biology 205 6
TRANSCRIPT
Biology 205Ecology and Adaptation
Lecture 6:Water relations
Dr. Erik D. Davenport
Learning Outcomes
Water Availability – what determines it? Water Content In the
– Water content in air – humidity– Water content in water -- osmosis
Water Regulation on Land– Water Acquisition and conservation by Plants and
Animals on the Land Water and Salt Balance in Aquatic
Environments
Water availability
Water Concentration
Water is not pure in the environments.
There are many substrates that dissolve into water
and dilute water (less water concentration).
Water availability
What determine whether an organism tends to lose water or gain water from the environment?
The tendency of water to move down water concentrations, Water will move from high water concentration place to low water concentration
place.
Water content of Air
The water in the air (water content of air) is mostly from evaporation
Evaporation accounts for much of water lost by terrestrial organisms.
How is the water content of air measured?
The quantity of water vapor in the air is expressed conveniently in relative terms:
Relative humidity = (x 100)
Water vapor density is measured as the amount of water vapor per unit volume of air (how much water in the air).
Saturation water vapor density is measured as the quantity of water vapor air can potentially hold (how much water the air can hold).
Temperature strongly influence the relative humidity -- Warm air hold more water vapor than cold air!!!!
density or water vapSaturationdensityr water vapo
Relative Humidity
Which color represents water vapor density?
Which color represents saturation water vapor density?
True or False?
If the water content (water vapor density) in the air is constant. Increasing of the air temperature will cause the increase of relative humidity.
This statement is True or False?
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Relative humidity and evaporative water lossFigure 5.3
5-3
Low relative humidityStronger evaporation
High relative humidityweak evaporation
Water movement in the aquatic environments
Sounds silly…. However, in aquatic environment, water also moves
down a concentration gradients. The salt in the water dilutes the water. From this perspective, water is more concentrated in
freshwater than sea water. The relative concentration of water strongly influence
the biology of the organisms live in them.
Water osmosis
The fluids in the body of organisms contain water and solutes (salt, inorganic ions and amino acids.)
They are separated from the external environment by a permeable membrane.
If there is a water concentration gradients: The water will move down the concentration
gradient, this water movement is called diffusion, also called osmosis.
Three kinds of aquatic organisms
Isosmotic organisms: the organisms with body fluids containing the same concentration of water as the external environments.
Hypoosmotic organisms: organisms with body fluids containing high concentration of water than external environment. Water move out from the body.
Hyperosmotic organisms: organisms with body fluids containing a lower water concentration than the external medium. And water move into the body.
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Isosmotic, hyperosmotic, and hypoosmotic aquatic organismsFigure 5.4
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Water movement between plant and soils
Water moving from the soil through aplant and into atmosphere flows down a gradient of water potential
(still water concentration)
Water regulation on the land
Terrestrial plants and animals regulate their internal water by balancing water acquisition
against water loss
Potential water lose:– Evaporation– Reduce access to replacement of water
Water regulation by terrestrial animals
Water within the body is a function of: Water gain:
– Water taken by drinking– Water taken in with food– Water absorb from the air
Water loss:– Water lost by evaporation– Water lost with various secretions and excretions in
including urine, mucus, and feces.
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Water gains/losses by terrestrial plants and animalsFigure 5.8
5-8
Water acquisition by animals
most terrestrial animals satisfy their need for water by drinking or taking water in with food. However, under water limiting environments, they have evolved adaptation for living in arid environments.– Behavioral activities– Metabolic water (metabolize the carbohydrates,
proteins to produce the water)
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Fog harvesting by desert beetleFigure 5.9
5-9
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Water balance in kangaroo ratFigure 5.11
5-11 Source: Schmidt-Nielsen 1964
Water acquisition by plants
In the dry climates, plant roots tend to grow deeper in the soil and to constitute a greater proportion of plant biomass.
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Desert living approaches in dissimilar organismsFigure 5.21
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Dissimilar Organisms with Similar Approaches to Desert Life
Camels– Can withstand water loss up to 20%.
Face into sun to reduce exposure. Thick hair: Increased body temperature lowers heat
gradient. Saguaro Cactus
– Trunk / arms act as water storage organs.– Dense network of shallow roots.– Reduces evaporative loss.
Water and salt balance in aquatic environments
Marine and freshwater organisms use complementary mechanisms for water and salt regulation.
Most marine invertebrates maintain an internal concentration of solute equivalent to that in the seawater around them. (isosmotic organisms)
Sharks, skates generally elevate the concentration of solutes in their blood to levels slight hyperosmotic to seawater. So they slowly gain water through osmosis, and had to excrete excess water through urine.
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Osmoregulation by sharksFigure 5.27
5-24
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Osmoregulation by marine fish and mosquitoesFigure 5.28
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In contrast to most marine invertebrates and sharks, marine bony fish have body fluids that are strongly hypoosmotic (less salts) to the surrounding medium.
They will lose the water to the environments. Marine bony fish make up this by drinking. However, they have the specialized cell at the
gill to excrete the excess salts to the surrounding seawater.
Other Marine fishes -- Marine bony fish
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Osmoregulation by freshwater fish and mosquitoesFigure 5.29
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Freshwater fish and invertebrates
Freshwater fish and invertebrates are hyperosmotic They have body fluids that contains more salts and
less water than the surrounding medium. Water diffuse inwards and salt diffuse outward
across their gills. Excrete excess internal water as large quantities of
dilute urine. They use the specialized cells at gills to absorb the
salt.