NCERT Solutions for Class 7 Science (Curiosity) Chapter 9: Life Processes in Animals (NCERT 2026–27)

These Class 7 Science Curiosity Chapter 9 solutions cover Life Processes in Animals from the new NCF-2023 textbook (2026–27). The chapter explains two key life processes in detail — nutrition (how food is digested in humans and other animals) and respiration (how we breathe and how oxygen releases energy from food). Every “Let Us Enhance Our Learning” exercise question is reproduced verbatim and answered in step-by-step, exam-ready style below.

Class: 7 Subject: Science Book: Curiosity Chapter: 9 Topic: Nutrition & Respiration in Animals Session: 2026–27
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Class 7 Science Curiosity Chapter 9 Solutions – Overview

Chapter 9 of Curiosity, Life Processes in Animals, builds on the Grade 6 idea that nutrition, respiration, excretion and reproduction are the life processes essential for survival. This chapter studies two of them closely. In nutrition, food travels through the alimentary canal — mouth, oesophagus (food pipe), stomach, small intestine, large intestine and anus — helped by the liver and pancreas, and the digested nutrients are absorbed mainly in the small intestine. Animals like ruminants (cows) and birds (using a gizzard) digest differently. In respiration, the respiratory system carries air to the lungs, gases are exchanged in the alveoli, and oxygen breaks down glucose to release energy: Glucose + Oxygen → Carbon dioxide + Water + Energy. The chapter clearly separates breathing (a physical process) from respiration (a chemical process).

Key Concepts & Definitions

Life processes: processes essential for survival of living beings — nutrition, circulation, respiration, excretion and reproduction.

Alimentary canal: a long tube from mouth to anus where complex food is broken into simpler forms; includes mouth, oesophagus, stomach, small intestine, large intestine and anus.

Mechanical digestion: the initial breakdown of food into fine pieces by crushing and chewing with the teeth.

Digestion: the process of breaking complex food components into simpler forms in the body; saliva, for example, breaks starch into sugar.

Absorption: the passing of digested nutrients from the small intestine into the blood; finger-like projections increase the surface area for this.

Egestion: the removal of semi-solid undigested waste (stool) through the anus.

Rumination: grass-eating animals (ruminants like cows) partially chew and swallow food, then bring it back to the mouth for thorough chewing.

Breathing: the physical process of inhaling and exhaling air; the diaphragm and ribs change the space inside the chest.

Respiration: the chemical process in which oxygen breaks down glucose to release energy — Glucose + Oxygen → Carbon dioxide + Water + Energy.

Alveoli: tiny balloon-like sacs in the lungs where exchange of oxygen and carbon dioxide takes place.

“Let Us Enhance Our Learning” — NCERT Solutions

All questions below are reproduced verbatim from the NCERT Curiosity textbook (Grade 7), in the exact order printed. Answers are original and exam-ready.

1. Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts—
Food → Mouth → ____ → Stomach → ____ → ____ → Anus

ANSWER The complete journey of food through the alimentary canal is: Food → Mouth → Oesophagus (food pipe) → Stomach → Small intestine → Large intestine → Anus. Food enters the mouth, is pushed through the oesophagus to the stomach, then to the small intestine (where most digestion and absorption happen), then to the large intestine (which absorbs water), and the undigested waste finally leaves through the anus.

2. Sahil placed some pieces of chapati in test tube A. Neha placed chewed chapati in test tube B, and Santushti took boiled and mashed potato in test tube C. All of them added a few drops of iodine solution to their test tubes—A, B, and C, respectively. What would be their observations? Give reasons.

ANSWER Test tube A (plain chapati pieces): turns blue-black. Chapati contains starch, and iodine gives a blue-black colour with starch. Test tube B (chewed chapati): shows no colour change or only a very faint blue-black. While chewing, the saliva breaks down the starch into simple sugars, so little or no starch is left to react with iodine. Test tube C (boiled, mashed potato): turns blue-black. Potato is rich in starch and was not chewed, so the starch is still present and reacts with iodine.

3. What is the role of the diaphragm in breathing?
(i) To filter the air   (ii) To produce sound   (iii) To help in inhalation and exhalation   (iv) To absorb oxygen

ANSWER Correct option: (iii) To help in inhalation and exhalation. The diaphragm is a dome-shaped muscle below the lungs. During inhalation it moves downwards, increasing the space in the chest so air enters the lungs; during exhalation it moves upwards, reducing the space and pushing air out. It does not filter air, produce sound or absorb oxygen.

