Phylum - Chordata
Class - Amphibia
Order - Anura
Genus - Rana
Species - tigrina (Indian frog)
Frogs can live both on land and in freshwater and belong to class Amphibian of phylum Chordata.
The most common species of frog found in India is Rana tigrina, found in ponds, lakes and streams.
Frogs body temperature varies with the temperature of the environment. Such animals are called cold blooded or poikilotherms.
Their body color changes while they are in grasses and on dry land, to hide from their enemies (camouflage). This protective coloration is called mimicry.
During summer/winter they take shelter in deep burrows to protect them from extreme heat and cold. This is called as summer sleep (aestivation) and winter sleep (hibernation).
MORPHOLOGY
$\displaystyle \small \bullet$ Body is bilaterally symmetrical and divided into head and trunk.
$\displaystyle \small \bullet$ It has a smooth, moist and slimy skin. Body do not consist exoskeleton or scales.
$\displaystyle \small \bullet$ The head is almost triangular with a blunt snout.
$\displaystyle \small \bullet$ The head bears a pair of eyes with movable eyelids called nictitating membrane.
$\displaystyle \small \bullet$ Nostrils are used for perceiving odour and to take air during respiration.
$\displaystyle \small \bullet$ Mouth is large with bilobed tongue that is attached in front.
$\displaystyle \small \bullet$ Presence of tympanum on the sides of head helps in hearing the sound.
$\displaystyle \small \bullet$ Trunk has 2 pairs of limbs. The forelimbs are shorter, which have 4 digits. Hindlimbs are with 5 webbed digits. Digits are without claws but have pedded joints.
ANATOMY
Digestive System
$\displaystyle \small \bullet$ The digestive system consists of alimentary canal and digestive glands.
$\displaystyle \small \bullet$ The alimentary canal is short because frogs are carnivores and hence the length of intestine is reduced.
$\displaystyle \small \bullet$ The mouth opens into the buccal cavity that leads to the oesophagus through pharynx.
$\displaystyle \small \bullet$ Oesophagus is a short tube that opens into the stomach which in turn continues as the intestine, rectum and finally opens outside by the cloaca.
$\displaystyle \small \bullet$ Liver secretes bile that is stored in the gall bladder.
$\displaystyle \small \bullet$ Pancreas, a digestive gland produces pancreatic juice containing digestive enzymes.
$\displaystyle \small \bullet$ Food is captured by the bilobed tongue.
$\displaystyle \small \bullet$ Digestion of food takes place by the action of HCl and gastric juices secreted from the walls of the stomach.
$\displaystyle \small \bullet$ Partially digested food called chyme is passed from stomach to the first part of the intestine, the duodenum.
$\displaystyle \small \bullet$ The duodenum receives bile from gall bladder and pancreatic juices from the pancreas through a common bile duct.
$\displaystyle \small \bullet$ Bile emulsifies fat and pancreatic juices digest carbohydrates and proteins.
$\displaystyle \small \bullet$ Final digestion takes place in the intestine.
$\displaystyle \small \bullet$ Digested food is absorbed by the numerous finger-like folds in the inner wall of intestine called villi and microvilli.
$\displaystyle \small \bullet$ The undigested solid waste moves into the rectum and passes out through cloaca.
Respiratory System
$\displaystyle \small \bullet$ Frogs respire on land and in the water by two different methods.
$\displaystyle \small \bullet$ In water, skin acts as aquatic respiratory organ (cutaneous respiration).
$\displaystyle \small \bullet$ Dissolved oxygen in the water is exchanged through the skin by diffusion.
$\displaystyle \small \bullet$ During aestivation and hibernation also, they respire by skin.
$\displaystyle \small \bullet$ On land, the buccal cavity, skin and lungs act as the respiratory organs.
$\displaystyle \small \bullet$ The respiration by lungs is called pulmonary respiration.
$\displaystyle \small \bullet$ The lungs are a pair of elongated, pink coloured sac- like structures present in the upper part of the trunk region (thorax).
