Class 10 Science Chapter 5 Life Processes

Class 10 Science Chapter 5 Life Processes

Topic 1: Introduction to Life Processes

1. How do we initially tell the difference between what is alive and what is not alive? We tend to observe some sort of movement, either growth-related or not.
2. What is considered common evidence for being alive? Some sort of movement, either growth-related or not, is common evidence for being alive.
3. Is visible movement sufficient as a defining characteristic of life? No, because a plant not visibly growing is still alive, and some animals breathe without visible movement.
4. What kind of movements are invisible to the naked eye but necessary for life? Movements of molecules are invisible to the naked eye but considered necessary for life by professional biologists.
5. Why is there controversy about whether viruses are truly alive? Viruses do not show any molecular movement in them until they infect some cell.
6. Why are molecular movements needed for life? Living organisms are well-organised structures that are likely to break down over time due to environmental effects, so they must keep repairing and maintaining their structures, which are made of molecules.
7. What happens if the organized, ordered nature of living structures breaks down? If order breaks down, the organism will no longer be alive.
8. What are the maintenance processes in living organisms called? The processes which together perform the maintenance job are called life processes.
9. When must these maintenance functions go on in living organisms? These functions must go on even when organisms are not doing anything particular, like sitting in class or being asleep.
10. Why is energy needed for maintenance processes? Energy is needed to prevent damage and break-down of structures.
11. Where does the energy for maintenance processes come from? This energy comes from outside the body of the individual organism.
12. What is the process called that transfers a source of energy (food) from outside the body to the inside? This process is commonly called nutrition.
13. What additional raw material is needed if the body size of an organism is to grow? Additional raw material will also be needed from outside.
14. What is the basis of most food sources for life on Earth? Life on Earth depends on carbon-based molecules, so most food sources are carbon-based.
15. How do organisms use different kinds of nutritional processes? They use different kinds of nutritional processes depending on the complexity of the carbon sources.
16. Why do outside sources of energy need to be broken down or built up in the body? The environment is not under the control of the individual organism, and these sources need to be converted to a uniform energy source and molecules for growth.
17. What type of chemical reactions are common for breaking down molecules in the body? Oxidising-reducing reactions are some of the most common chemical means to break down molecules.
18. What substance do many organisms use from outside the body for break-down reactions? Many organisms use oxygen sourced from outside the body.
19. What is respiration? Respiration is the process of acquiring oxygen from outside the body and using it to break down food sources for cellular needs.
20. Why are specific organs for taking in food, exchange of gases, or waste removal not always needed in single-celled organisms? In single-celled organisms, the entire surface of the organism is in contact with the environment.
21. Why is simple diffusion insufficient for multi-cellular organisms? In multi-cellular organisms, all cells may not be in direct contact with the surrounding environment, so simple diffusion will not meet their requirements.
22. What is the role of specialized tissues in multi-cellular organisms regarding life processes? Various body parts have specialized in functions like uptake of food and oxygen.
23. What problem arises from specialized tissues taking up food and oxygen at one place in multi-cellular organisms? It creates a need for a transportation system to carry food and oxygen to all parts of the body.
24. What happens to by-products created during energy generation from carbon sources and oxygen? They are waste by-products that are useless or even harmful, so they need to be removed from the body.
25. What is the process of removing waste by-products from the body called? This process is called excretion.
26. According to the basic rules for body design in multi-cellular organisms, what is developed for excretion? A specialized tissue for excretion will be developed.
27. What is the role of the transportation system in relation to excretory tissue? The transportation system will need to transport waste away from cells to this excretory tissue.
28. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans? Because the body size of the organism increases and the body design becomes more complex, meaning all cells may not be in direct contact with the surrounding environment.
29. What criteria do we use to decide whether something is alive? We observe visible movements, breathing, growth over time, and molecular movements.
30. What outside raw materials are used by an organism? Food (source of energy and materials), oxygen for respiration, and additional raw materials for growth.
31. What processes are considered essential for maintaining life? Nutrition, respiration, transportation, and excretion are essential for maintaining life.

