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Human excretion
Assertion and Reason Questions on Human Excretion
Instructions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option:
- (A) Both A and R are true, and R is the correct explanation of A.
- (B) Both A and R are true, but R is NOT the correct explanation of A.
- (C) A is true, but R is false.
- (D) A is false, but R is true.
Assertion (A): The primary biological purpose of making urine in human beings is to filter out harmful metabolic waste products from the blood.
Reason (R): The kidneys, as part of the human excretory system, contain numerous specialized filtration units called nephrons that are equipped to perform this function.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source clearly states that the “purpose of making urine is to filter out waste products from the blood”. The reason further explains how this is achieved, by stating that the kidneys contain “large numbers of these filtration units called nephrons” that are packed close together, directly supporting the mechanism for filtration. Thus, R provides the correct explanation for A.
Assertion (A): Many unicellular organisms effectively remove their metabolic wastes through simple diffusion from their body surface.
Reason (R): These organisms are typically in direct contact with the surrounding water, which facilitates the outward movement of waste substances.
Answer: (B)
Explanation: Both the assertion and the reason are true statements. Unicellular organisms indeed “remove these wastes by simple diffusion from the body surface into the surrounding water”. The reason accurately describes the condition (“body surface into the surrounding water”) that makes simple diffusion effective for unicellular organisms. However, the reason describes how diffusion is facilitated rather than why simple diffusion is the chosen strategy over, say, complex organs. It states a contributing factor, not the underlying biological imperative explaining the strategy itself.
Assertion (A): The human excretory system comprises a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.
Reason (R): The kidneys are strategically located in the chest cavity, well-protected by the rib cage.
Answer: (C)
Explanation: The assertion is true, as the source lists these components as part of the human excretory system. However, the reason is false. The source explicitly states that “Kidneys are located in the abdomen, one on either side of the backbone,” not the chest cavity.
Assertion (A): Substances like glucose, amino acids, and salts are selectively re-absorbed from the initial filtrate primarily in the urinary bladder.
Reason (R): The amount of water re-absorbed during urine formation is directly dependent on how much excess water is in the body and the concentration of dissolved waste needing excretion.
Answer: (D)
Explanation: The assertion is false. Selective re-absorption of “glucose, amino acids, salts and a major amount of water” occurs as the urine flows along the coiled tube (part of the nephron), not in the urinary bladder. The urinary bladder is where urine is stored. The reason is true, as the source states that “The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted”.
Assertion (A): Unlike unicellular organisms, complex multi-cellular organisms have evolved specialized organs to perform the function of excretion.
Reason (R): Simple diffusion from the body surface is an insufficient mechanism for waste removal in complex multi-cellular organisms due to their larger volume and intricate internal structures.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source highlights that “complex multi-cellular organisms use specialised organs to perform the same function” as waste removal. The reason accurately explains why this specialization is necessary, implying that the simple diffusion strategy of unicellular organisms would be inadequate for the scale and complexity of multicellular life. Therefore, R is the correct explanation for A.
Assertion (A): Nitrogenous wastes such as urea or uric acid are effectively removed from the blood by the kidneys.
Reason (R): The process of waste removal in the kidneys can be conceptually compared to how the lungs remove carbon dioxide from the blood.
Answer: (B)
Explanation: Both the assertion and the reason are true statements. The source explicitly mentions that “nitrogenous waste such as urea or uric acid are removed from blood in the kidneys”. The source also draws an analogy: “Just as CO2 is removed from the blood in the lungs, nitrogenous waste… are removed from blood in the kidneys”. However, while the analogy (R) states a functional similarity, it does not explain how or why kidneys specifically remove nitrogenous wastes (A). It’s a comparison, not an explanation of the underlying mechanism.
Assertion (A): The fundamental filtration unit in the kidneys is characterized by a cluster of very thin-walled blood capillaries.
Reason (R): This capillary cluster is directly connected to the ureter, which transports the initial filtrate to the urinary bladder.
Answer: (C)
Explanation: The assertion is true, as the source states that “the basic filtration unit in the kidneys… is a cluster of very thin-walled blood capillaries”. However, the reason is false. The capillary cluster is “associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate,” not directly connected to the ureter. The urine eventually enters the ureter after flowing along the coiled tube.
Assertion (A): The urge to pass urine is an entirely involuntary reflex that humans cannot consciously control.
