NCERT CLASS 10 SCIENCE CHAPTER 5 LIFE PROCESSES
NCERT CLASS 10 SCIENCE
CHAPTER 5 – LIFE PROCESSES
IN-TEXT QUESTIONS AND ANSWERS
1. What are life processes?
Life processes are the basic activities performed by living organisms to maintain their lives. These include nutrition, respiration, transportation and excretion.
2. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms?
In multicellular organisms, all cells are not directly in contact with the environment. Diffusion is too slow to supply oxygen to every cell. Therefore, specialised transport systems are required.
3. What criteria can be used to decide whether something is alive?
Movement, growth, respiration, nutrition, excretion and response to stimuli are some characteristics used to identify living organisms. Metabolic activities are especially important indicators of life.
4. What are the differences between autotrophic and heterotrophic nutrition?
Autotrophic nutrition is the process in which organisms prepare their own food from simple substances, usually using sunlight. Heterotrophic nutrition is the process in which organisms obtain food from other organisms.
5. Where do plants obtain the materials required for photosynthesis?
Plants obtain carbon dioxide from the air through stomata, water from the soil through roots and sunlight from the Sun. Chlorophyll present in leaves absorbs light energy.
6. What is the role of acid in the stomach?
Hydrochloric acid creates an acidic medium in the stomach, which helps the enzyme pepsin digest proteins. It also helps destroy many harmful microorganisms present in food.
7. What is the function of digestive enzymes?
Digestive enzymes break down complex food substances into simpler, soluble substances that can be absorbed by the body.
8. How is the small intestine designed to absorb digested food?
The inner surface of the small intestine contains numerous finger-like projections called villi. Villi increase the surface area for absorption. They contain blood vessels that carry absorbed nutrients to different parts of the body.
9. What advantage do terrestrial organisms have over aquatic organisms in obtaining oxygen?
Air contains a higher concentration of oxygen than water. Therefore, terrestrial organisms can obtain oxygen more easily than aquatic organisms.
10. What are the different ways in which glucose is broken down to release energy?
Glucose is first broken down into pyruvate in the cytoplasm. Pyruvate can then follow different pathways:
In the presence of oxygen, it breaks down into carbon dioxide and water in mitochondria.
In the absence of oxygen in yeast, it forms ethanol and carbon dioxide.
In muscle cells when oxygen is insufficient, it forms lactic acid.
11. Why do we get muscle cramps after vigorous physical activity?
During vigorous exercise, muscle cells may not receive enough oxygen. They produce energy through anaerobic respiration, which results in the formation of lactic acid. Its accumulation can cause muscle cramps.
12. What is the role of the nasal cavity during breathing?
The nasal cavity filters dust particles, warms the air and adds moisture to the air before it reaches the lungs.
13. What prevents food from entering the windpipe?
The epiglottis is a flap-like structure that covers the opening of the windpipe during swallowing. It prevents food from entering the respiratory tract.
14. How are the lungs designed to maximise the exchange of gases?
The lungs contain millions of tiny air sacs called alveoli. Their walls are thin and moist, and they have a rich network of blood capillaries. This provides a large surface area for the exchange of oxygen and carbon dioxide.
15. What is the role of haemoglobin in respiration?
Haemoglobin is a respiratory pigment present in red blood cells. It combines with oxygen in the lungs and transports it to different body tissues.
16. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Mammals and birds maintain a constant body temperature and require a continuous supply of energy. Separation of oxygenated and deoxygenated blood ensures an efficient supply of oxygen to body tissues.
17. What are the differences between arteries and veins?
Arteries carry blood away from the heart and generally have thick, elastic walls. Veins carry blood towards the heart and have thinner walls. Veins also contain valves to prevent the backward flow of blood.
18. What is the function of valves in the heart?
Valves prevent the backward flow of blood and ensure that blood moves through the heart in one direction.
19. What is the advantage of having separate chambers in the heart?
Separate chambers prevent the mixing of oxygenated and deoxygenated blood. This makes the supply of oxygen more efficient.
20. What are the functions of xylem and phloem?
Xylem transports water and minerals from the roots to other parts of the plant. Phloem transports prepared food from leaves to different parts of the plant.
21. How is the amount of water absorbed by roots regulated?
The amount of water absorbed depends on the water available in the soil and the plant's requirements. Transpiration creates a pull that helps water move upwards through the xylem.
