Detailed study of frog (rana tigrina)

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. S horter 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. T hey 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 S mall intestine L arge intestine and C loaca .

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 Maxillary teeth Vomarine teeth Fossae Internal nares 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.

26. 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.

27. Small intestine (Duodenum and Ileum ): F irst 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 .

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

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

30. Function of liver : The liver secrets bile, which helps in digestion of food. S tore excess of sugar as glycogen. R egulates the amount of sugar in the blood. M aintains the protein concentration in blood. S tores copper and iron and forms vitamin A. D estroys the injured RBC. H elps to detoxify the toxins. H elps in the removal of waste substances.

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

32. 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

33. Physiology of digestion:  Frog is insectivorous (insects eating ). C atch prey by the action of tongue S wallow without mastication. The food becomes lubricated by mucous secreted by mucin gland.

34. 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 . C hyme slowly moves towards duodenum.

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

36. Absorption of Digested food . It is the process by which digested food is taken into blood . G lucose, 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.

37. RESPIRATORY SYSTEM

38. Respiration The process of gaseous exchange (O 2  and CO 2 ) i.e . intake of oxygen and liberation of carbon-dioxide and utilization of oxygen to breakdown food to release energy is called respiration.

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

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

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

42. 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

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

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

45. 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.

46. Buccopharyngeal respiration R espiration 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.

47. 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 .

48. O rgans during the respiration 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 .

49. iii) Buccopharynheal cavity : T he 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

50. 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

51. 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.  

52. 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 .

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

54. 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 . * * *

55. REPRODUCTIVE SYSTEM

56. 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

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

58. 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.

59. 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.

60. 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.

61. 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.

62. Structure of Sperm

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

64. 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.

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

66. 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.

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

68. 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.

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

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