Reason (R): The urinary bladder is a muscular organ that is under nervous control, enabling individuals to typically control the urge to urinate.
Answer: (D)
Explanation: The assertion is false. The source states, “As a result, we can usually control the urge to urinate”. The reason is true, as the source mentions that “The bladder is muscular, so it is under nervous control”.
Assertion (A): The amount of water re-absorbed from the initial filtrate by the kidneys is not constant but varies based on physiological needs.
Reason (R): This variability in water re-absorption is crucial for the body to regulate its overall water balance and efficiently excrete dissolved waste products.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source explicitly states, “The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted”. The reason correctly explains the physiological purpose and benefit of this variability, which is to maintain bodily homeostasis.
Assertion (A): Each human kidney contains an exceptionally large number of microscopic filtration units called nephrons.
Reason (R): These numerous nephrons are densely packed close together within the kidney structure to maximize efficiency.
Answer: (B)
Explanation: Both the assertion and the reason are true statements. The source confirms that “Each kidney has large numbers of these filtration units called nephrons packed close together”. However, while R describes the arrangement of the nephrons (packed closely), it doesn’t explain why there are “large numbers” of them or their fundamental role as filtration units (A). It’s a descriptive fact about their organization, not an explanation for the assertion.
Assertion (A): Gaseous wastes, like those generated during respiration, are considered metabolic wastes that require removal from the body.
Reason (R): The biological process of excretion is defined as the removal of harmful metabolic wastes and specifically excludes the removal of gaseous byproducts.
Answer: (C)
Explanation: The assertion is true. The source introduces excretion by stating, “We have already discussed how organisms get rid of gaseous wastes generated during photosynthesis or respiration. Other metabolic activities generate nitrogenous materials which need to be removed”, implying gaseous wastes are part of metabolic waste needing removal. The reason is false. The definition of excretion given in the source (“The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion”) precedes and encompasses the discussion of gaseous wastes, meaning it includes them, not excludes them.
Assertion (A): The ureters are the primary organs responsible for producing urine in the human excretory system.
Reason (R): Urine produced in the kidneys travels through the ureters into the urinary bladder for storage.
Answer: (D)
Explanation: The assertion is false. The source clearly states, “Urine produced in the kidneys passes through the ureters”, indicating that kidneys produce urine, not ureters. The reason is true, as it accurately describes the pathway of urine: “Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored”.
Assertion (A): The Bowman’s capsule is structurally adapted to initiate the collection of filtrate from the blood in the kidneys.
Reason (R): It is a cup-shaped end of a coiled tube precisely associated with a cluster of thin-walled blood capillaries, forming a unit designed for initial filtration.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source describes Bowman’s capsule as the “cup-shaped end of a coiled tube” associated with the “capillary cluster” that “collects the filtrate”. The reason directly explains the structural arrangement that enables the Bowman’s capsule to perform its collection function as stated in the assertion.
Assertion (A): Useful substances like glucose, amino acids, and a major amount of water are selectively re-absorbed from the initial filtrate as it flows through the coiled tube.
Reason (R): This re-absorption ensures that the body retains vital nutrients and sufficient water, preventing their loss in urine.
Answer: (B)
Explanation: Both the assertion and the reason are true. The source states that “Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube”. The reason accurately describes the purpose or benefit of this re-absorption (retaining vital nutrients and water). However, the reason does not explain the process or mechanism of selective re-absorption itself; it explains why it happens, not how it happens.
Assertion (A): The urinary bladder functions primarily as a temporary storage organ for urine.
Reason (R): The bladder continuously releases small, regulated amounts of urine to prevent excessive pressure buildup within the excretory system.
Answer: (C)
Explanation: The assertion is true; urine “is stored in the urinary bladder until it is released through the urethra”. The reason is false. The source indicates that urine is stored “until the pressure of the expanded bladder leads to the urge to pass it out,” implying storage until a significant volume is reached, not continuous release.
Assertion (A): The kidneys are primarily responsible for removing carbon dioxide from the blood, similar to how the lungs remove nitrogenous wastes.
Reason (R): The fundamental purpose of making urine is to filter out waste products from the blood.
Answer: (D)
Explanation: The assertion is false. The source clarifies that “Just as CO2 is removed from the blood in the lungs, nitrogenous waste such as urea or uric acid are removed from blood in the kidneys”. So, kidneys remove nitrogenous wastes, and lungs remove CO2. The reason is true, as stated: “The purpose of making urine is to filter out waste products from the blood”.