4. Match the following

ANSWER
Name of the partFunction
(i) Nostrils(a) fresh air from outside enters
(ii) Nasal passages(d) tiny hair and mucus help to trap dust and dirt from the air we breathe
(iii) Windpipe(e) air reaches our lungs through this part
(iv) Alveoli(b) exchange of gases occurs
(v) Ribcage(c) protects lungs
So the matching is: (i)–(a), (ii)–(d), (iii)–(e), (iv)–(b), (v)–(c).

5. Anil claims to his friend Sanvi that respiration and breathing are the same process. What question(s) can Sanvi ask him to make him understand that he is not correct?

ANSWER Sanvi can ask questions that reveal the difference between the two: • “If breathing and respiration are the same, then how does the food we eat give us energy — isn’t energy released only when oxygen breaks down glucose inside the body?” • “Breathing is just the movement of air in and out of the lungs — a physical process. Is that the same as a chemical reaction (Glucose + Oxygen → Carbon dioxide + Water + Energy) that happens inside the body?” These questions show that breathing is a physical process (inhaling and exhaling air), while respiration is a chemical process that uses oxygen to break down food and release energy — so they are not the same.

6. Which of the following statements is correct and why?
Anu: We inhale air.   Shanu: We inhale oxygen.   Tanu: We inhale air rich in oxygen.

ANSWER Tanu’s statement — “We inhale air rich in oxygen” — is the most correct. The air we inhale is a mixture of gases (nearly 21% oxygen, a small amount of carbon dioxide, and a large amount of other gases like nitrogen). We do not inhale pure oxygen, so Shanu is wrong. Anu’s statement is true but incomplete — she only says “air” without mentioning that it is rich in oxygen. Tanu correctly states that the inhaled air is a mixture that is rich in oxygen, which is what the body uses for respiration.

7. We often sneeze when we inhale a lot of dust-laden air. What can be possible explanations for this?

ANSWER The tiny hair and mucus inside our nostrils and nasal passages trap dust and dirt from the air we breathe. When we inhale a lot of dust, these particles irritate the inner lining of the nose. Sneezing is the body’s natural reflex to throw out the trapped dust and irritating particles forcefully through the nose. It is a protective action that helps clean the respiratory passage and stops the harmful particles from reaching the lungs.

8. Paridhi and Anusha of Grade 7 started running for their morning workout. After they completed their running, they counted their breaths per minute. Anusha was breathing faster than Paridhi. Provide at least two possible explanations for why Anusha was breathing faster than Paridhi.

ANSWER During running, muscles work hard and need more energy, so the body needs more oxygen and produces more carbon dioxide. To meet this demand, the breathing rate increases. Two possible reasons Anusha breathed faster: (1) Anusha may have run faster or for a longer distance, so her muscles needed more oxygen and her body had to remove more carbon dioxide, increasing her breathing rate. (2) Paridhi may be more physically fit or used to exercise; a fitter person’s lungs and heart work more efficiently, so they need fewer, deeper breaths to get the same oxygen, while Anusha (less practised) breathes faster.

9. Yadu conducted an experiment to test his idea. He took two test tubes, A and B, and added a pinch of rice flour to the test tubes, half-filled with water and stirred them properly. To test tube B, he added a few drops of saliva. He left the two test tubes for 35–45 min. After that, he added iodine solution into both the test tubes. Experimental results are as shown in Fig. 9.15. What do you think he wants to test?

ANSWER Yadu wants to test the action of saliva on starch — that is, whether saliva breaks down the starch present in rice flour into simpler sugars. Test tube A (no saliva) turns blue-black on adding iodine, showing starch is still present. Test tube B (with saliva) shows little or no colour change, showing the starch has been broken down by the digestive juice in saliva. This proves that saliva digests starch.

10. Rakshita designed an experiment taking two clean test tubes, A and B and filled them with lime water as shown in the figure. In test tube A, the surrounding air that we inhale was passed on by sucking air from the pipe, and in test tube B, the exhaled air was blown through the pipe (Fig. 9.16). What do you think she is trying to investigate? How can she confirm her findings?

ANSWER Rakshita is investigating whether exhaled air contains more carbon dioxide than inhaled air. Findings: The lime water in test tube B (exhaled air) turns milky/cloudy, while the lime water in test tube A (inhaled surrounding air) stays clear or changes very little. Lime water turns milky only when it reacts with carbon dioxide. How to confirm: She can repeat the experiment several times with fresh lime water, and compare the time taken for each test tube to turn milky — B should turn milky much faster. This confirms that the air we breathe out is richer in carbon dioxide than the air we breathe in.

