Lecture 12: Osmoregulation Part 2

Question 1

What is osmoregulation?
a) Maintenance of constant temperature in body fluids.
b) Regulation of osmotic pressure (OP) in body fluids, regardless of external environment.
c) The movement of water to balance solute concentrations.
d) The process of excreting salts to maintain equilibrium.

Answer 1

Answer: b) Regulation of osmotic pressure (OP) in body fluids, regardless of external environment.

Question 2

Osmoregulation is considered a form of:
a) Cellular respiration
b) Metabolism
c) Homeostasis
d) Adaptation to freshwater environments only

Answer 2

Answer: c) Homeostasis

Question 3

What is the approximate salinity (NaCl concentration) of freshwater?
a) 24000 ppm
b) 2 ppm
c) 10 ppm
d) 5000 ppm

Answer 3

Answer: b) 2 ppm

Question 4

What is the approximate salinity (NaCl concentration) of saltwater?
a) 1000 ppm
b) 2 ppm
c) 24000 ppm
d) 500 ppm

Answer 4

Answer: c) 24000 ppm

Question 5

What is unique about estuaries (brackish water)?
a) They have a constant salinity level equal to freshwater.
b) They have intermediate salinity levels between freshwater and saltwater.
c) They contain the same salinity as saltwater.
d) They are isotonic environments for all aquatic animals.

Answer 5

Answer: b) They have intermediate salinity levels between freshwater and saltwater.

Question 6

What challenge do animals in estuaries face?
a) Adapting to constantly high salinity.
b) Maintaining osmotic pressure in changing salinity conditions.
c) Preventing water loss due to low osmotic pressure.
d) Excreting excess salts constantly.

Answer 6

Answer: b) Maintaining osmotic pressure in changing salinity conditions.

Question 7

In freshwater environments, water flows:
a) Out of the fish, causing dehydration.
b) Into the fish, causing swelling.
c) Equally into and out of the fish.
d) Only within the fish’s plasma.

Answer 7

Answer: b) Into the fish, causing swelling.

Question 8

Osmotic pressure is:
a) Higher in freshwater than in fish plasma.
b) Lower in freshwater than in fish plasma.
c) Equal in freshwater and saltwater environments.
d) Always higher in saltwater fish than in their environment.

Answer 8

Answer: b) Lower in freshwater than in fish plasma.

Question 9

Saltwater fish must:
a) Excrete large amounts of water and retain salts.
b) Retain water and excrete salts.
c) Maintain isotonic balance without osmotic regulation.
d) Absorb salts to prevent dehydration.

Answer 9

Answer: b) Retain water and excrete salts.

Question 10

Animals in estuaries adapt to changing salinity by:
a) Maintaining a constant internal osmotic pressure.
b) Changing their internal salinity to match the environment.
c) Excreting large amounts of water to maintain equilibrium.
d) Moving to freshwater areas when salinity increases.

Answer 10

Answer: a) Maintaining a constant internal osmotic pressure.

Question 11

Osmoregulation is necessary because:
a) Organisms need to regulate their temperature.
b) Water movement can cause osmotic swelling (lysis) or desiccation (shrinking).
c) Organisms only interact with isotonic environments.
d) It prevents the diffusion of solutes across cell membranes.

Answer 11

Answer: b) Water movement can cause osmotic swelling (lysis) or desiccation (shrinking).

Question 12

What does osmoregulation primarily regulate?
a) Temperature and pressure in body fluids.
b) Levels of water and salts (ions) in the body.
c) The flow of oxygen in aquatic environments.
d) The movement of proteins in the bloodstream.

Answer 12

Answer: b) Levels of water and salts (ions) in the body.

Question 13

Which of the following is TRUE for isosmotic solutions?
a) One solution has higher osmotic pressure than the other.
b) Both solutions have the same osmotic pressure.
c) Water flows from the solution with higher osmotic pressure to lower pressure.
d) Water flows out of both solutions equally.

Answer 13

Answer: b) Both solutions have the same osmotic pressure.

