1. Which of the following shows the correct order of organization?

• tissues --> organs --> cells --> systems
• cells --> tissues --> systems --> organs
• cells --> organs --> tissues --> systems
• cells --> tissues --> organs --> systems

2. A salmon is a multicellular organism. The fish's bladder, which helps it regulate its salt concentration, is best described as which part of the organism?

• a system of many different organs
• a single cell within the whole organism
• a tissue; a collection of specialized cells
• an organ with a specific function

3. Tissues and organs in the body are .

4. Salmon are organisms that have systems of such gills and kidneys that contribute to the salmon's survival.

5. feedback is a response that reverses a change to body systems to maintain homeostasis.

6. When Salmon are exposed to very fresh water, they will dilute their urine so that they can retain salt. This can best be described as:

• positive feedback
• negative feedback
• intermediate feedback
• It is impossible to tell.

7. Osmoregulation is an example of a feedback loop.

8. The external stimulus that's impacting homeostasis is .

9. If a pollutant in the water were to affect a salmon’s bladder and its ability to osmoregulate it would:

• stabilize the typical positive feedback loop.
• stabilize the typical negative feedback loop.
• destabilize the typical positive feedback loop.
• destabilize the typical negative feedback loop.

10. Which of the following best illustrates how salmon use feedback to regulate salt levels in their body?

• They rely entirely on their diet to regulate salt levels, regardless of the salinity of the water, which is an example of negative feedback.
• In saltwater, their gills shut down salt excretion, while in freshwater, their kidneys release large amounts of salts, both using positive feedback to maintain balance.
• Their salt levels increase or decrease uncontrollably depending on the environment, showing no regulation due to positive feedback.
• In saltwater, their gills excrete excess salts, and in freshwater, their kidneys retain more salts, using negative feedback to maintain balance.

11. How does feedback allow salmon to live in both freshwater and saltwater environments?

• Positive feedback enables salmon to stop osmoregulation in stable water conditions, allowing them to adapt.
• Negative feedback adjusts their salt and water balance by regulating gill and kidney function depending on the salinity of the water.
• Negative feedback helps their bodies absorb water in freshwater environments and excrete water in saltwater environments.
• Positive feedback triggers a complete shutdown of metabolic processes when salt concentrations are too high or too low.

12. One of the MOST difficult things about designing experiments to determine what concentration of salt causes salmon to no longer be able to effectively osmoregulate is:

• salmon respond to changes in salt concentrations very slowly over many years.
• salmon live in very very deep water and cannot survive in study tanks or pools.
• testing the upper limits of salmons' environment can harm or kill them.
• salmon are a rare fish and they are very hard to find and catch.

13. Your classmate suggests testing how well salmon osmoregulate in a fish tank. Another classmate suggests experimenting a river or stream.
Which option offers better control over the salmon’s environment?

• Both options make it difficult to measure the salmon’s environment accurately.
• A fish tank allows for better control of the environment, improving the reliability of the results.
• A river or stream, because salmon cannot survive in fish tanks.
• Neither option will significantly affect the accuracy of the measurements.

14. Based on the Figures and data from the experiment, which conclusion describes the role of feedback in maintaining homeostasis in salmon through osmoregulation?

• Negative feedback is used to detect changes in external salinity and adjusts salt and water excretion/retention to maintain internal stability.
• Positive feedback ensures salmon absorb the same amount of salts and water regardless of their environment.
• Negative feedback stops the excretion of salts entirely, preventing water loss in all environments.
• Positive feedback eliminates the need for osmoregulation by matching the external salt concentration.

15. A group of scientists wants to study how salmon use feedback to maintain stability in freshwater and saltwater environments. Which experimental setup would best test this?

• Observe the behavior of salmon in a freshwater tank and compare it to their behavior in a saltwater tank to identify patterns that may indicate positive feedback.
• Measure the salt concentration in the blood of salmon after placing them in fresh water for one day, then in salt water for one day to observe negative feedback in osmoregulation.
• Place salmon in tanks with varying salinity levels and measure changes in gill function and kidney output over time to analyze negative feedback mechanisms.
• Record the weight of salmon before and after placing them in water of different salinity levels to test if feedback mechanisms affect water retention.

16. In the student experiment (Figure 2), each gummy bear started at the same size to simulate how a salmon's cells might be affected by salt concentration if it could not osmoregulate.

