Lecture 8

Question 1

Humans and other mammals can tolerate how much dehydradtion

Answer 1

~12-14%

Question 2

Most organisms are what percent in water?

Answer 2

50-90%

Question 3

Water budgets - aquatic organisms

Answer 3

Water (internal) = Water gain (drinking) - Water loss (secretion) + or - Water (osmosis)

Question 4

Salinity in aquatic systems

Answer 4

Freshwater - 5 ppt
Estuaries - 10-25 ppt
Oceans - 35 ppt
Lakes - 1-400 ppt

Question 5

What’s Diffusion

Answer 5

movement of soluble salts or water due to random movement of particles (down a concentration gradient)

Question 6

What’s Osmosis

Answer 6

Similar to diffusion but involves movement across a semipermeable membrane

Question 7

What’s Hypoosmotic

Answer 7

low solute concentration, high water concentration
- prefix relates to [solute]

Question 8

What’s Hyperosmotic

Answer 8

High solute concentration, low water concentration
- prefix relates to [solute]

Question 9

What’s Isosmotic

Answer 9

same solute and water concentration
- prefix relates to [solute]
- iso means equal
- most marine fish and invertebrates

Question 10

Osmolarity

Answer 10

Refers amount of solute/water in an organism in relation to its environment

Question 11

Hypoosmotic (some) marine organisms

Answer 11

• internal [salt] is lower and [water] is higher compared to environment
• risk dehydration and surplus salt intake through gills, therefore drink constantly, low urination rates, excess salt excreted through specialized chloride cells

Question 12

Most Freshwater organisms are hyperosmotic

Answer 12

• internal [salt] is higher and [water] is lower compared to environment
• risk is too much water enters organism
• solution: produce high amounts of dilute (minimize salt loss) urine

Question 13

Relationship between [salt] and [water]

Answer 13

• inverse relationship, if water is moving in, salt is moving out and vice versa
• high salt conc. equals low water conc. and vice versa

Question 14

What’s Acclimation

Answer 14

It’s a reversible physical change due to an organism being placed in a new environment

Question 15

What’s Anadromous

Answer 15

• Fish born in fresh water, spend most of its life in the sea, returns to freshwater to spawn
• i.e. salmon, striped bass

Question 16

How do salmon cope with changes in salinity

Answer 16

By shifting their secretion cells
freshwater = take in salt (hypoosmotic)
ocean = excrete salt (hyperosmotic)

Question 17

What’s Catadromous

Answer 17

• Fish born in the ocean, spends most of its life in fresh water, returns to ocean to spawn
• i.e eels

Question 18

Water Budgets - Terrestrial Systems (Plants)

Answer 18

Water (internal) = +Wr (gained from roots) + Wa (from air) - Wt (to transpiration) - Ws (to secretion)

Question 19

Water Budgets - Terrestrial Systems (Animals)

Answer 19

Water (internal = + Wd (from drinking) + Wf ( from food) + Wa (from air) - We (to evaporation) - Ws (to secretion)

Question 20

Water Potential

Answer 20

Water moves from high to low water potential
- usually a negative value
- different from osmosis because of pressure

Question 21

Water Vapour pressure

Answer 21

As temperature of air increases, its ability to hold water vapour increases = high water vapour pressure
- cold air can hold less water vapour = low water vapour pressure

Question 22

Saturation water vapour density

Answer 22

maximum amount of water vapour that air can potentially hold

Question 23

Water potential in plants

Answer 23

Soil -> Roots -> Tree trunk -> Tree Canopy -> air
Highest to lowest water potential

Question 24

How do terrestrial animals minimize water loss

Answer 24

conservation of urine, feces and sweat
behavioural adaptations i.e burrows

Question 25

How do terrestrial plants reduce water loss

Answer 25

wilting (reduces surface area= lower transpiration and photosynthesis)