AMPHIBIANS
Asma Thebo
PH.D (CONT…)
UNIVERSITY OF SINDH, JAMSHORO.
The First Terrestrial Vertebrates
1

GENERAL CHARACTERS OF AMPHIBIANS
 Amphibians are cold blooded vertebrates which can hue on land and in
water.
 Amphibians show four limbs with which they can swim in water and jump
or walk on the land, (But in apoda limbs are absent.)
 In Amphibians animals exoskeleton is absent. But in apoda animals small
cycloid scales are present.
 In Amphibians the adult animals lungs are present. Gills are absent. But In
some urodelans the gills are present.
 Amphibians Skin is a respiratory organ.
 The Amphibians skull is dicondylic.
 Amphibians Ribs are absent.
 In Amphibians The body divisible into head and trunk Tail is present in,
urodela animals.
 Amphibians Digestive system is well developed. A well developed liver Is
present
2

GENERAL CHARACTERS OF AMPHIBIANS
 External ear is absent. Middle and inner ears are present, the middle ear
columella auris Is present.
 Amphibians Heart is 3 chambered with 2 auricles and 1 ventricle The blood
contains R.B.C. They are nucleated. They contain hemoglobin.
 Blood vascular system contain hepatic and renal portal systems.
 Amphibians Kidneys are mesonephric. Urinary bladder is present. It stores
urine.
 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.
 Sexes are separate.
 Male and female can be indentified - Sexual dimorphism.
 In Amphibians the life history a larva stage may be present.
 Amphibian Eggs are telolecithal, Cleavage is holoblastic unequal.
3

Amphibians are animals that either move back and forth between water
and land or live one of their stages of life in water and another on land.
Amphibians are tetrapods“Four-foot” • The presence of four muscular
limbs and feet with toes and fingers
First amphibian: No one knows what the first amphibian was. The
structure of limbs, skulls and teeth of lchthyostega are similar to the
earliest amphibians.
Two lineages of amphibians are formed in the late Devonian and early
Carboniferous periods. These lineage can be differentiated by the
structure of roof and the attachment of posterior portion of the skull to
each other.
Evolutionary Perspective •
4

Amniotic lineage: One lineage of
amphibians became extinct in the
late Carboniferous period. An
amniotic egg evolved in this group. It
resisted dryness. This lineage is
called the amniotic lineage. This
lineage formed reptiles, birds; and
mammals.
2. Nonamniote lineage: A second
lineage flourished in the Jurassic
period. Most of animals of lineage
have become extinct. But some of
them gave rise to the three orders of
living amphibians. This lineage is
called the nonamniote lineage.
5

PHYLOGENETIC RELATIONSHIPS
Fossil record provides evidence of many extinct taxa and no
one knows what animal was the first stegocephalian.
Taxonomists agree that amphibians are monophyletic and
closely related to reptiles, birds, and mammals
6

01. ORDER CAUDATA
This order consists of salamanders.
Means “tail-bearing”
Characteristics of order Caudata
The 358 species belonging to the order Caudata can be generally divided into
newts and salamanders.
These animals are normally nocturnal and found in cool, shady habitats in the
Northern Hemisphere.
Some caudates are amphibious, others are entirely aquatic, yet others are
entirely terrestrial and some burrow.
Aquatic or burrowing species may have reduced or rudimentary limbs.
7

Habitat:
Caudates are restricted to damp or wet habitats because their skin acts as a
respiratory organ through which oxygen enters the body. All are carnivorous
Reproduction:
Internal fertilization • Produce aquatic larvae • Larvae are similar to adults but
smaller
Newts
Newts differ from salamanders in that adult newts are always terrestrial,
returning to water only to breed in spring; larvae develop in water and then
emerge onto land until mature and ready to breed in their turn.
Salamanders have very diverse range of life cycles and many families are
normally paedomorphic � adults retaining larval features, that may be
more or less visible from the exterior.
01.ORDER CAUDATA
8

01. Order Caudata
9

This order consists of caecilians.
Means “naked like a snake”
Characteristics of order Gymnophion
Worm-like
appear segmented because of skin folds that overlie separations between muscle
bundles.
Skin over eyes (most likely blind)
Habitat:
Burrow into the ground
Reproduction:
fertilization is internal. Can have aquatic larvae or embryotic larvae that develop on
land. Young are miniature adults.
Feeding:
Eat soil and worms when they burrow.
02. ORDER GYMNOPHIONA
10

02. Order Gymnophiona
11

This order consists of frogs and Toads.
Means “without tail”
Characteristics of order Anura
About 4,000 species
Long muscular hind limbs
Webbed feet
Habitat:
Generally moist environments (can really be found almost anywhere)
Reproduction:
External fertilization • Undergoes metamorphosis from tadpole to adult
Feeding:
They mostly eat small insects and some plants.
They utilize a sticky tongue, located on their lower jaw, that is extended from their
mouth as a sort of sticky lasso to catch their prey.
Most frogs sit and wait for their prey.
Their skin colors and textures perfectly camouflages them in their surroundings.
03. ORDER ANURA
12

03. Order Anura
13