Topic 2: Nutrition

32. Why do we need energy even when not doing any apparent activity? Energy is needed to maintain a state of order in our body.
33. Besides energy, what other materials do we need from outside our body? Materials are needed for growth, development, synthesis of proteins, and other substances.
34. What is the source of energy and materials for living things? The food we eat is the source of energy and materials.
35. How do autotrophs obtain their food? Autotrophs use simple food material obtained from inorganic sources like carbon dioxide and water.
36. Name some examples of autotrophic organisms. Green plants and some bacteria are examples of autotrophs.
37. How do heterotrophs obtain their food? Heterotrophs utilize complex substances prepared by other organisms.
38. What must happen to complex substances before heterotrophs can use them? These complex substances have to be broken down into simpler ones.
39. What biological catalysts do organisms use to break down complex substances? Organisms use bio-catalysts called enzymes.
40. Why does heterotrophic survival depend directly or indirectly on autotrophs? Autotrophs produce the complex substances that heterotrophs utilize for nutrition.
41. Name some examples of heterotrophic organisms. Animals and fungi are examples of heterotrophic organisms.

Topic 2.1: Autotrophic Nutrition (Photosynthesis)

42. How are carbon and energy requirements of autotrophic organisms fulfilled? They are fulfilled by photosynthesis.
43. What is photosynthesis? Photosynthesis is the process by which autotrophs take in substances from outside and convert them into stored forms of energy.
44. What materials are taken in during photosynthesis? Carbon dioxide and water are taken in.
45. What is converted into carbohydrates during photosynthesis? Carbon dioxide and water are converted into carbohydrates.
46. What external conditions are necessary for photosynthesis to occur? Photosynthesis requires the presence of sunlight and chlorophyll.
47. What are carbohydrates utilized for in plants? Carbohydrates are utilized for providing energy to the plant.
48. How do plants store carbohydrates not used immediately? They are stored in the form of starch, which serves as an internal energy reserve.
49. How is energy derived from food stored in human beings? Some energy is stored in our body in the form of glycogen.
50. What are the three main events that occur during photosynthesis? Absorption of light energy by chlorophyll, conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen, and reduction of carbon dioxide to carbohydrates.
51. Do the steps of photosynthesis always take place one after another immediately? No, for example, desert plants take up carbon dioxide at night and prepare an intermediate, which is then acted upon by absorbed energy during the day.
52. What are the green dots observed in a cross-section of a leaf under a microscope? These green dots are cell organelles called chloroplasts.
53. What do chloroplasts contain? Chloroplasts contain chlorophyll.
54. What are stomata? Stomata are tiny pores present on the surface of the leaves.
55. What is the primary purpose of stomata in leaves? Massive amounts of gaseous exchange take place through stomata for photosynthesis.
56. Where else can gas exchange occur in plants besides leaf stomata? Exchange of gases occurs across the surface of stems, roots, and leaves.
57. Why do plants close their stomata? To prevent large amounts of water loss through transpiration when carbon dioxide is not needed for photosynthesis.
58. What cells control the opening and closing of stomatal pores? The guard cells control the opening and closing of the stomatal pore.
59. How do guard cells cause the stomatal pore to open? Guard cells swell when water flows into them, causing the stomatal pore to open.
60. How do guard cells cause the stomatal pore to close? The pore closes if the guard cells shrink.
61. What raw material for photosynthesis is taken up from the soil by roots in terrestrial plants? Water is taken up from the soil by the roots.
62. Name some other raw materials (elements) plants need for building their body, taken up from the soil. Nitrogen, phosphorus, iron, and magnesium are taken up from the soil.
63. Why is nitrogen an essential element for plants? Nitrogen is an essential element used in the synthesis of proteins and other compounds.
64. In what forms is nitrogen taken up by plants from the soil? It is taken up as inorganic nitrates or nitrites, or as organic compounds prepared by bacteria from atmospheric nitrogen.
65. What are the raw materials required for autotrophic nutrition? Carbon dioxide and water, chlorophyll, and sunlight are the raw materials required for autotrophic nutrition.
66. What is the role of chlorophyll in photosynthesis? Chlorophyll absorbs light energy.

Topic 2.2: Heterotrophic Nutrition

67. How does the form of nutrition differ among heterotrophic organisms? It differs depending on the type and availability of food material, and how it is obtained.
68. Name some organisms that break down food material outside their body before absorbing it. Fungi like bread moulds, yeast, and mushrooms break down food outside the body.
69. What determines what can be taken in and broken down by an organism? It depends on the body design and functioning of the organism.
70. What is parasitic nutritive strategy? It is when organisms derive nutrition from plants or animals without killing them.
71. Name some examples of organisms that use a parasitic nutritive strategy. Cuscuta (amar-bel), ticks, lice, leeches, and tape-worms are examples of parasites.