While this experiment effectively demonstrates the concept, what is the biggest limitation of using gummy bears to model osmoregulation?

• The change in gummy bear size is hard to observe and measure.
• The gummy bear experiment is hard to re-create or replicate.
• The gummy bears are not made of cells and don’t maintain stable internal conditions.
• All of the gummy bears should have been the same color.

17. Which experiment would produce results that could be generalized beyond the study to help understand feedback mechanisms in salmon?

• Take 100 salmon out of different natural habitats, that are both saltwater and freshwater. Measure the differences between their internal salt content and the external environments to find the average ability of salmon to regulate internal salt content.
• Place one salmon into one hundred different bodies of water. Measure the salt content of the body of water and the internal salt content of the salmon to find the average ability of salmon to regulate internal salt content.
• Place hundreds of salmon into a large swimming pool and gradually increase the salt content 10 times. Measure the internal salt content of each salmon and find the average difference between the water's salt content and each salmon's internal salt content.
• Place ten salmon into 5 different rivers and gradually increase the salt content of the river water 10 times. Measure the internal salt content of each salmon and find the average difference between the water's salt content and each salmon's internal salt content.

18. Why might someone experiment on gummy bears to understand osmoregulation rather than live salmon? How could the gummy bear experiment explain how salmon survive different salt concentrations? What are the limitations of using gummy bears?

In your response be sure to discuss:
• How osmoregulation operates through feedback mechanisms
• The conditions of the experiment
• The type of data that could and could not be collected
• How well the experiment represents both internal and external conditions of this system.

19.
Salmon osmoregulate by removing excess salt through salt concentration in their urine (bottom image) or retaining salt by diluting their urine (top image). One of your classmates suggests an experimental design to test osmoregulation in salmon:

"To test how much salt salmon can maintain homeostasis in, we can place a salmon into a tank and slowly add 5 grams of salt each minute to see how the fish responds. When they start struggling to breathe, we can dump them into a large freshwater tank to make sure they're ok. The minute before the fish struggles to breathe, will be considered the amount of salt the fish can survive in."

Refine the experimental design and make suggestions for what they could do to improve the accuracy and reliability of their conclusion along with addressing the ethical concerns of the design.

20. Tissues and organs in the body are .

21. Osmoregulation BEST helps the individual salmon to:

• survive
• communicate
• reproduce
• grow

22. In Figure 2, the fish is responding to by using which causes excess salt to be removed.

23. One of your classmates recommends that the best way to test how well salmon osmoregulate is in a large fish tank. Another classmate suggests that the experiments be done in a river or stream.

Which answer best explains the option to have better measurements of the salmon's internal salt concentration?

• The similarity of the pond or stream environment to the salmon's natural habitat will give the most reliable measurements of the salmon's internal salt content.
• Both options will have little impact on the measurement of the salmon's internal salt content.
• Both options will make it hard to measure the responses of the salmon's internal system and the internal salt content.
• The fish tank is a more controllable environment, which makes it better for the reliability of the measurements of the salmon's internal salt content.

24. What evidence would be necessary to answer the following question with an experiment:

How well do salmon regulate the amount of salt water in their body?

25. What concerns do you have about the data you'll collect or methods you'll use to collect that data?

26. Osmoregulation is a process that:

• uses positive feedback to maintain the fish’s internal environment.
• uses negative feedback to maintain the fish’s external environment.
• uses positive feedback to maintain the fish’s external environment.
• uses negative feedback to maintain the fish’s internal environment.

27. Your classmate recommends that the best way to test how well salmon osmoregulate is in a large fish tank. A different classmate suggests that the experiments be done in a river or stream.



Which answer best explains the option to have better control over the external environment of the salmon?

• The similarity of the pond or stream environment to the salmon's natural habitat will give the most reliable measurements of the salmon's external environment.
• Either option will have little impact on accuracy in measuring the salmon's external environment.
• Both options will make it hard to measure the salmon's external environment.
• The fish tank is a more controllable environment, which makes it better for the reliability of the measurements of the salmon's external environment.

28. Which part of the process of osmoregulation in salmon does the gummy bear show very well?

• The ability of salmon to adapt to both fresh and salt water.
• The concentration of urine to excrete salt.
• The process of negative feedback.
• Water loss and absorption through “skin.”

29. In the space below, describe in detail the experimental procedure you would recommend going through to measure salmon's ability to regulate their internal salt content.