An amphibian like the frog has several key biological systems: 1. It is poikilothermic and can undergo winter and summer dormancy. 2. Its digestive system includes a short alimentary canal and organs like the stomach, liver, and pancreas that secrete digestive juices and enzymes. 3. It has both cutaneous and pulmonary respiration and lungs located in the thoracic region as well as a three-chambered heart.

1. STRUCTURAL ORGANISATION IN ANIMALS
• Cold-blooded or poikilotherms
• Shows summer sleep (aestivation) and winter sleep (hibernation)
amphibian
DIGESTIVE SYSTEM
Alimentary canal is short
Tongue is bilobed
Buccal cavity-
Oesophagus- Stomach-
Intestine- Rectum- Anus
• Stomach has gastric glands which secrete digestive juice and HCl
• Liver: It secretes bile that is stored in the gall bladder
• Pancreas: it secretes pancreatic juice
RESPIRATION SYSTEM
Shows both cutaneous and pulmonary skin.
• Pair of lungs is a thoracic region (upper part of the trunk)
BLOOD VASCULAR SYSTEM
Closed type
Consists of heart, blood vessels and blood
Heart is three-chambered- two atria and one ventricle
Heart is covered by a membrane called pericardium
blood is carried to all parts of the body by the arteries (arterial system).
Veins collect blood from different parts of the body to the heart and form
the venous system.
EXCRTORY SYSTEM
ureotelic
consists of a pair of kidneys, ureters, cloaca and urinary bladder
In males the ureters act as a urinogenital duct which opens into the cloaca
In females the ureters and oviduct open separately in the cloaca
NERVOUS SYSTEM
CNS + PNS
Brain- For brain + mid brain + hind brain
Forebrain- olfactory lobes, paired cerebral hemispheres & unpaired diencephalon
• Midbrain- It has a pair of optic lobes
• Hind-brain- It consists of the cerebellum and medulla oblongata
• The medulla oblongata passes out through the foramen magnum and
continues into the spinal cord.
• Spinal cord is enclosed in the vertebral column
SENSORY ORGANS
• For touch (sensory papillae), taste (taste buds), smell (nasal epithelium),
vision (eyes) and hearing (tympanum)
• Eyes in a frog are a pair of spherical structures situated in the orbit in the
skull. These are simple eyes (possessing only one unit).
• Ear is an organ of hearing as well as balancing (equilibrium).
MALE REPRODUCTIVE ORGANS
• From testes 10-12 vasa efferentia arises
vasa efferentia.----- kidneys-----Bidder’s canal-----urinogenital duct----
-----cloaca-----release of sperm
FEMALE REPRODUCTIVE ORGANS
Ovary------oviduct------cloaca----release of 25000- 3000 ova at a time
FERTLIZATION
• External
• Development is indirect
• tadpole formation
• tadpole ....adult
Phylum – Chordata
Subphylum – Gnathostomata
Superclass- Tetrapoda
Class- Amphibia
Order- Anura
Genus- Rana
Species- tigrina