Question 14

In a hypoosmotic environment:
a) The surrounding solution has a higher osmotic pressure than the organism’s body fluids.
b) Water flows out of the organism.
c) The surrounding solution has a lower osmotic pressure than the organism’s body fluids.
d) Solutes move into the organism, balancing the osmotic pressure.

Answer 14

Answer: c) The surrounding solution has a lower osmotic pressure than the organism’s body fluids.

Question 15

What is the key feature of an isosmotic solution?
a) Water flows out to balance osmotic pressure.
b) There is no net movement of water between the solutions.
c) Solutes move to balance concentrations.
d) Osmotic pressure increases over time.

Answer 15

Answer: b) There is no net movement of water between the solutions.

Question 16

Which of the following describes an osmotic regulator?
a) An organism whose internal osmotic pressure matches that of the external environment.
b) An organism that maintains a relatively constant internal osmotic pressure regardless of the environment.
c) An organism whose internal osmotic pressure varies with external osmotic pressure.
d) An organism that cannot adapt to changes in osmotic pressure.

Answer 16

Answer: b) An organism that maintains a relatively constant internal osmotic pressure regardless of the environment.

Question 17

An osmotic conformer is an organism that:
a) Maintains a higher internal osmotic pressure than the external environment.
b) Matches its internal osmotic pressure to the ambient osmotic pressure.
c) Maintains a lower internal osmotic pressure than the external environment.
d) Actively adjusts osmotic pressure in response to environmental changes.

Answer 17

Answer: b) Matches its internal osmotic pressure to the ambient osmotic pressure.

Question 18

What is a key characteristic of mussels as osmotic conformers?
a) They actively regulate their blood osmotic pressure.
b) Their blood osmotic pressure remains constant regardless of the environment.
c) Their blood osmotic pressure matches the osmolarity of the environment.
d) They excrete excess water to maintain osmotic balance.

Answer 18

Answer: c) Their blood osmotic pressure matches the osmolarity of the environment.

Question 19

Which of the following is TRUE for isosmotic lines?
a) Isosmotic lines show a constant osmotic pressure difference between blood and the environment.
b) Isosmotic lines represent perfect osmoregulation.
c) Isosmotic lines indicate when blood osmotic pressure is equal to ambient osmotic pressure.
d) Isosmotic lines are only seen in freshwater environments.

Answer 19

Answer: c) Isosmotic lines indicate when blood osmotic pressure is equal to ambient osmotic pressure.

Question 20

Humans are more similar to which aquatic organism in terms of osmoregulation?
a) Mussels
b) Green crabs
c) Shrimp
d) Squid

Answer 20

Answer: c) Shrimp

Question 21

Why are green crabs considered good osmoregulators?
a) They perfectly match their blood osmotic pressure to the environment.
b) They maintain constant blood osmotic pressure over a wide range of environmental osmotic pressures.
c) They do not experience changes in osmotic pressure.
d) They conform to changes in environmental osmolarity from freshwater to saltwater.

Answer 21

Answer: b) They maintain constant blood osmotic pressure over a wide range of environmental osmotic pressures.

Question 22

Which of the following best differentiates conformers and regulators?
a) Regulators maintain a fixed osmotic pressure; conformers actively adjust to changes.
b) Regulators maintain internal osmotic pressure constant; conformers match their internal osmotic pressure to the environment.
c) Conformers actively excrete salts, while regulators do not.
d) Conformers are found only in freshwater environments.

Answer 22

Answer: b) Regulators maintain internal osmotic pressure constant; conformers match their internal osmotic pressure to the environment.

Question 23

On a graph of blood osmotic pressure vs. ambient osmotic pressure, a conformer’s line:
a) Is horizontal, showing constant blood osmotic pressure.
b) Is diagonal, matching ambient osmotic pressure.
c) Has a steep positive slope but does not reach the isosmotic line.
d) Remains below the isosmotic line at all times.

Answer 23

Answer: b) Is diagonal, matching ambient osmotic pressure.