Topic 2.3: How do Organisms obtain their Nutrition?

72. How does a single-celled organism like Amoeba take in food? Amoeba takes in food using temporary finger-like extensions of the cell surface, forming a food-vacuole.
73. What happens inside the food-vacuole of Amoeba? Complex substances are broken down into simpler ones, which then diffuse into the cytoplasm.
74. How does Amoeba get rid of undigested material? The remaining undigested material is moved to the surface of the cell and thrown out.
75. How does Paramoecium obtain food? Paramoecium has a definite shape, and food is taken in at a specific spot, moved by cilia covering the cell surface.

Topic 2.4: Nutrition in Human Beings

76. What is the alimentary canal? The alimentary canal is basically a long tube extending from the mouth to the anus.
77. Why does the food need to be processed in the digestive tract? To generate particles that are small and of the same texture, and to break down complex molecules for absorption.
78. How is food processed mechanically in the mouth? Food is crushed with our teeth.
79. What fluid is secreted in the mouth when we eat? A fluid called saliva, secreted by the salivary glands, is released.
80. What enzyme does saliva contain? Saliva contains an enzyme called salivary amylase.
81. What is the function of salivary amylase? Salivary amylase breaks down starch (a complex molecule) to give simple sugar.
82. How is food moved around the mouth while chewing? Food is mixed thoroughly with saliva and moved around by the muscular tongue.
83. What ensures the regulated movement of food along the digestive tube? The lining of the canal has muscles that contract rhythmically in peristaltic movements.
84. Where do peristaltic movements occur? These peristaltic movements occur all along the gut.
85. What is the food-pipe also known as? The food-pipe is also known as the oesophagus.
86. What happens when food enters the stomach? The stomach, a large organ, expands, and its muscular walls mix the food thoroughly with digestive juices.
87. What do the gastric glands present in the stomach wall release? Gastric glands release hydrochloric acid, a protein-digesting enzyme called pepsin, and mucus.
88. What is the role of hydrochloric acid in the stomach? Hydrochloric acid creates an acidic medium, which facilitates the action of the enzyme pepsin.
89. What protects the inner lining of the stomach from the action of hydrochloric acid? Mucus protects the inner lining of the stomach from the action of the acid under normal conditions.
90. How is the exit of food from the stomach regulated? It is regulated by a sphincter muscle, which releases food in small amounts into the small intestine.
91. Which part of the alimentary canal is the longest? The small intestine is the longest part of the alimentary canal.
92. Why does the length of the small intestine differ in various animals? It depends on the food they eat; herbivores eating grass need a longer small intestine to digest cellulose, while carnivores have a shorter one.
93. Where does the complete digestion of carbohydrates, proteins, and fats occur? The small intestine is the site of the complete digestion of carbohydrates, proteins, and fats.
94. What secretions does the small intestine receive for digestion? It receives secretions from the liver and pancreas.
95. Why must the food coming from the stomach be made alkaline in the small intestine? The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act.
96. What accomplishes the alkalinization of food and acts on fats? Bile juice from the liver accomplishes this.
97. How do bile salts help in fat digestion? Bile salts break down large fat globules into smaller globules, increasing the efficiency of enzyme action.
98. What does the pancreas secrete, and what enzymes does it contain? The pancreas secretes pancreatic juice, which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.
99. What do the glands in the walls of the small intestine secrete? They secrete intestinal juice.
100. What are the final products of digestion of proteins, complex carbohydrates, and fats by intestinal enzymes? Proteins are converted to amino acids, complex carbohydrates into glucose, and fats into fatty acids and glycerol.
101. How is digested food absorbed in the small intestine? Digested food is taken up by the walls of the intestine, specifically through numerous finger-like projections called villi.
102. What are villi, and what is their function? Villi are numerous finger-like projections on the inner lining of the small intestine that increase the surface area for absorption.
103. How is absorbed food transported from the small intestine to the rest of the body? Villi are richly supplied with blood vessels that take the absorbed food to each and every cell of the body.
104. What is the absorbed food utilized for in body cells? It is utilized for obtaining energy, building up new tissues, and the repair of old tissues.
105. Where is unabsorbed food sent? Unabsorbed food is sent into the large intestine.
106. What is the function of the large intestine? Its wall absorbs more water from the unabsorbed material.
107. How is the rest of the unabsorbed material removed from the body? The rest of the material is removed from the body via the anus.
108. What regulates the exit of waste material from the body? The exit of waste material is regulated by the anal sphincter.
109. What is dental caries? Dental caries, or tooth decay, causes gradual softening of enamel and dentine.
110. How do dental caries begin? They begin when bacteria acting on sugars produce acids that soften or demineralize the enamel.
111. What is dental plaque? Dental plaque is formed when masses of bacterial cells together with food particles stick to the teeth.
112. Why is dental plaque harmful? Plaque covers the teeth, preventing saliva from reaching the tooth surface to neutralize the acid.
113. How can plaque be removed? Brushing the teeth after eating removes the plaque before bacteria produce acids.
114. What happens if dental caries are left untreated? Microorganisms may invade the pulp, causing inflammation and infection.
115. What is the role of the acid in our stomach? The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin, and mucus protects the inner lining of the stomach from its action.
116. What is the function of digestive enzymes? Digestive enzymes (bio-catalysts) break down complex food substances into simpler molecules so they can be absorbed from the alimentary canal.
117. How is the small intestine designed to absorb digested food? Its inner lining has numerous finger-like projections called villi, which increase the surface area for absorption and are richly supplied with blood vessels.