$\displaystyle \small \bullet$ Air enters through the nostrils into the buccal cavity and then to lungs. It is also called land respiration.
Circulatory System
$\displaystyle \small \bullet$ The vascular system of frog is well-developed and closed type. Frogs have a lymphatic system also.
$\displaystyle \small \bullet$ The blood vascular system involves heart, blood vessels and blood.
$\displaystyle \small \bullet$ The lymphatic system consists of lymph, lymph channels and lymph nodes.
$\displaystyle \small \bullet$ Heart is a muscular structure situated in the upper part of the body cavity.
$\displaystyle \small \bullet$ It has three chambers, two atria and one ventricle and is covered by a membrane called pericardium.
$\displaystyle \small \bullet$ A triangular structure called sinus venosus joins the right atrium. It receives blood through the major veins called vena cava.
$\displaystyle \small \bullet$ The ventricle opens into a sac-like conus arteriosus on the ventral side of the heart.
$\displaystyle \small \bullet$ The blood from the heart is carried to all parts of the body by the arteries (arterial system).
$\displaystyle \small \bullet$ The veins collect blood from different parts of body to the heart and form the venous system.
$\displaystyle \small \bullet$ Special venous connection between liver and intestine forms hepatic portal system.
$\displaystyle \small \bullet$ Special venous connection between the kidney and lower parts forms renal portal system.
$\displaystyle \small \bullet$ The blood is composed of plasma and cells. The blood cells are RBC (erythrocytes), WBC (leucocytes) and platelets.
$\displaystyle \small \bullet$ The blood carries nutrients, gases and water to the respective sites during the circulation.
$\displaystyle \small \bullet$ The blood flows through two different systems from heart, one from lungs to heart another from heart to body tissues.
$\displaystyle \small \bullet$ In the heart both oxygenated and deoxygenated blood mixes hence it is called imperfect double circulation.
Excretory System
$\displaystyle \small \bullet$ The elimination of nitrogenous wastes is carried out by a well-developed excretory system.
$\displaystyle \small \bullet$ The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder.
$\displaystyle \small \bullet$ These are compact, dark red and bean like structures situated a little posteriorly in the body cavity on both sides of vertebral column.
$\displaystyle \small \bullet$ Each kidney is composed of several structural and functional units called uriniferous tubules or nephrons.
$\displaystyle \small \bullet$ Two ureters emerge from the kidneys in the male frogs. The ureters act as urinogenital duct which opens into the cloaca.
$\displaystyle \small \bullet$ In females the ureters and oviduct open separately in the cloaca.
$\displaystyle \small \bullet$ The thin-walled urinary bladder is present ventral to the rectum which also opens in the cloaca.
$\displaystyle \small \bullet$ The frog excretes urea and thus is a ureotelic animal.
$\displaystyle \small \bullet$ Excretory wastes are carried by blood into the kidney where it is separated and excreted.
Nervous System
$\displaystyle \small \bullet$ The system for control and coordination is highly evolved in the frog. It includes both neural system and endocrine glands.
$\displaystyle \small \bullet$ The chemical coordination of various organs of the body is achieved by hormones which are secreted by the endocrine glands.
$\displaystyle \small \bullet$ The nervous system is organized into a central nervous system (brain and spinalcord), a peripheral nervous system (cranial and spinal nerves) and an autonomic nervous system (sympathetic and parasympathetic).
$\displaystyle \small \bullet$ There are ten pairs of cranial nerves arising from the brain.
$\displaystyle \small \bullet$ Brain is enclosed in a bony structure called brain box(cranium).
$\displaystyle \small \bullet$ The brain is divided into fore-brain, mid-brain and hind-brain.
$\displaystyle \small \bullet$ Forebrain includes olfactory lobes, paired cerebral hemispheres and unpaired diencephalon.
$\displaystyle \small \bullet$ Midbrain is characterised by a pair of optic lobes.
