Question Answer Chapter 9 Class 7 Science Curiosity NCERT

Life Processes in Animals

1. Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts-

Food → Mouth → ______ → Stomach → ______ → ______ → Anus

Answer: Food → Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → 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 (chapati): The solution turns blue-black because chapati contains starch, and iodine reacts with starch to produce a blue-black color.

Test tube B (chewed chapati): The solution shows no change or a very light blue-black color because saliva in the chewed chapati breaks down starch into sugar, reducing or eliminating the starch content.

Test tube C (boiled and mashed potato): The solution turns blue-black because boiled and mashed potato still contains starch, which reacts with iodine to give a blue-black color.

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 (iii) To help in inhalation and exhalation

Explanation: The diaphragm is a muscle that moves downward during inhalation to increase the chest space, allowing air to enter the lungs, and moves upward during exhalation to push air out of the lungs.

4. Match the following

Answer

• (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

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 the following questions:

1. What is the difference between the physical process of moving air in and out of the lungs and the chemical process of breaking down food to release energy?

2.Why do we say breathing involves only the lungs, but respiration happens in all body cells to produce energy?

3. How does oxygen help convert glucose into energy, and is that part of breathing or a separate process called respiration?

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 is correct: “We inhale air rich in oxygen.”

 Why: We inhale air, which contains about 21% oxygen along with other gases like nitrogen and carbon dioxide. Shanu’s statement is incorrect because we do not inhale only oxygen but a mixture of gases. Anu’s statement is too general as it does not specify the presence of oxygen, while Tanu’s statement accurately describes that the air we inhale is rich in oxygen.

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

Answer

• Sneezing occurs because dust particles irritate the nasal passages, triggering the body to expel them through a forceful sneeze to clear the airways.
• The tiny hairs and mucus in the nostrils trap dust, which stimulates a reflex action in the body, causing a sneeze to remove the dust and protect the respiratory system.

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

• Anusha may have run faster or covered a longer distance than Paridhi, causing her body to require more oxygen, which leads to faster breathing.
• Anusha might have lower stamina or be less physically fit than Paridhi, making her body work harder during the run, resulting in faster breathing to meet the oxygen demand.

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 whether saliva can break down starch in rice flour into sugar.

Explanation:

1.  In test tube A (rice flour without saliva), the iodine solution will turn blue-black, indicating the presence of starch.

2. In test tube B (rice flour with saliva), the solution may show no color change or a lighter color, indicating that saliva has broken down the          starch into sugar, which does not react with iodine.

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:

Investigation: Rakshita is trying to investigate whether exhaled air contains more carbon dioxide than inhaled air.

How to confirm findings: She can confirm her findings by observing that the lime water in test tube B (exhaled air) turns milky or cloudy due to the reaction of carbon dioxide with lime water, while the lime water in test tube A (inhaled air) remains clear or shows minimal change. To ensure accuracy, she can repeat the experiment multiple times and compare the results consistently.