Amphibians live part of their lives in water and part on land. They hatch from eggs as aquatic larvae with gills, then undergo metamorphosis to grow lungs and legs to live on land as adults. Amphibians have moist, permeable skin and small lungs allowing for gas exchange, as well as a three-chambered heart. They reproduce via external fertilization of eggs in water. There are three main orders of amphibians: salamanders, frogs and toads, and legless caecilians.

2. Animal Diversity: Vertebrates
by
Maryam Riasat
AMPHIBIANS

4. 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.

5. 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)

6. 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.

7. 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.

8. 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

9. 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.

10. 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

11. 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

13. 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

14. 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

15. 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

16. 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.