Question 24

What defines a euryhaline species?
a) It can only survive in a narrow range of salinities.
b) It tolerates a wide range of salinities without dying.
c) It conforms its internal osmolarity to the environment.
d) It requires a constant external osmotic pressure.

Answer 24

Answer: b) It tolerates a wide range of salinities without dying.

Question 25

A stenohaline species:
a) Can survive in both freshwater and saltwater environments.
b) Tolerates only a narrow range of salinities.
c) Always maintains constant osmotic pressure.
d) Is an osmoregulator in all environments.

Answer 25

Answer: b) Tolerates only a narrow range of salinities.

Question 26

Which of the following best describes an euryhaline osmoregulator?
a) Maintains a relatively constant internal osmolarity over a wide range of salinities.
b) Matches its internal osmolarity to external osmolarity.
c) Can only tolerate narrow changes in external osmolarity.
d) Dies in environments with variable salinity.

Answer 26

Answer: a) Maintains a relatively constant internal osmolarity over a wide range of salinities.

Question 27

What characteristic is TRUE for euryhaline osmoconformers?
a) They actively maintain their internal osmolarity constant regardless of the environment.
b) Their internal osmolarity matches the external environment across a wide range of salinities.
c) They can only survive in isotonic environments.
d) They maintain low osmotic pressure in all environments.

Answer 27

Answer: b) Their internal osmolarity matches the external environment across a wide range of salinities.

Question 28

A stenohaline osmoregulator:
a) Can survive large changes in external osmotic pressure.
b) Maintains internal osmolarity constant but only in a narrow range of external salinities.
c) Matches internal osmolarity to external conditions in all environments.
d) Can survive in both freshwater and saltwater environments equally.

Answer 28

Answer: b) Maintains internal osmolarity constant but only in a narrow range of external salinities.

Question 29

What is a primary characteristic of osmoconformers?
a) They maintain constant osmotic pressure in varying environments.
b) They conform their internal osmolarity to match the environment.
c) They can only live in freshwater environments.
d) They are always euryhaline species.

Answer 29

Answer: b) They conform their internal osmolarity to match the environment.

Question 30

Which of the following species is most likely to survive in both freshwater and saltwater?
a) Stenohaline osmoconformer
b) Euryhaline osmoregulator
c) Stenohaline osmoregulator
d) Euryhaline osmoconformer

Answer 30

Answer: b) Euryhaline osmoregulator

Question 31

On a graph of internal vs. external osmolarity, a stenohaline osmoconformer would show:
a) A flat line regardless of external osmolarity.
b) A steep diagonal line matching external osmolarity.
c) A flat line over a narrow range of external osmolarity, then a steep slope.
d) No change in internal osmolarity as external osmolarity increases.

Answer 31

Answer: c) A flat line over a narrow range of external osmolarity, then a steep slope.

Question 32

A euryhaline osmoconformer is placed in an environment where salinity rapidly increases. What will happen?
a) It will actively adjust to maintain constant internal osmolarity.
b) Its internal osmolarity will match the increasing external salinity.
c) It will die immediately due to osmotic shock.
d) It will excrete salts to reduce internal osmolarity.

Answer 32

Answer: b) Its internal osmolarity will match the increasing external salinity.

Question 33

An aquatic animal lives in an environment with frequent, significant fluctuations in salinity. Despite this, it maintains a stable internal osmolarity. This animal is likely:
a) A stenohaline osmoconformer
b) A euryhaline osmoregulator
c) A euryhaline osmoconformer
d) A stenohaline osmoregulator

Answer 33

Answer: b) A euryhaline osmoregulator

Question 34

Why does water flow into freshwater fish?
a) The osmotic pressure of the environment is higher than the fish’s blood plasma.
b) The fish is hyperosmotic relative to the environment.
c) The fish is hypoosmotic relative to the environment.
d) Ion gradients drive water into the fish through active transport.

Answer 34

Answer: b) The fish is hyperosmotic relative to the environment.

