RBSE Solutions Class 7 Science Chapter 9 Life Processes in Animals

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Question 1. Complete the journey of food through the alimentary canal by filling up the boxes with appropriate parts Food → Mouth → → Stomach → → Anus
Answer: The journey of food through the alimentary canal involves several organs. Food first enters the mouth, then moves down the food pipe. After that, it reaches the stomach for initial digestion. From the stomach, it goes to the small intestine, then the large intestine, and finally leaves the body through the anus. Each part plays a vital role in breaking down and absorbing nutrients.
In simple words: Food goes from the mouth to the food pipe, then stomach, small intestine, large intestine, and out through the anus.

🎯 Exam Tip: Remember the correct sequence of organs in the human digestive system: Mouth → Food Pipe (Oesophagus) → Stomach → Small Intestine → Large Intestine → Anus.

Question 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:
(1) Test tube 'A' (Pieces of chapati): A blue-black color would appear. This is because starch is present in the chapati pieces, and iodine solution turns blue-black in the presence of starch.
(2) Test tube 'B' (Chewed chapati): A light or no blue-black color would appear. This happens because the amylase enzyme in saliva starts breaking down the starch in the chewed chapati into simpler sugars, so less starch remains to react with iodine.
(3) Test tube 'C' (Boiled potato): A blue-black color would appear. This is because boiled potatoes contain a good amount of starch, which reacts with the iodine solution to show the blue-black color. Boiling does not remove the starch, making it a clear test for its presence.
In simple words: Test tube A (chapati) and C (potato) will turn blue-black because of starch. Test tube B (chewed chapati) will be light or no blue-black because saliva started breaking down the starch.

🎯 Exam Tip: The iodine test is a common way to detect starch. A blue-black color means starch is present, while no color change or a lighter color suggests starch is absent or has been broken down.

Question 3. What is the role of 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
Diaphragm helps the lungs to contract and expand. When the diaphragm moves down, air enters the lungs (inhalation). When it moves up, air leaves the lungs (exhalation). This muscle's movement creates the pressure changes needed for breathing.
In simple words: The diaphragm is a muscle that moves up and down to help us breathe air in and out of our lungs.

🎯 Exam Tip: Understand the dual role of the diaphragm: it contracts and moves down for inhalation, and relaxes and moves up for exhalation, causing air pressure changes.

Question 4. Match the following.

Answer:

In simple words: Each part of the respiratory system has a specific job. Nostrils let air in, nasal passages clean it, the windpipe carries it to lungs, alveoli swap gases, and the ribcage keeps the lungs safe.

🎯 Exam Tip: When matching, read both lists carefully and think about the main function of each organ before drawing lines or writing pairs.

Question 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 Anil, "If breathing and respiration are the same, then why don't we get energy just by breathing?" This question highlights the main difference. Breathing is just taking air in and out. Respiration, however, is a chemical process inside cells that releases energy from food. Breathing is a physical process, while respiration is a biochemical one.
In simple words: Sanvi can ask why we don't get energy from just breathing if it's the same as respiration. Breathing is moving air, but respiration is about getting energy from food.

🎯 Exam Tip: Clearly distinguish between breathing (physical act of inhaling/exhaling) and respiration (chemical process of energy release from food within cells).

Question 6. Which of the following statements is- correct and why?
(a) Anu: We inhale air
(b) Shanu: We inhale oxygen
(c) Tanu: We inhale air rich in oxygen
Answer: (c) Tanu: We inhale air rich in oxygen
Tanu's statement is correct because we breathe in air, which is a mix of different gases, not just pure oxygen. This inhaled air has more oxygen than the air we breathe out, but it also contains nitrogen, carbon dioxide, and other gases. We don't inhale 100% oxygen; we inhale atmospheric air that has a higher concentration of oxygen compared to exhaled air.
In simple words: We breathe in air that has a lot of oxygen in it, not just oxygen alone or all kinds of air equally.

🎯 Exam Tip: Remember that air is a mixture of gases. Inhaled air is rich in oxygen, while exhaled air is rich in carbon dioxide, but neither is pure.

Question 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 might have been breathing faster than Paridhi for two main reasons:
(1) Anusha's physical capacity or fitness level might be lower than Paridhi's. This means her body needs to work harder to get enough oxygen during exercise, leading to a faster breathing rate.
(2) Anusha may have run faster or exerted more effort than Paridhi. Higher intensity exercise demands more energy, and thus more oxygen, causing the body to increase its respiratory rate to meet that demand.
Both explanations point to the body's need for more oxygen to produce energy during physical activity.
In simple words: Anusha might be breathing faster because she is less fit or she ran harder than Paridhi. Both mean her body needed more oxygen.

🎯 Exam Tip: When explaining physiological responses like breathing rate, connect them to the body's demand for oxygen and energy production.

Question 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 if saliva can change starch, found in food, into sugar. In test tube A, which did not have saliva, a blue-black color appeared when iodine was added, showing that starch was still present. In test tube B, which had saliva, no blue-black color or only a light color appeared because the salivary amylase (an enzyme in saliva) had broken down the starch into sugar. This experiment clearly demonstrates the digestive action of saliva.
In simple words: Yadu wants to find out if saliva can break down starch into sugar. Test tube with saliva did not turn dark with iodine, proving saliva changes starch.

🎯 Exam Tip: Remember that enzymes are biological catalysts, and salivary amylase is an enzyme that specifically starts the digestion of complex carbohydrates (starch) in the mouth.

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Question 1. I have seen cows keep chewing the food even when they are not actively grazing or eating anything. Why?
Answer: Cows chew their food again even when not grazing, a process called rumination. Grass-eating animals like cows first swallow their food (grass) partially chewed into a special stomach chamber. Later, they bring this partially digested food back into their mouth to chew it properly. These animals are called ruminants. Chewing the food thoroughly the second time helps in better digestion and absorption of nutrients.
In simple words: Cows chew food again later because they are ruminants. They swallow grass first, then bring it back to chew properly to digest it better.

🎯 Exam Tip: Key terms like 'rumination' and 'ruminants' are crucial for explaining this process. Remember that this secondary chewing helps break down tough plant material for efficient digestion.