$\displaystyle \small \bullet$ Hindbrain consists of cerebellum and medulla oblongata.
$\displaystyle \small \bullet$ The medulla oblongata passes out through the foramen magnum and continues into spinal cord, which is enclosed in the vertebral column.
$\displaystyle \small \bullet$ Frog has different types of sense organs, namely organs of touch(sensory papillae),taste(taste buds), smell (nasal epithelium), vision (eyes) and hearing (tympanum with internal ears).
$\displaystyle \small \bullet$ Out of these, eyes and internal ears are well-organized structures and the rest are cellular aggregations around nerve endings.
$\displaystyle \small \bullet$ The ear is an organ of hearing as well as balancing (equilibrium).
$\displaystyle \small \bullet$ The prominent endocrine glands found in frog are pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and gonads.
Reproductive System
Male reproductive system consists of a pair of yellowish ovoid testes , which are found adhered to the upper part of kidneys by a double fold of peritoneum called mesorchium.
$\displaystyle \small \bullet$ Vasa efferentia are 10-12 in number that arise from testes. They enter the kidneys on their side and open into Bidder’s canal.
$\displaystyle \small \bullet$ Finally it communicates with the urinogenital duct that comes out of the kidneys and opens into the cloaca.
$\displaystyle \small \bullet$ The cloaca is a small, median chamber that is used to pass faecal matter, urine and sperms to the exterior.
Female reproductive system consists of a pair of ovaries situated near kidneys.
$\displaystyle \small \bullet$ A mature female can lay 2500 to 3000 ova.
$\displaystyle \small \bullet$ Near each ovary arises an oviduct (formed by Mullerian duct) and opens into the cloaca separately.
$\displaystyle \small \bullet$ Oviduct collects ova from the ovaries and pass them to cloaca.
$\displaystyle \small \bullet$ Fertilization is external and it takes place in water. Development is by metamorphosis.
$\displaystyle \small \bullet$ The larval stage is called tadpole, it metamorphosed into adult.
Class - Amphibia
Order - Anura
Genus - Rana
Species - tigrina (Indian frog)
Frogs can live both on land and in freshwater and belong to class Amphibian of phylum Chordata.
The most common species of frog found in India is Rana tigrina, found in ponds, lakes and streams.
Frogs body temperature varies with the temperature of the environment. Such animals are called cold blooded or poikilotherms.
Their body color changes while they are in grasses and on dry land, to hide from their enemies (camouflage). This protective coloration is called mimicry.
During summer/winter they take shelter in deep burrows to protect them from extreme heat and cold. This is called as summer sleep (aestivation) and winter sleep (hibernation).
MORPHOLOGY
$\displaystyle \small \bullet$ Body is bilaterally symmetrical and divided into head and trunk.
$\displaystyle \small \bullet$ It has a smooth, moist and slimy skin. Body do not consist exoskeleton or scales.
$\displaystyle \small \bullet$ The head is almost triangular with a blunt snout.
$\displaystyle \small \bullet$ The head bears a pair of eyes with movable eyelids called nictitating membrane.
$\displaystyle \small \bullet$ Nostrils are used for perceiving odour and to take air during respiration.
$\displaystyle \small \bullet$ Mouth is large with bilobed tongue that is attached in front.
$\displaystyle \small \bullet$ Presence of tympanum on the sides of head helps in hearing the sound.
$\displaystyle \small \bullet$ Trunk has 2 pairs of limbs. The forelimbs are shorter, which have 4 digits. Hindlimbs are with 5 webbed digits. Digits are without claws but have pedded joints.
ANATOMY
Digestive System
$\displaystyle \small \bullet$ The digestive system consists of alimentary canal and digestive glands.
$\displaystyle \small \bullet$ The alimentary canal is short because frogs are carnivores and hence the length of intestine is reduced.
$\displaystyle \small \bullet$ The mouth opens into the buccal cavity that leads to the oesophagus through pharynx.