Question 35

Freshwater fish face two major problems due to living in a hypoosmotic environment. These are:
a) Losing water via osmosis and gaining ions via diffusion.
b) Gaining water via osmosis and losing ions via diffusion.
c) Maintaining isotonic balance and regulating pH.
d) Gaining ions and losing water via active transport.

Answer 35

Answer: b) Gaining water via osmosis and losing ions via diffusion.

Question 36

How do freshwater fish deal with the loss of ions?
a) By drinking large amounts of water to absorb ions.
b) By actively transporting ions into their bodies through the gills.
c) By allowing ions to diffuse back into their bodies.
d) By decreasing their metabolic rate to reduce ion loss.

Answer 36

Answer: b) By actively transporting ions into their bodies through the gills.

Question 37

Which of the following is NOT an adaptation of freshwater fish to maintain osmotic balance?
a) Diluting body fluids to reduce osmotic gradients.
b) Excreting large volumes of dilute urine.
c) Actively excreting salts through their gills.
d) Having scales that reduce water permeability.

Answer 37

Answer: c) Actively excreting salts through their gills.

Question 38

What happens to the volume of blood plasma in freshwater fish?
a) It decreases due to water loss.
b) It increases as water enters the body via osmosis.
c) It remains constant because of impermeable scales.
d) It fluctuates randomly with the environment.

Answer 38

Answer: b) It increases as water enters the body via osmosis.

Question 39

Why do freshwater crayfish have lower ion concentrations than saltwater lobsters?
a) Freshwater crayfish are hypoosmotic to their environment.
b) Lobsters require higher ion levels to survive in freshwater.
c) Crayfish have adaptations to reduce ionic gradients and permeability.
d) Lobsters have a more impermeable body wall than crayfish.

Answer 39

Answer: c) Crayfish have adaptations to reduce ionic gradients and permeability.

Question 40

What is a key role of the impermeable body wall in freshwater animals?
a) To actively absorb water from the environment.
b) To prevent water loss through osmosis.
c) To reduce water entry and salt loss.
d) To excrete waste products more efficiently.

Answer 40

Answer: c) To reduce water entry and salt loss.

Question 41

Which of the following is NOT an adaptation of freshwater fish to maintain osmotic balance?
a) Diluting body fluids to reduce osmotic gradients.
b) Excreting large volumes of dilute urine.
c) Actively excreting salts through their gills.
d) Having scales that reduce water permeability.

Answer 41

Answer: c) Actively excreting salts through their gills.

Question 42

Why is it impossible for a freshwater fish’s body surface to be completely impermeable?
a) It must allow water to flow freely across its skin.
b) Its gills must be permeable for gas exchange (O₂/CO₂).
c) Its body must absorb salts directly from the environment.
d) It requires a thin surface to conserve metabolic energy.

Answer 42

Answer: b) Its gills must be permeable for gas exchange (O₂/CO₂).

Question 43

If a freshwater fish takes in water via osmosis, what happens to the osmotic pressure of its plasma?
a) It increases.
b) It decreases.
c) It remains constant.
d) It fluctuates randomly.

Answer 43

Answer: b) It decreases.

Question 44

Why is the urine of freshwater fish hypoosmotic to their plasma?
a) It contains high concentrations of salts.
b) It has a very low concentration of salts.
c) It has the same osmolarity as the plasma.
d) It actively removes Na⁺ and Cl⁻ from the body.

Answer 44

Answer: b) It has a very low concentration of salts.

Question 45

How do freshwater fish compensate for salt loss by diffusion?
a) By drinking large amounts of water.
b) By actively transporting Na⁺ and Cl⁻ ions into the body through gills.
c) By excreting hyperosmotic urine.
d) By reducing gill permeability to salts.

Answer 45

Answer: b) By actively transporting Na⁺ and Cl⁻ ions into the body through gills.

Question 46

How do freshwater fish use active transport to cope with ion loss?
a) By passively absorbing ions through gills.
b) By using ATP to pump ions like Na⁺ and Cl⁻ back into their bodies.
c) By reducing the osmotic gradient between plasma and the environment.
d) By excreting hypertonic urine to retain salts.

