Water, Water, Everywhere and Nary a Drop to Drink

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Water, Water, Everywhere and Nary a Drop to Drink

• The Rime of the Ancient Mariner
• Coleridge, 1797

Last week Over 70 of the earths surface is
covered by water Today Water is a limiting
resource for pretty much everything
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Water Availability

• Organisms can gain or lose water
• Partly determined by concentration gradient
• Water moves down the gradient

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Water Content of Air

• Relative Humidity - quantity of water vapor in
  air
• RH Water vapor density X 100
• Saturation water vapor density
• Water vapor pressure - pressure exerted by water
  vapor in air
• Vapor pressure deficit - the relative saturation
  of air with water

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Determining the Gradient

• Terrestrial animals - vapor pressure deficit
• Aquatic animals - relative osmolarity
• Terrestrial plants - water potential

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Terrestrial Animals -VPD
? Vpd ? ability of air to take up water
In dry air - evaporation increases In wet air -
evaporation decreases
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Terrestrial Plants - Water Potential

• Plants gain and lose water
• Moves along gradient of water potential from high
  to low
• Will go from plant --gt air due to vpd
• Need it to go
• Soil -- Plant -- Air

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Water Movement in Aquatic Environments

• Diffusion - move down concentration gradients
• Osmosis - diffusion of water across a
  semipermeable membrane

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Aquatic Animals - Osmolarity

• Water still moves down gradient
• ? solutes in water ? osmolarity
• Water goes low osmolarity to high
• Isosmotic - no change
• Hypoosmotic - lose water
• Hyperosmotic - gain water

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Aquatic Animals
-
Water stored

Water gain
Water loss
Osmosis Secretions/ excretions
Drink Food Osmosis

• Fish are not waterproof!

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Freshwater vs. Marine Bony Fish
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Marine Cartilagenous Fish

• Same problems as marine teleosts
• Barely hyperosmotic
• urine

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Terrestrial Animals
-
Water stored

Water gain
Water loss
Evaporation Secretions/ excretions
Drink Food Absorb
Can alter all of these to maximize water
conservation!
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Water Regulation on Land
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Water Acquisition by a Desert Beetle
Obtains most of its water from fog Loses most of
its water through evaporation
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Water Acquisition

• Merriams Kangaroo Rat
• Drinking
• Eating food
• Metabolic water -
• water released
• during cellular
• respiration

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Water Conservation

• Lower evaporation

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Water Conservation

• Increase gain

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Water Conservation

• Alter secretions

Ammonia Urea Uric Acid
Med Lo Concentration Lo Med Hi Water
loss Hi Med Lo
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Uric Acid
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Terrestrial Plants
-
Water stored

Water gain
Water loss
Evaporation Secretions Repro structures
Absorb-roots Absorb-air
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Water Conservation

• ? Evaporation

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Water Conservation

• Increase absorption

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Water Conservation

• Less leaf area per length of root
• Drop leaves in response to drought
• Produce leaves in response to soaking rain the
  shed them when desert dies out.