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Ch. 40 - Water and Electrolyte Balance in Animals
All textbooksFreeman 8th EditionCh. 40 - Water and Electrolyte Balance in AnimalsProblem 12
Chapter 39, Problem 12

Fish and other aquatic organisms are exposed to many types of water pollutants, including metals such as aluminum. Although a low level of aluminum is found in unpolluted water, many lakes and streams have an increased level because of mining, sewage treatment, and accidental spills of toxic materials. Aluminum pollution can result in mass fish die-offs. In a laboratory, scientists exposed freshwater bony fish (Prochilodus lineatus) to water with a high level of aluminum and compared their blood osmolarity to that of fish exposed to water with a normal aluminum level (control). The results of the experiment are shown here (asterisks indicate P<0.05 between control and treated groups at a given time; BioSkills 3). Do the data support the hypothesis that aluminum interferes with osmoregulation in freshwater fishes? Explain.

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Step 1: Understand the problem. The question is asking whether the data supports the hypothesis that aluminum interferes with osmoregulation in freshwater fishes. Osmoregulation is the process by which organisms regulate the osmotic pressure of their body fluids to maintain the homeostasis of the body's water content. In this case, the scientists are comparing the blood osmolarity of fish exposed to high levels of aluminum to those exposed to normal levels.
Step 2: Analyze the data. Unfortunately, the problem does not provide the actual data from the experiment. However, in a real-life scenario, you would look at the blood osmolarity levels of the fish exposed to high levels of aluminum and compare them to the control group. If the blood osmolarity levels of the fish exposed to high levels of aluminum are significantly different from the control group, this could indicate that the aluminum is interfering with osmoregulation.
Step 3: Understand the significance level. The asterisks in the data indicate a P-value of less than 0.05. This means that the difference between the control and treated groups is statistically significant, and the likelihood that the difference is due to chance is less than 5%. If there are asterisks next to the data points comparing the control and treated groups, this would support the hypothesis that aluminum interferes with osmoregulation.
Step 4: Draw conclusions. Based on the statistical significance of the data, you can conclude whether or not the data supports the hypothesis. If the blood osmolarity levels of the fish exposed to high levels of aluminum are significantly different from the control group, and the P-value is less than 0.05, then the data would support the hypothesis that aluminum interferes with osmoregulation in freshwater fishes.
Step 5: Communicate your findings. After analyzing the data and drawing conclusions, you would then communicate your findings in a clear and concise manner, explaining whether the data supports the hypothesis and how you arrived at your conclusion.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Osmoregulation

Osmoregulation is the process by which organisms regulate the balance of water and solutes in their bodies to maintain homeostasis. In freshwater fish, this involves the uptake of water through their skin and gills while excreting excess salts. Disruption in osmoregulation can lead to physiological stress, affecting the fish's ability to survive in their environment, especially when exposed to pollutants like aluminum.
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Effects of Aluminum on Aquatic Life

Aluminum is a toxic metal that can accumulate in aquatic environments, primarily due to human activities such as mining and industrial discharges. Elevated levels of aluminum can impair the gill function of fish, leading to reduced oxygen uptake and disrupted ion balance. This toxicity can result in physiological changes, including altered blood osmolarity, which is critical for understanding the impact of aluminum on fish health.
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Experimental Control and Comparison

In scientific experiments, a control group is essential for establishing a baseline for comparison. In this study, the control group consisted of fish exposed to normal aluminum levels, while the experimental group was subjected to high aluminum levels. By comparing the blood osmolarity of both groups, researchers can determine the specific effects of aluminum on osmoregulation, providing evidence to support or refute the hypothesis.
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Related Practice
Textbook Question

Biologists have been able to produce mice that lack functioning genes for aquaporins. How would the urine of these mice compare to that of mice with normal aquaporins? a. lower volume and lower osmolarity b. lower volume and higher osmolarity c. higher volume and lower osmolarity d. higher volume and higher osmolarity

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Textbook Question

To test the hypothesis that mussels are osmoconformers, researchers exposed mussels to water of varying osmolarities and then drew hemolymph samples from the mussels. Graph the data provided here. Put the independent variable on the x--axis and the dependent variable on the y-axis. Is the researchers' hypothesis supported by the data? Explain.

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Textbook Question

Fish and other aquatic organisms are exposed to many types of water pollutants, including metals such as aluminum. Although a low level of aluminum is found in unpolluted water, many lakes and streams have an increased level because of mining, sewage treatment, and accidental spills of toxic materials. Aluminum pollution can result in mass fish die-offs such as the one pictured here. How does this occur? Which of the following is an osmoregulatory challenge that freshwater fishes need to overcome? a. diffusion of sodium ions out of the body b. diffusion of water out of the body c. active transport of sodium ions out of the body d. active transport of water out of the body

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Textbook Question

Fish and other aquatic organisms are exposed to many types of water pollutants, including metals such as aluminum. Although a low level of aluminum is found in unpolluted water, many lakes and streams have an increased level because of mining, sewage treatment, and accidental spills of toxic materials. Aluminum pollution can result in mass fish die-offs. Why did the scientists do this experiment in a laboratory instead of simply collecting fish from a river with a high aluminum level and documenting their osmoregulatory ability?

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Textbook Question

Fish and other aquatic organisms are exposed to many types of water pollutants, including metals such as aluminum. Although a low level of aluminum is found in unpolluted water, many lakes and streams have an increased level because of mining, sewage treatment, and accidental spills of toxic materials. Aluminum pollution can result in mass fish die-offs. The scientists also measured the activity of Na+/K+-ATPase, in the gills of the fish exposed to aluminum and compared it to that of the control fish. What do you suppose were their results? Explain.

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Textbook Question

Fish and other aquatic organisms are exposed to many types of water pollutants, including metals such as aluminum. Although a low level of aluminum is found in unpolluted water, many lakes and streams have an increased level because of mining, sewage treatment, and accidental spills of toxic materials. Aluminum pollution can result in mass fish die-offs. True or false: Water moves by osmosis across a fish's gills to an area with a higher sodium ion concentration because water molecules are attracted to the sodium ions.

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