Useful for Grade XI Biology Students!!

1. Detailed Study of Frog
(Rana tigrina)
 Characteristics and External Features
 Digestive System
 Respiratory System
 Reproductive System
Prepared By: Dr. Ganesh Adhikari
(B.V.Sc. & AH, TU)

2. Taxonomic position of Frog
Kingdom: Animalia
Phylum: Chordata
Sub Phylum: Vertebrata
Group: Gnathostomata
Class: Amphibia
Order: Anura
Genus: Rana
Species: tigrina
Common Name: Frog

3. Habit and Habitat:
 Frog is a group of short-bodied, tailless
Amphibian composing the order Anura.
 They can live both in water and land.
 Tadpole larva is completely aquatic in habitat.
Later metamorphos into adult.
 On the land frog locomotes by jumping
movement and in the water swims actively due to
webbed foot.

4. Tadpole:

5. Locomotion:
Webbed Toes

6.  Respiration: Respire by cutaneous respiration.
(Skin surface)
 Nutrition: larva is herbivorous and adult is
carnivorous or insectivorous.
 Breeding: During Rainy season usually at night,
frogs gather nearby the pond or shallow water
 Unisexual, External Fertilization

7. Croaking and Copulation:
The sound made by the male frog during
breeding season is called croaking.
It is a call for mating.

8. Hibernation:
Is also called winter sleep. It is the resting period.
They burry themselves into the deep mug and take
rest. When summer start they become active again.

9. Body structure:
Body is short and broad possesses head and trunk
only due to absence of neck.
Head is almost triangular shape possess;
1 pair of buldging eye ball.
1 pair of nostrils or nasal opening.
1 pair of tympanum or eardrum and a terminal
mouth.

10. External Structure:

11. External features:
Head immediately follows broad trunk due to absent
of neck.
Shorter 4 limbs with 4 digits
and longer hind limbs with 5 webbed digits.
Body skin is moist due to secretion of mucin or
mucus.
Skin may or may not possess pigments and poison
glands.

12. Mouth:
Terminal mouth
A wide opening called mouth is situated at the
anterior end of the snout.

13. Eyes:
Its eyes protrude in such a way that they are above
water when the rest of the body is immersed.
The eyes have movable.
Tympanum: A pair of tympanum below eyes.
Eardrum, helps to transmit sound wave and protect
water from entering

14. Nostrils:
A pair of nostrils are situated so that air can be
breathed while the frog is swimming at the surface.
They can also be closed.

15. DIGESTIVE SYSTEM

16. Digestive is a process by which the complex
insoluble food particles are converted into soluble
form by action of enzymes.
The digestive system consists of the alimentary
canal and digestive gland.

17. Alimentary canal of Frog

18. The alimentary canal is a long, coiled path starts
from mouth and ends in cloaca.
It consists of:
 Mouth & buccal cavity
 Pharynx
 Oesophagus
 Stomach
 Small intestine
 Large intestine and
 Cloaca.

19. Mouth:
The digestive system of a frog starts with the
mouth.
Mouth is a wide opening lies in between upper and
lower jaw.
Mouth helps in ingestion of food.

20. Buccal cavity:
Mouth leads into the buccal cavity and it is a wide
space between upper and lower halves of the head.

21. Structure present on the upper jaw
i) Maxillary teeth
ii) Vomarine teeth
iii) Fossae
iv) Internal nares
v) Eustachian tube

22. Structure present on the lower jaw
Tongue:
The tongue of frog is long, large, fleshy, thick.
Attached in front and free behind.
Bears the taste buds in the form of small papillae.
The tongue can be thrownout and retracted
suddenly to capture and engulf prey.

23. Glottis:
Glottis is a longitudinal median slit behind the
tongue
guards the entrance to the lungs.
It is always opened during the breathing but
become closed during the swallowing of food.

24. Vocal sac:
In male frog, a pair of vocal sacs.
Production of croaking sound.
Gullet:
Just above the glottis, there is horizontal opening
called gullet.
The food enters from the gullet to esophagus to
stomach.

25. Pharynx:
The buccal cavity leads into the narrow pharynx.
The buccal cavity and pharynx is collectively known
as bucco-pheryngeal cavity.
Oesophagus:
Pharynx leads into a small but wider tube called
oesophagus.
The oesophagus opens into the stomach.

27. Stomach:
The oesophagus opens into a large and thick sac
like structure known as stomach.
The anterior end of stomach is called Cardiac end
while the posterior end is called pyloric end
The secretions of stomach have different enzymes
which help in chemical digestion.
In stomach, digestion of protein of food is started.

