NCERT Solutions for Class 7 Science Curiosity Chapter 9: Life Processes in Animals by PW

Digestion and breathing are essential processes that allow the body to obtain nutrients and energy and maintain its normal functions. Understanding how food moves through the digestive tract, how starch is broken down and how air travels through the respiratory system can sometimes be difficult. Questions about the role of the diaphragm, movement of the ribs, gas exchange in the lungs and the composition of inhaled and exhaled air also require careful understanding of each process.

The Class 7 Science Curiosity Chapter 9 NCERT Solutions provide clear answers to the multiple-choice questions from Life Processes in Animals. They cover the sequence of the digestive tract, digestion of starch, breathing movements, alveoli, cellular respiration, oxygen and carbon dioxide levels, sneezing and the lime water test for carbon dioxide.

Class 7 Science Curiosity Chapter 9 NCERT Solutions

The following solutions cover questions related to digestion, breathing and respiration in animals.

1. What is the correct sequence of the human digestive tract (alimentary canal)?

A) Mouth → Stomach → Food pipe → Small intestine → Large intestine → Anus
B) Mouth → Food pipe → Stomach → Small intestine → Large intestine → Anus
C) Mouth → Food pipe → Small intestine → Stomach → Large intestine → Anus
D) Mouth → Stomach → Large intestine → Small intestine → Food pipe → Anus

Answer: B) Mouth → Food pipe → Stomach → Small intestine → Large intestine → Anus

Food passes through the mouth, food pipe, stomach, small intestine, large intestine and finally leaves the body through the anus.

2. Which organ stores food and continues its digestion between the food pipe and small intestine?

A) Liver
B) Pancreas
C) Stomach
D) Anus

Answer: C) Stomach

The stomach receives food from the food pipe, stores it for some time and continues its digestion before passing it to the small intestine.

3. What colour change indicates the presence of starch when iodine solution is added?

A) Red-orange
B) Pink-red
C) Blue-black
D) Pale yellow

Answer: C) Blue-black

Iodine solution produces a blue-black colour when it comes in contact with starch, indicating its presence in the food sample.

4. What effect does salivary amylase in saliva have on starch?

A) Converts starch into proteins
B) Breaks starch down into simpler sugars
C) Turns starch into fats
D) Prevents starch absorption

Answer: B) Breaks starch down into simpler sugars

Salivary amylase helps break down starch into simpler sugars during digestion in the mouth.

5. Which food item contains a very high concentration of starch and turns strongly blue-black with iodine?

A) Boiled mashed potato
B) Cooked meat
C) Pure water
D) Vegetable oil

Answer: A) Boiled mashed potato

Potato contains a high amount of starch. When iodine solution is added, the starch produces a blue-black colour.

6. What primary role does the diaphragm play during breathing?

A) To filter dust particles from air
B) To produce sound during speech
C) To help in inhalation and exhalation
D) To absorb oxygen directly into blood

Answer: C) To help in inhalation and exhalation

The diaphragm changes its position during breathing, helping air move into and out of the lungs.

7. What happens to the diaphragm and ribs during inhalation?

A) Diaphragm moves upward; ribs move inwards
B) Diaphragm moves downward; ribs move outwards
C) Diaphragm moves upward; ribs move outwards
D) Diaphragm moves downward; ribs move inwards

Answer: B) Diaphragm moves downward; ribs move outwards

During inhalation, the diaphragm moves downward and the ribs move outward. This increases the space inside the chest, allowing air to enter the lungs.

8. What is the function of tiny hair and mucus inside the nasal passages?

A) To absorb oxygen
B) To warm up food
C) To trap dust and dirt from inhaled air
D) To expel carbon dioxide

Answer: C) To trap dust and dirt from inhaled air

Tiny hairs and mucus in the nasal passages help trap dust and other particles present in inhaled air.

9. Where does the actual exchange of gases (oxygen and carbon dioxide) occur in the lungs?

A) Nostrils
B) Nasal passages
C) Windpipe
D) Alveoli

Answer: D) Alveoli

The exchange of oxygen and carbon dioxide takes place in the alveoli, which are tiny air sacs present in the lungs.