$\displaystyle \small \bullet$ Oesophagus is a short tube that opens into the stomach which in turn continues as the intestine, rectum and finally opens outside by the cloaca.
$\displaystyle \small \bullet$ Liver secretes bile that is stored in the gall bladder.
$\displaystyle \small \bullet$ Pancreas, a digestive gland produces pancreatic juice containing digestive enzymes.
$\displaystyle \small \bullet$ Food is captured by the bilobed tongue.
$\displaystyle \small \bullet$ Digestion of food takes place by the action of HCl and gastric juices secreted from the walls of the stomach.
$\displaystyle \small \bullet$ Partially digested food called chyme is passed from stomach to the first part of the intestine, the duodenum.
$\displaystyle \small \bullet$ The duodenum receives bile from gall bladder and pancreatic juices from the pancreas through a common bile duct.
$\displaystyle \small \bullet$ Bile emulsifies fat and pancreatic juices digest carbohydrates and proteins.
$\displaystyle \small \bullet$ Final digestion takes place in the intestine.
$\displaystyle \small \bullet$ Digested food is absorbed by the numerous finger-like folds in the inner wall of intestine called villi and microvilli.
$\displaystyle \small \bullet$ The undigested solid waste moves into the rectum and passes out through cloaca.
Respiratory System
$\displaystyle \small \bullet$ Frogs respire on land and in the water by two different methods.
$\displaystyle \small \bullet$ In water, skin acts as aquatic respiratory organ (cutaneous respiration).
$\displaystyle \small \bullet$ Dissolved oxygen in the water is exchanged through the skin by diffusion.
$\displaystyle \small \bullet$ During aestivation and hibernation also, they respire by skin.
$\displaystyle \small \bullet$ On land, the buccal cavity, skin and lungs act as the respiratory organs.
$\displaystyle \small \bullet$ The respiration by lungs is called pulmonary respiration.
$\displaystyle \small \bullet$ The lungs are a pair of elongated, pink coloured sac- like structures present in the upper part of the trunk region (thorax).
$\displaystyle \small \bullet$ Air enters through the nostrils into the buccal cavity and then to lungs. It is also called land respiration.
Circulatory System
$\displaystyle \small \bullet$ The vascular system of frog is well-developed and closed type. Frogs have a lymphatic system also.
$\displaystyle \small \bullet$ The blood vascular system involves heart, blood vessels and blood.
$\displaystyle \small \bullet$ The lymphatic system consists of lymph, lymph channels and lymph nodes.
$\displaystyle \small \bullet$ Heart is a muscular structure situated in the upper part of the body cavity.
$\displaystyle \small \bullet$ It has three chambers, two atria and one ventricle and is covered by a membrane called pericardium.
$\displaystyle \small \bullet$ A triangular structure called sinus venosus joins the right atrium. It receives blood through the major veins called vena cava.
$\displaystyle \small \bullet$ The ventricle opens into a sac-like conus arteriosus on the ventral side of the heart.
$\displaystyle \small \bullet$ The blood from the heart is carried to all parts of the body by the arteries (arterial system).
$\displaystyle \small \bullet$ The veins collect blood from different parts of body to the heart and form the venous system.
$\displaystyle \small \bullet$ Special venous connection between liver and intestine forms hepatic portal system.
$\displaystyle \small \bullet$ Special venous connection between the kidney and lower parts forms renal portal system.
$\displaystyle \small \bullet$ The blood is composed of plasma and cells. The blood cells are RBC (erythrocytes), WBC (leucocytes) and platelets.
$\displaystyle \small \bullet$ The blood carries nutrients, gases and water to the respective sites during the circulation.
$\displaystyle \small \bullet$ The blood flows through two different systems from heart, one from lungs to heart another from heart to body tissues.
$\displaystyle \small \bullet$ In the heart both oxygenated and deoxygenated blood mixes hence it is called imperfect double circulation.
Excretory System
$\displaystyle \small \bullet$ The elimination of nitrogenous wastes is carried out by a well-developed excretory system.