EXERCISE QUESTIONS AND ANSWERS
1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms?
Diffusion is a slow process and can transport substances only over short distances. In multicellular organisms, many cells are located far from the external environment. Therefore, diffusion alone cannot supply sufficient oxygen to all cells.
2. What are the differences between autotrophic and heterotrophic nutrition?
Autotrophic nutrition:
Organisms prepare their own food.
It generally requires sunlight, chlorophyll, carbon dioxide and water.
Examples: Green plants and some bacteria.
Heterotrophic nutrition:
Organisms depend on other organisms for food.
They cannot prepare their own food from simple inorganic substances.
Examples: Humans, animals and fungi.
3. How are carbohydrates, proteins and fats digested in humans?
Carbohydrates: Digestion begins in the mouth with salivary amylase. Further digestion takes place in the small intestine, where carbohydrates are converted into simple sugars.
Proteins: Protein digestion begins in the stomach with pepsin. It continues in the small intestine with the help of pancreatic and intestinal enzymes.
Fats: Bile breaks large fat globules into smaller droplets. Lipase enzymes then break fats into fatty acids and glycerol.
4. How is the small intestine designed to absorb digested food?
The small intestine has numerous finger-like projections called villi. These increase the surface area for absorption. Each villus contains blood capillaries and lymph vessels that help transport absorbed nutrients.
5. What is the role of saliva in digestion?
Saliva moistens and softens food, making it easier to swallow. It contains salivary amylase, which begins the digestion of starch into simpler sugars.
6. What are the necessary conditions for photosynthesis?
The main conditions required for photosynthesis are:
Sunlight
Chlorophyll
Carbon dioxide
Water
7. Explain the process of nutrition in Amoeba.
Amoeba takes in food with the help of temporary finger-like projections called pseudopodia. These surround and engulf the food, forming a food vacuole. Digestive enzymes break down the food. The digested nutrients are absorbed into the cytoplasm, and undigested waste is expelled through the cell surface.
8. Explain the process of respiration in humans.
Air enters through the nostrils and passes through the nasal cavity, trachea and bronchi before reaching the lungs. In the lungs, oxygen passes from the alveoli into the blood. Blood transports oxygen to body cells, where it is used to release energy from food. Carbon dioxide is carried back to the lungs and removed during exhalation.
9. What are the functions of the different parts of the human respiratory system?
Nostrils: Allow air to enter the respiratory system.
Nasal cavity: Filters, warms and moistens air.
Trachea: Carries air towards the lungs.
Bronchi: Carry air into the lungs.
Bronchioles: Distribute air within the lungs.
Alveoli: Provide the surface for gas exchange.
Diaphragm: Helps in inhalation and exhalation.
10. Explain double circulation in humans.
Double circulation means that blood passes through the heart twice during one complete cycle.
First circulation – Pulmonary circulation: Deoxygenated blood moves from the right side of the heart to the lungs. In the lungs, it receives oxygen and releases carbon dioxide. Oxygenated blood returns to the left side of the heart.
Second circulation – Systemic circulation: Oxygenated blood is pumped from the left side of the heart to the body. Deoxygenated blood returns to the right side of the heart.
Double circulation prevents the mixing of oxygenated and deoxygenated blood and ensures an efficient oxygen supply.
11. Why is the separation of oxygenated and deoxygenated blood useful in mammals and birds?
Mammals and birds need a large amount of energy to maintain a constant body temperature. Complete separation of oxygenated and deoxygenated blood ensures an efficient oxygen supply to the body.
12. Explain the transportation of water and minerals in plants.
Roots absorb water and minerals from the soil. These substances enter the xylem vessels and are transported upwards. Root pressure and transpiration pull help in the movement of water from roots to leaves and other plant parts.
13. Explain the transportation of food in plants.
Food prepared during photosynthesis is transported through the phloem. This process is called translocation. It requires energy in the form of ATP and can occur in both upward and downward directions according to the needs of the plant.
FEW IMPORTANT ADDITIONAL QUESTIONS AND ANSWERS
1. What is photosynthesis? Write its chemical equation.
Photosynthesis is the process by which green plants prepare food using carbon dioxide and water in the presence of sunlight and chlorophyll.