Topic 3: Respiration

118. What is the purpose of using food material taken in during nutrition? It is used in cells to provide energy for various life processes.
119. What is the first step in the break-down of glucose in all organisms? The first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate.
120. Where does the break-down of glucose into pyruvate occur? This process takes place in the cytoplasm.
121. What happens to pyruvate during fermentation in yeast? Pyruvate is converted into ethanol and carbon dioxide.
122. Why is respiration in yeast during fermentation called anaerobic respiration? Because this process takes place in the absence of air (oxygen).
123. Where does the break-down of pyruvate using oxygen take place? This process takes place in the mitochondria.
124. What are the products of aerobic respiration from pyruvate? Three molecules of carbon dioxide and water are produced.
125. Why is respiration using oxygen called aerobic respiration? Because this process takes place in the presence of air (oxygen).
126. Which type of respiration releases a greater amount of energy, aerobic or anaerobic? The release of energy in aerobic process is a lot greater than in the anaerobic process.
127. What happens when there is a lack of oxygen in human muscle cells during sudden activity? Pyruvate is converted into lactic acid, a three-carbon molecule.
128. What causes muscle cramps during sudden activity? The build-up of lactic acid in our muscles causes cramps.
129. What molecule is synthesized using the energy released during cellular respiration? A molecule called ATP is synthesized.
130. What is ATP? ATP (Adenosine Triphosphate) is the energy currency for most cellular processes.
131. How is an ATP molecule formed? Energy released during respiration is used to make an ATP molecule from ADP (Adenosine Diphosphate) and inorganic phosphate.
132. What happens when the terminal phosphate linkage in ATP is broken using water? Energy equivalent to 30.5 kJ/mol is released, which drives endothermic reactions in the cell.
133. Name some activities for which ATP can be used in cells. ATP can be used for the contraction of muscles, protein synthesis, conduction of nervous impulses, and many other activities.
134. Why do aerobic organisms need to ensure sufficient oxygen intake? Because the aerobic respiration pathway depends on oxygen.
135. How do plants exchange gases? Plants exchange gases through stomata.
136. How do plants ensure all cells are in contact with air for gas exchange? Large inter-cellular spaces ensure that all cells are in contact with air.
137. What determines the direction of diffusion of carbon dioxide and oxygen in plants? The direction of diffusion depends upon the environmental conditions and the requirements of the plant.
138. What is the major exchange activity in plants at night? CO2 elimination is the major exchange activity at night, as no photosynthesis occurs.
139. What happens to CO2 generated during respiration in plants during the day? CO2 generated during respiration is used up for photosynthesis, so there is no CO2 release.
140. What is the major event of gas exchange in plants during the day? Oxygen release is the major event at this time.
141. How do animals obtain oxygen from the environment? Animals have evolved different organs for the uptake of oxygen from the environment.
142. How do terrestrial animals breathe? Terrestrial animals can breathe the oxygen in the atmosphere.
143. How do aquatic animals obtain oxygen? Animals that live in water need to use the oxygen dissolved in water.
144. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms? Because the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air.
145. How do fish take up dissolved oxygen? Fishes take in water through their mouths and force it past the gills, where dissolved oxygen is taken up by blood.
146. What is a common structural feature of organs for oxygen absorption in terrestrial animals? All these organs have a structure that increases the surface area in contact with the oxygen-rich atmosphere.
147. Why is the gas exchange surface in respiratory organs fine and delicate? Because the exchange of oxygen and carbon dioxide has to take place across this surface.