Assertion (A): Humans possess the ability to consciously control the urge to urinate.
Reason (R): This control is possible because the urinary bladder is a muscular organ under the influence of the nervous system.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source states, “The bladder is muscular, so it is under nervous control… As a result, we can usually control the urge to urinate”. The reason directly explains the physiological basis (muscular, nervous control) that enables the conscious control mentioned in the assertion.
Assertion (A): Excretion is a vital biological process defined by the removal of harmful metabolic wastes from an organism’s body.
Reason (R): Organisms employ varied strategies to accomplish the process of excretion, reflecting their diverse biological structures and environments.
Answer: (B)
Explanation: Both the assertion and the reason are true statements. The source defines excretion as “The biological process involved in the removal of these harmful metabolic wastes from the body”. It also immediately follows with, “Different organisms use varied strategies to do this”. While both statements are true and related to the concept of excretion, the reason describes a characteristic of excretion across life forms (varied strategies) rather than providing an explanation for the definition or purpose of excretion given in the assertion.
Assertion (A): The basic filtration unit in the kidneys is structurally and functionally analogous to the alveoli in the lungs due to their shared role in gas exchange.
Reason (R): Both the kidney’s filtration unit and the lung’s functional unit (alveoli) involve clusters of very thin-walled blood capillaries for efficient substance transfer.
Answer: (C)
Explanation: The assertion is false. While the source draws an analogy between kidneys and lungs, it is about filtering substances from blood (nitrogenous waste in kidneys, CO2 in lungs) and the presence of “cluster of very thin-walled blood capillaries” in their basic filtration units. The analogy is not about gas exchange in the kidney, nor is the filtration unit directly analogous to alveoli for the purpose of gas exchange in the kidney. The reason is true, as the source states the kidney’s basic filtration unit is a “cluster of very thin-walled blood capillaries,” and implies a similar structure in the lungs for CO2 removal.
Assertion (A): The extent of water re-absorption in the kidneys is primarily regulated by the initial concentration of glucose present in the filtrate.
Reason (R): Urine that forms in each kidney ultimately enters a long tube known as the ureter.
Answer: (D)
Explanation: The assertion is false. The source states that “The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted,” not primarily on glucose concentration. While glucose is re-absorbed, its presence doesn’t dictate water re-absorption. The reason is true: “The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder”.
Assertion (A): The human excretory system is characterized by its complexity, featuring multiple specialized organs working in concert.
Reason (R): This intricate design is essential for the effective removal of metabolic wastes from a complex multicellular organism, a task that simple diffusion cannot adequately accomplish.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source details the multiple specialized organs of the human excretory system. The reason explains the necessity for this complexity, drawing a contrast with the simpler diffusion method used by unicellular organisms and implying its inadequacy for complex multicellular organisms. Therefore, R provides a correct explanation for A.
Assertion (A): The human kidneys are located in the abdomen, specifically one on either side of the backbone.
Reason (R): This anatomical placement ensures their direct and optimal access to the major blood vessels for efficient blood filtration.
Answer: (B)
Explanation: Both the assertion and the reason are true statements. The source explicitly states the kidney’s location: “Kidneys are located in the abdomen, one on either side of the backbone”. While their location does facilitate blood access, the source states their location but does not explain the specific anatomical reasoning for this placement as directly related to “optimal access” for “major blood vessels.” It is a reasonable inference, but not directly stated as the reason in the source.
Assertion (A): The filtration unit in the kidneys contains a cluster of very thin-walled blood capillaries.
Reason (R): These specific capillaries are primarily responsible for the selective re-absorption of useful substances like glucose and amino acids from the filtrate back into the blood.
Answer: (C)
Explanation: The assertion is true, as the source states the “basic filtration unit in the kidneys… is a cluster of very thin-walled blood capillaries”. However, the reason is false. While selective re-absorption occurs, it happens “as the urine flows along the tube” (after the Bowman’s capsule), not primarily within the initial capillary cluster itself (which is for initial filtration).
Assertion (A): Nitrogenous materials are the exclusive type of harmful metabolic wastes that require removal from the human body.
Reason (R): The biological process of excretion is fundamentally defined as the removal of harmful metabolic wastes from the body.
Answer: (D)
Explanation: The assertion is false. The source initially mentions “gaseous wastes generated during photosynthesis or respiration” also needing to be removed, in addition to “nitrogenous materials”, indicating that nitrogenous wastes are not the only type. The reason is true, as it correctly defines excretion: “The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion”.
