a cold-blooded vertebrate animal of a class that comprises the frogs, toads, newts, and salamanders. They are distinguished by having an aquatic gill-breathing larval stage followed (typically) by a terrestrial lung-breathing adult stage.
1 of 27
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
More Related Content
Amphibia class
1. Class Amphibia
Gr. Amphi-double and bios-life
Aquatic or semi-aquatic, air and water breathing, cold-blooded,
oviparous, tetrapod vertebrates
Skin soft, moist and glandular. Pigment cells present
Head distnict, trunk elongated. Neck and tail may be present
Endoskeleton mostlybony
Respiration by lungs, skin and mouth-lining.
Heart 3-chambered
Fertilization mostly external
e.g. Bufo, Rana
2. Subclass 1. Stegocephalia (Extinct)
Limbs pentadactyle
Skin with scales and bony plates
Skull with a solid bony roof leaving openings for eyes and nostrils
Order 1. Labyrinthodontia
Oldest known tetrapods called stem amphibia
Salamander or crocodile like
e.g. Eryops
Order 2. Phyllospondyli
Small salamander-like.
Heads large, flat
Vertebrae tubular
Notochord and spinal cord housed in common cavity
e.g. Branchiosaurs
3. Order 3. Lepospondyli
Small salamander or eel-like
Vertebrae cylindrical, each made of a single piece
e.g. Diplocaulus
4. Subclass 2. Lissamphibia
Living
Modern amphibia lacking dermal bony skeleton
Teeth small, simple
Order 1. Gymnophiona or apoda
Limbless, blind, elongated worm-like, burrowing
Known as caecilians
Tail short or absent, cloaca terminal
Males have protrusible copulatory organ
e.g. Ichthyophis
5. Order 2. Urodela or Caudata
Lizard-like amphibians with a distnict tail
Limbs 2 pairs, usually weak
Skin devoid of scales and tympanum
Gills permanent or lost in adult
e.g. Salamandra
Order 3. Salientia or anura
Specialized amphibia without tail in adults
Hindlimbs usually adapted for leaping and swimming
Adults without gills or gill openings
Eyelids well-formed. Tympanum present
e.g. Bufo, Rana
6. Evolution of amphibians
The earliest fossils of Amphibia are known as
Labyrinthodonts under the subclass of
Labyrinthodontia.
They probably originated 300 million years
ago during Devonian period and flourished
through Carboniferous and Permian periods
before extinction in Triassic.
7. Piscine ancestry:
Resemblance of Amphibia to fish:
Both are cold-blooded
Both respire by gills early in life, in some cases
throughout life
Both have air-bladders serving an lungs
To prevent desiccation in air, both usually lay
eggs in water where larval development usually
take place
8. Which of fish groups
(Actinopterygii, Dipnoi and Crossopterygii)
gave rise to the
first amphibians?
9. Homologies between the limb bones of
crossopterygians and early tetrapods
Their skulls and jaws are similar and can be
equated bone by bone
Position of external and internal nares is
similar
Air bladders were used as lungs
12. Adaptations in amphibious life
Locomotion- Streamlined body, limbs in place of paired fins
Skeleton- Vertebral columns become more rigid
Muscles- Stronger muscles to lift body above ground
Respiration- Lungs in spite of gills, Cutaneous respiration
Circulatory system
Sensory system- Addition of middle ear containing a bone
for transmitting sound vibrations from tympanum to inner ear.
19. Digestive system of frog
Alimentary canal
I. Mouth
II. Buccal cavity
III. Pharynx
IV. Oesophagus
V. Stomach
VI. Small intestine-Duodenum and ileum
VII.Large intestine or rectum
VIII.Cloaca
Digestive gland
i. Liver
ii. Pancreas
22. Neotony
The retention of a larval or embryonic trait in the adult body.
e.g. the retention of embryonic cartilaginous skeleton in adult in
Chondrichthyes
Larval gills in some adult salamanders. This sexually mature but
morphologically immature, larval stage with external gills is called axololt.
Types: 3 types
Partial-metamorphosis is delayed due to temporary
ecological or physiological changes in environment
Intermediate- axololt reproduce sexually but
undergo metamorphosis in suitable conditions
Extreme or total- they remain larval throughout their
life e.g. Siren, Proteus
Factors
Abundance of food, cold temperature and
insufficient iodine
26. Defense mechanism of amphibians
Mucous secretion from their skin which make their body soft and
slippery
Toads have parotoid gland behind the eyes which secrete poison.
When distrubed, toads frequently urinate and produce noxious
unpalatable secretions from glands.
Some Salamander’s skin is poisonous
Some newt (Triton) discharges a sufficiently venomous secretion
from its dorsal glands to ward off enemies
Different coloration of frog
Frog mimic other harmful species or use bright coloration to warn
potential predators
27. Economic importance of Amphibia
Scientific study
As food
Predation
Medicinal value
Trade, Art and recreation
Poisonous Amphibia