Lecture 13: Osmoregulation on Land Part 1

Question 1

What happens to a saltwater fish because it is hyposmotic to the ambient water?
a) Gains water by osmosis and retains salt
b) Loses water by osmosis and gains salt by diffusion
c) Loses salt and water through diffusion
d) Gains both salt and water through active transport

Answer 1

Answer: b) Loses water by osmosis and gains salt by diffusion

Question 2

How do saltwater fish cope with high salt levels in their body?
a) By producing large volumes of dilute urine
b) By holding on to water and producing small amounts of urine rich in Mg and sulfate
c) By excreting large amounts of water with no salts
d) By storing salts in their gills

Answer 2

Answer: b) By holding on to water and producing small amounts of urine rich in Mg and sulfate

Question 3

What process do saltwater fish use to handle monovalent ions like chloride?
a) Passive diffusion through their gills
b) Active transport, which requires energy
c) Filtration through their kidneys
d) Storage in specialized cells

Answer 3

Answer: b) Active transport, which requires energy

Question 4

What is the primary function of gills in fish?
a) To regulate body temperature
b) To exchange oxygen (O₂) and carbon dioxide (CO₂) and regulate ions
c) To filter food from water
d) To store energy

Answer 4

Answer: b) To exchange oxygen (O₂) and carbon dioxide (CO₂) and regulate ions

Question 5

What structure in the gills is used for oxygen and carbon dioxide exchange?
a) Gill arches
b) Secondary lamellae
c) Mitochondria-rich cells
d) NKCC1 transporters

Answer 5

Answer: b) Secondary lamellae

Question 6

What are mitochondria-rich cells in gills also known as?
a) Lamellae cells
b) Chloride cells
c) ATPase cells
d) Filtration cells

Answer 6

Answer: b) Chloride cells

Question 7

What is the role of Na⁺/K⁺ ATPase in gill cells?
a) To facilitate passive diffusion of gases
b) To actively transport sodium and potassium ions
c) To generate oxygen
d) To eliminate waste products

Answer 7

Answer: b) To actively transport sodium and potassium ions

Question 8

What would happen if the sodium-potassium ATPase pump in chloride cells were inhibited?
a) Sodium would accumulate in the blood, reducing chloride excretion.
b) Chloride excretion would increase, causing a loss of ions.
c) The cell would switch to passive transport mechanisms.
d) Potassium levels in the cell would remain unaffected.

Answer 8

Answer: a) Sodium would accumulate in the blood, reducing chloride excretion.

Question 9

If a fish experiences low environmental sodium levels, how might its chloride cells respond?
a) Increase ATPase activity to pump more ions
b) Reduce ATPase activity to conserve energy
c) Stop chloride excretion entirely
d) Begin absorbing chloride from the water

Answer 9

Answer: a) Increase ATPase activity to pump more ions

Question 10

Which step is responsible for creating a favorable gradient for sodium to enter the cell?
a) Sodium-potassium ATPase activity
b) Passive diffusion of potassium out of the cell
c) Passive diffusion of chloride into the water
d) Increased mitochondrial activity

Answer 10

Answer: a) Sodium-potassium ATPase activity

Question 11

In the Na⁺/K⁺ ATPase pump, for every ATP molecule used, how many sodium and potassium ions are exchanged?
a) 3 sodium out, 2 potassium in
b) 2 sodium out, 3 potassium in
c) 2 sodium in, 3 potassium out
d) 3 sodium in, 2 potassium out

Answer 11

Answer: a) 3 sodium out, 2 potassium in

Question 12

What percentage of a marine teleost fish’s metabolic rate is used for ionoregulation?
a) 2-5%
b) 8-17%
c) 25-30%
d) 50-60%

Answer 12

Answer: b) 8-17%

Question 13

What is the primary driver for the movement of sodium out of the blood during paracellular transport?
a) The buildup of negative charges in the gill cells
b) The direct use of ATP by sodium channels
c) The chloride gradient in the water
d) Mitochondrial production of ATP

Answer 13

Answer: a) The buildup of negative charges in the gill cells

Question 14

How does transcellular chloride transport differ from paracellular sodium transport?
a) Chloride transport requires ATP, while sodium transport occurs between cells passively.
b) Sodium transport relies on ATPase, while chloride transport does not.
c) Chloride transport occurs between cells, while sodium transport is transcellular.
d) Both use the same electrochemical gradient but in opposite directions.

Answer 14

Answer: a) Chloride transport requires ATP, while sodium transport occurs between cells passively.