Chemical equation:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
2. What are stomata? Write their functions.
Stomata are tiny pores generally found on the surface of leaves. They help in the exchange of gases and regulate the loss of water vapour through transpiration.
3. What is transpiration?
Transpiration is the loss of water in the form of water vapour from the aerial parts of plants, mainly through stomata.
Importance of transpiration:
Helps in the upward movement of water.
Helps transport minerals.
Cools the plant.
Maintains water movement through the plant.
4. What is the function of bile juice?
Bile is produced by the liver and stored in the gall bladder. It neutralises acidic food coming from the stomach and helps in the emulsification of fats.
5. What is the role of the pancreas in digestion?
The pancreas produces pancreatic juice containing enzymes that help digest carbohydrates, proteins and fats. It also releases bicarbonate, which helps neutralise acidic food entering the small intestine.
6. What is the difference between aerobic and anaerobic respiration?
Aerobic respiration:
Takes place in the presence of oxygen.
Complete breakdown of glucose occurs.
Produces carbon dioxide, water and a large amount of energy.
Anaerobic respiration:
Takes place without oxygen.
Glucose is incompletely broken down.
Produces less energy.
May produce ethanol and carbon dioxide or lactic acid, depending on the organism or cells.
7. What is the function of the diaphragm?
The diaphragm is a muscular sheet below the lungs. During inhalation, it contracts and moves downwards, increasing the chest cavity's volume. During exhalation, it relaxes and moves upwards, decreasing the volume of the chest cavity.
8. What are alveoli?
Alveoli are tiny balloon-like air sacs present in the lungs. They provide a large surface area for the exchange of oxygen and carbon dioxide between air and blood.
9. What is the difference between blood and lymph?
Blood:
It is a red-coloured fluid connective tissue.
It contains plasma, red blood cells, white blood cells and platelets.
It transports gases, nutrients, hormones and waste materials.
Lymph:
It is a pale-yellow fluid.
It contains mainly white blood cells.
It helps in transporting absorbed fats and returning excess tissue fluid to the blood.
10. What are the main components of blood and their functions?
Plasma: Transports nutrients, hormones, carbon dioxide and waste products.
Red blood cells: Carry oxygen with the help of haemoglobin.
White blood cells: Protect the body against infections.
Platelets: Help in blood clotting.
11. What is the function of the human heart?
The human heart is a muscular organ that pumps blood throughout the body. It sends deoxygenated blood to the lungs and oxygenated blood to all body parts.
12. What is the difference between arteries and veins?
Arteries:
Carry blood away from the heart.
Usually carry oxygenated blood.
Have thick and elastic walls.
Blood flows under relatively high pressure.
Veins:
Carry blood towards the heart.
Usually carry deoxygenated blood.
Have comparatively thin walls.
Contain valves to prevent backward flow.
13. What is the function of the nephron?
A nephron is the structural and functional unit of the kidney. It filters blood, reabsorbs useful substances and helps remove wastes and excess water to form urine.
14. Explain the process of urine formation.
Urine formation mainly involves three processes:
Filtration: Blood is filtered in the glomerulus.
Selective reabsorption: Useful substances such as glucose, amino acids, salts and water are reabsorbed into the blood.
Secretion: Certain additional waste substances and ions are transferred into the filtrate.
The remaining fluid forms urine, which passes through the ureters to the urinary bladder.
15. What are the main parts of the human excretory system?
The main parts are:
Two kidneys
Two ureters
Urinary bladder
Urethra
16. What is artificial kidney or dialysis?
Dialysis is a medical process used when kidneys cannot adequately remove wastes from the blood. A dialysis machine filters the blood and removes excess salts, water and waste substances.
17. What is the difference between xylem and phloem?
Xylem:
Transports water and minerals.
Movement is mainly upward from roots.
Most conducting elements are dead.
Phloem:
Transports prepared food.
Movement can occur in both directions.
Its conducting elements are living.
18. Why do plants need a transport system?
Plants need a transport system to carry water and minerals from roots to leaves and to distribute food prepared in leaves to other parts of the plant.
19. Why is the human digestive system important?
The digestive system breaks down complex food into simpler substances. These nutrients are absorbed into the blood and used by the body for energy, growth and repair.
20. What is the importance of life processes?
Life processes are essential for the survival and maintenance of living organisms. Nutrition provides food, respiration releases energy, transportation distributes materials and excretion removes harmful waste products.
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