Question 1

Tissues of sharks are isotonic to seawater, but their concentrations of sodium ions, potassium ions, and chloride ions in cells and extracellular fluids are similar to those of freshwater fishes. What can you infer about the movement of sodium and chloride in these animals?

Accepted Answer

Since the concentrations of sodium and chloride ions in shark cells and extracellular fluids are similar to those of freshwater fishes, it can be inferred that these ions diffuse into shark gills from seawater down their concentration gradient to maintain homeostasis. Therefore, option B is the correct answer. Options A, C, and D are not correct as they do not explain the movement of sodium and chloride in these animals.

Question 2

Osmoregulation in the Shark
-The interstitial fluid concentration of three electrolytes is compared with the concentration of these electrolytes in fluid eliminated from the shark rectal gland as indicated in the accompanying table. Based on these data, which of the following is a likely function of the rectal gland?

Accepted Answer

The data in the table show that the concentrations of Na+, K+, and Cl− in the fluid eliminated from the shark rectal gland are higher than the concentrations in the interstitial fluid. This indicates that the rectal gland is able to concentrate these electrolytes. Therefore, choice B is the best answer. Choices A, C, and D are not supported by the data provided.

Question 3

Salmon and sea bass are useful for studies of the role of the gills in osmoregulation in fishes because ________.

Accepted Answer

Salmon and sea bass have different life history stages where they live in freshwater and seawater. This makes them ideal for studying the role of gills in osmoregulation, as they must adapt to different levels of salt and water balance in their environments.

Question 4

Which nitrogenous waste requires hardly any water for its excretion?

Accepted Answer

Uric acid requires hardly any water for its excretion as it is insoluble in water and can be eliminated as a semi-solid paste. This is advantageous for organisms that live in dry environments as they do not need to use as much water to eliminate nitrogenous waste.

Question 5

Through studies of insect Malpighian tubules, researchers found that K+ accumulated on the inner face of the tubule, against its concentration gradient. What can you infer about the mechanism of transport?

Accepted Answer

The fact that K+ is accumulating against its concentration gradient indicates that its movement into the lumen of the Malpighian tubule is an energy-requiring process, which suggests an active transport mechanism.

Question 6

What role does Na+/K+-ATPase play in salt excretion by the shark rectal gland?

Accepted Answer

Na+/K+-ATPase plays a crucial role in salt excretion by the shark rectal gland. It pumps sodium out and potassium into the cells across the basolateral membrane, establishing a concentration gradient that drives diffusion of ions across the apical membrane. This creates a net movement of sodium and chloride ions into the gland lumen, which is then excreted as a hypertonic fluid.

Question 7

Osmoregulation in the Shark
-Refer to the accompanying table. Because the shark rectal gland functions only when ATP molecules are present, what can you infer about the movement of Na+, K+, and Cl−?

Accepted Answer

The requirement of ATP molecules for the function of the shark rectal gland indicates that the movement of Na+, K+, and Cl− ions involves active transport, which is an active process that moves ions against their concentration gradient, requiring energy.

Question 8

Water loss from a terrestrial insect's surface is minimal due to which of the following structures?

Accepted Answer

Chitin and the cuticle form a protective barrier on the surface of the insect, which reduces water loss through evaporation. The tracheae and spiracles are respiratory structures, and the proteinaceous epidermis provides structural support and protection against foreign objects, but they do not have a direct role in reducing water loss. The alimentary canal is involved in digestion and absorption of nutrients and does not play a role in reducing water loss.

Question 9

Salmon eggs hatch in freshwater. The fish then migrate to the ocean (a hypertonic solution) and, after several years of feeding and growing, return to freshwater to breed. How can these organisms make the transition from freshwater to ocean water and back to freshwater?

Accepted Answer

Different gill cells are involved in osmoregulation in freshwater than in salt water, allowing salmon to adapt to the different osmotic conditions in each environment.

Question 10

African lungfish, which are often found in small, stagnant pools of freshwater, produce urea as a nitrogenous waste. What is the advantage of this adaptation?

Accepted Answer

Small, stagnant pools do not provide enough water to dilute the toxic ammonia. Urea production allows for the excretion of nitrogenous waste without the need for large amounts of water for dilution, making it an advantageous adaptation in these environments.

Question 11

Freshwater fish reside in hypotonic environments. They do not drink water, and they excrete large volumes of hypotonic urine in an effort to osmoregulate. How do they obtain an adequate supply of electrolytes?

Accepted Answer

Freshwater fish obtain an adequate supply of electrolytes by absorbing additional electrolytes from freshwater through chloride cells on the gill filaments. This allows them to maintain their intracellular and extracellular electrolyte balance.

Question 12

How do spiracles contribute to the minimization of water loss in insects?

Accepted Answer

The answer of How do spiracles contribute to the minimization...

Question 13

Terrestrial organisms lose water through evaporation. In what ecosystem might an entomologist find a good study organism to examine the prevention of water loss?

Accepted Answer

In a desert ecosystem, where water is scarce, organisms have adapted various ways to minimize water loss through evaporation. This would make a suitable ecosystem for studying organisms that have evolved strategies to prevent dehydration.

Question 14

Insect Malpighian tubules form pre-urine, which is further processed by which of the following anatomical structures?

Accepted Answer

Insect Malpighian tubules form pre-urine, which is then emptied into the hindgut where further processing occurs. The hindgut reabsorbs some of the water and solutes, helping to concentrate the pre-urine into a more solid form before excretion.

Question 15

What role do chloride cells play in osmoregulation of marine bony fishes?

Accepted Answer

Chloride cells in marine bony fishes are specialized cells in the gills that help in the excretion of excess salt, maintaining osmotic balance in a high-salinity environment.

Question 16

The Na+/Cl−/K+ cotransporter in the epithelial cells of the gills of bony fishes is found ________.

Accepted Answer

In marine fishes, the Na+/Cl−/K+ cotransporter is located on the basolateral membrane to help excrete excess salts, while in freshwater fishes, it is on the apical membrane to aid in ion uptake from the dilute environment.

Question 17

The necropsy (postmortem analysis) of a freshwater fish that died after being placed accidentally in saltwater would likely show that ________.

Accepted Answer

When fish are placed in a hyperosmotic environment (saltwater), water is drawn out of their cells by osmosis, resulting in cell death and organ failure, including the kidneys which are responsible for regulating water balance. This would likely be reflected in the necropsy of the fish.

Question 18

Birds secrete uric acid as their nitrogenous waste because uric acid ________.

Accepted Answer

Birds have a unique adaptation for conserving water in their excretory process. They produce uric acid, which requires minimal water for disposal in comparison to other nitrogenous waste products. This adaptation enables them to conserve water, which is vital for their survival in arid environments.

Question 19

In animals, nitrogenous wastes are produced mostly from the catabolism of ________.

Accepted Answer

Nitrogenous wastes are produced from the breakdown of amino acids that make up proteins and nucleic acids. These wastes include urea, uric acid, and ammonia, which are usually filtered out of the blood and excreted as urine by the kidneys.

Question 20

The shark rectal gland ________.

Accepted Answer

The shark rectal gland is involved in osmoregulation by secreting a concentrated salt solution, helping to maintain the shark's internal salt balance in a marine environment.

Quiz 40: Water and Electrolyte Balance in Animals