few
species
care for
eggs by
incubating
in mouth,
or on their
back or
stomach!
METAMORPHOSIS
Series of changes that occur as an organism
grows
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.
Eggs 
larva 
young adult
adult
Amphibian Metamorphosis
 It affects nearly every organ in the
tadpole’s body
 Tadpoles:
 Herbivorous, Aquatic, Single-loop
circulation, Gills
 Frogs:
 Carnivorous, Terrestrial or aquatic,
Double-loop circulation, Lungs
Amphibian Evolution
Biologist conclude that amphibians appeared
during the late Devonian period, about 345
million years ago.
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Paleontologists have discovered fossils of a
species that provides the missing evolutionary link
between fish and the first animals that walked
out of water onto land about 375 million years
ago. The newly found species, Tiktaalik roseae,
has a skull, a neck, ribs and parts of the limbs
that are similar to four-legged animals known as
tetrapods, as well as fish-like features such as a
primitive jaw, fins and scales.
Amphibian Adaptations for Life
on Land
●Bones became stronger
●Lungs to breath air
●Limbs to walk on land
●Sternum (breast bone) and ribs to protect
internal
History
• Carboniferous Period = Age of Amphibians
• Climate change caused habitats to
disappear
• 3 groups survive today
- salamanders, frogs, and caecilians
Amphibian Groups
Kingdom Animalia
…..Phylum Chordata
……...Subphylum Vertebrata
………….Class Amphibia
Order Urodela
Order Anura
Order Apoda
Order Anura
• Means “Without a tail”
• Frogs and Toads
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There are about 3,500 known
species of frogs and 300 kinds of
toads
They are found on every
continent except Antarctica
Frogs have smooth, moist skin
Toads have dry, bumpy skin
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Some types spend their entire life in or
near water, but others live mainly on
land and come to the water only to
mate
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Some frogs and toads are climbers that
dwell in trees or burrowers that live
underground.
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See videos at
http://video.nationalgeographic.com
Order Urodela
• Means “visible tail”
• Salamanders and Newts
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Salamanders, typical members of the
Order Urodela, have elongated bodies,
long tails, and smooth, moist skin
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Compared to the anurans, salamanders are
less able to remain on dry land, although
some can live in dry areas by remaining
inactive during the day
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Salamander lay their eggs in water
and like anurans they hatch into
swimming larva
Salamander eggs
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Other species can reproduce in
damp land environments. Eggs laid
on land hatch into miniature adult
salamanders
Marbled Salamander
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Order Apoda
• Means “without feet”
• Caecilians
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• tropical, burrowing worm-like
amphibian that is often legless
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• Have fish-like scales
 These creatures average 30
cm, but they can be up to
1.3m long.
 They have very small eyes
and are often blind.
 They eat worms and other
invertebrates
The caecilian male deposits sperm
directly into the female, and the
female bears live young
Amphibian Ecology
 Number of living species is declining
 Environmental threats:
 Decreasing habitat
 Pollution
 Fungal infections
 Introduced predators
 Increasing human population
Amphibian Habitats
forests
grasslands
lakes, ponds, marshes
rivers and streams
Quick Check
1. How many chambers does the heart of a frog have? ____
2. The opposite of terrestrial is ___________
3. A series of changes that occur from birth to adulthood
(tadpole → frog) is called _______________
4. Tadpoles breathe using _______.
5. The main organ of excretion is the _____________
6. Urine, eggs, and other wastes exit through the __________
7. The opposite of carnivorous is _____________
8. A caecilian is an amphibian that does not have ________
9. The study of reptiles and amphibians is ___________
10. To what kingdom do frogs belong? _________
what phylum? ____________
what class ? _____________