Extra Practice Questions

Short Answer Type Questions

Q1. Why is starchy food like chapati tasting sweet when chewed for a long time?

ANSWERSaliva contains a digestive juice that breaks down the starch in chapati into sugar. The longer we chew, the more starch is converted to sugar, so the food begins to taste sweet.

Q2. Why is the small intestine called “small” even though it is the longest part of the alimentary canal?

ANSWERIt is called “small” because it is narrower (smaller in width) than the large intestine, even though it is about 6 metres long — the longest part of the canal. The large intestine (about 1.5 m) is shorter but wider.

Q3. What is the role of bile in digestion?

ANSWERBile is secreted by the liver and is mildly basic. It neutralises the acids in the food coming from the stomach and breaks down fats into tiny droplets, making the digestion of fats easier.

Q4. How do fish breathe under water?

ANSWERMost aquatic animals like fish have specialised structures called gills, which are richly supplied with blood vessels. The exchange of oxygen and carbon dioxide between the blood and the gases dissolved in water takes place across the gills.

Q5. Why should we breathe through the nose and not the mouth?

ANSWERThe tiny hair and mucus inside the nostrils and nasal passages trap dust and dirt from the air. Breathing through the nose cleans the air before it reaches the lungs, while breathing through the mouth skips this filtering.

Long Answer Type Questions

Q1. Describe the journey of food through the human alimentary canal, naming the parts and what happens at each.

ANSWERFood first enters the mouth, where teeth crush and chew it (mechanical digestion) and saliva begins breaking down starch into sugar. The tongue mixes the food with saliva and pushes it into the oesophagus (food pipe), whose walls contract and relax in wave-like motion to push food into the stomach. In the stomach, churning mixes food with digestive juice, acid (which also kills bacteria) and mucus (which protects the stomach lining); proteins begin to break down. The semi-liquid food then enters the small intestine (about 6 m long), where bile from the liver and pancreatic juice from the pancreas, along with the intestine’s own juice, break down carbohydrates, proteins and fats into simple forms. The finger-like projections of the small intestine absorb these nutrients into the blood. Undigested food passes into the large intestine, which absorbs water and salts, forming semi-solid stool stored in the rectum. Finally, the waste is expelled through the anus (egestion).

Q2. Explain the mechanism of breathing in humans, including the role of the diaphragm and ribs.

ANSWERBreathing has two steps — inhalation and exhalation. During inhalation, the ribs move up and outwards and the diaphragm (a dome-shaped muscle below the lungs) moves downwards. This increases the space inside the chest, so air is drawn into the lungs through the nostrils, nasal passages and windpipe. During exhalation, the ribs move down and inwards and the diaphragm moves upwards, reducing the space in the chest and pushing air out of the lungs. Inside the lungs, air fills the balloon-like alveoli, where oxygen passes into the blood and carbon dioxide passes out, to be breathed out. Thus the ribs and diaphragm together change the chest volume to move air in and out.

Q3. How is the digestive system of a ruminant (cow) and a bird different from that of humans?

ANSWERRuminants (cows, buffaloes) are grass-eaters. They partially chew the grass and swallow it into their stomach, which has a part called the rumen where partial digestion occurs. The partially digested food is then brought back to the mouth and chewed gradually — a process called rumination. A cow may chew for about 8 hours a day before the food passes down for further digestion. Birds have no teeth, so they cannot chew. They have a muscular chamber called the gizzard, where food is ground by the contraction and relaxation of its walls, often helped by grit (small stones) the bird swallows. Humans, in contrast, chew food in the mouth with teeth and do not ruminate or use a gizzard. These differences show how animals adapt their alimentary canal to the kind of food they eat.