28. Small intestine (Duodenum and Ileum):
First part of intestine is called duodenum.
The ducts from liver and pancreas open into the
duodenum and helps in digestion.
The second part of intestine is Ilium.
Digested food is absorbed by illium.

29. Large intestine (rectum):
It is wide tube with numerous folds.
Undigested food material is stored
Cloaca:
It is a small sac like structure used to remove
undigested food material.

30. Digestive gland:
Liver:
Largest gland of the body.
It secretes fluid called bile.
Bile juice produced by the liver is stored in the gall
bladder.
Help in breaking Fat into small globules. The acidic
food coming from the stomach becomes alkaline,
when it is mixed with the bile

31. Function of liver:
 The liver secrets bile, which helps in digestion of
food.
 Store excess of sugar as glycogen.
 Regulates the amount of sugar in the blood.
 Maintains the protein concentration in blood.
 Stores copper and iron and forms vitamin A.
 Destroys the injured RBC.
 Helps to detoxify the toxins.
 Helps in the removal of waste substances.

32. Gastric glands:
They are present on the stomach wall.
They secret HCL and enzyme pepsinogen.

33. Pancreas:
It is long and irregularly lobed yellowish gland.
Secretion known as pancreatic juice
poured into duodenum
The enzymes help digestion of ingested food.
Hormone insulin help to convert glucose into
glycogen.
helps in metabolism of carbohydrates

35. Physiology of digestion:
Frog is insectivorous (insects eating).
Catch prey by the action of tongue
Swallow without mastication.
The food becomes lubricated by mucous secreted
by mucin gland.

36. When the food reaches stomach the chemical
digestion starts.
Gastric Digestion:
Pepsinogen + HCl >> Active Pepsin
Pepsin + Protein >> Proteoses and peptones
The food is gradually digested and changed into a
semi-liquid state called Chyme.
Chyme slowly moves towards duodenum.

37. Intestinal Digestion:
Bile from liver neutralizes the acidic food and It
emulsifies fat.
Pancreatic Juice contains:
Protein + Trypsin >> Peptones and polypeptide
Amylase -
Carbohydrate into maltose.
Proteoses and peptones >> Amino acid
Maltose >> Glucose
Fats >> Fatty acids + glycerol
Sucrose >> Simple sugar

38. Absorption of Digested food.
It is the process by which digested food is taken into
blood.
Glucose, amino acids, fatty acids, glycerols etc. are
absorbed through the villi of intestine.
There are two methods:
 by diffusion or osmosis through the villi
called passive method.
 by using energy against concentration gradient from
the lumen of intestine into the blood.
The undigested and unabsorbed materials are stored in
rectum for short time & passed out through anus.

39. RESPIRATORY SYSTEM

40. Respiration
The process of gaseous exchange (O2 and CO2)
i.e. intake of oxygen and liberation of carbon-
dioxide
and utilization of oxygen to breakdown food to
release energy is called respiration.

41. The inhale of Oxygen and exhale of Carbondioxide
takes place during respiration.
The process of Respiration involves three stages:
1. External Respiration
2. Internal or tissue respiration
3. Transport of respiratory Gases

42. 1. External Respiration
Usually called breathing.
Mechanish by which Oxygen is brought into body
from environment and Carbondioxide is expelled.

43. 2. Internal or tissue respiration
Includes all forms of oxygen consumption by cells
in the body.
Oxidation of food takes place
Production of Carbondioxide

44. 3. Transport of Respiratory gases
Involves the transportation of Oxygen from
respiratory surface to body tissues
O2 + Hb >> HbO2 (Oxyhaemoglobin)
And
Carbondioxide from body tissues to respiratory
surface
This function is done through blood.
O2 + Hb >> HbO2 (Oxyhaemoglobin)
CO2 + Hb >> Carboxyhaemoglobin

45. Respiration in frog takes place by following four
ways:
1. Gills
2. By bucco-pharyngeal cavity
3. Skin (Cutaneous respiration)
4. By lungs (Pulmonary respiration)

46. Gills
Tadpole is completely aquatic
During tadpole stage.
Four pairs of gills present for gaseous exchange.
Takes place by the process of diffusion

47. Skin or Cutaneous respiration
The skin of frog is thin and has fine blood vessels.
Due the presence of mucous gland the skin of frog
always remains moist.
During gaseous exchange the oxygen first dissolve
moisture of body and then diffuse into the blood
capillaries. And the carbon dioxide diffuses out
from the blood into the environment.

48. Buccopharyngeal respiration
Respiration done through the buccopharyngeal
cavity
The buccal cavity consists of moist mucous
membrane and richly supplied with blood
capillaries.
The air enters into cavity through external nares
and gaseous exchange takes place through the
lining of buccal cavity between blood and oxygen
(air) present in the cavity
by diffusion process.

