Life Processes in AnimalsClass 7 Science NCERT Solutions
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Q1Let Us Enhance Our Learning
Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts-
Solution
The journey of food through the alimentary canal is as follows:
Mouth Food Pipe (Oesophagus) Stomach Small Intestine Large Intestine Anus
Q2Let Us Enhance Our Learning
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.
Solution
Here are the expected observations:
- Test tube A (Chapati pieces): The iodine solution will turn blue-black because chapati contains starch, and the starch has not been broken down.
- Test tube B (Chewed chapati): The iodine solution may show a lighter blue-black colour or no colour change. This is because the saliva in the mouth breaks down some of the starch into sugars during chewing.
- Test tube C (Boiled and mashed potato): The iodine solution will turn blue-black. Boiled and mashed potato contains a high amount of starch. The boiling and mashing process does not break down the starch into simpler forms.
Q3Let Us Enhance Our Learning
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
Solution
The correct answer is (iii) To help in inhalation and exhalation.
The diaphragm is a dome-shaped muscle located below the lungs. It contracts and moves downwards during inhalation, increasing the space in the chest cavity and allowing air to enter the lungs. During exhalation, the diaphragm relaxes and moves upwards, decreasing the space in the chest cavity and forcing air out of the lungs. (See Figure 9.10 in textbook)
Q4Let Us Enhance Our Learning
Match the following Name of the part
(i)
Nostrils
(ii)
Nasal passages
(iii)
Windpipe
(iv)
Alveoli
(v)
Ribcage Functions
(a)
fresh air from outside enters
(b)
exchange of gases occurs
(c)
protects lungs
(d)
tiny hair and mucus help to trap dust and dirt from the air we breathe
(e) air reaches our lungs through this part
Solution
The correct matches are:
(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
Q5Let Us Enhance Our Learning
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?
Solution
Sanvi can ask Anil the following questions:
- What happens to the air after it enters your lungs?
- What is the purpose of breathing in oxygen?
- Is there a chemical reaction happening when we breathe?
- What is the equation for respiration?
These questions will help Anil understand that breathing is a physical process of inhaling and exhaling air, while respiration is a chemical process that occurs inside the cells to release energy from food using oxygen.
Q6Let Us Enhance Our Learning
Which of the following statements is correct and why? Anu: We inhale air. Shanu: We inhale oxygen. Tanu: We inhale air rich in oxygen.
Solution
Tanu's statement is correct: We inhale air rich in oxygen.
Air is a mixture of gases, including oxygen, carbon dioxide, nitrogen, and other gases. When we inhale, we take in the entire mixture of gases that make up air. While oxygen is essential for respiration, it is not the only gas we inhale. The air we inhale has a higher concentration of oxygen compared to the air we exhale.
Q7Let Us Enhance Our Learning
We often sneeze when we inhale a lot of dust-laden air. What can be possible explanations for this?
Solution
Sneezing is a reflex action that helps to clear the nasal passages of irritants, such as dust, pollen, or other foreign particles. The possible explanations are:
- Irritation: Dust particles irritate the lining of the nasal passages.
- Defense Mechanism: Sneezing is the body's way of expelling these irritants to prevent them from entering the lungs.
- Nerve Stimulation: The dust particles stimulate nerve endings in the nasal passages, triggering the sneeze reflex.
Q8Let Us Enhance Our Learning
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.
Solution
Here are two possible explanations for why Anusha was breathing faster than Paridhi after running:
- Fitness Level: Anusha might have a lower fitness level than Paridhi. During exercise, the body needs more oxygen. If Anusha is less fit, her body needs to work harder to deliver oxygen to the muscles, resulting in a faster breathing rate.
- Intensity of Workout: Anusha might have been running at a higher intensity compared to Paridhi. A more intense workout requires more energy, which in turn requires more oxygen. To meet this increased demand, Anusha's breathing rate would increase more than Paridhi's.
Q9Let Us Enhance Our Learning
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, halffilled with water and stirred them properly. To test tube B, he added a few drops of saliva. He left the two test tubes for . 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?
Solution
Yadu wants to test the effect of saliva on starch. By adding saliva to test tube B, he is investigating whether saliva can break down the starch present in the rice flour. The iodine test will indicate the presence of starch: a blue-black colour indicates starch is present, while a lighter colour or no colour change suggests that the starch has been broken down.
Q10Let Us Enhance Our Learning
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?
Solution
Rakshita is trying to investigate the difference in carbon dioxide content between inhaled air and exhaled air.
She can confirm her findings by observing the change in the lime water in both test tubes. Lime water turns milky in the presence of carbon dioxide. If the lime water in test tube B (exhaled air) turns milky faster or becomes more cloudy than the lime water in test tube A (inhaled air), it indicates that exhaled air contains more carbon dioxide than inhaled air.