Beavers have relatively little need to conserve water and could therefore be expected to have _______ than humans do.
a. fewer nephrons
b. longer nephron loops
c. shorter nephron loops
d. longer collecting ducts
e. longer convoluted tubules
Introduction:
The kidney’s structural unit is nephrons. Glomeruli are a network of capillaries that help in blood filtration. This yields filtered water and soluble substances into a cup-like sac called the Bowman’s capsule. Glomerulus is supported structurally by glomerular mesangial cells.
Answer to Problem 9TYR
Correct answer:
Beavers have relatively little need to conserve water and could therefore be expected to have shorter nephron loops than humans do. Therefore, option c is correct.
Explanation of Solution
Justify reasons for the correct statement:
Animals that are in need to preserve water have numerous and lengthier nephron loops compared to the other animals with a slight need to conserve water.
Option (c) is given as “shorter nephron loop”.
Due to the absence of a nephron loop, the amphibians and fish produce urine that is isotonic to their blood plasma. For example, beavers, which are aquatic mammals, have smaller nephron loops, and thus the conservation of water is less.
Hence, option (c) is correct.
Justify reasons for the incorrect statements:
Option (a) is given as “fewer nephrons”.
Humans can survive with few nephrons, but the output of urine will be only 30mL per hour. Inadequate nephrons will lead to uremia. Hence, it is a wrong answer.
Option (b) is given as “longer nephron loops”.
The longer length of the loop helps in more reabsorption of salts in the medulla and increases more the volume of water to be absorbed. Hence, it is a wrong answer.
Option (d) is given as “longer collecting ducts”.
The longer collecting duct aids in making the urine more concentrated by absorbing more volume water in the medulla. Hence, it is a wrong answer.
Option (e) is given as “longer convoluted tubules”.
The proximal convoluted tubule is the longest of the convoluted tubules, and its major purpose is absorption. Hence, it is a wrong answer.
Hence, options (a), (b), (d), and (e) are incorrect.
The beavers normally have a shorter nephron loop because there is no need for water conservation, as they are aquatic mammals.
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