Passage
Within the Actinopterygii (bony fish) lineage, marine teleosts (bony fish with mobile jaws) live in an aquatic environment where there is a higher external concentration of salt and a lower concentration of water relative to the internal concentrations. Owing to these conditions, salt ions tend to diffuse into the teleost through its skin, whereas water molecules within the organism osmotically traverse the opposite path.Irrespective of lineage, many fish species actively assess their environment and regulate their internal concentration of fluids and electrolytes via a homeostatic process known as osmoregulation. Teleosts with either glomerular kidneys (eg, eels, sculpin) or aglomerular kidneys that are purely tubular (eg, goosefish, toadfish) have served as experimental subjects for the study of marine teleost osmoregulation. Analyzing the ionic (ie, Na + , Cl − , Mg 2+ , SO 4 2− ) concentration of intestinal fluids, urine, and plasma in each species led to the discovery that the renal tubule of the goosefish has both excretory and reabsorptive functions.Scientists have concluded that marine teleost osmoregulation involves the ingestion of seawater, retrieval of NaCl and water from the intestine, and primary excretion of divalent ions via urine and monovalent ions through the gills (thin barriers between the organism's blood and the aquatic environment).In an experiment to further study osmoregulatory mechanisms, researchers emptied the gut of an eel and sealed the anus to prevent fluid loss. The eel was transported into seawater that had been treated with the volume marker phenol red. After 20 hours, the eel's gut contained 2.3 mL of fluid but showed a phenol red concentration equivalent to 12.3 mL of ingested seawater. Researchers found that the eel lost 2.3 g of weight due to urine output. They ultimately reported that the eel had lost all the seawater it absorbed through the gut via various mechanisms.
-Based on the passage, to confirm that the inorganic composition of marine teleost urine is independent of glomerular function, researchers would most likely have to discover:

Question

Passage
Within the Actinopterygii (bony fish) lineage, marine teleosts (bony fish with mobile jaws) live in an aquatic environment where there is a higher external concentration of salt and a lower concentration of water relative to the internal concentrations.  Owing to these conditions, salt ions tend to diffuse into the teleost through its skin, whereas water molecules within the organism osmotically traverse the opposite path.Irrespective of lineage, many fish species actively assess their environment and regulate their internal concentration of fluids and electrolytes via a homeostatic process known as osmoregulation.  Teleosts with either glomerular kidneys (eg, eels, sculpin) or aglomerular kidneys that are purely tubular (eg, goosefish, toadfish) have served as experimental subjects for the study of marine teleost osmoregulation.  Analyzing the ionic (ie, Na + , Cl − , Mg 2+ , SO 4 2− ) concentration of intestinal fluids, urine, and plasma in each species led to the discovery that the renal tubule of the goosefish has both excretory and reabsorptive functions.Scientists have concluded that marine teleost osmoregulation involves the ingestion of seawater, retrieval of NaCl and water from the intestine, and primary excretion of divalent ions via urine and monovalent ions through the gills (thin barriers between the organism's blood and the aquatic environment).In an experiment to further study osmoregulatory mechanisms, researchers emptied the gut of an eel and sealed the anus to prevent fluid loss.  The eel was transported into seawater that had been treated with the volume marker phenol red.  After 20 hours, the eel's gut contained 2.3 mL of fluid but showed a phenol red concentration equivalent to 12.3 mL of ingested seawater.  Researchers found that the eel lost 2.3 g of weight due to urine output.  They ultimately reported that the eel had lost all the seawater it absorbed through the gut via various mechanisms.
-Based on the passage, to confirm that the inorganic composition of marine teleost urine is independent of glomerular function, researchers would most likely have to discover:

Quizplus · Accepted Answer

11ecba2d_1028_3dc0_a3bf_f5c4ae5c0c5d_MD0008_00 According to the passage, marine teleosts such as the eel and the goosefish live in an aquatic environment that, when compared to their internal environment, has more salt and less water. In addition, the passage states that scientists concluded that osmoregulation in marine teleosts involves: Seawater ingestion. Retrieval (absorption) of salt and water from the intestine. Excretion of divalent ions primarily through the urine and monovalent ions through the gills. In the given scenario, researchers are trying to determine whether the inorganic composition of marine teleost urine is independent of glomerular function. To accomplish this, scientists studying teleosts with glomerular kidneys (eg, eels) and aglomerular kidneys (eg, goosefish) would have to assess how kidney structure affects urine production in these two anatomically different fish species. To confirm that the inorganic composition of urine is independent of glomerular function, scientists would have to find similar concentrations of inorganic substances in the urine of both glomerular and aglomerular fish. This finding would signify that inorganic urine composition is the same regardless of whether the fish possess a glomerular kidney. Because divalent ions (eg, Mg²⁺ and SO₄²⁻) are primarily excreted in the urine and monovalent ions (Na⁺ and Cl⁻) are primarily excreted through the gills of marine teleosts, researchers would have to find equally high urinary concentrations of Mg²⁺ and SO₄²⁻ ions in the glomerular eel and the aglomerular goosefish. (Choice A) Finding higher urinary concentrations of Mg²⁺ and SO₄²⁻ in the eel than in the goosefish would mean that the glomerular eel has a greater inorganic urine composition than the aglomerular goosefish. This result would indicate that efficiency of renal Mg²⁺ and SO₄²⁻ excretion is dependent on the better functionality of the glomerular kidney. (Choices B and D) The passage states that monovalent ions (eg, Na⁺ and Cl⁻) are mainly excreted through the gills, not through the kidney. Therefore, measurement of monovalent ions would provide a poor assessment of kidney function. Educational objective: To claim that a particular function is independent of an anatomical structure, researchers must show similar function-related findings in organisms with and without the anatomical structure of interest.

Passage Within the Actinopterygii (Bony Fish) Lineage, Marine Teleosts (Bony Fish