Lec 8- water constraints Flashcards
What kills humans?
dehydration
- increase in temps outside of tolerance leads to water loss which kills them
How much of a human is water?
50-90%
water content of human male?
60%
water content of jellyfish?
95%
water availability?
planet hostile to organisms bc water is limited
- limited esp in desert environments but is limiting in all
water budget
- organisms regulate internal water concentration by balancing water inputs w outputs
- inputs and outputs differ b/w plants and animals and b/w terrestrial and aquatic animals
water budget eqn
main avenues of water regulations
Wi= Wd - Ws +/- Wo
internal water, drinking, secretion, osmosis
salinity in aquatic sys
regulation of water important for aquatic organisms b/c diff salt concentrations in aquatic sys
- fresh = 5 ppt
- estuaries = 10-25 ppt (brackish water)
- oceans = 35 ppt
saline and brackish
salt marshes and lakes in eastern AB
- lakes display a wide range of salinity and diff ion content
osmolarity
osmotic concentration
- refers to amount of solute and water in a solution in relation to reference sys
- water moves down water gradient through membrane and twds solutions with higher salt concentrations until water concentration is equalozed
hypoosmotic
low solute and high water
hyperosmotic
high solute and low water
isosmotic organism
organism has same water concentration as environment
hyperosmotic
organism has lower water concentration as environment
- higher concentration of solute inside
- can become overflushed with water
hypoosmotic
organism has higher water concentration
freshwater fish
most are hyperosmotic
- internal water concentration is lower in external environment
- risk surplus water inflow and loss of salts
freshwater fish
do not drink water
excrete excess internal water- large amounts of dilute urine
- replace salts by absorbing sodium/chloride in gills by ingesting food
marine fish
most are isosmotic
- internal body concentration of salts and water equivalent to external environment
many marine fish = hypoosmotic
- risk loss of water and surplus salt intake through gills
- drink to counteract dehydration
- specialized chloride cells in gills to rid of excess salts
sharks/skates
slightly hyperosmotic
- retain urea in blood to avoid osmotic water loss
- surplus water gained through gills is counteracted by urea production in kidneys
- when sharks die the urine is broken down into ammonia
anadromous
acclimate to salinity of new environment
- born in freshwater but spends most of life in sea then returns to freshwater to spawn
- salmon, smelt, shad, striped bass, sturgeon
- most common
catadromous
lives in freshwater but spawns in salt
- most eels
salmon
anadromous
- cope w changes in salinity and water concentration through shifting secretion cells from taking in salt to freshwater
to
excreting salt in marine
water regulation eqn - animals
Wi = Wd + Wf + Wa - We - Ws
drinking, food, air, evaporation, secretion
water regulation eqn - plants
Wi = Wr + Wa - Wt - Ws
roots, air, transpiration, secretion
how does water go up plants?
vascular plants gain water through root uptake
water vapour density
quantity of water vapor that air actually holds
saturation water vapor density
quantity of water vapor that air can potentially hold
water vapor pressure
pressure exerted by water vapor in air
saturation water vapor pressure
total pressure exerted by water vapor in water-saturated air
does cold air hold less or more water vapor?
less
- low water vapor pressure
does warm air hold less or more water vapor?
more
- higher water vapor pressure
water potential
ability of water to do work
- water moves from high to low water potential
- if there are diff in water potential, water will move
- usually neg value
- ranges from 0 to -100
- the more neg, the lower the water potential
water potential eqn
pure water + gravity + solute (osmotic pressure) + humidity + matric (matric pressure) + pressure (sum of extraneous pressures)
water potential in plants
tree canopy: low water potential (most neg)
tree trunk: low to moderate water potential
roots: medium to high water potential
soil: high water potential
- potential becomes more neg allowing water to get pulled up and resist gravity as it goes up tree
water acquisition - terrestrial
deep roots is a strategy to acquire water
deepest in dry climates
water acquisition - animals
food and drinking
from respiration
water conservation
thick waxy cuticles
hard layer covering epidermis of plants and body and shells
camels and cacti water conservations
cacti: stores in trunks and arms
camels: water stored in blood stream
efficient kidney: urine highly concentrated and thick
kangaroo rats and camels water conservation
low moisture feces
burrows = cooler and less transpiration
water conservation- leaves
wilting
- reduce water loss and SA decreases during prolonged water stress and drop in turgor pressure