Assertion (A): The ability to consciously delay or initiate urination in humans is directly linked to the muscular nature and nervous control of the urinary bladder.
Reason (R): Although pressure from an expanded bladder creates the urge to urinate, the nervous system allows for voluntary control to override this urge until an appropriate time.
Answer: (A)
Explanation: Both the assertion and the reason are true. The source states, “The bladder is muscular, so it is under nervous control, as we have discussed elsewhere. As a result, we can usually control the urge to urinate”. The reason explains how this control is exerted: the urge is felt due to pressure, but nervous control permits conscious regulation. Therefore, R is the correct explanation for A.
Quiz Human Excretion Assertion And Reason Question Class 10 CBSE
Assertion (A): The primary biological purpose of making urine in human beings is to filter out harmful metabolic waste products from the blood.
Reason (R): The kidneys, as part of the human excretory system, contain numerous specialized filtration units called nephrons that are equipped to perform this function.
Show Answer & Explanation
Answer: (A)
Explanation: Both the assertion and the reason are true. The source clearly states that the “purpose of making urine is to filter out waste products from the blood”. The reason further explains how this is achieved, by stating that the kidneys contain “large numbers of these filtration units called nephrons” that are packed close together, directly supporting the mechanism for filtration. Thus, R provides the correct explanation for A.
Assertion (A): Many unicellular organisms effectively remove their metabolic wastes through simple diffusion from their body surface.
Reason (R): These organisms are typically in direct contact with the surrounding water, which facilitates the outward movement of waste substances.
Show Answer & Explanation
Answer: (B)
Explanation: Both the assertion and the reason are true statements. Unicellular organisms indeed “remove these wastes by simple diffusion from the body surface into the surrounding water”. The reason accurately describes the condition (“body surface into the surrounding water”) that makes simple diffusion effective for unicellular organisms. However, the reason describes how diffusion is facilitated rather than why simple diffusion is the chosen strategy over, say, complex organs. It states a contributing factor, not the underlying biological imperative explaining the strategy itself.
Assertion (A): The human excretory system comprises a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.
Reason (R): The kidneys are strategically located in the chest cavity, well-protected by the rib cage.
Show Answer & Explanation
Answer: (C)
Explanation: The assertion is true, as the source lists these components as part of the human excretory system. However, the reason is false. The source explicitly states that “Kidneys are located in the abdomen, one on either side of the backbone,” not the chest cavity.
Assertion (A): Substances like glucose, amino acids, and salts are selectively re-absorbed from the initial filtrate primarily in the urinary bladder.
Reason (R): The amount of water re-absorbed during urine formation is directly dependent on how much excess water is in the body and the concentration of dissolved waste needing excretion.
Show Answer & Explanation
Answer: (D)
Explanation: The assertion is false. Selective re-absorption of “glucose, amino acids, salts and a major amount of water” occurs as the urine flows along the coiled tube (part of the nephron), not in the urinary bladder. The urinary bladder is where urine is stored. The reason is true, as the source states that “The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted”.
Assertion (A): Unlike unicellular organisms, complex multi-cellular organisms have evolved specialized organs to perform the function of excretion.
Reason (R): Simple diffusion from the body surface is an insufficient mechanism for waste removal in complex multi-cellular organisms due to their larger volume and intricate internal structures.
Show Answer & Explanation
Answer: (A)
Explanation: Both the assertion and the reason are true. The Chapter highlights that “complex multi-cellular organisms use specialised organs to perform the same function” as waste removal. The reason accurately explains why this specialization is necessary, implying that the simple diffusion strategy of unicellular organisms would be inadequate for the scale and complexity of multicellular life. Therefore, R is the correct explanation for A.
Assertion (A): Nitrogenous wastes such as urea or uric acid are effectively removed from the blood by the kidneys.
Reason (R): The process of waste removal in the kidneys can be conceptually compared to how the lungs remove carbon dioxide from the blood.
Show Answer & Explanation
Answer: (B)
Explanation: Both the assertion and the reason are true statements. The source explicitly mentions that “nitrogenous waste such as urea or uric acid are removed from blood in the kidneys”. The source also draws an analogy: “Just as CO₂ is removed from the blood in the lungs, nitrogenous waste… are removed from blood in the kidneys”. However, while the analogy (R) states a functional similarity, it does not explain how or why kidneys specifically remove nitrogenous wastes (A). It’s a comparison, not an explanation of the underlying mechanism.
