A deep dive into the 'Life Processes' chapter is fundamental for any student aiming to excel in the CBSE Class 10 Science examination. This chapter, a cornerstone of the 'World of Living' unit, carries significant weightage and tests a student's understanding of the core physiological functions essential for life. An analysis of previous years' question papers reveals a clear pattern of inquiry that emphasizes conceptual clarity, application of knowledge, and the ability to differentiate between related biological processes.
This curated list of 50 of the most important short answer questions has been compiled after a meticulous review of CBSE question papers from the last seven years, ensuring strict alignment with the latest NCERT and CBSE curriculum. The questions are categorized into the four essential life processes—Nutrition, Respiration, Transportation, and Excretion—to provide a structured and comprehensive resource for exam preparation. The solutions provided are framed to meet the specific requirements of 2 and 3-mark questions, focusing on precision, key terminology, and lucid explanations.
 |
| Life Processes: Top 50 Previous Short Answer Questions for CBSE Class 10 |
Section 1: Nutrition
-
What is the role of saliva in the digestion of food?
Solution: Saliva plays two crucial roles in digestion. Firstly, it contains the enzyme salivary amylase, which begins the chemical digestion of starch (a complex carbohydrate) into simpler sugars in the mouth. Secondly, it moistens the food, which helps in chewing and forming a bolus, making it easier to swallow.
-
State the functions of the following in the human digestive system: (i) Hydrochloric acid (ii) Villi
Solution:
(i) Hydrochloric acid (HCl): Secreted by the gastric glands in the stomach, HCl creates an acidic medium which is essential for the activation of the enzyme pepsin. It also kills most of the harmful bacteria that enter the body with food.
(ii) Villi: These are small, finger-like projections on the inner wall of the small intestine. Their primary function is to vastly increase the surface area for the absorption of digested food into the bloodstream.
-
Why is the small intestine in herbivores longer than in carnivores?
Solution: Herbivores consume a diet rich in plants, which contain cellulose. The digestion of cellulose is a complex and time-consuming process. A longer small intestine provides a greater surface area and more time for the complete breakdown and absorption of cellulose. In contrast, carnivores consume meat, which is easier to digest, and therefore, they have a shorter small intestine.
-
What is the function of digestive enzymes? Name any two digestive enzymes and the glands that secrete them.
Solution: Digestive enzymes are biological catalysts that break down complex food molecules into simpler, soluble molecules that can be absorbed by the body. Two examples are:
-
How do guard cells regulate the opening and closing of stomatal pores?
Solution: The opening and closing of stomatal pores are controlled by the turgor pressure in the guard cells. When water flows into the guard cells, they become turgid and swell, causing them to curve outwards and open the pore. Conversely, when the guard cells lose water, they become flaccid and shrink, causing the pore to close.
-
List the three events that occur during the process of photosynthesis.
Solution: The three key events during photosynthesis are:
- Absorption: Chlorophyll pigments absorb light energy.
- Conversion: Light energy is converted into chemical energy, and water molecules are split into hydrogen and oxygen.
- Reduction: Carbon dioxide is reduced to form carbohydrates like glucose.
-
How does Amoeba take in food? Explain the process.
Solution: Amoeba exhibits a holozoic mode of nutrition through a process called phagocytosis. It extends temporary finger-like projections called pseudopodia to engulf the food. The pseudopodia fuse around the food particle, forming a food vacuole into which digestive enzymes are secreted to break down the food.
-
What is the function of bile juice in digestion?
Solution: Bile juice performs two vital functions: First, it emulsifies fats (breaks down large fat globules into smaller droplets), increasing the surface area for enzymes to act. Second, it creates an alkaline environment in the small intestine, which is necessary for the action of pancreatic enzymes.
-
What will happen if mucus is not secreted by the gastric glands?
Solution: If mucus is not secreted, the stomach wall would be exposed to the highly corrosive hydrochloric acid and the enzyme pepsin. This would lead to the erosion of the stomach lining, causing acidity and potentially leading to gastric ulcers.
-
How can we demonstrate that carbon dioxide is essential for photosynthesis?
Solution: To demonstrate this, two destarched potted plants are taken. One is placed in a bell jar with potassium hydroxide (KOH), which absorbs CO2. The other is placed in a bell jar without KOH. After keeping them in sunlight, a starch test is performed on a leaf from each plant. The leaf from the setup with KOH will test negative for starch, proving that CO2 is necessary for photosynthesis.
-
Differentiate between autotrophic and heterotrophic nutrition.
Solution:
Feature Autotrophic Nutrition Heterotrophic Nutrition Definition Organisms synthesize their own food from simple inorganic substances. Organisms obtain food from other organisms. Energy Source Light energy (photosynthesis) or chemical energy. Consumed organic matter. Examples Green plants, algae. Animals, fungi, most bacteria. -
What are the final products of the digestion of carbohydrates, proteins, and fats?
Solution:
- Carbohydrates: Glucose
- Proteins: Amino acids
- Fats: Fatty acids and glycerol
Section 2: Respiration
-
Differentiate between aerobic and anaerobic respiration.