Question 15

Why do fish migrating from freshwater to saltwater show an increase in NKCC1 and Na⁺/K⁺-ATPase abundance?
a) To absorb more oxygen for osmoregulation
b) To actively excrete excess salts in saltwater
c) To store more sodium in their cells
d) To increase water uptake through osmosis

Answer 15

Answer: b) To actively excrete excess salts in saltwater

Question 16

What happens to the expression of NKCC1 and Na⁺/K⁺-ATPase when a saltwater fish is transferred back to freshwater?
a) Both are upregulated to retain salts
b) Both are downregulated to conserve energy
c) NKCC1 increases, while Na⁺/K⁺-ATPase remains unchanged
d) Na⁺/K⁺-ATPase increases, while NKCC1 decreases

Answer 16

Answer: b) Both are downregulated to conserve energy

Question 17

If a trout were unable to upregulate Na⁺/K⁺-ATPase after transitioning to saltwater, what is the most likely outcome?
a) It would retain more sodium, leading to dehydration.
b) It would lose excess water, causing osmotic shock.
c) It would be unable to actively excrete sodium, leading to ion imbalance.
d) It would passively excrete chloride through paracellular transport.

Answer 17

Answer: c) It would be unable to actively excrete sodium, leading to ion imbalance.

Question 18

A scientist keeps a trout in freshwater for 30 days and then transfers it to saltwater. What trend in gill protein expression is expected after the transfer?
a) Immediate and permanent decrease in NKCC1 and Na⁺/K⁺-ATPase
b) Gradual increase in NKCC1 and Na⁺/K⁺-ATPase over 60 days
c) Immediate increase in NKCC1 followed by a decrease in Na⁺/K⁺-ATPase
d) No change in protein expression

Answer 18

Answer: b) Gradual increase in NKCC1 and Na⁺/K⁺-ATPase over 60 days

Question 19

If the NKCC1 co-transporter in a migratory fish were genetically inhibited, how would its osmoregulatory ability change in saltwater?
a) It would increase passive excretion of salts.
b) It would lose the ability to excrete chloride ions effectively.
c) It would compensate by upregulating paracellular sodium transport.
d) It would rely entirely on passive chloride diffusion.

Answer 19

Answer: b) It would lose the ability to excrete chloride ions effectively.

Question 20

If a fish spends prolonged time in an environment with fluctuating salinity, what strategy might it use to conserve energy?
a) Downregulate proteins during transitions
b) Upregulate proteins regardless of environment
c) Maintain constant osmoregulatory protein levels
d) Rely solely on passive ion diffusion

Answer 20

Answer: a) Downregulate proteins during transitions

Question 21

Why is the kangaroo rat more efficient at conserving water than laboratory rats?
a) It produces more metabolic water per gram of glucose oxidized.
b) It has lower obligatory water losses in urine and feces.
c) It breathes less frequently than laboratory rats.
d) It consumes more water-rich food.

Answer 21

Answer: b) It has lower obligatory water losses in urine and feces.

Question 22

If a kangaroo rat loses 0.14 g of water through urine and a lab rat loses 0.24 g, what is the kangaroo rat’s primary adaptation for water conservation?
a) Greater fecal water loss to compensate
b) Reduced urea excretion in urine
c) Higher metabolic water production
d) Reduced kidney filtration

Answer 22

Answer: b) Reduced urea excretion in urine

Question 23

What is a major problem for tetrapods living in aquatic environments?
a) Excess water absorption through the skin
b) Gaining salt while eating
c) Increased metabolic water production
d) Limited oxygen diffusion in water

Answer 23

Answer: b) Gaining salt while eating

Question 24

How do air-breathing tetrapods reduce water loss via respiration?
a) Through specialized gills
b) By using blowholes and labyrinth nasal passages
c) By excreting salts through nasal glands
d) Through increased metabolic water production

Answer 24

Answer: b) By using blowholes and labyrinth nasal passages

Question 25

Why do seabirds rely on salt glands for osmoregulation?
a) Their kidneys can excrete highly concentrated urine.
b) Their kidneys cannot produce urine more concentrated than their blood.
c) They absorb water directly from seawater.
d) Their gills actively excrete salt.

Answer 25

Answer: b) Their kidneys cannot produce urine more concentrated than their blood.

Question 25

If a sea bird consumes krill, which are isosmotic with seawater, what osmotic challenge does it face?
a) Water absorption through osmosis
b) Salt overload from its diet
c) Reduced respiratory water loss
d) Fecal water conservation

Answer 25

Answer: b) Salt overload from its diet

Question 26

Why do sea turtles and sea birds gain salt while eating jellyfish and krill?
a) These prey items have higher salt content than seawater.
b) Jellyfish and krill are mostly seawater, so they are isosmotic.
c) Their diet promotes passive salt diffusion into the body.
d) They use metabolic water to counter salt gain.

Answer 26

Answer: b) Jellyfish and krill are mostly seawater, so they are isosmotic.

Question 27

The salt solution produced by avian salt glands is typically how much more concentrated than blood plasma?
a) 1–2 times
b) 4–5 times
c) 10–12 times
d) It is equal to blood plasma concentration.

