NCERT Solutions for Class 11 Biology Chapter 7: Structural Organisation in Animals (NCERT 2026–27)

These Class 11 Biology Chapter 7 solutions cover Structural Organisation in Animals, the chapter that introduces how cells, tissues, organs and organ systems work together, and then studies the morphology and anatomy of the frog (Rana tigrina) as a representative vertebrate. Every NCERT exercise question is reproduced verbatim and answered in clear, exam-ready prose for session 2026–27.

Class: 11 Subject: Biology Chapter: 7 Title: Structural Organisation in Animals Topics: Organ & organ system, Frog Session: 2026–27
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Class 11 Biology Chapter 7 Solutions – Overview

In unicellular organisms a single cell performs every function, but in multicellular animals these tasks are shared among groups of cells, showing division of labour. A group of similar cells with intercellular substances forms a tissue; all complex animals are built from only four basic tissue types — epithelial, connective, muscular and neural. Tissues combine to form organs (stomach, lung, heart, kidney), and two or more organs working together form an organ system (digestive, respiratory, etc.). The chapter then explores the morphology (external form) and anatomy (internal organs) of the frog, Rana tigrina — a cold-blooded amphibian of phylum Chordata — covering its skin, body divisions, and its digestive, respiratory, circulatory, excretory, nervous and reproductive systems. The end-of-chapter Exercises contain two questions, both solved fully below.

Key Concepts & Definitions

Tissue: a group of similar cells along with intercellular substances that together perform a specific function.

Four basic tissues: epithelial, connective, muscular and neural — the building blocks of all organs.

Organ & organ system: tissues organise into organs; organs interacting for a common function form an organ system.

Poikilotherm (cold-blooded): an animal like the frog whose body temperature varies with the environment.

Aestivation & hibernation: summer sleep and winter sleep in deep burrows to escape extreme heat and cold.

Camouflage / mimicry: protective colour change that hides the frog from enemies.

Cutaneous & pulmonary respiration: gas exchange through the moist skin (in water) and through the lungs (on land).

Hepatic portal & renal portal systems: special venous links between liver–intestine and kidney–lower body respectively.

Ureotelic animal: the frog excretes nitrogenous waste mainly as urea.

Sexual dimorphism: males bear vocal sacs and a copulatory pad on the first digit of the forelimb; females do not.

NCERT Exercises — Solutions

Questions below are reproduced verbatim from the NCERT textbook (Reprint 2026–27). Answers are original and exam-ready.

1. Draw a neat diagram of digestive system of frog.

ANSWER A neat labelled diagram should be drawn (a clear line drawing). Since the digestive tract must be shown as a continuous, correctly ordered tube with its glands, draw the pathway in this sequence and label every part: Mouth → buccal cavity (with the bilobed tongue) → pharynx → oesophagus (short tube) → stomach → small intestine (beginning with the duodenum) → large intestine / rectum → cloaca → cloacal aperture. Also show the two main digestive glands: the liver (with the gall bladder that stores bile) and the pancreas; show the common bile duct opening into the duodenum, carrying bile from the gall bladder and pancreatic juice from the pancreas. Labelling checklist for full marks: mouth, buccal cavity, tongue, oesophagus, liver, gall bladder, stomach, pancreas, duodenum, small intestine, rectum, cloaca and cloacal aperture — with the alimentary canal drawn as one continuous, correctly proportioned tube (short, because the frog is carnivorous).

2. Mention the function of the Ureters in frog.

ANSWER The ureters are a pair of ducts that emerge from the kidneys and carry urine away from them, opening into the cloaca from where it is finally expelled. In the male frog: each ureter acts as a urinogenital duct — it carries both urine and sperms from the kidney region to the cloaca, so it serves a combined urinary and reproductive role. In the female frog: the ureters carry only urine; the ureters and the oviducts open separately into the cloaca, so the ureter is purely a urinary duct.

Extra Practice Questions

Short Answer Type Questions

Q1. Why is the alimentary canal of the frog short?

ANSWERThe frog is carnivorous, feeding mainly on insects. Animal food is easier to digest than plant material, so a long absorptive intestine is not needed; hence the length of the intestine, and the whole alimentary canal, is reduced.

Q2. Distinguish between cutaneous and pulmonary respiration in a frog.

