Case Based Questions: Life Processes | Science Class 10 PDF Download

Mohan and Rajat were discussing how different organisms obtain nutrition. Mohan argued that plants make their own food, while Rajat explained that not all organisms can do this. Rajat gave examples of fungi that decompose food externally and some animals that directly depend on plants for survival. They also discussed the process of digestion in humans and how food is broken down into simpler forms.

(a) What is the main difference between autotrophic and heterotrophic nutrition? (1 Mark)
(b) How does Amoeba obtain its food? Describe the process. (2 Marks)
(c) Compare the nutrition in Amoeba with that in human beings. (1 Mark) 
OR
(c) How is digestion in humans different from digestion in fungi? (1 Mark)

Ans:
(a) Autotrophic nutrition involves organisms making their own food using sunlight, water, and carbon dioxide, whereas heterotrophic nutrition involves organisms obtaining food from other organisms.
(b) Amoeba engulfs food using finger-like projections called pseudopodia. The food is enclosed in a food vacuole, where digestive enzymes break it down into simpler substances for absorption. 
(c) Amoeba digests food inside the food vacuole, whereas in humans, digestion occurs through a specialized alimentary canal. 
OR
(c) Fungi digest food externally by releasing enzymes that break down complex substances outside their body, while humans digest food internally in the alimentary canal. 

Q2: Read the source below and answer the questions that follow:

During a science experiment, Riya placed two potted plants in different conditions. One was kept in complete darkness, while the other was exposed to sunlight. After three days, she tested both plants for starch presence using iodine solution and observed a color change only in the plant exposed to sunlight. She wanted to understand why this happened.

(a) What is the role of chlorophyll in photosynthesis? (1 Mark)
(b) Describe the process of photosynthesis and its three main steps. (2 Marks)
(c) Why did the plant kept in darkness not show a positive starch test? (1 Mark) 
OR
(c) Explain why stomata are essential for photosynthesis. (1 Mark)

Ans:
(a) Chlorophyll captures sunlight energy, which is essential for converting carbon dioxide and water into glucose. 
(b) Photosynthesis occurs in three steps:

• Absorption of sunlight by chlorophyll.
• Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
• Reduction of carbon dioxide to carbohydrates.

(c) The plant in darkness could not produce starch because photosynthesis did not occur due to the absence of sunlight.
OR
(c) Stomata are tiny pores in leaves that allow the exchange of gases (CO₂ and O₂), which is necessary for photosynthesis.

Anjali and Varun were discussing the importance of respiration. Anjali said respiration provides energy, while Varun argued that not all respiration requires oxygen. To demonstrate this, their teacher conducted an experiment using yeast and sugar solution. The lime water turned milky, indicating CO₂ production, proving anaerobic respiration.

(a) What is the basic difference between aerobic and anaerobic respiration? (1 Mark)
(b) Explain the process of respiration in human muscles during heavy exercise. (2 Marks)
(c) What are the products of anaerobic respiration in yeast? (1 Mark) 
OR
(c) How does the energy released in aerobic respiration compare to anaerobic respiration? (1 Mark)

Ans:
(a) Aerobic respiration occurs in the presence of oxygen, producing CO₂, water, and large amounts of energy, whereas anaerobic respiration occurs without oxygen and produces less energy. 
(b) During heavy exercise, muscle cells lack sufficient oxygen, leading to anaerobic respiration, where glucose is converted into lactic acid, causing cramps.
(c) Anaerobic respiration in yeast produces ethanol (alcohol), carbon dioxide, and energy.
OR
(c) Aerobic respiration releases much more energy (38 ATP molecules) compared to anaerobic respiration (only 2 ATP molecules).

Q4: Read the source below and answer the questions that follow:

A scientist conducted an experiment to compare the transport systems in plants and animals. He observed how water moves through a plant's xylem and how blood circulates in the human body. He noted that in humans, blood is pumped by the heart, while in plants, water is pulled up due to transpiration.

(a) What is the main function of the xylem in plants? (1 Mark)
(b) Explain the double circulation of blood in human beings. (2 Marks)
(c) How does transpiration help in the movement of water in plants? (1 Mark) 
OR
(c) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds? (1 Mark)

Ans:
(a) Xylem transports water and minerals from roots to other parts of the plant. 
(b) Double circulation ensures complete separation of oxygen-rich and oxygen-poor blood. 
The heart pumps blood twice:

• Oxygenated blood from the heart is sent to body parts.
• Deoxygenated blood from the body returns to the heart, which then pumps it to the lungs for oxygenation.

(c) Transpiration creates a suction force that pulls water upward from roots through the xylem. 
OR
(c) Separation of oxygenated and deoxygenated blood ensures an efficient supply of oxygen, which is essential for high-energy needs in warm-blooded animals.

Q5: Read the source below and answer the questions that follow:

During a science lecture, the teacher explained how excretion removes waste materials from the body. She described the role of nephrons in the kidney and how urine is formed. She also mentioned how plants remove waste through transpiration, vacuoles, and leaf shedding.

(a) What is the primary function of nephrons in human kidneys? (1 Mark)
(b) How is urine produced in human beings? (2 Marks)
(c) How do plants get rid of their waste materials? (1 Mark) 
OR
(c) What is the role of transpiration in plant excretion? (1 Mark)

Ans:
(a) Nephrons filter waste from the blood and help in urine formation. 
(b) Blood is filtered in the nephrons, removing nitrogenous waste (urea). The filtered substances are reabsorbed based on body needs, and the remaining waste is expelled as urine.
(c) Plants store waste in vacuoles, shed leaves, and secrete resins and gums for excretion.
OR
(c) Transpiration helps remove excess water from plants, aiding in waste removal and temperature regulation. 

