Life Processes | Class 10, CBSE Biology | Chapter 6, NCERT Science Textbook In-text Questions - Answers


Class X, Cbse Ncert Science(Biology)
In-Text Questions (Page 95)
Q.1: Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Answer: Unlike the unicellular organisms, the multi-cellular organisms have complex body structures with specialized cells and tissues to perform various necessary functions of the body. Since these cells are not in direct contact with surrounding environment so, simple diffusion cannot meet the oxygen requirement of all these cells. 
Q.2: What criteria do we use to decide whether something is alive?
Answer: Living organisms must keep repairing and maintaining their body structures. All these structures are made up of molecules. They must be capable of moving molecules around, all the time. So, molecular movement is one necessary criterion for something to be alive. However, molecular movements are generally not visible to the naked eye. Other such criteria including visible movements are like – walking, breathing etc.
Q.3: What are outside raw materials used by an organism?
Answer: Various outside raw materials used by an organism are as follows:
a. Food as source of supplying energy and materials.
b. Oxygen for breakdown of food to obtain energy.
c. Water for proper digestion of food and other functions inside the body.
The raw materials required by an organism will vary depending on the complexity of the organism and its environment.  
Q.4: What processes would you consider essential for maintaining life?
Answer: There are various life processes which are essential for maintaining life. Some of them are as follows:
a. Nutrition
b. Respiration
c. Excretion
d. Transportation
(Page 101)  
Q.1: What are the differences between autotrophic nutrition and heterotrophic nutrition?
Autotrophic Nutrition
Heterotrophic Nutrition
1. In this type of nutrition food is synthesized from simple inorganic raw materials.
2. For autotrophic nutrition, presence of chlorophyll (green pigment) and sunlight are necessary. So, autotrophic nutrition generally takes place during day time.
3. For example, all green plants and some bacteria have this type of nutrition.
1. In this type of nutrition food is obtained from autotrophs.
2. No pigment and sunlight is required for heterotrophic nutrition. Food can be prepared at any time.
3. For example, all animals including human being and fungi have this type of nutrition.
Q.2: Where do the plants get each of the raw materials required for photosynthesis?
Answer: Plants need the following things for photosynthesis:
Carbon Dioxide - Plants get CO2 from atmosphere through stomata.
Water - Plants absorb water from soil through roots and transport to leaves.
Sunlight - Sunlight, which is absorbed by the chlorophyll and other green parts of the plant.  
Q.3: What is the role of acid in our stomach?
Answer: Roles of acid in our stomach are -
1. It makes an acidic medium in our stomach which is necessary for activation of pepsin enzyme.
2. It kills germs present in the food.
Q.4: What is the function of digestive enzymes?
Answer: The food materials are very complex in nature. Digestive enzymes such as, amylase, lipase, pepsin, Trypsin etc.  Help to break these complex molecules into smaller molecules so that they can be absorbed by the walls of small intestine.     
Q.5: How is the small intestine designed to absorb digested food?   
Answer: Small intestine is designed to more and more area for absorption of digested food and transfer into the blood for circulation throughout the body. The inner lining of small intestine has a large number of finger-like projections called villi. These villi provide a large surface area for absorption of food. These villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body, where it is used for obtaining energy, building up new tissues and repairing of old tissues.      
(Page 105)
Q.1: What advantage over an aquatic organism does a terrestrial organism have with regard to obtain oxygen for respiration?
Answer: The organisms that live in water use oxygen dissolved in surrounding water. Since, air dissolved in water has fairly low concentration of oxygen, the aquatic organisms has much faster rate of breathing.
Terrestrial organisms take oxygen from the oxygen - rich atmosphere through respiratory organs. So, they have much less breathing rate than aquatic organism.    
Q.2: What are the different ways in which glucose is oxidized to provide energy in various organisms?
Answer: At first glucose (6 carbon molecules) is broken in the cytoplasm of cells of all organisms. This process yields a 3 carbon molecule compound called pyruvate.
Further break down of pyruvate takes place in different manners in different organisms. 
1. Anaerobic Respiration
This process takes place in absence of oxygen, e.g. in yeast during fermentation. In this case pyruvate is converted into ethanol and carbon dioxide.
2. Aerobic Respiration
In aerobic respiration, breakdown of pyruvate takes place in presence of oxygen to give rise 3 molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.
3. Lack of Oxygen
Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compounds). Formation of lactic acid in muscles causes cramp.   
Q.3: How are oxygen and carbon dioxide transported in human beings?
Answer: (a) Transport of Oxygen
The respiratory pigments (haemoglobin) present in red blood cells takes up the oxygen from the air to the lungs. They carry the oxygen to tissues which are deficient in oxygen.
(b) Transport of carbon dioxide
Carbon Dioxide is more soluble in water. Hence, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs where it diffuses from blood to air in the lungs and then expelled out through nostrils.    
Q.4: How are lungs designed in human beings to maximize the area for exchange of gases?  