Assertion (A): The fundamental filtration unit in the kidneys is characterized by a cluster of very thin-walled blood capillaries.
Reason (R): This capillary cluster is directly connected to the ureter, which transports the initial filtrate to the urinary bladder.
Show Answer & Explanation
Explanation: The assertion is true, as the source states that “the basic filtration unit in the kidneys… is a cluster of very thin-walled blood capillaries”. However, the reason is false. The capillary cluster is “associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate,” not directly connected to the ureter. The urine eventually enters the ureter after flowing along the coiled tube.
Assertion (A): The urge to pass urine is an entirely involuntary reflex that humans cannot consciously control.
Reason (R): The urinary bladder is a muscular organ that is under nervous control, enabling individuals to typically control the urge to urinate.
Show Answer & Explanation
Explanation: The assertion is false. The source states, “As a result, we can usually control the urge to urinate”. The reason is true, as the source mentions that “The bladder is muscular, so it is under nervous control”.
Assertion (A): The amount of water re-absorbed from the initial filtrate by the kidneys is not constant but varies based on physiological needs.
Reason (R): This variability in water re-absorption is crucial for the body to regulate its overall water balance and efficiently excrete dissolved waste products.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true. The source explicitly states, “The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted”. The reason correctly explains the physiological purpose and benefit of this variability, which is to maintain bodily homeostasis.
Assertion (A): Each human kidney contains an exceptionally large number of microscopic filtration units called nephrons.
Reason (R): These numerous nephrons are densely packed close together within the kidney structure to maximize efficiency.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true statements. The source confirms that “Each kidney has large numbers of these filtration units called nephrons packed close together”. However, while R describes the arrangement of the nephrons (packed closely), it doesn’t explain why there are “large numbers” of them or their fundamental role as filtration units (A). It’s a descriptive fact about their organization, not an explanation for the assertion.
Assertion (A): Gaseous wastes, like those generated during respiration, are considered metabolic wastes that require removal from the body.
Reason (R): The biological process of excretion is defined as the removal of harmful metabolic wastes and specifically excludes the removal of gaseous byproducts.
Show Answer & Explanation
Explanation: The assertion is true. The source introduces excretion by stating, “We have already discussed how organisms get rid of gaseous wastes generated during photosynthesis or respiration. Other metabolic activities generate nitrogenous materials which need to be removed”, implying gaseous wastes are part of metabolic waste needing removal. The reason is false. The definition of excretion given in the source (“The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion”) precedes and encompasses the discussion of gaseous wastes, meaning it includes them, not excludes them.
Assertion (A): Useful substances like glucose, amino acids, and a major amount of water are selectively re-absorbed from the initial filtrate as it flows through the coiled tube.
Reason (R): This re-absorption ensures that the body retains vital nutrients and sufficient water, preventing their loss in urine.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true. The source states that “Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube”. The reason accurately describes the purpose or benefit of this re-absorption (retaining vital nutrients and water). However, the reason does not explain the process or mechanism of selective re-absorption itself; it explains why it happens, not how it happens.
Assertion (A): The urinary bladder functions primarily as a temporary storage organ for urine.
Reason (R): The bladder continuously releases small, regulated amounts of urine to prevent excessive pressure buildup within the excretory system.
Show Answer & Explanation
Explanation: The assertion is true; urine “is stored in the urinary bladder until it is released through the urethra”. The reason is false. The source indicates that urine is stored “until the pressure of the expanded bladder leads to the urge to pass it out,” implying storage until a significant volume is reached, not continuous release.
Assertion (A): Humans possess the ability to consciously control the urge to urinate.
Reason (R): This control is possible because the urinary bladder is a muscular organ under the influence of the nervous system.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true. The source states, “The bladder is muscular, so it is under nervous control… As a result, we can usually control the urge to urinate”. The reason directly explains the physiological basis (muscular, nervous control) that enables the conscious control mentioned in the assertion.
Assertion (A): Excretion is a vital biological process defined by the removal of harmful metabolic wastes from an organism’s body.
