Class 7 Science · Chapter 9

9. Life Processes in Animals

Complete solutions to Let Us Enhance Our Learning. CBSE / NCERT Class 7 Science (Curiosity).

Let Us Enhance Our Learning

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

Food → Mouth → Oesophagus (food pipe) → Stomach → Small intestine → Large intestine → Anus

2Sahil placed 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. What would be their observations? Give reasons.

Test tube A (chapati pieces): turns blue-black. Chapati contains starch.
Test tube B (chewed chapati): shows little or no blue-black colour. Saliva in the mouth breaks down starch into sugar. So less starch is left.
Test tube C (boiled potato): turns blue-black. Potato is rich in starch.

3What 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

When the diaphragm moves down, air is drawn into the lungs. When it moves up, air is pushed out.

4Match the following.

Name of the part	Function
(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

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

Where does breathing take place, and where does respiration take place?
Is breathing just the movement of air in and out of the lungs?
In which process is food (glucose) broken down to release energy?
Which of these is a physical process and which is a chemical process?

Breathing is the physical process of taking in and giving out air. Respiration is the chemical process in which glucose is broken down using oxygen to release energy.

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

Anu is correct.

We inhale the air around us. It is a mixture of gases — mainly nitrogen and oxygen, with a little carbon dioxide and water vapour. Inhaled air has only nearly 21% oxygen, so it is not ‘rich’ in oxygen, and we do not inhale only oxygen.

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

Dust particles irritate the lining of the nasal passages. Sneezing is a quick, forceful push of air out of the nose. It throws out the dust and other particles. This helps to keep the air passages and lungs clean.

8After running, Anusha was breathing faster than Paridhi. Provide at least two possible explanations.

Anusha may have run faster or for a longer distance. Her body needed more energy and more oxygen.
Paridhi may exercise regularly, so her body is used to running.
Anusha may have rested for a shorter time before counting her breaths.

During exercise, the body needs more energy. To get more oxygen, we breathe faster.

9Yadu took rice flour in water in two test tubes A and B. He added saliva to B, left them for 35–45 min and then added iodine. A turned blue-black, B did not. What do you think he wants to test?

Yadu wants to test whether saliva breaks down starch.

A turned blue-black because starch was present. B did not, because saliva broke down the starch into sugar.

10Rakshita passed inhaled air through lime water in test tube A and blew exhaled air through lime water in test tube B. What is she trying to investigate? How can she confirm her findings?

She wants to find out whether exhaled air contains more carbon dioxide than inhaled air.

Carbon dioxide turns lime water milky. Lime water in B (exhaled air) turns milky quickly. Lime water in A changes very little. This confirms that exhaled air has more carbon dioxide.

She can repeat the activity a few times, passing air for the same amount of time in both test tubes, to be sure of the result.

Exploratory Projects

Exploratory Projects are hands-on tasks. Do them with your classmates under the guidance of your teacher, and write your own observations.

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