Answer: In the lungs, the air passage (wind pipe) divides into smaller tubes, called ‘bronchi’ in turn form ‘bronchioles’. The bronchioles which terminate in balloon - like structures, are called ‘alveoli’. Each lung contains 300 - 350 million alveoli. The alveoli present in the lungs provide maximum surface for exchange of gases. The alveoli have very thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.
(Page 110)
Q.1: What are the components of the transport system in human beings? What are the functions of these components?  
Answer: Transport system in human beings consists of heart, blood and blood vessels.
Heart - Heart is a pumping organ to push and pull blood around the body. Heart receives the deoxygenated blood from various parts of the body. It sends this impure blood to lungs for oxygenation. Again after receiving pure blood from lungs it sends this oxygenated blood throughout the body.
Blood - It is a fluid connective tissue. It consists of: (a) plasma, (b) RBC, (c) WBC, and (d) blood platelets. Plasma transports food, CO2 and nitrogenous wastes in dissolved form. RBC transports respiratory gases and hormones. WBC protects the body from infections and platelets prevent the loss of blood at the time of injury by forming blood clots.
Blood vessels - There is a network of blood vessels which contain arteries, veins and capillaries. They help in the circulation of blood throughout the body.      
Q.2: Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds? 
Answer: It is necessary to separate oxygenated and deoxygenated blood to maintain efficient supply of oxygen into the body. This system is essential in animals that have high energy need. For example, animals like mammals and birds which constantly use this energy to maintain their body temperature.
Q.3: What are the components of the transport system in highly organized plants?
Answer: The main components of transport system in plants are:
1. Xylem, 2. Phloem.
Xylem - It consists of vessels and tracheids. Xylem helps to conduct water and minerals from soil to the leaves.
Phloem - It consists of sieve tubes and companion cell. Phloem helps to transport food materials from leaves to various parts of the plant. This process is called translocation.    
Q.4: How are water and minerals transported in plants?
Answer: Water and minerals are transported through xylem cells from soil to the leaves. The xylem cells of roots stem and leaves are interconnected to form a conducting channel that reaches all parts of the plant. The root cells take ions from the soil. This creates a difference between the concentration of ions of roots and soil. Therefore, there is a steady movement of water into xylem. An osmotic pressure is formed and water and minerals are transported from one cell to the other cell due to osmosis. The continuous loss of water takes place due to transpiration. Because of transpiration, also a suction pressure is created as a result of which water is forced into the xylem cells of roots. The effect of root pressure for transportation in plants is more important in night while during day time transpiration pull becomes the major driving force.      
Q.5: How is the food transported in plants?  
Answer: The prepared food is transported in the plants through phloem to the storage organs of roots, fruits, seeds and growing parts. This process is called translocation. This function is done by sieve tubes and companion cells. The movement of food particles takes place upward and downward.
Mechanism of translocation is an active process that utilizes energy. Materials are transferred from leaf cells or from the site of storage into phloem tissue. For this energy is required which is provided by the ATP molecules. This energy increases the osmotic pressure, as a result, water from outside moves into the phloem. This pressure maintains the movement of food through all the parts of plants.
(Page 112)      
Q.1: Describe the structure and functioning of nephron.
Answer: Structure of Nephron
Nephron is the filtration unit of kidney. It consists of a tubule which is connected with collecting duct at one end and a cup - shaped structure at the other end.
This cup-shaped structure is called ‘Bowman’s capsule’. Every Bowman’s capsule contains a cluster of capillaries, called ‘Glomerulus’, within the cup - shaped structure. The blood enters into Glomerulus through afferent arteriole of renal artery and leaves it through efferent arteriole.  
Functioning of Nephron
1. Filtration: Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.
2. Re-absorption: As the filtrate flows along the tubule useful substances such as glucose, amino acids, salts and water are selectively re-absorbed into the blood by capillaries surrounding the nephron tubule.
The amount of water re-absorbed depends on the need of the body and also on the amount of wastes to be excreted.
3. Urine: The filtrate which remains after re-absorption is called urine. Urine contains dissolved nitrogenous waste, i.e. urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting duct to carry it to the ureter.  
Q.2: What are the methods used by plants to get rid of excretory products?
Answer: To get rid of excretory products, plants use the following ways:
(1) Many waste products are stored in vacuoles of the cells. Plant cells have comparatively large vacuoles. 
(2) Some waste products are stored in the leaves. They are removes as the leaves fall off.
(3) Some waste products such as resins and gums are stored, especially in non-functional old xylem.
(4) Some waste products such as tannins, resins, gums are stored in bark, thereby removed as peeled off.
(5) Plants excrete some waste products through roots into the soil around them.
(6) Plants also get rid of excess water through transpiration.  
Q.3: How is the amount of urine produced regulated?  
Answer: The amount of urine largely depends on the amount of excess water or water reabsorbed and also dissolved wastes present in the body. When excess water in the body is more, large quantities of dilute urine is excreted out. On the other hand if the excess water is less, a small quantity of concentrated urine is excreted. When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. As a result of which, the urine produced increases.
The amount of urine produced also depends on some other factors like:
(a) Habitat of an organism
(b) Anti-diuretic hormone (ADH).       
Further Study on the chapter ‘Life Processes’

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