Reason (R): Organisms employ varied strategies to accomplish the process of excretion, reflecting their diverse biological structures and environments.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true statements. The source defines excretion as “The biological process involved in the removal of these harmful metabolic wastes from the body”. It also immediately follows with, “Different organisms use varied strategies to do this”. While both statements are true and related to the concept of excretion, the reason describes a characteristic of excretion across life forms (varied strategies) rather than providing an explanation for the definition or purpose of excretion given in the assertion.
Assertion (A): The basic filtration unit in the kidneys is structurally and functionally analogous to the alveoli in the lungs due to their shared role in gas exchange.
Reason (R): Both the kidney’s filtration unit and the lung’s functional unit (alveoli) involve clusters of very thin-walled blood capillaries for efficient substance transfer.
Show Answer & Explanation
Explanation: The assertion is false. While the source draws an analogy between kidneys and lungs, it is about filtering substances from blood (nitrogenous waste in kidneys, CO₂ in lungs) and the presence of “cluster of very thin-walled blood capillaries” in their basic filtration units. The analogy is not about gas exchange in the kidney, nor is the filtration unit directly analogous to alveoli for the purpose of gas exchange in the kidney. The reason is true, as the source states the kidney’s basic filtration unit is a “cluster of very thin-walled blood capillaries,” and implies a similar structure in the lungs for CO₂ removal.
Assertion (A): The extent of water re-absorption in the kidneys is primarily regulated by the initial concentration of glucose present in the filtrate.
Reason (R): Urine that forms in each kidney ultimately enters a long tube known as the ureter.
Show Answer & Explanation
Explanation: The assertion is false. The source states that “The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted,” not primarily on glucose concentration. While glucose is re-absorbed, its presence doesn’t dictate water re-absorption. The reason is true: “The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder”.
Assertion (A): The human excretory system is characterized by its complexity, featuring multiple specialized organs working in concert.
Reason (R): This intricate design is essential for the effective removal of metabolic wastes from a complex multicellular organism, a task that simple diffusion cannot adequately accomplish.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true. The source details the multiple specialized organs of the human excretory system. The reason explains the necessity for this complexity, drawing a contrast with the simpler diffusion method used by unicellular organisms and implying its inadequacy for complex multicellular organisms. Therefore, R provides a correct explanation for A.
Assertion (A): The human kidneys are located in the abdomen, specifically one on either side of the backbone.
Reason (R): This anatomical placement ensures their direct and optimal access to the major blood vessels for efficient blood filtration.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true statements. The source explicitly states the kidney’s location: “Kidneys are located in the abdomen, one on either side of the backbone”. While their location does facilitate blood access, the source states their location but does not explain the specific anatomical reasoning for this placement as directly related to “optimal access” for “major blood vessels.” It is a reasonable inference, but not directly stated as the reason in the source.
Assertion (A): The filtration unit in the kidneys contains a cluster of very thin-walled blood capillaries.
Reason (R): These specific capillaries are primarily responsible for the selective re-absorption of useful substances like glucose and amino acids from the filtrate back into the blood.
Show Answer & Explanation
Explanation: The assertion is true, as the source states the “basic filtration unit in the kidneys… is a cluster of very thin-walled blood capillaries”. However, the reason is false. While selective re-absorption occurs, it happens “as the urine flows along the tube” (after the Bowman’s capsule), not primarily within the initial capillary cluster itself (which is for initial filtration).
Assertion (A): Nitrogenous materials are the exclusive type of harmful metabolic wastes that require removal from the human body.
Reason (R): The biological process of excretion is fundamentally defined as the removal of harmful metabolic wastes from the body.
Show Answer & Explanation
Explanation: The assertion is false. The source initially mentions “gaseous wastes generated during photosynthesis or respiration” also needing to be removed, in addition to “nitrogenous materials”, indicating that nitrogenous wastes are not the only type. The reason is true, as it correctly defines excretion: “The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion”.
Assertion (A): The ability to consciously delay or initiate urination in humans is directly linked to the muscular nature and nervous control of the urinary bladder.
Reason (R): Although pressure from an expanded bladder creates the urge to urinate, the nervous system allows for voluntary control to override this urge until an appropriate time.
Show Answer & Explanation
Explanation: Both the assertion and the reason are true. The source states, “The bladder is muscular, so it is under nervous control, as we have discussed elsewhere. As a result, we can usually control the urge to urinate”. The reason explains how this control is exerted: the urge is felt due to pressure, but nervous control permits conscious regulation. Therefore, R is the correct explanation for A.
Conclusion Life Processes Human Excretion Class 10 Assertion-Reason Questions
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