49. Pulmonary respiration
Frog respires by pulmonary respiration when it lives
on land
and during the time of swimming and jumping.
The respiration through the lungs is called
pulmonary respiration.

50. Organs during the respiration
i) External nares: A pair of opening lies between
the eyes and snout. Air is exhaled and inhaled
through these nares.
ii) Internal nares: A pair of small opening is found in
between the maxillary and vomer teeth on buccal
cavity.

51. iii) Buccopharynheal cavity:
The space between buccal cavity and pharynx. The
air reservior and passes to the bronchi and lungs.
iv) Bronchi: It is a pair of small tubes passing to the
lungs

52. V) Lungs
There is a pair of lungs which are thin walled elastic
sacs.
They are present within thoracic cavity on either
side of heart.
Numerous small air sacs are present in the lungs
called alveoli.
The alveoli are very thin walled and supplied by
blood vessels.
Alveoli are site for gases exchange

53. Mechanism of pulmonary respiration
During pulmonary respiration the mouth of the frog
remains closed. The inspiration and expiration of
the air is done by the action of the buccal cavity.

54. Inspiration
The process of intake of air is called inspiration.
The mouth remains closed.
air is taken into cavity through external nares.
Then, the nares remain closed which decrease the
space in cavity and pressure is increased.
By this mechanism the air passed into lungs.

55. Gaseous exchange
In lungs, alveoli are filled with air.
Gaseous exchange takes place between blood and
alveoli by diffusion.
Both O2 and CO2

56. Expiration
The process of exhaling of CO2 is called expiration.
It is the reverse process of inspiration.
The external nares remains closed, air is drawn into
the cavity from the lungs.
Finally the glottis is closed, external nares open and
then the air is passed out through the external
nares.
* * *

57. REPRODUCTIVE SYSTEM

58. Reproductive System:
Unixexual and shows sexual dimorphism.
The male frog is slightly smaller than female frog.
During breeding season male frog produce croaking
sound by the help of vocal sac.
The croaking is invitation for copulation.
External Fertilization
Development: indirect

59. Male reproductive system:
It consists of a pair of testes, vasa efferentia,
seminal vesicles and urogenital ducts.

60. Testes:
Testes are yellowish, elongated or oval, is found
attached to the anterior ventral side of each kidney.
They are suspended by a double fold of peritoneum
called Mesorchium.
Each testes consists coiled structures called
seminiferous tubules or crypts. The epithelial lining
of seminiferous tubules consists of germinal cells,
which produce spermatozoa.

62. Vasa efferentia:
Many seminiferous tubules unite to form vasa
efferentia, which is narrow tube like structure.
The vasa efferentia conduct mature sperms from
testis to the ureter.

64. Seminal Vesicle:
Each urinogenital duct expands to form seminal
vesicle where the sperms are stored until they are
ejected out during copulation.
Urinogenital Duct:
it is a tubular duct where the urine and sperms pass
through ureter so that it is also called as
urinogenital duct.

65. Sperm of Frog
Sperm consists of three parts:
Head, middle piece and tail
Head is enlarged region.
Acrosome lies at the top.
Head consists of Nucleus and Genetic materials.
Middle piece consists of centrosome and
mitochondria.
Tail is last and longest part helps in locomotion.

66. Structure of Sperm

67. Female reproductive system
It consists of ovaries, oviducts, ovisacs.

68. Ovary:
They are paired folded sac. They lies on ventral to
the kidneys
They are composed of ovarian follicles which
consists countless ova.
Groups of germ cells form ovarian follicles, ovarian
follice undergoes oogenesis to form ovum.
The mature ova are shed into the abdominal cavity
and reach to the oestium by pressure of fore arms
of clasping of male during copulation.

70. Oviduct:
They are long coiled tubes one on either side of
abdominal cavity.
Anterior of oviducts, oviducal funnel called ostium
is present.
At maturity the eggs are shed and ultimately find
their way into the oviduct.

71. Ovisacs:
The coiled part of the oviduct posteriorly dilates to
form a thin-walled ciliated ovisacs.
They opens by a narrow aperture in the cloaca.

72. Copulation:
During breeding season>> croaking sound>>
female frog approach the male frog.
The male frog rides over the female frog and
embraces firmly by its forelimbs.

73. The couple takes a long time to become sexually
excited. (cold-blooded and devoid of copulatory
organs)
At the state of orgasm the female discharges a large
number of eggs in water from its ovisac through the
cloacal aperture.
The male frog discharges its sperms over the eggs.

74. Fertilization: Male gametes (sperm) fertilizes the
female ova.
External (in water)
Development: Indirect
Egg >> Tadpole>> Adult frog

75. Thank You!!