Water Constraints

Question 1

How much dehydration can mammals tolerate?

Answer 1

12-14% dehydration

Question 2

What are water budgets?

Answer 2

All organisms regulate their internal water concentration by balancing water inputs with water outputs

Question 3

What are the main avenues of water regulation?

Answer 3

Water gain through drinking
Water loss through secretion
Water loss/gain through osmosis

Question 4

How does deeper water affect salinity?

Answer 4

Deeper = more salt

Question 5

What is osmolarity?

Answer 5

Refers to the amount of solute/water in a solution in relation to a reference system

Question 6

What is a hypoosmotic condition?

Answer 6

Low solute concentration, high water concentration
An organism has higher water concentration than environment

Question 7

What is a hyperosmotic condition?

Answer 7

High solute concentration, low water concentration
Organism has a lower water concentration than environment

Question 8

What is an isosmotic condition?

Answer 8

Same solute and water concentration
Organism has the same water concentration as environment

Question 9

What is the salt-water balance in marine organisms?

Answer 9

Most marine fish and invertebrates are isosmotic

Question 10

What is the salt-water balance in freshwater organisms?

Answer 10

Most freshwater organisms are hyperosmotic
Risk surplus water inflow and loss of salts

Question 11

How does freshwater organisms adapt to freshwater conditions?

Answer 11

Do not drink
Excrete excess internal water
Replace salts by absorbing Na/Cl in gills and by food ingestion

Question 12

What is the salt-water balance in saltwater?

Answer 12

Many saltwater fish are hypoosmotic
Low osmotic pressure in blood
Risk of water loss and surplus salt intake

Question 13

How do saltwater organisms adapt to saltwater conditions?

Answer 13

Drink to prevent dehydration
Low urination rate
Gets rid of excess salt through cells in gills

Question 14

What are sharks/skates and how do they cope with those conditions?

Answer 14

Hyperosmotic
Retain urea in blood to avoid osmotic water loss
Surplus water gain is counteracted with urea production

Question 15

How do anadromous fish acclimate to the salinity of their new environment?

Answer 15

Born in fresh water spends most of its life in the sea and returns to fresh water to spawn

Question 16

How do catadromous fish acclimate to the salinity of their new environment?

Answer 16

Lives in fresh water and enters salt to spawn

Question 17

How do animals gain and lose water?

Answer 17

Gain = drinking, food, air
Loss = evaporation, secretion

Question 18

How do plants gain and lose water?

Answer 18

Gain = roots, air
Loss = transpiration, secretion

Question 19

How do vascular plants gain water?

Answer 19

Through root uptake via water potential, water moves from high to low water potential

Question 20

What is water vapour density?

Answer 20

Quantity of water vapour that air actually holds

Question 21

What is saturation water vapour density?

Answer 21

Quantity of water vapour that air can potentially hold

Question 22

What air can hold more water?

Answer 22

Warm air can hold more water than cold air = high water vapour pressure

Question 23

What is the water potential in all parts of the tree?

Answer 23

Soil>roots>tree trunk>tree canopy

Question 24

What is water acquisition in terrestrial plants?

Answer 24

Acquisition of water in roots is essential for the water pump to work but water is limited in many environments
Deep roots help plants acquire more water

Question 25

What do thick, waxy cuticles do?

Answer 25

Help to avoid water loss

Question 26

What are some ways that organisms might minimize water loss?

Answer 26

Storing water when it is available for use during a drought
Conservation of urine, feces, and sweat
Wilting in plants to reduce transpiration and photosynthesis