ANSWERCutaneous respiration is gas exchange through the moist, vascular skin and takes place when the frog is in water (and during aestivation and hibernation), where dissolved oxygen diffuses through the skin. Pulmonary respiration is gas exchange through the pair of lungs and occurs on land, with air entering through the nostrils into the buccal cavity and then to the lungs.

Q3. What is meant by sexual dimorphism in frogs? Give the male features.

ANSWERSexual dimorphism is the existence of distinguishing external features between males and females of a species. In frogs, the male can be identified by the presence of sound-producing vocal sacs and a copulatory pad on the first digit of the forelimb; both are absent in the female.

Q4. Name the heart chambers of a frog and the structures associated with it.

ANSWERThe frog’s heart is three-chambered, with two atria and one ventricle, enclosed in a membrane called the pericardium. A triangular sinus venosus joins the right atrium and receives blood through the vena cava, while the ventricle opens into a conus arteriosus on the ventral side.

Q5. Why is the frog called a ureotelic animal?

ANSWERA ureotelic animal excretes its nitrogenous waste mainly in the form of urea. The frog removes excretory wastes through its kidneys as urea, so it is described as ureotelic.

Long Answer Type Questions

Q1. Describe the digestive system of the frog, including its digestive glands.

ANSWERThe digestive system of the frog consists of the alimentary canal and associated digestive glands. The mouth opens into the buccal cavity, which leads through the pharynx into a short oesophagus; this opens into the stomach, which continues as the intestine, rectum, and finally the cloaca. The alimentary canal is short because the frog is carnivorous. Food is captured by the bilobed, muscular tongue. In the stomach, HCl and gastric juices act on the food, and the partially digested food (chyme) passes into the duodenum, the first part of the small intestine. The duodenum receives bile from the gall bladder and pancreatic juice from the pancreas through a common bile duct; bile emulsifies fats while pancreatic juice digests carbohydrates and proteins. Final digestion occurs in the intestine, and digested food is absorbed through finger-like villi and microvilli of the inner intestinal wall. Undigested solid waste moves to the rectum and is expelled through the cloaca. The chief digestive glands are the liver (secreting bile, stored in the gall bladder) and the pancreas (secreting pancreatic juice with digestive enzymes).

Q2. Explain the circulatory system of the frog.

ANSWERThe frog has a well-developed closed type of vascular system along with a lymphatic system. The blood vascular system comprises the heart, blood vessels and blood, while the lymphatic system has lymph, lymph channels and lymph nodes. The muscular heart, situated in the upper body cavity and covered by the pericardium, has three chambers — two atria and one ventricle. A triangular sinus venosus joins the right atrium and receives blood from the major veins (vena cava); the ventricle opens into a conus arteriosus on the ventral side. Arteries (the arterial system) carry blood from the heart to all body parts, and veins (the venous system) return blood to the heart. Two special venous connections exist: the hepatic portal system between the liver and intestine, and the renal portal system between the kidney and the lower parts of the body. Blood is made of plasma and cells — nucleated RBCs (erythrocytes) containing haemoglobin, WBCs (leucocytes) and platelets. The lymph lacks some proteins and RBCs and is therefore different from blood. The blood carries nutrients, gases and water, and circulation is driven by the pumping of the muscular heart.

Q3. Give an account of the nervous system and sense organs of the frog.

ANSWERControl and coordination in the frog involve both the neural system and the endocrine glands; the prominent endocrine glands are the pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals and gonads. The nervous system is organised into a central nervous system (brain and spinal cord), a peripheral nervous system (cranial and spinal nerves, with ten pairs of cranial nerves) and an autonomic nervous system (sympathetic and parasympathetic). The brain is enclosed in a bony cranium (brain box) and is divided into the forebrain (olfactory lobes, paired cerebral hemispheres, unpaired diencephalon), midbrain (a pair of optic lobes) and hindbrain (cerebellum and medulla oblongata). The medulla oblongata passes through the foramen magnum and continues as the spinal cord within the vertebral column. The frog has sense organs for touch (sensory papillae), taste (taste buds), smell (nasal epithelium), vision (eyes) and hearing (tympanum with internal ears). The eyes are simple spherical structures in the orbit, and the internal ears serve both hearing and balance; the external ear is absent, only the tympanum being visible.