Q6: Read the source below and answer the questions that follow:

During a biology class, Ananya's teacher explained how blood circulates in the human body. She mentioned that the heart pumps oxygen-rich blood to different parts of the body and collects carbon dioxide-rich blood to send it to the lungs for purification. Ananya was curious about why the heart has four chambers and how it ensures continuous circulation.

(a) What is the function of valves in the human heart? (1 Mark)
(b) Explain the role of the left ventricle and right ventricle in blood circulation. (2 Marks)
(c) How does the heart prevent the mixing of oxygenated and deoxygenated blood? (1 Mark) 
OR
(c) What would happen if the heart’s ventricles were not able to contract properly? (1 Mark)

Ans:
(a) Valves prevent the backflow of blood, ensuring unidirectional circulation. 
(b) The left ventricle pumps oxygenated blood to the body, while the right ventricle pumps deoxygenated blood to the lungs for oxygenation. 
(c) The septum divides the right and left sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.
OR
(c) If ventricles fail to contract properly, blood circulation would slow down, leading to reduced oxygen supply to the body.

Q7: Read the source below and answer the questions that follow:

Sanya and her friends were running during their sports practice. After some time, they noticed that they were breathing heavily. Their coach explained that during physical activity, the body requires more oxygen to generate energy, leading to an increased breathing rate.

(a) What is the function of alveoli in the human respiratory system? (1 Mark)
(b) Why do we breathe faster during exercise? (2 Marks)
(c) How does the exchange of gases occur in alveoli? (1 Mark) 
OR
(c) Why do aquatic organisms breathe faster than terrestrial organisms? (1 Mark)

Ans: 
(a) Alveoli provide a large surface area for the exchange of oxygen and carbon dioxide between the lungs and blood. 
(b) During exercise, muscle cells need more oxygen to produce energy through aerobic respiration. To meet this demand, the breathing rate increases.
(c) Oxygen diffuses from alveoli into blood capillaries, while carbon dioxide diffuses from blood into alveoli to be exhaled.
OR
(c) Aquatic organisms breathe faster because the oxygen concentration in water is much lower than in the air, requiring more frequent respiration.

Q8: Read the source below and answer the questions that follow:

Rahul observed that water moves from the roots of a plant to its leaves. His teacher explained that plants have a specialized transport system that helps in the movement of water and food. She also demonstrated that when a plant loses water through its leaves, more water is pulled up from the roots.

(a) Which tissue in plants is responsible for the transport of water? (1 Mark)
(b) How does transpiration help in the upward movement of water in plants? (2 Marks)
(c) What is the role of root pressure in water transport? (1 Mark) 
OR
(c) How does phloem transport food in plants? (1 Mark)

Ans:
(a) Xylem is responsible for transporting water and minerals from roots to other parts of the plant. 
(b) Transpiration creates a suction force that pulls water upward through the xylem from roots to leaves. 
(c) Root cells actively absorb minerals from the soil, creating root pressure, which pushes water upward in xylem.
OR
(c) Phloem transports food from leaves to other plant parts through translocation, which occurs due to pressure created by loading sucrose into sieve tubes using ATP. 

Q9: Read the source below and answer the questions that follow:

Priya was watching a medical show where a patient had kidney failure and required dialysis. She was curious to learn how kidneys function and why dialysis is needed when they fail. Her biology teacher explained that kidneys remove nitrogenous wastes from the blood and maintain water balance.

(a) What is the role of nephrons in the excretory system? (1 Mark)
(b) How does the process of dialysis help in kidney failure? (2 Marks)
(c) Why is urine formation important in human beings? (1 Mark) 
OR
(c) What happens if excess water is not removed from the body? (1 Mark)

Ans:
(a) Nephrons filter waste products (urea, uric acid) from the blood and help in urine formation.
(b) In dialysis, the patient’s blood is passed through a machine where waste materials are removed by diffusion, similar to kidney function.
(c) Urine formation removes toxic nitrogenous wastes, preventing their accumulation in the body.
OR
(c) Excess water must be removed to maintain fluid balance; otherwise, it may cause swelling, high blood pressure, and kidney damage.

Q10: Read the source below and answer the questions that follow:

During an experiment, Rohit observed that yeast produced bubbles when added to sugar solution. His teacher explained that this was due to anaerobic respiration, where glucose breaks down without oxygen, releasing energy and carbon dioxide.

(a) What are the two types of respiration? (1 Mark)
(b) How does anaerobic respiration occur in yeast? (2 Marks)
(c) Why do muscle cells sometimes switch to anaerobic respiration? (1 Mark) 
OR
(c) Which type of respiration produces more energy: aerobic or anaerobic? (1 Mark)

Ans:
(a) Aerobic respiration occurs in the presence of oxygen, while anaerobic respiration occurs without oxygen. 
(b) In yeast, glucose breaks down into ethanol, carbon dioxide, and energy in the absence of oxygen (fermentation).
(c) During intense exercise, oxygen supply is insufficient, so muscle cells switch to anaerobic respiration, leading to lactic acid buildup and muscle cramps. 
OR
(c) Aerobic respiration produces more energy (38 ATP molecules) compared to anaerobic respiration, which produces only 2 ATP molecules.