Osmotic Homeostasis

Question 1

Homeostasis

Answer 1

Maintenance of internal environment to maintain stable PH, ion concentrations, temperature etc.

Question 2

Osmosis

Answer 2

The passive movement of water from an area of low solute concentration to high solute concentration

Question 3

Osmoregulation / Osmotic Homeostasis

Answer 3

Maintaining water-ion balance within a physiologically viable range

Question 4

Osmoregulator

Answer 4

Organism can regulate solutes of its body at a higher or lower concentration than the external environment

Question 5

Osmoconformer

Answer 5

Osmolarity of body fluids = osmolarity of external environment

Question 6

Isosmotic

Answer 6

Osmolarity inside = osmolarity outside

Question 7

Hypoosmotic

Answer 7

Osmolarity inside < osmolarity outside

Question 8

Hyperosmotic

Answer 8

Osmolarity inside > osmolarity outside

Question 9

In what ways can water and ions become available to seabirds (input)?

Answer 9

• Food
• Drink
• Digestion

Question 10

In what ways can water and ions be expelled from the bodies of seabirds (output)?

Answer 10

• Evaporation (cutaneous or respiratory)
• Excretion
• Kidneys
• Intestines
• Salt glands

Question 11

What is cutaneous evaporation?

Answer 11

Evaporation of water through the skin (ions cannot evaporate through the skin in seabirds (no sweat glands))

Question 12

What is respiratory evaporation?

Answer 12

Evaporation of water through the water vapor of exhaled air

Question 13

How do seabirds osmoregulate?

Answer 13

Seabirds are hypoosmotic and osmoregulate by:
1. Prey selection
2. Minimizing saltwater intake
3. Filter feeding

Question 14

Why is prey selection important in seabirds?

Answer 14

• Certain types of prey are higher in sodium
• Feeding on more salty food will result in the enlargement of the salt glands

Question 15

How do seabirds minimize salt water intake?

Answer 15

• Filter feeding
• Adherent water is removed from prey items before swallowing

Question 16

How do seabirds filter feed?

Answer 16

Excess water is removed from food by compression between tongue and palate

Question 17

Describe the solute concentration of the urine of seabirds

Answer 17

Urine is hyperosmotic to plasma

Question 18

What is the purpose of salt glands?

Answer 18

Allow seabirds to drink salt water by secreting a salt solution that is more concentrated than seawater and plasma

Question 19

How does counter current exchange remove salt ions from the blood?

Answer 19

• Capillaries and veins are less salty than arteries
• Arteries (salty) empty into central duct of secretory tubule of salt gland
• Central duct drains into nasal cavity

Question 20

Describe the concentration of salt glands when they are inactive

Answer 20

Salt gland secretions are isosmotic to plasma

Question 21

Describe the concentration of salt glands when they are active

Answer 21

Salt gland secretions are hyperosmotic to plasma and seawater

Question 22

Describe the properties of uric acid

Answer 22

• Non-toxic
• Does not dissolves easily in water
• Energetically costly to produce
• Expels nitrogenous waste

Question 23

Why is uric acid important?

Answer 23

It reduces the overall need for water by expelling salts ingested from food and water from the body

Question 24

How is salt gland activity affected by temperature?

Answer 24

Salt glands have the lowest mass at intermediate temperatures

Question 25

How does reducing the rate of glomular filtration aid seabirds during water scarcity?

Answer 25

Reducing GFR produces less urine