MCQs & Assertion–Reason

1. The common Indian frog belongs to the species:

(a) Rana esculenta    (b) Rana tigrina    (c) Bufo melanostictus    (d) Hyla arborea

2. The number of basic tissue types in complex animals is:

(a) two    (b) three    (c) four    (d) five

3. The heart of a frog has:

(a) two atria and two ventricles    (b) one atrium and one ventricle    (c) two atria and one ventricle    (d) one atrium and two ventricles

4. Summer sleep in a frog is called:

(a) hibernation    (b) aestivation    (c) camouflage    (d) metamorphosis

5. In water, the frog respires mainly through its:

(a) lungs    (b) gills    (c) skin    (d) buccal cavity

6. The bilobed structure used by the frog to capture prey is the:

(a) tympanum    (b) tongue    (c) nictitating membrane    (d) cloaca

7. The frog excretes its nitrogenous waste mainly as:

(a) ammonia    (b) uric acid    (c) urea    (d) amino acids

8. The special venous connection between the liver and the intestine is the:

(a) renal portal system    (b) hepatic portal system    (c) sinus venosus    (d) conus arteriosus

9. The testes of a male frog are attached to the kidneys by a double fold of peritoneum called:

(a) mesentery    (b) mesorchium    (c) pericardium    (d) peritoneum

10. A mature female frog can lay how many ova at a time?

(a) 100–200    (b) 500–1000    (c) 2500–3000    (d) 10000–12000

Answer key: 1-(b), 2-(c), 3-(c), 4-(b), 5-(c), 6-(b), 7-(c), 8-(b), 9-(b), 10-(c).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: The frog is called a cold-blooded animal.

Reason: The body temperature of the frog varies with the temperature of its environment.

A-R 2. Assertion: In the male frog the ureter acts as a urinogenital duct.

Reason: In the male, the ureter carries both urine and sperms to the cloaca.

A-R 3. Assertion: The alimentary canal of the frog is long.

Reason: The frog is a carnivore that feeds mainly on insects.

A-R 4. Assertion: The skin of the frog helps in respiration.

Reason: The skin is moist and highly vascularised, allowing exchange of gases by diffusion.

A-R 5. Assertion: The RBCs of the frog lack a nucleus.

Reason: The RBCs of the frog contain the red pigment haemoglobin.

Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(D).

Common Mistakes to Avoid

Watch out for these

  • Writing that the frog’s heart has four chambers — it has three (two atria, one ventricle).
  • Saying frog RBCs are non-nucleated — frog RBCs are nucleated (unlike mammalian RBCs).
  • Confusing the hepatic portal system (liver–intestine) with the renal portal system (kidney–lower body).
  • Confusing aestivation (summer sleep) with hibernation (winter sleep).
  • Forgetting that in the male the ureter is a urinogenital duct, while in the female the ureter and oviduct open separately.
  • Calling the frog warm-blooded — it is a poikilotherm (cold-blooded).

How to score full marks in this chapter

For diagram questions, draw a clean line diagram and label every part neatly — for the digestive system, show the alimentary canal as one continuous tube plus the liver, gall bladder and pancreas. For the frog’s organ systems, learn the exact sequence (digestive: mouth → cloaca; circulatory: three-chambered heart with sinus venosus and conus arteriosus). Always state the male vs female difference for the ureter, and remember key facts that examiners love: Rana tigrina, three-chambered heart, nucleated RBCs, ureotelic, hepatic vs renal portal systems, and 2500–3000 ova.

Frequently Asked Questions

What is Class 11 Biology Chapter 7 about?

Chapter 7, Structural Organisation in Animals, explains how cells, tissues, organs and organ systems are organised in multicellular animals, and then studies the morphology and anatomy of the frog (Rana tigrina), including its digestive, respiratory, circulatory, excretory, nervous and reproductive systems.

How many questions are there in the NCERT exercise of Chapter 7?

The end-of-chapter Exercises contain two questions: drawing the digestive system of the frog, and stating the function of the ureters. Both are solved fully on this page, along with extra practice questions, MCQs and Assertion–Reason questions.

What is the function of the ureters in a frog?

The ureters carry urine from the kidneys to the cloaca. In the male they act as urinogenital ducts carrying both urine and sperms, while in the female they carry only urine and open into the cloaca separately from the oviducts.

Are these Class 11 Biology Chapter 7 solutions free?

Yes. All solutions are free and follow the official NCERT Biology textbook for session 2026–27.

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