MCQs & Assertion–Reason

1. The breaking down of complex food into simpler forms in the body is called:

(a) absorption    (b) digestion    (c) egestion    (d) respiration

2. The longest part of the human alimentary canal is the:

(a) oesophagus    (b) stomach    (c) small intestine    (d) large intestine

3. Iodine gives a blue-black colour when it reacts with:

(a) sugar    (b) starch    (c) fat    (d) protein

4. Bile is secreted by the:

(a) pancreas    (b) stomach    (c) liver    (d) small intestine

5. The exchange of gases in the lungs takes place in the:

(a) windpipe    (b) nostrils    (c) alveoli    (d) diaphragm

6. Which animals chew the partially digested food again, a process called rumination?

(a) birds    (b) fish    (c) ruminants like cows    (d) frogs

7. Birds break down food using a muscular chamber called the:

(a) gizzard    (b) rumen    (c) rectum    (d) alveolus

8. The word equation for respiration is Glucose + Oxygen → :

(a) Starch + Water    (b) Carbon dioxide + Water + Energy    (c) Oxygen + Sugar    (d) Protein + Energy

9. Lime water turns milky in the presence of:

(a) oxygen    (b) nitrogen    (c) carbon dioxide    (d) water vapour

10. Which of these is a chemical process that occurs inside the body?

(a) breathing    (b) inhalation    (c) exhalation    (d) respiration

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

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 inner lining of the small intestine has thousands of finger-like projections.

Reason: These projections increase the surface area for efficient absorption of nutrients.

A-R 2. Assertion: Breathing and respiration are exactly the same process.

Reason: Breathing is a physical process, while respiration is a chemical process that releases energy.

A-R 3. Assertion: Chewed chapati shows little colour change with iodine.

Reason: Saliva breaks down the starch in chapati into simple sugars while chewing.

A-R 4. Assertion: We should breathe through the nose rather than the mouth.

Reason: Tiny hair and mucus in the nostrils trap dust and dirt from the inhaled air.

A-R 5. Assertion: Exhaled air turns lime water milky.

Reason: Exhaled air contains more carbon dioxide than inhaled air, and carbon dioxide turns lime water milky.

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

Quick Revision Summary

  • Life processes (nutrition, circulation, respiration, excretion, reproduction) are essential for survival.
  • The alimentary canal: mouth → oesophagus → stomach → small intestine → large intestine → anus, with the liver and pancreas as associated parts.
  • Saliva breaks starch into sugar; the stomach breaks down proteins; bile and pancreatic juice neutralise acid and digest fats.
  • Nutrients are absorbed mainly in the small intestine; the large intestine absorbs water and salts.
  • Ruminants (cows) chew food again (rumination); birds use a gizzard instead of teeth.
  • Breathing (physical) moves air in/out using ribs and diaphragm; gases are exchanged in the alveoli.
  • Respiration (chemical): Glucose + Oxygen → Carbon dioxide + Water + Energy.
  • Exhaled air has more carbon dioxide (turns lime water milky) and less oxygen than inhaled air.

Common Mistakes to Avoid

Watch out for these

  • Confusing breathing (physical, air in/out) with respiration (chemical, energy release) — they are not the same.
  • Thinking we inhale pure oxygen — we inhale air rich in oxygen, a mixture of gases.
  • Calling the small intestine “small” because of length — it is the longest part; it is only narrower than the large intestine.
  • Forgetting that iodine turns blue-black with starch, not with sugar — chewed/saliva-treated food shows little colour.
  • Mixing up the liver (secretes bile) with the pancreas (secretes pancreatic juice).
  • Writing that gills are in the lungs — gills are separate breathing organs in fish.

How to score full marks in this chapter

Learn the order of the alimentary canal and one job for each part — examiners love “name the part and its function” questions. Always write the respiration word equation correctly. In experiment-based questions (iodine–starch or lime water–carbon dioxide), state both the observation and the reason. Clearly distinguish breathing from respiration in one line. Use the textbook’s own examples — saliva on rice, lime water, ruminants and the gizzard — to show you have studied the chapter.

Frequently Asked Questions

What is Class 7 Science Curiosity Chapter 9 about?

Chapter 9, Life Processes in Animals, explains two key life processes in detail: nutrition (digestion of food through the alimentary canal in humans and other animals) and respiration (breathing and how oxygen releases energy from glucose). It also covers digestion in ruminants and birds, and the difference between breathing and respiration.

What is the difference between breathing and respiration?

Breathing is a physical process — the movement of air into the lungs (inhalation) and out of the lungs (exhalation). Respiration is a chemical process inside the body in which oxygen breaks down glucose to release energy: Glucose + Oxygen → Carbon dioxide + Water + Energy.

Why does chewed rice or chapati taste sweet?

Saliva contains a digestive juice that breaks down the starch in rice or chapati into simple sugars. The longer you chew, the more sugar is formed, so the food begins to taste sweet.

Are these Class 7 Science Curiosity Chapter 9 solutions free?

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

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