Skip to content

Frog Digestive and Respiratory System Class 11

questionbuddy.in/cbse/class-11/biology/structural-organisation-in-animals/frog-digestive-and-respiratory-systems

BiologyCBSE Class 11 · Structural Organisation in Animals

Frog (Rana tigrina): Digestive and Respiratory Systems

Updated 17 October 2026 · Fact-checked

The frog has a short alimentary canal suited to a carnivorous diet: mouth, buccal cavity, pharynx, oesophagus, stomach, intestine, rectum and cloaca, with liver and pancreas as glands. It respires through the skin (cutaneous respiration) in water and through buccal cavity and lungs on land, and exchanges gases through the skin during aestivation and hibernation.

Understand Frog: Digestive and Respiratory Systems

Digestive system. The frog is carnivorous (insects, worms) and so has a short alimentary canal, since the proteins it eats are easy to digest.

  • Mouth opens wide into the buccal cavity; a bilobed, muscular tongue, attached at the front and free at the back, is flicked to catch prey. Small maxillary teeth and vomerine teeth hold prey; they do not chew.
  • Buccal cavity leads to the pharynx, then the short oesophagus and stomach.
  • Stomach leads to the intestine (a long, coiled tube with duodenum and ileum), then the rectum, ending in the cloaca, a common chamber through which faeces, urine and sperm or eggs pass out via the cloacal aperture.
  • Digestive glands: the liver (bile stored in the gall bladder; bile emulsifies fat), the pancreas (pancreatic juice with digestive enzymes, passing along the bile duct into the duodenum).
  • Digestion: food is caught by the tongue, swallowed, and in the stomach the HCl and gastric juices convert it into chyme; bile and pancreatic juices act in the duodenum; absorption occurs in the intestine by finger-like folds, villi, and microvilli; undigested waste goes to the cloaca.

Respiratory system. Frogs respire in two ways:

  • Cutaneous respiration: in water, gases dissolve through the moist skin (also during hibernation and aestivation, the long dormant periods).
  • Pulmonary respiration: on land, through lungs, elongated, pinkish, sac-like structures in the upper part of the trunk (thorax).
  • Buccal (bucco-pharyngeal) respiration: the lining of the buccal cavity is also moist and vascular, so gas exchange takes place there too.
  • Air enters through the nostrils into the buccal cavity and then to the lungs. Gas exchange takes place at the lungs by diffusion; the frog uses a buccal floor pump to push air.

Summary: water: skin; land: lungs + buccal cavity + skin.

Table: digestive tract. Mouth to pharynx; oesophagus short; stomach J-shaped; intestine coiled; cloaca common.

Draw and label: the digestive system of a frog: tongue, buccal cavity, oesophagus, stomach, liver, gall bladder, pancreas, intestine, rectum, cloaca. Title: 'Digestive system of frog'.

Frog: Digestive and Respiratory Systems: key facts

Gut sequence
  • Mouth
  • buccal cavity
  • pharynx
  • oesophagus
  • stomach
  • intestine
  • rectum
  • cloaca
In order
Digestive glands
Liver (bile, stored in gall bladder) | Pancreas (enzymes)
Two glands
Respiration
Water: cutaneous | Land: lungs, buccal cavity, skin
Three surfaces
Diet
Carnivorous | short alimentary canal
Insects, worms

How to answer Frog: Digestive and Respiratory Systems questions

Questions give a function or part and ask for its location, or compare modes of respiration.

  1. 1Write the gut in sequence from mouth to cloaca.
  2. 2Place the glands and mention bile storage in the gall bladder.
  3. 3Match the mode of respiration to the habitat or state.
  4. 4Mention the role of the cloaca.
  5. 5Link a short gut to a carnivorous diet.

Frog: Digestive and Respiratory Systems in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Frog in a monsoon puddle

Suppose a frog sits half submerged in a puddle at night, holds its throat pulsing, and catches a passing moth.

Name the respiratory surfaces and the tool used for hunting.

Try it first, then show the solutionSolution
  1. Submerged skin exchanges gases (cutaneous).
  2. Throat movement pushes air to buccal cavity and lungs.
  3. A bilobed muscular tongue flicks to capture prey.

Answer: Skin, buccal cavity, lungs; tongue.

Memory hook: Wet skin breathes; tongue hunts.

Tricks to remember Frog: Digestive and Respiratory Systems

Short memory aids. Say each one aloud once, then use it on a question the same day.

  • Mouth to cloaca

    M-B-P-O-S-I-R-C: My Big Pet Often Sleeps In Red Cloaks.

    Use it when: Gut order

  • Water skin, land lung

    Skin in water; lungs on land.

    Use it when: Respiration

  • Bile in bag

    Gall bladder stores bile.

    Use it when: Liver

Frog: Digestive and Respiratory Systems: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Alimentary canal · 3 marks · Short answerBoard level

Follow a captured insect through the frog gut and state where acid, bile and absorption are involved.

Try it first, then show the solutionSolution
  1. Tongue captures prey; buccal cavity, pharynx and oesophagus pass it on (1 mark).
  2. Stomach: HCl and gastric juice make chyme; duodenum: bile and pancreatic juice act (1 mark).
  3. Absorption by villi and microvilli in the intestine; residue to rectum and cloaca (1 mark).

Answer: Mouth to stomach, duodenum, intestine, cloaca with the role at each stage.

Example 2: Respiratory modes · 3 marks · Short answerBoard level

Name the three modes of respiration in a frog and when each is used.