10. What chemical process occurs during cellular respiration in our body?

A) Glucose + Oxygen → Energy + Carbon Dioxide + Water
B) Glucose + Carbon Dioxide → Energy + Oxygen
C) Starch + Water → Glucose
D) Oxygen + Nitrogen → Energy + Carbon Dioxide

Answer: A) Glucose + Oxygen → Energy + Carbon Dioxide + Water

During cellular respiration, glucose reacts with oxygen to release energy, producing carbon dioxide and water.

11. Why is it most accurate to say “We inhale air rich in oxygen” rather than “We inhale pure oxygen”?

A) Air is a mixture of nitrogen, oxygen, carbon dioxide, and other gases.
B) Oxygen cannot exist in gas form.
C) Humans only inhale nitrogen.
D) Lungs convert air into pure oxygen before taking it in.

Answer: A) Air is a mixture of nitrogen, oxygen, carbon dioxide, and other gases.

We inhale air, which contains several gases. Oxygen forms only a part of the inhaled air, so it is more accurate to say that we inhale air rich in oxygen.

12. What percentage of inhaled air consists of oxygen?

A) Nearly 0.04%
B) Nearly 16–17%
C) Nearly 21%
D) Nearly 78%

Answer: C) Nearly 21%

Oxygen makes up approximately 21% of inhaled air.

13. What percentage of carbon dioxide is present in exhaled air compared to inhaled air?

A) Inhaled: ~0.04%, Exhaled: ~4–5%
B) Inhaled: ~4–5%, Exhaled: ~0.04%
C) Inhaled: ~21%, Exhaled: ~16%
D) Inhaled: ~10%, Exhaled: ~50%

Answer: A) Inhaled: ~0.04%, Exhaled: ~4–5%

The amount of carbon dioxide in exhaled air is much higher than in inhaled air because carbon dioxide is produced during cellular respiration and removed from the body through exhalation.

14. Why do we sneeze when inhaling dust-laden air?

A) Dust stimulates oxygen absorption.
B) Dust irritates the inner nasal lining, triggering sneezing to expel particles.
C) Sneezing increases carbon dioxide absorption.
D) The diaphragm contracts to prevent dust from reaching the mouth.

Answer: B) Dust irritates the inner nasal lining, triggering sneezing to expel particles.

Dust can irritate the inner lining of the nose. Sneezing is a protective response that helps remove unwanted particles from the nasal passages.

15. Which chemical solution is used to test for the presence of carbon dioxide in exhaled air?

A) Iodine solution
B) Saline water
C) Lime water
D) Distilled water

Answer: C) Lime water

Lime water is used to test for carbon dioxide. When carbon dioxide is passed through lime water, it turns milky.

NCERT Solutions for Class 7 Science Curiosity Chapter 9 PDF

Having the questions and answers together can make chapter revision more convenient. The Class 7 Science Curiosity Chapter 9 Solutions PDF includes questions on digestion, starch, breathing, respiration, gas exchange and the composition of inhaled and exhaled air.

What Can You Learn from NCERT Class 7 Science Chapter 9 Solutions by PW?

The NCERT Class 7 Science Chapter 9 Solutions by PW  make the concepts of digestion and respiration easier to understand through clear answers and relatable examples. Key learning areas include:

• Understand Digestion: Learn how food passes through the digestive tract and gets broken down.

• Explore Starch Digestion: Understand how saliva and salivary amylase act on starch.

• Learn About Breathing: Understand the role of the diaphragm and ribs during inhalation and exhalation.

• Understand Gas Exchange: Learn how alveoli help exchange oxygen and carbon dioxide in the lungs.

• Explore Cellular Respiration: Understand how glucose and oxygen help release energy in the body.

• Compare Inhaled and Exhaled Air: Identify changes in oxygen and carbon dioxide levels during breathing.

• Understand Protective Responses: Learn how mucus, nasal hairs and sneezing help protect the respiratory system.

• Practise Concept-Based Questions: Apply these concepts to MCQs and everyday situations related to life processes.

Digestion and respiration involve several organs and processes that work together to support life. The NCERT Class 7 Science Chapter 9 Solutions explain questions on the digestive tract, starch digestion, breathing movements, alveoli, cellular respiration and gas exchange. Revising these concepts can help children understand how the body processes food and exchanges gases during everyday life.

Related Resources

• CBSE Class 7 Science Syllabus

• CBSE Class 7 Science NCERT Solutions

• CBSE Class 7 Science Sample Papers

• CBSE Class 7 Science Notes