Life Processes in Animals — Class 7 Science
Curiosity · Chapter 9
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7- Mathematics
- Science
- + 3 more
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
2- Mathematics
- Social Science
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
Chapter summary
Key ideas & terms
- Digestion
- The process of breaking complex food components into simpler forms that the body can absorb and use.
- Alimentary canal
- The long tube from the mouth to the anus along which food is digested and absorbed.
- Absorption
- The passing of digested nutrients from the small intestine into the blood through finger-like projections.
- Rumination
- The process in animals like cows of bringing partially digested food back to the mouth for thorough chewing.
- Respiration
- The process by which oxygen is used to break down glucose, releasing carbon dioxide, water, and energy.
- Breathing
- The physical process of inhaling and exhaling air, moving it in and out of the lungs.
- Alveoli
- The tiny balloon-like air sacs in the lungs where oxygen and carbon dioxide are exchanged with the blood.
Extra questions & answers
What is digestion?
Digestion is the process of breaking complex food components such as carbohydrates, proteins, and fats into simpler forms the body can absorb and use.
What role does saliva play in the mouth?
Saliva moistens food and contains a digestive juice that begins breaking down starch into sugar, which is why chewed rice tastes sweet.
Why is the small intestine called the longest part of the alimentary canal?
The small intestine is about 6 metres long — almost twice the height of a classroom — making it the longest part of the alimentary canal.
What is the role of bile in digestion?
Bile, secreted by the liver, is mildly basic; it neutralises the acid coming from the stomach and breaks fats into tiny droplets to ease their digestion.
How are nutrients absorbed in the small intestine?
The inner lining has thousands of finger-like projections that increase surface area, allowing digested nutrients to pass into the blood.
What is rumination?
Rumination is the process in which grass-eating animals like cows partially chew and swallow food, then bring it back to the mouth for thorough chewing.
Write the word equation for respiration.
Glucose + Oxygen gives Carbon dioxide + Water + Energy.
Where in the lungs does the exchange of gases take place?
Gas exchange takes place in the alveoli, tiny balloon-like sacs with thin walls surrounded by fine blood vessels.
How can you show that exhaled air contains more carbon dioxide?
When exhaled air is blown through lime water it turns milky, while inhaled air passed through lime water does not, showing exhaled air has more carbon dioxide.
How is breathing different from respiration?
Breathing is a physical process of moving air in and out of the lungs, while respiration is a chemical process that uses oxygen to break down food and release energy.
Let Us Enhance Our Learning
1. Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts— Food Mouth Stomach Anus
The complete journey is: Food → Mouth → Oesophagus or Food pipe → Stomach → Small intestine → Large intestine → Rectum → Anus. Food is chewed in the mouth and mixed with saliva, pushed through the oesophagus to the stomach where it is churned, then to the small intestine where digestion is completed and absorption occurs, then undigested food passes to the large intestine and rectum and is expelled through the anus as stool.
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.
Test tube A with plain chapati will turn blue-black on adding iodine because chapati contains starch and starch gives a blue-black colour with iodine. Test tube B with chewed chapati will show no colour change or only a very light blue-black because chewing mixes the chapati with saliva. Saliva breaks down starch into sugar, so little or no starch remains to react with iodine. Test tube C with boiled and mashed potato will also turn blue-black because potato is rich in starch and no saliva was added, so the starch remains 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
Correct option is (iii) To help in inhalation and exhalation. The diaphragm is a dome-shaped muscle below the lungs. During inhalation it moves downwards and the ribs move outwards, increasing chest space so air is drawn in. During exhalation it moves upwards and the ribs move inwards, decreasing chest space and pushing air out. It does not filter air, produce sound or directly absorb oxygen.
(i) Nostrils
(a) fresh air from outside enters - The nostrils are the pair of openings through which air enters the respiratory system.
(ii) Nasal passages
(d) tiny hair and mucus help to trap dust and dirt from the air we breathe - The nasal passages contain hair and mucus that filter dust from inhaled air.
(iii) Windpipe
(e) air reaches our lungs through this part - The windpipe carries air from the nasal passages to the lungs and branches into the two lungs.
(iv) Alveoli
(b) exchange of gases occurs - Alveoli are tiny balloon-like sacs in the lungs surrounded by blood vessels where oxygen enters the blood and carbon dioxide leaves the blood.
(v) Ribcage
(c) protects lungs - The ribcage forms a bony cage around the lungs and protects them.
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?
Sanvi can ask: Is breathing a physical movement of air in and out, while respiration is a chemical process inside cells? Does breathing only involve inhalation and exhalation, while respiration breaks down glucose with oxygen to release energy, carbon dioxide and water? Where does each process occur - breathing in the lungs and respiratory system and respiration in every cell? Does only respiration release energy needed for work? These questions show breathing brings oxygen and removes carbon dioxide, while respiration uses that oxygen to produce energy.
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.
Tanu's statement is the most correct. We inhale air, which is a mixture of gases containing about
7. We 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 nose and nasal passages. The tiny hair and mucus in the nose normally trap dust, but when a lot of dust is inhaled they cannot trap all of it. The irritated lining triggers a reflex to forcefully expel air through the nose and mouth - a sneeze. This helps to clear the dust and protect the lungs from harmful particles.
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.
Two possible reasons are: 1. Anusha may have run faster or with more effort, so her muscles needed more energy and therefore more oxygen, causing faster breathing to supply oxygen and remove extra carbon dioxide. 2. Anusha may have lower physical fitness, smaller lung capacity or less practice in running, so she gets tired sooner and breathes faster. Other factors can be differences in age, body weight, health or excitement.
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?
Yadu wants to test whether saliva can digest starch. Tube A without saliva still contains starch so it gives a blue-black colour with iodine as shown in Fig. 9.15 A. Tube B with saliva does not give a blue-black colour as shown in Fig. 9.15 B because salivary juice has broken down the rice starch into sugar during the 35-45 minutes. The absence of colour in B 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?
Rakshita is investigating whether exhaled air contains more carbon dioxide than inhaled air. Lime water turns milky or cloudy when it reacts with carbon dioxide. She can confirm by observing that lime water in tube B into which exhaled air was blown turns milky, while lime water in tube A through which inhaled surrounding air was passed remains clear or turns much less milky. This shows exhaled air has a higher percentage of carbon dioxide, about