148. How is the delicate gas exchange surface protected in animals? It is usually placed within the body, requiring passages to take air to this area.
149. How is air taken into the human body? Air is taken into the body through the nostrils.
150. What filters the air passing through the nostrils? Fine hairs that line the passage, and mucus, filter the air.
151. Where does air pass after the nostrils in humans? From here, the air passes through the throat and into the lungs.
152. What ensures that the air-passage in the throat does not collapse? Rings of cartilage are present in the throat to ensure this.
153. What are the balloon-like structures at the termination of smaller tubes within the lungs? These are called alveoli.
154. What is the function of alveoli? Alveoli provide a surface where the exchange of gases can take place.
155. What structure surrounds the walls of the alveoli? The walls of the alveoli contain an extensive network of blood vessels.
156. How does air get sucked into the lungs during breathing in? We lift our ribs and flatten our diaphragm, making the chest cavity larger, which sucks air into the lungs.
157. How is oxygen transported from the alveoli to body cells? Oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all cells.
158. How is carbon dioxide brought to the alveoli for release? The blood brings carbon dioxide from the rest of the body for release into the alveoli.
159. Why do the lungs always contain a residual volume of air? So that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released during the breathing cycle.
160. Why is diffusion alone insufficient for oxygen delivery in large animals? When the body size of animals is large, diffusion pressure alone cannot take care of oxygen delivery to all parts of the body.
161. What takes up oxygen from the air in the lungs and carries it to tissues? Respiratory pigments take up oxygen.
162. What is the respiratory pigment in human beings? The respiratory pigment in human beings is haemoglobin.
163. What is a characteristic of haemoglobin regarding oxygen? Haemoglobin has a very high affinity for oxygen.
164. Where is haemoglobin present in the blood? This pigment is present in the red blood corpuscles.
165. How is carbon dioxide mostly transported in human blood? Carbon dioxide is more soluble in water than oxygen and is mostly transported in the dissolved form in our blood.
166. What is the estimated surface area of the alveolar surface if spread out? It would cover about 80 m^2.
167. How long would it take for a molecule of oxygen to get to our toes from our lungs if diffusion alone moved it? It is estimated that it would take 3 years.
168. What advantage does a terrestrial organism have over an aquatic organism in obtaining oxygen? Terrestrial organisms have access to a much higher concentration of oxygen in the air compared to dissolved oxygen in water.
169. What are the different ways glucose is oxidized to provide energy? Glucose is broken down into pyruvate in the cytoplasm, which can then be converted to ethanol and carbon dioxide (anaerobic) or carbon dioxide and water (aerobic), or lactic acid (anaerobic in muscles).
170. How is oxygen transported in human beings? Oxygen is transported by haemoglobin present in red blood corpuscles.
171. How is carbon dioxide transported in human beings? Carbon dioxide is mostly transported in the dissolved form in blood.
172. How are the lungs designed to maximize gas exchange area? The lungs have millions of balloon-like alveoli, which provide a vast surface area (about 80 m^2) for gas exchange, and their walls are extensively supplied with blood vessels.
173. What are the differences between aerobic and anaerobic respiration? Aerobic respiration uses oxygen, occurs in mitochondria, completely breaks down glucose to CO2 and water, and releases much more energy; anaerobic respiration does not use oxygen, occurs in the cytoplasm, and produces ethanol/CO2 or lactic acid with less energy.
174. Name some organisms that use the anaerobic mode of respiration. Yeast uses the anaerobic mode of respiration (fermentation).
175. What would be the consequences of a deficiency of haemoglobin in our bodies? A deficiency of haemoglobin would lead to reduced oxygen delivery to tissues, resulting in less energy production and conditions like anaemia.