Answer 27

Answer: b) 4–5 times

Question 28

What is the role of secretory tubules in avian salt glands?
a) They absorb salts from seawater.
b) They concentrate salt solutions and direct them to the central canal.
c) They prevent salt from entering the bloodstream.
d) They store metabolic water for later use.

Answer 28

Answer: b) They concentrate salt solutions and direct them to the central canal.

Question 29

What is the primary function of the integumentary system?
a) Excretion of metabolic waste
b) Protection and maintaining body heat
c) Absorption of water from the environment
d) Production of oxygen for respiration

Answer 29

Answer: b) Protection and maintaining body heat

Question 30

What component of the integumentary system is made up of keratin?
a) Sweat glands and sebaceous glands
b) Hair, feathers, scales, and nails
c) Bone and cartilage
d) Blood vessels and capillaries

Answer 30

Answer: b) Hair, feathers, scales, and nails

Question 31

What is the stratum corneum, and what is its primary role?
a) It is the vascular layer of the skin that provides nutrients to cells.
b) It is the thickened, acellular outer layer that prevents water loss and provides protection.
c) It is a muscle layer that regulates body heat.
d) It is the innermost skin layer responsible for keratin production.

Answer 31

Answer: b) It is the thickened, acellular outer layer that prevents water loss and provides protection.

Question 32

How does the integument of amphibians differ from that of mammals?
a) Amphibians have a thicker keratinized outer layer.
b) Amphibian skin is thinner, smooth, and moist with minimal keratinization.
c) Amphibian skin contains a highly vascularized stratum corneum.
d) Amphibians lack an integumentary system.

Answer 32

Answer: b) Amphibian skin is thinner, smooth, and moist with minimal keratinization.

Question 33

What cells in the epidermis produce keratin, and what is their function?
a) Keratinocytes; to form a waterproof and protective barrier
b) Melanocytes; to regulate pigment production
c) Fibroblasts; to strengthen connective tissue
d) Osteoblasts; to support skeletal growth

Answer 33

Answer: a) Keratinocytes; to form a waterproof and protective barrier

Question 34

Why is amphibian skin particularly prone to desiccation?
a) It has a thick stratum corneum.
b) It is thin, smooth, and moist with a very thin stratum corneum.
c) It contains large numbers of salt glands.
d) It has lipids that prevent water loss.

Answer 34

Answer: b) It is thin, smooth, and moist with a very thin stratum corneum.

Question 35

What adaptation allows amphibians to use their skin for respiration?
a) Thick, keratinized skin
b) High vascularization and thin epidermal layers
c) Lipid secretions covering the skin
d) Presence of salt glands

Answer 35

Answer: b) High vascularization and thin epidermal layers

Question 36

What strategy do Phyllomedusa frogs use to reduce desiccation in dry habitats?
a) Thickened keratin layers in their skin
b) Secretion of lipids from skin glands, spread across the body
c) Absorption of water from the air through their skin
d) Reducing their metabolic rate

Answer 36

Answer: b) Secretion of lipids from skin glands, spread across the body

Question 37

How does amniote skin differ from amphibian skin?
a) Amniote skin is thicker, more keratinized, and less permeable to water.
b) Amniote skin contains specialized cells for cutaneous respiration.
c) Amniote skin lacks stratum corneum entirely.
d) Amniote skin absorbs water directly from the air.

Answer 37

Answer: a) Amniote skin is thicker, more keratinized, and less permeable to water.

Question 38

What is the primary role of lipids secreted by the epidermis in amniotes?
a) To serve as an energy reserve
b) To fill gaps in the stratum corneum, acting as a sealant
c) To enable oxygen diffusion through the skin
d) To regulate body temperature

Answer 38

Answer: b) To fill gaps in the stratum corneum, acting as a sealant

Question 39

In amniotes, where does most water loss occur?
a) Through the skin
b) Through respiratory surfaces
c) Through fecal excretion
d) Through urinary excretion

Answer 39

Answer: b) Through respiratory surfaces

Question 40

What structural feature contributes to the diversity of vertebrate skin?
a) Differences in the structure and arrangement of the stratum corneum
b) Presence of unique epidermal glands in each species
c) Variation in blood vessels under the skin
d) Thickness of the hypodermis

Answer 40

Answer: a) Differences in the structure and arrangement of the stratum corneum

Question 41

What is unique about reptilian scales compared to mammalian skin?
a) Reptilian scales are formed by interconnected patches of stratum corneum.
b) Reptilian scales lack keratin entirely.
c) Mammalian skin has no keratinized layers.
d) Reptilian scales are only present on the ventral surface.

Answer 41

Answer: a) Reptilian scales are formed by interconnected patches of stratum corneum.