$\displaystyle \small \bullet$ The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder.
$\displaystyle \small \bullet$ These are compact, dark red and bean like structures situated a little posteriorly in the body cavity on both sides of vertebral column.
$\displaystyle \small \bullet$ Each kidney is composed of several structural and functional units called uriniferous tubules or nephrons.
$\displaystyle \small \bullet$ Two ureters emerge from the kidneys in the male frogs. The ureters act as urinogenital duct which opens into the cloaca.
$\displaystyle \small \bullet$ In females the ureters and oviduct open separately in the cloaca.
$\displaystyle \small \bullet$ The thin-walled urinary bladder is present ventral to the rectum which also opens in the cloaca.
$\displaystyle \small \bullet$ The frog excretes urea and thus is a ureotelic animal.
$\displaystyle \small \bullet$ Excretory wastes are carried by blood into the kidney where it is separated and excreted.
Nervous System
$\displaystyle \small \bullet$ The system for control and coordination is highly evolved in the frog. It includes both neural system and endocrine glands.
$\displaystyle \small \bullet$ The chemical coordination of various organs of the body is achieved by hormones which are secreted by the endocrine glands.
$\displaystyle \small \bullet$ The nervous system is organized into a central nervous system (brain and spinalcord), a peripheral nervous system (cranial and spinal nerves) and an autonomic nervous system (sympathetic and parasympathetic).
$\displaystyle \small \bullet$ There are ten pairs of cranial nerves arising from the brain.
$\displaystyle \small \bullet$ Brain is enclosed in a bony structure called brain box(cranium).
$\displaystyle \small \bullet$ The brain is divided into fore-brain, mid-brain and hind-brain.
$\displaystyle \small \bullet$ Forebrain includes olfactory lobes, paired cerebral hemispheres and unpaired diencephalon.
$\displaystyle \small \bullet$ Midbrain is characterised by a pair of optic lobes.
$\displaystyle \small \bullet$ Hindbrain consists of cerebellum and medulla oblongata.
$\displaystyle \small \bullet$ The medulla oblongata passes out through the foramen magnum and continues into spinal cord, which is enclosed in the vertebral column.
$\displaystyle \small \bullet$ Frog has different types of sense organs, namely organs of touch(sensory papillae),taste(taste buds), smell (nasal epithelium), vision (eyes) and hearing (tympanum with internal ears).
$\displaystyle \small \bullet$ Out of these, eyes and internal ears are well-organized structures and the rest are cellular aggregations around nerve endings.
$\displaystyle \small \bullet$ The ear is an organ of hearing as well as balancing (equilibrium).
$\displaystyle \small \bullet$ The prominent endocrine glands found in frog are pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and gonads.
Reproductive System
Male reproductive system consists of a pair of yellowish ovoid testes , which are found adhered to the upper part of kidneys by a double fold of peritoneum called mesorchium.
$\displaystyle \small \bullet$ Vasa efferentia are 10-12 in number that arise from testes. They enter the kidneys on their side and open into Bidder’s canal.
$\displaystyle \small \bullet$ Finally it communicates with the urinogenital duct that comes out of the kidneys and opens into the cloaca.
$\displaystyle \small \bullet$ The cloaca is a small, median chamber that is used to pass faecal matter, urine and sperms to the exterior.
Female reproductive system consists of a pair of ovaries situated near kidneys.
$\displaystyle \small \bullet$ A mature female can lay 2500 to 3000 ova.
$\displaystyle \small \bullet$ Near each ovary arises an oviduct (formed by Mullerian duct) and opens into the cloaca separately.
$\displaystyle \small \bullet$ Oviduct collects ova from the ovaries and pass them to cloaca.
$\displaystyle \small \bullet$ Fertilization is external and it takes place in water. Development is by metamorphosis.
$\displaystyle \small \bullet$ The larval stage is called tadpole, it metamorphosed into adult.
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