Topic 4: Transportation

176. What materials does blood transport in our bodies? Blood transports food, oxygen, and waste materials.
177. What type of tissue is blood? Blood is a fluid connective tissue.
178. What is the fluid medium in blood called, and what does it transport? The fluid medium is called plasma, and it transports food, carbon dioxide, and nitrogenous wastes in dissolved form.
179. What carries oxygen in the blood? Oxygen is carried by the red blood corpuscles.
180. What other substances are transported by blood? Many other substances like salts are also transported by the blood.
181. What is the pumping organ for blood circulation? The heart is the muscular pumping organ.
182. How big is the human heart? The human heart is as big as our fist.
183. Why does the heart have different chambers? To prevent oxygen-rich blood from mixing with blood containing carbon dioxide.
184. Where does carbon dioxide-rich blood go from the heart? It has to reach the lungs for the carbon dioxide to be removed.
185. Where does oxygenated blood from the lungs go after returning to the heart? This oxygen-rich blood is then pumped to the rest of the body.
186. Which chamber of the heart receives oxygen-rich blood from the lungs? The thin-walled upper chamber on the left, the left atrium, receives it.
187. What happens after the left atrium collects blood and contracts? Blood is transferred to the left ventricle as it relaxes.
188. Which chamber pumps blood to the rest of the body? The muscular left ventricle contracts and pumps blood out to the body.
189. Which chamber receives de-oxygenated blood from the body? The upper chamber on the right, the right atrium, receives it.
190. What happens after the right atrium contracts? Blood is transferred to the right ventricle as it dilates.
191. Which chamber pumps de-oxygenated blood to the lungs for oxygenation? The right ventricle pumps it to the lungs.
192. Why do ventricles have thicker muscular walls than atria? Because ventricles have to pump blood into various organs.
193. What ensures that blood does not flow backwards in the heart? Valves ensure that blood does not flow backwards when atria or ventricles contract.
194. Why is the separation of the right and left sides of the heart useful in mammals and birds? It keeps oxygenated and de-oxygenated blood from mixing, allowing for a highly efficient supply of oxygen to meet high energy needs for maintaining body temperature.
195. How many chambers do amphibians and many reptiles have in their hearts? They have three-chambered hearts.
196. Why can amphibians and many reptiles tolerate some mixing of blood streams? They do not use energy to maintain body temperature, which depends on the environment.
197. How many chambers do fish hearts have? Fishes have only two chambers in their hearts.
198. Describe the blood flow in fish hearts. Blood is pumped to the gills, oxygenated there, and passes directly to the rest of the body, going only once through the heart per cycle.
199. What is “double circulation”? It is when blood goes through the heart twice during each cycle of passage through the body, as seen in most vertebrates other than fish.
200. What is blood pressure? Blood pressure is the force that blood exerts against the wall of a vessel.
201. Is blood pressure greater in arteries or veins? Blood pressure is much greater in arteries than in veins.
202. What is systolic pressure? The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure.
203. What is diastolic pressure? The pressure in the artery during ventricular diastole (relaxation) is called diastolic pressure.
204. What are the normal systolic and diastolic pressures in humans? The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.
205. What is hypertension? High blood pressure is also called hypertension.
206. What causes hypertension? It is caused by the constriction of arterioles, resulting in increased resistance to blood flow.
207. What are the dangers of hypertension? It can lead to the rupture of an artery and internal bleeding.
208. What are arteries? Arteries are the vessels which carry blood away from the heart to various organs of the body.
209. Why do arteries have thick, elastic walls? Because the blood emerges from the heart under high pressure.
210. What are veins? Veins collect the blood from different organs and bring it back to the heart.
211. Why do veins not need thick walls? Because the blood is no longer under pressure in veins.
212. What ensures blood flows only in one direction in veins? Veins have valves that ensure blood flows only in one direction.
213. What are capillaries? Capillaries are the smallest vessels that have walls which are one-cell thick.
214. Where does the exchange of material between blood and surrounding cells take place? Exchange of material takes place across the thin walls of capillaries.
215. What happens to capillaries after material exchange? Capillaries then join together to form veins that convey blood away from the organ or tissue.
216. What are platelet cells responsible for in blood? Platelet cells circulate around the body and plug leaks by helping to clot blood at injury points.
217. What is lymph? Lymph, also called tissue fluid, is another type of fluid involved in transportation.
218. How is lymph formed? Some plasma, proteins, and blood cells escape through pores in capillary walls into intercellular spaces in tissues to form lymph.
219. How is lymph similar to blood plasma? It is similar to the plasma of blood.
220. How does lymph differ from blood plasma? Lymph is colorless and contains less protein than blood plasma.
221. How does lymph return to the blood? Lymph drains into lymphatic capillaries from intercellular spaces, which join to form large lymph vessels that finally open into larger veins.
222. What are the functions of lymph? Lymph carries digested and absorbed fat from the intestine and drains excess fluid from the extracellular space back into the blood.
223. Describe double circulation of blood in human beings. In humans, blood passes through the heart twice in one complete cycle: once for pulmonary circulation (to lungs and back) and once for systemic circulation (to the body and back).
224. Why is double circulation necessary in humans? Double circulation ensures efficient oxygen supply by preventing mixing of oxygenated and deoxygenated blood, which is crucial for high energy needs and maintaining body temperature.

