Lecture 8 Flashcards
Humans and other mammals can tolerate how much dehydradtion
~12-14%
Most organisms are what percent in water?
50-90%
Water budgets - aquatic organisms
Water (internal) = Water gain (drinking) - Water loss (secretion) + or - Water (osmosis)
Salinity in aquatic systems
Freshwater - 5 ppt
Estuaries - 10-25 ppt
Oceans - 35 ppt
Lakes - 1-400 ppt
What’s Diffusion
movement of soluble salts or water due to random movement of particles (down a concentration gradient)
What’s Osmosis
Similar to diffusion but involves movement across a semipermeable membrane
What’s Hypoosmotic
low solute concentration, high water concentration
- prefix relates to [solute]
What’s Hyperosmotic
High solute concentration, low water concentration
- prefix relates to [solute]
What’s Isosmotic
same solute and water concentration
- prefix relates to [solute]
- iso means equal
- most marine fish and invertebrates
Osmolarity
Refers amount of solute/water in an organism in relation to its environment
Hypoosmotic (some) marine organisms
- 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
Most Freshwater organisms are hyperosmotic
- 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
Relationship between [salt] and [water]
- inverse relationship, if water is moving in, salt is moving out and vice versa
- high salt conc. equals low water conc. and vice versa
What’s Acclimation
It’s a reversible physical change due to an organism being placed in a new environment
What’s Anadromous
- Fish born in fresh water, spend most of its life in the sea, returns to freshwater to spawn
- i.e. salmon, striped bass
How do salmon cope with changes in salinity
By shifting their secretion cells
freshwater = take in salt (hypoosmotic)
ocean = excrete salt (hyperosmotic)
What’s Catadromous
- Fish born in the ocean, spends most of its life in fresh water, returns to ocean to spawn
- i.e eels
Water Budgets - Terrestrial Systems (Plants)
Water (internal) = +Wr (gained from roots) + Wa (from air) - Wt (to transpiration) - Ws (to secretion)
Water Budgets - Terrestrial Systems (Animals)
Water (internal = + Wd (from drinking) + Wf ( from food) + Wa (from air) - We (to evaporation) - Ws (to secretion)
Water Potential
Water moves from high to low water potential
- usually a negative value
- different from osmosis because of pressure
Water Vapour pressure
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
Saturation water vapour density
maximum amount of water vapour that air can potentially hold
Water potential in plants
Soil -> Roots -> Tree trunk -> Tree Canopy -> air
Highest to lowest water potential
How do terrestrial animals minimize water loss
conservation of urine, feces and sweat
behavioural adaptations i.e burrows