Solution:
Feature Aerobic Respiration Anaerobic Respiration Oxygen Occurs in the presence of oxygen. Occurs in the absence of oxygen. Energy Release A large amount of energy is released. A small amount of energy is released. End Products Carbon dioxide, water, and energy. Ethanol and CO₂ or Lactic acid. Location Cytoplasm and mitochondria. Only in the cytoplasm. -
How are the alveoli designed to maximize the exchange of gases?
Solution: The alveoli are designed for maximum gas exchange with their large surface area (millions of alveoli), extremely thin walls (one-cell thick), and a rich network of blood capillaries surrounding them. This minimizes diffusion distance and maximizes contact with blood.
-
What causes muscle cramps during vigorous exercise?
Solution: During vigorous exercise, muscle cells may respire anaerobically due to a lack of oxygen. This leads to the conversion of pyruvate into lactic acid. The accumulation of lactic acid in the muscle cells causes painful cramps.
-
Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
Solution: The amount of dissolved oxygen in water is significantly lower than the concentration of oxygen in the air. To obtain the required amount of oxygen, aquatic organisms must pass a large volume of water over their gills, which requires a much faster rate of breathing.
-
State the function of the rings of cartilage present in the trachea.
Solution: The rings of cartilage provide structural support to the trachea (windpipe) and prevent it from collapsing when there is low air pressure, ensuring the air passage remains open.
-
Describe the mechanism of breathing (inhalation and exhalation) in human beings.
Solution: During inhalation, the diaphragm contracts and flattens, and the ribs move upwards and outwards, increasing the chest cavity volume and causing air to rush in. During exhalation, the diaphragm relaxes and moves up, and the ribs move downwards and inwards, decreasing the chest cavity volume and forcing air out.
-
Name the respiratory pigment in human beings. What is its function?
Solution: The respiratory pigment is hemoglobin. Its function is to bind with oxygen in the lungs and transport it to the body's tissues for cellular respiration.
-
Show the breakdown of glucose by various pathways using a flowchart.
Solution: In the cytoplasm, Glucose (6-carbon) breaks down into Pyruvate (3-carbon). From here, the pathway depends on oxygen:
- Presence of O₂ (in mitochondria): → CO₂ + Water + Energy
- Absence of O₂ (in yeast): → Ethanol + CO₂ + Energy
- Lack of O₂ (in muscles): → Lactic acid + Energy
-
Why do the walls of the trachea not collapse when there is less air in it?
Solution: The walls of the trachea are supported by C-shaped rings of cartilage, which are rigid and prevent the trachea from collapsing, ensuring the air passage remains open at all times.
-
Lungs always contain a residual volume of air. What is its significance?
Solution: The residual volume of air ensures that there is sufficient time for oxygen to be absorbed and for carbon dioxide to be released. It allows for continuous gas exchange between the alveoli and the blood, even during exhalation, and prevents the lungs from collapsing.
-
Explain how the exchange of gases occurs in plants.
Solution: Plants exchange gases primarily through stomata on the leaves. Carbon dioxide enters for photosynthesis, and oxygen is released as a byproduct. This gaseous exchange occurs through diffusion, driven by the concentration gradients of the gases.
-
What advantage does a terrestrial organism have over an aquatic organism with regard to obtaining oxygen?
Solution: A terrestrial organism has a significant advantage because the concentration of oxygen in the air (about 21%) is much higher than the concentration of dissolved oxygen in water. This allows them to obtain sufficient oxygen with less effort and a slower breathing rate.
Section 3: Transportation
-
What are the components of the transport system in human beings and their functions?
Solution: The main components are the heart, blood, and blood vessels.
- Heart: Acts as a pump to circulate blood.
- Blood: Transports oxygen, nutrients, hormones, and waste products.
- Blood Vessels (Arteries, Veins, Capillaries): Carry blood throughout the body.
-
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Solution: Mammals and birds are warm-blooded and require a high amount of energy to maintain a constant body temperature. Separating oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the cells, which supports a high rate of metabolism and energy production.
-
What is meant by 'double circulation'? State its importance.
Solution: Double circulation is a system where blood passes through the heart twice during one complete cycle (once to the lungs and once to the body). Its importance lies in preventing the mixing of oxygenated and deoxygenated blood, ensuring a more efficient supply of oxygen to the body's tissues.
-
Differentiate between arteries and veins.
Solution:
Feature Arteries Veins Function Carry blood away from the heart. Carry blood towards the heart. Wall Thickness Thick, elastic, and muscular walls. Thin, less muscular walls. Valves Absent (except at the base of the aorta). Present to prevent the backflow of blood. -
What is the function of xylem and phloem in plants?
Solution:
- Xylem: Transports water and dissolved minerals from the roots up to all other parts of the plant.
- Phloem: Transports food (soluble products of photosynthesis) from the leaves to other parts of the plant.
-
What would be the consequences of a deficiency of hemoglobin in our bodies?
Solution: A deficiency of hemoglobin (anemia) would reduce the oxygen-carrying capacity of the blood. This would lead to fatigue, weakness, and shortness of breath, as the body's cells would not receive enough oxygen to meet their energy demands.