Topic 4.1: Transportation in Plants

225. What is the nearest and richest source of raw materials like nitrogen, phosphorus, and other minerals for plants? The soil is the nearest and richest source.
226. Through what part do plants absorb substances from the soil? Absorption occurs through the roots, which are in contact with the soil.
227. Why are diffusion processes insufficient for transport in large plants? If distances between soil-contacting organs and chlorophyll-containing organs become large, diffusion is not enough to provide raw materials.
228. Do plants have high or low energy needs, and why? Plants have low energy needs because they do not move and have a large proportion of dead cells in many tissues.
229. Can plant transport systems be slow? Yes, plants can use relatively slow transport systems due to their low energy needs.
230. What are the two independently organized conducting tubes in plant transport systems? Xylem and phloem are the two conducting tubes.
231. What does the xylem transport? The xylem moves water and minerals obtained from the soil.
232. What does the phloem transport? The phloem transports products of photosynthesis from the leaves to other parts of the plant.
233. What tissues are interconnected to form a continuous system of water-conducting channels in xylem? Vessels and tracheids of the roots, stems, and leaves are interconnected.
234. How does water initially move into the root from the soil? Cells in contact with the soil actively take up ions, creating a concentration difference, causing water to move into the root.
235. What is created by the steady movement of water into root xylem? A column of water is created that is steadily pushed upwards.
236. What additional strategy do plants use to move water to the highest points of the plant body? Plants use transpiration pull.
237. What is transpiration? Transpiration is the loss of water in the form of vapor from the aerial parts of the plant.
238. How does transpiration help in water movement? Evaporation of water molecules from leaf cells creates a suction which pulls water from the xylem cells of roots.
239. What are the functions of transpiration? Transpiration helps in the absorption and upward movement of water and dissolved minerals from roots to leaves, and also helps in temperature regulation.
240. When is root pressure more important for water transport? The effect of root pressure in transport of water is more important at night.
241. When does the transpiration pull become the major driving force for water movement? During the day when the stomata are open, the transpiration pull becomes the major driving force.
242. What is translocation in plants? Translocation is the transport of soluble products of photosynthesis from leaves to other parts of the plant.
243. Where does translocation occur? Translocation occurs in the phloem.
244. Besides photosynthesis products, what else does the phloem transport? The phloem transports amino acids and other substances.
245. To what parts are these substances especially delivered by phloem? They are delivered to storage organs of roots, fruits, and seeds, and to growing organs.
246. How does translocation in phloem occur (mechanistically)? It takes place in sieve tubes with the help of adjacent companion cells, in both upward and downward directions.
247. How is material like sucrose transferred into phloem tissue? Material like sucrose is transferred into phloem tissue using energy from ATP.
248. What effect does the transfer of sucrose into phloem have? This increases the osmotic pressure of the tissue, causing water to move into it.
249. How does this pressure drive material movement in phloem? This pressure moves the material in the phloem to tissues which have less pressure.
250. What are the components of the transport system in highly organized plants? The vascular tissue, consisting of xylem and phloem, is the component.
251. How are water and minerals transported in plants? Water and minerals are transported by the xylem tissue, driven by root pressure (at night) and transpiration pull (during the day).
252. How is food transported in plants? Food (soluble products of photosynthesis) and other substances like amino acids are transported by the phloem through translocation, using ATP to create osmotic pressure.
253. What are the differences between the transport of materials in xylem and phloem? Xylem transports water and minerals upwards using root pressure and transpiration pull; phloem transports food and other organic substances (e.g., sucrose, amino acids) bidirectionally using ATP-driven osmotic pressure.