Answer 46

Answer: b) By using ATP to pump ions like Na⁺ and Cl⁻ back into their bodies.

Question 47

What is a significant challenge of having permeable gills in freshwater fish?
a) Excessive salt gain by diffusion.
b) Water loss through osmosis.
c) Unregulated water gain and salt loss.
d) Reduced gas exchange efficiency.

Answer 47

Answer: c) Unregulated water gain and salt loss.

Question 48

Why do freshwater species, like crayfish, have lower ion concentrations compared to marine species, like lobsters?
a) Freshwater species excrete more salts than marine species.
b) Freshwater species have lower osmotic pressure relative to the environment.
c) Freshwater species have adaptations to minimize ionic gradients and water permeability.
d) Marine species lack the ability to regulate salts effectively.

Answer 48

Answer: c) Freshwater species have adaptations to minimize ionic gradients and water permeability.

Question 49

Describe the role of bicarbonate (HCO₃⁻) in ion exchange across the gills of freshwater fish. How does this process contribute to ionic regulation?

Answer 49

In freshwater fish, bicarbonate (HCO₃⁻) plays a crucial role in the active transport of ions across the gills. It is produced when carbon dioxide (CO₂) from metabolism combines with water (H₂O) to form carbonic acid (H₂CO₃), which dissociates into bicarbonate (HCO₃⁻) and a proton (H⁺). Bicarbonate ions are then exchanged for chloride ions (Cl⁻) from the surrounding water through an active chloride-bicarbonate transporter. This process helps maintain ionic balance by replenishing chloride ions lost to the environment. Similarly, protons (H⁺) are exchanged for sodium ions (Na⁺) via another transporter, ensuring sodium levels are also regulated. These exchanges are energy-dependent and are critical for ionic regulation in freshwater fish living in hypoosmotic environments.

Question 50

What is the primary role of bicarbonate (HCO₃⁻) in freshwater fish ion regulation?
a) To increase the osmotic gradient between plasma and water.
b) To actively transport chloride ions into the fish.
c) To excrete excess sodium ions from the body.
d) To reduce the production of carbonic acid.

Answer 50

Answer: b) To actively transport chloride ions into the fish.

Question 51

How is bicarbonate (HCO₃⁻) produced in the gills of freshwater fish?
a) By the breakdown of ATP.
b) By combining water and oxygen.
c) By the reaction of carbon dioxide with water.
d) Through active transport from the plasma.

Answer 51

Answer: c) By the reaction of carbon dioxide with water.

Question 52

Which ions are actively exchanged in freshwater fish gills during ionic regulation?
a) Chloride (Cl⁻) is exchanged for bicarbonate (HCO₃⁻), and sodium (Na⁺) is exchanged for protons (H⁺).
b) Sodium (Na⁺) is exchanged for bicarbonate (HCO₃⁻), and chloride (Cl⁻) is exchanged for oxygen.
c) Potassium (K⁺) is exchanged for chloride (Cl⁻), and bicarbonate (HCO₃⁻) is exchanged for protons (H⁺).
d) Chloride (Cl⁻) is exchanged for water, and sodium (Na⁺) is exchanged for bicarbonate (HCO₃⁻).

Answer 52

Answer: a) Chloride (Cl⁻) is exchanged for bicarbonate (HCO₃⁻), and sodium (Na⁺) is exchanged for protons (H⁺).

Question 53

What is the key difference between active transport in freshwater fish and saltwater fish?
a) Freshwater fish actively excrete ions, while saltwater fish actively absorb them.
b) Freshwater fish absorb chloride ions, while saltwater fish excrete chloride ions.
c) Both freshwater and saltwater fish excrete bicarbonate ions through their gills.
d) Saltwater fish rely entirely on passive transport, while freshwater fish use active transport.

Answer 53

Answer: b) Freshwater fish absorb chloride ions, while saltwater fish excrete chloride ions.