-
What is lymph? Write its functions.
Solution: Lymph is a colorless fluid that escapes from blood capillaries into intercellular spaces. Its functions include collecting waste products, carrying absorbed fat from the intestine, and helping in fighting infections as part of the immune system.
-
How is food transported in plants?
Solution: The transport of food in plants is called translocation, and it occurs through the phloem tissue. Food (sucrose) is loaded from the leaves into the phloem using energy from ATP. This creates a pressure gradient that drives the movement of the food to other parts of the plant where it is needed.
-
Explain how water and minerals are transported in plants.
Solution: Water and minerals are transported through the xylem tissue. The main driving force is the transpirational pull, a suction force created by the evaporation of water from the leaves (transpiration). This pulls the water column upwards from the roots through the stem.
-
Give reasons: (a) The muscular walls of ventricles are thicker than the atria. (b) Veins have valves.
Solution:
(a) Ventricles pump blood out of the heart to the entire body or lungs, requiring high pressure, hence they have thicker walls. Atria only pump blood into the adjacent ventricles.
(b) Veins have valves to prevent the backflow of blood, as the blood in them flows under low pressure and often against gravity.
-
What is the role of platelets in the blood?
Solution: Platelets play a vital role in blood clotting. When a blood vessel is injured, they gather at the site and initiate a chain reaction that leads to the formation of a clot, which seals the wound and prevents excessive blood loss.
-
Trace the movement of oxygenated blood from the lungs to the body cells.
Solution: Lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta → Arteries → Capillaries in body tissues → Delivered to body cells.
Related Posts
Section 4: Excretion
-
Describe the structure and function of a nephron.
Solution: The nephron is the functional unit of the kidney. It consists of a glomerulus and a renal tubule (including Bowman's capsule). Its function is to filter blood and produce urine through ultrafiltration, selective reabsorption, and tubular secretion.
-
How is the amount of urine produced regulated?
Solution: The amount of urine is regulated by the reabsorption of water in the nephrons, which depends on the body's hydration level and is controlled by the hormone ADH (Antidiuretic Hormone). More ADH leads to more water reabsorption and less urine production.
-
What is hemodialysis? When is it required?
Solution: Hemodialysis is the process of purifying blood using an artificial kidney. It is required in cases of kidney failure, where the kidneys are unable to filter waste products like urea from the blood, leading to their toxic accumulation.
-
How do plants get rid of their waste products?
Solution: Plants get rid of waste through various methods: releasing gaseous wastes (O₂, CO₂) via stomata, removing excess water via transpiration, storing wastes in leaves that are then shed, and storing wastes as gums and resins in old xylem.
-
Draw a well-labeled diagram of the human excretory system.
Solution: A diagram should be drawn showing the pair of kidneys, a pair of ureters, the urinary bladder, and the urethra. The renal artery and renal vein should also be labeled.
-
What are the methods used by plants to get rid of excretory products?
Solution: Plants use strategies like transpiration for water, shedding leaves to remove stored wastes, and storing waste products like resins and gums in old xylem tissue. They also release gaseous wastes through stomata.
-
Compare the functioning of alveoli in the lungs and nephrons in the kidneys.
Solution: Alveoli are sites of gaseous exchange (O₂ and CO₂) via diffusion, while nephrons are sites of blood filtration and urine formation via ultrafiltration and reabsorption. Both have a large surface area and a rich blood supply to maximize their efficiency.
-
Explain the principle of hemodialysis.
Solution: The principle is based on diffusion across a semi-permeable membrane. The patient's blood flows on one side of the membrane, and a dialyzing fluid (free of wastes) flows on the other. Waste products from the blood diffuse into the fluid due to the concentration gradient.
-
Name the main nitrogenous waste in human blood and the organ that removes it.
Solution: The main nitrogenous waste is urea, and the organ that removes it is the kidney.
-
What is the composition of the glomerular filtrate?
Solution: Glomerular filtrate is essentially blood plasma minus the proteins and blood cells. It contains water, glucose, amino acids, mineral salts, urea, and uric acid.
-
Why is urine more concentrated in summer?
Solution: In summer, the body loses a significant amount of water through sweating. To conserve water, the kidneys reabsorb more water from the filtrate, leading to the production of a smaller volume of more concentrated urine.
-
How is the exit of urine from the bladder regulated?
Solution: The exit of urine is regulated by a muscular sphincter at the junction of the bladder and the urethra. This sphincter is under nervous control and relaxes under conscious command to allow urination.
-
What is osmoregulation? How do the kidneys help in it?
Solution: Osmoregulation is the process of maintaining a constant water and salt balance in the body. The kidneys help by regulating the amount of water reabsorbed from the filtrate, excreting excess water when the body is hydrated and conserving water when it is dehydrated.
-
List two vital functions of the human kidney apart from excretion.
Solution: Two vital functions apart from excretion are:
- Osmoregulation: Regulating the water and salt balance of the body.
- Regulation of Blood pH: Maintaining the pH of the blood by excreting excess acids or bases.