Topic 5: Excretion

254. How do organisms get rid of gaseous wastes generated during photosynthesis or respiration? Plants get rid of oxygen as a waste during photosynthesis and CO2 during respiration, and animals get rid of CO2 during respiration.
255. What kind of materials do other metabolic activities generate that need to be removed? Other metabolic activities generate nitrogenous materials.
256. What is excretion? Excretion is the biological process involved in the removal of harmful metabolic wastes from the body.
257. How do many unicellular organisms remove wastes? They remove wastes by simple diffusion from the body surface into the surrounding water.
258. How do complex multi-cellular organisms perform excretion? They use specialized organs to perform this function.

Topic 5.1: Excretion in Human Beings

259. What organs are included in the human excretory system? The human excretory system includes a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.
260. Where are the kidneys located? Kidneys are located in the abdomen, one on either side of the backbone.
261. How does urine produced in the kidneys exit the body? Urine passes through the ureters into the urinary bladder, where it is stored until released through the urethra.
262. What is the purpose of making urine? The purpose of making urine is to filter out waste products from the blood.
263. What nitrogenous wastes are removed from blood in the kidneys? Nitrogenous waste such as urea or uric acid are removed from blood in the kidneys.
264. What is the basic filtration unit in the kidneys? The basic filtration unit in the kidneys is a cluster of very thin-walled blood capillaries.
265. What is the cup-shaped end of a coiled tube associated with each capillary cluster in the kidney? It is called Bowman’s capsule, which collects the filtrate.
266. What are the filtration units in the kidney called? Each kidney has large numbers of these filtration units called nephrons.
267. What substances are selectively re-absorbed from the initial filtrate as urine flows along the tube? Glucose, amino acids, salts, and a major amount of water are selectively re-absorbed.
268. What factors determine the amount of water re-absorbed in the kidneys? The amount of water re-absorbed depends on how much excess water there is in the body and how much dissolved waste needs to be excreted.
269. Where is urine stored before release? Urine is stored in the urinary bladder.
270. How is the urge to urinate controlled? The bladder is muscular and under nervous control, allowing for control over the urge to urinate.
271. What happens if kidney activity is reduced due to infection, injury, or restricted blood flow? This leads to accumulation of poisonous wastes in the body, which can even lead to death.
272. What is an artificial kidney (hemodialysis)? An artificial kidney is a device used to remove nitrogenous waste products from the blood through dialysis in case of kidney failure.
273. How does an artificial kidney work? Patient’s blood is passed through tubes with a semi-permeable lining suspended in dialyzing fluid; waste products diffuse from blood into the fluid.
274. How does dialyzing fluid differ from blood plasma? Dialyzing fluid has the same osmotic pressure as blood, except that it is devoid of nitrogenous wastes.
275. What is a key difference between the function of a natural kidney and an artificial kidney? In artificial kidneys (dialysis), there is no re-absorption involved.
276. What is the normal volume of initial filtrate in healthy adult kidneys daily? The initial filtrate is about 180 L daily.
277. Why is the volume of urine actually excreted much less than the initial filtrate? The volume actually excreted is only a litre or two a day because the remaining filtrate is re-absorbed in the kidney tubules.
278. Describe the structure and functioning of nephrons. Each nephron has a capillary cluster (glomerulus) associated with Bowman’s capsule, where filtration occurs; as filtrate flows along the coiled tubule, selective re-absorption of useful substances (glucose, amino acids, salts) and water takes place.
279. How is the amount of urine produced regulated? The amount of water re-absorbed depends on the body’s excess water and the amount of dissolved waste to be excreted.

Topic 5.2: Excretion in Plants

280. Can oxygen be considered a waste product in plants? Yes, oxygen itself can be thought of as a waste product generated during photosynthesis.
281. How do plants deal with excess water? They get rid of excess water by transpiration.
282. What strategy do plants use for other wastes, given that many tissues consist of dead cells? They can lose some parts, such as leaves, which may store waste products.
283. Where are many plant waste products stored? Many plant waste products are stored in cellular vacuoles.
284. What are the methods used by plants to get rid of excretory products? Plants get rid of oxygen (from photosynthesis), excess water (by transpiration), store wastes in cellular vacuoles, in falling leaves, as resins and gums in old xylem, or excrete them into the surrounding soil.