1.
Animal Diversity: Vertebrates
by
Maryam Riasat
AMPHIBIANS

2.
Amphibians
 The word "amphibian" means
two-lives, one in the water and
one on land.
 They live the first part of their
lives in the water and the last part
on the land.
 When they hatch from their eggs,
amphibians have gills so they can
breathe in the water.
 They also have fins to help them
swim, just like fish.
 Later, their bodies change,
growing legs and lungs enabling
them to live on the land.

3.
General Characteristics
 Spends first stages of life in water as
tadpoles
 Tadpoles are herbivorous while adults are
carnivorous
 Have no nails or claws
 Minimal number of teeth
 Most have a tongue that is projectile and
sticky
 They are ectotherms
 During extreme environmental conditions
they either hibernate (winter) or aestivate
(summer)
 The skin is smooth and rough without any
scales, but with glands that make it moist
 Contains mucous glands, poison glands
and pigment cells (colored)

4.
Respiration
 Cutaneous – Gas exchange occurs
across moist skin
Pulmonary – Gas exchange occurs
in paired lungs (too small for all gas
exchange)
 Gills – Larval forms
 Amphibians have moist skin that is
smooth, thin, and without scales.
 They have many capillaries directly
beneath the skin and in the lining of
the mouth.
 This makes it possible for oxygen
and carbon dioxide to be exchanged.
 Amphibians also have small, simple,
sac-like lungs in the chest cavity for
the exchange of oxygen and carbon
dioxide.

5.
Circulation
 Blood system
 Heart: 2 atriums and 1 ventricle
 In an amphibian’s three-
chambered heart, one chamber
receives oxygen-filled blood
from the lungs and skin, and
another chamber receives carbon
dioxide-filled blood from the
body tissues.
 Blood moves from both of these
chambers to the third chamber,
which pumps oxygen-filled
blood to body tissues and carbon
dioxide-filled blood back to the
lungs.

6.
Nervous system
 Central nervous system is
well developed
 The brain occupies
completely the cranial
cavity The brain is divided
into fore, mid and hind
brains
 Brain continuous as spinal
cord.
 10 pairs of cranial nerves
will arise

7.
Muscular and sensory system
 Well developed brain attached
to the dorsal nerve cord
 They contain a well developed
muscular system. Sensory
receptors located all over the
skin
 Good vision since these
animals are mainly vision
feeders
 They use their sight to find and
capture food.

8.
Digestive System
 Amphibians have complete digestive
system
 Use mouth, stomach and small intestine for
digestion
 Contain the first true tongue, mucous and
gland secretions make the tip of the tongue
sticky
 Frogs have a long sticky tongue that is
usually folded backwards in their mouth
 Food is captured by a sticky tongue and
taken into the mouth
 It is then swallowed and moves through the
pharynx and elastic esophagus to the
stomach
 Once in the stomach, gastric digestive
juices are secreted by glands that line the
stomach allows the food to move into the
intestines
 The leftover waste is pushed into the
cloaca

9.
Reproduction
 Even though amphibians are
adapted for life on land, they
depend on water for reproduction
 Because their eggs do not have a
protective waterproof shell, they
can dry out easily, so amphibians
must have water to reproduce
 External fertilization in moist
environments
 Amphibian eggs are fertilized
externally by the male. As the
eggs come out of the female’s
body, the male releases sperm
over them
 In most species the female lays
eggs in a pond or other body of
water

10.
Urodels
 Urodels are group of amphibians with tail
 This order includes salamandars and newts
 The body is divisible into head, trunk and tail
 The fore limbs and hind limbs are equal and weak
 Skin is scaleless
 Teeth present on both the jaws
 Eyes are small and eyelids are present in some urodels

11.
Anures
 Anures are group of amphibians
without tail
 This order includes frogs and toads
 They can live in water and on land
 Body is short and broad with head
and trunk
 The fore limbs are small, the hind
limbs are long for leaping and
swimming, feet are webbed
 Skin is scaleless
 Teeth are on upper jaw or absent
 They show a pair of eyes
 External fertilization

12.
Gymnophions
 Gymnophions are group of
amphibians without legs
 Burrowing or aquatic
 Internal fertilization
 The body is long and snake like
 The body is divisible into head
and trunk
 Tail is absent
 On the head two eyes are present
 Skin is covered by scales
 Lungs are asymmetrical

13.
Ecological Importance
 They play an important role in nature as both predator and prey,
sustaining the delicate balance of nature.
 They eat pest insects, benefiting successful agriculture around the
world and minimizing the spread of disease, including malaria.
 Most adult amphibians are insect predators and are helpful in
keeping some insect populations in check.
 The skin of amphibians has substances that protect them from some
microbes and viruses, offering possible medical cures for a variety
of human diseases, including AIDS.
 Poison frogs, also known as poison dart frogs or poison arrow frogs,
produce a poison that can kill large animals.
 The toxin is secreted through their skin and can affect muscles and
nerves of animals that come in contact with it.