Name:______________________________
Pd:_____Date:_______________________
WATER AND ITS ROLE IN BIOLOGY
Water is in LIQUID form at most temperatures on the Earth’s Surface.
Water expands when it freezes, enabling it to float.
Water covers ~75% of the Earth’s surface.
Most abundant compound in nearly all organisms
Greatest SOLVENT in the world Known as the Universal Solvent
Uneven distribution of electrons makes it POLAR :
slightly positive at one end and slightly negative at the other
Because of its POLARITY it has strong attractive forces other polar molecules
Cohesive Force- attraction of molecules of the same substance, why some insects can “walk on water”
Adhesive Force- attraction of molecules of different substances, this is the force that causes water to
rise up in a narrow tube against the force of gravity. This effect is called capillary action. Example: water
moving from the ground intoa plants roots and up to the stems and leaves.
CHART OF BIOLOGICAL IMPORTANCE OF WATER:
PROPERTY OF WATER
Ice is less dense than water
SIGNIFICANCE FOR LIVING ORGANISMS
Ice floats and also insulates the underlying water
high surface tension
Water forms droplets on surfaces and runs off
Low viscosity
Liquid at room temperature
Water flows through very small spaces and
capillaries
Liquid medium for aquatic life and inside cells
Colourless with a high transmission of visible light
Light penetrates tissue and aquatic environments
Strong cohesive properties and high tensile
strength
Many substances can dissolve in water (known as
the universal solvent)
Water can be lifted and does not pull apart easily
Significant amounts of energy are required before
water will change its state
Medium for the chemical reactions of life
(metabolism) water is the main transport medium
In organisms
Contents of cells are unlikely to freeze
In order for water to evaporate it must absorb a
large amount of energy
Water can absorb a lot of energy for only a small
rise in temperature
Heat is lost by evaporation of water. Sweating and
transpiration causes rapid cooling
Aquatic environments are thermally stable.
Organisms have stable internal temperatures
when the external temperature is fluctuating.
Questions:
1. In the space below, draw a water molecule indicating its polarity.
2. With respect to aquatic ecosystems, explain the likely biological consequences if ice was DENSER
than liquid water:
3. For each example, state the property of water and explain its biological importance
a. Clarity of seawater
b. Water travelling up xylem tissue in plants
c. Transport of glucose around the human body
4. Create a concept map on the properties of water. Include the following terms: hydrogen bonds,
polarity, cohesion, adhesion, capillary action, solvent, solute, hydrophobic, and hydrophilic
Name:______________________________
Pd:_____Date:_______________________
WATER AND ITS ROLE IN BIOLOGY
Water is in ___________ form at most temperatures on the Earth’s Surface.
Water ________________ when it freezes, enabling it to ______________.
Water covers _________ of the Earth’s surface.
Most abundant __________________ in nearly all organisms
Greatest SOLVENT in the world Known as the ___________________________________
Uneven distribution of electrons makes it _________________:
slightly positive at one end and slightly negative at the other
Because of its POLARITY it has strong attractive forces other __________________________
______________- attraction of molecules of the same substance, why some insects can “walk on water”
________________________- attraction of molecules of different substances, this is the force that
causes water to rise up in a narrow tube against the force of gravity. This effect is called capillary action.
Example: water moving from the ground intoa plants roots and up to the stems and leaves.
CHART OF BIOLOGICAL IMPORTANCE OF WATER:
PROPERTY OF WATER
Ice is less dense than water
high surface tension
Low viscosity
Liquid at room temperature
Colourless with a high transmission of visible light
Strong cohesive properties and high tensile
strength
Many substances can dissolve in water (known as
the universal solvent)
Significant amounts of energy are required before
water will change its state
SIGNIFICANCE FOR LIVING ORGANISMS
In order for water to evaporate it must absorb a
large amount of energy
Water can absorb a lot of energy for only a small
rise in temperature
Questions:
5. In the space below, draw a water molecule indicating its polarity.
6. With respect to aquatic ecosystems, explain the likely biological consequences if ice was DENSER
than liquid water:
7. For each example, state the property of water and explain its biological importance
d. Clarity of seawater
e. Water travelling up xylem tissue in plants
f. Transport of glucose around the human body
8. Create a concept map on the properties of water. Include the following terms: hydrogen bonds,
polarity, cohesion, adhesion, capillary action, solvent, solute, hydrophobic, and hydrophilic