Try it first, then show the solutionSolution
  1. Cutaneous through the moist skin in water and in hibernation or aestivation (1 mark).
  2. Pulmonary through the lungs on land (1 mark).
  3. Buccal through the moist buccal lining (1 mark).

Answer: Skin, lungs, buccal cavity.

Example 3: Role of glands · 3 marks · Short answerHarder board level

Explain the function of liver and pancreas in the frog. Where do their secretions enter the gut?

Try it first, then show the solutionSolution
  1. Liver secretes bile, stored in the gall bladder, which emulsifies fats (1 mark).
  2. Pancreas secretes enzymes for digestion (1 mark).
  3. Both enter the duodenum through the common bile duct (1 mark).

Answer: Bile and pancreatic juice enter the duodenum.

Example 4: Cloaca · 2 marks · Very short answerHarder board level

What is the cloaca of the frog? Name four substances/structures that leave through it.

Try it first, then show the solutionSolution
  1. A common chamber into which the rectum, urinary and reproductive ducts open (1 mark).
  2. Faeces, urine, sperm and eggs pass out through the cloacal aperture (1 mark).

Answer: A common exit for digestive, excretory and reproductive systems.

Example 5: Dormant frog · 4 marks · Short answerHOTS / competency

A frog buried in mud during winter does not feed or use its lungs. Explain how it still obtains oxygen and why its demand is small.

Try it first, then show the solutionSolution
  1. It hibernates: a prolonged inactive period (1 mark).
  2. Gas exchange occurs through the moist skin by diffusion (1 mark).
  3. Metabolic rate is low, so oxygen demand is small and the skin can supply it (1 mark).
  4. Stored body fat is used instead of feeding (1 mark).

Answer: Cutaneous respiration meets the low oxygen demand.

Where students lose marks in Frog: Digestive and Respiratory Systems

The slips examiners see most often, and what to write instead.

  • Mistake: Frog stomach long

    Carnivores have short gut ignored.

    Wrong working

    Frog has a long gut.

    Right working

    Frog has a short gut.

    Do this: Carnivore: short.

    Usually costs: 1 mark.

  • Mistake: Lungs only

    Cutaneous forgotten.

    Wrong working

    Frogs breathe only through lungs.

    Right working

    Skin, buccal cavity and lungs.

    Do this: Three modes.

    Usually costs: 1 mark.

  • Mistake: Bile from gall bladder

    Source wrong.

    Wrong working

    Gall bladder makes bile.

    Right working

    Liver makes bile; gall bladder stores it.

    Do this: Make vs store.

    Usually costs: 1 mark.

Exam tips

  • Always give the gut sequence.
  • Connect diet to gut length.
  • Name three respiration modes.
  • Draw labelled diagrams neatly.

Practice questions on Frog: Digestive and Respiratory Systems

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

  1. Q1 · 1 mark · MCQBoard level

    The organ in which the frog's food is converted to chyme is the
    (a) buccal cavity (b) stomach (c) rectum (d) liver

    Hint

    HCl and gastric juice.

    Answer

    (b).

  2. Q2 · 1 mark · Assertion-reasonHarder board level

    Assertion (A): Frogs can breathe through their skin.
    Reason (R): The skin is thin, moist and supplied with blood vessels.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

    Hint

    Diffusion.

    Answer

    (a).

  3. Q3 · 2 marks · Very short answerHarder board level

    What are vomerine teeth and what is their role?

    Hint

    Holding prey.

    Answer

    Small teeth on the roof of the buccal cavity, together with maxillary teeth; they hold prey and prevent its escape, not chewing.

  4. Q4 · 4 marks · Case-basedHarder board level

    Read and answer.
    Suppose a student labels a frog gut: A is a bilobed muscular organ flicked out; B stores bile; C absorbs food through villi.
    (a) Name A, B, C. (1)
    (b) What does bile do? (1)
    (c) Name the common chamber at the end of the gut. (1)
    (d) Name the gland secreting enzymes into the duodenum. (1)

    Hint

    Tongue, gall bladder, intestine.

    Answer

    (a) Tongue, gall bladder, intestine. (b) Emulsifies fat. (c) Cloaca. (d) Pancreas.

  5. Q5 · 3 marks · Short answerHOTS / competency

    Suppose a frog's skin is coated in oil so that it cannot stay moist. Predict the effect on breathing in water and on land, and justify.

    Hint

    Skin must be moist.

    Answer

    In water cutaneous respiration would fail as dissolved oxygen could not diffuse across the oily skin; the frog would have to rely on its buccal cavity and lungs on land, which still work, so survival is better on land than underwater.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

  1. 1.Name the frog genus.Show answer

    Rana.

  2. 2.What stores bile?Show answer

    Gall bladder.

  3. 3.Where are the lungs?Show answer

    In the upper trunk (thorax).

  4. 4.What is the cloaca?Show answer

    Common chamber for faeces, urine and gametes.

  5. 5.What helps catch prey?Show answer

    Bilobed muscular tongue.

  6. 6.How does a frog breathe in water?Show answer

    Through the skin.

Frog: Digestive and Respiratory Systems: frequently asked questions

Why is the frog carnivorous?

It feeds on insects and worms.

How does the frog breathe?

Skin, buccal cavity and lungs.

What are villi?

Finger-like folds of the intestine for absorption.

What is aestivation?

A dormant period in summer.

What is the role of bile?

To emulsify fats.