1. Water and Life

2. The Hydrologic Cycle Water cycles through both biotic and abiotic
environment
Water exists on Earth
in 3 states at the same time:
solid, liquid and gas.
Of all the water cycling
through the environment
only about 1% is available
for living systems….

4. Which apply to all living organisms?

5. The chemistry of water makes it a very unique compound.
CHEMICAL PROPERTIES
The chemistry of water makes it a very unique compound.

6. Chemical Structure 2 hydrogen and 1 oxygen covalently bonded. H2O
Due to atom size difference;
H’s valence electrons spend
more time around the O
as a result, the H’s become
net (+)
The O, gaining 2
electrons from each H,
becomes net (-).
The molecule acts like a magnet
with a (+) and a (-) end…it is POLAR.

7. The Universal Solvent
Water dissolves more polar substances than other liquid and all without reacting to them!
Ions like Ca+, Fe+ , K+; necessary for nerves, muscles
Ionically bonded substances like NaCL
Organic polar molecules like mono and disaccharides, that are required for the processes of life…

8. PHYSICAL PROPERTIES
Due to its polarity, water is strongly attracted to itself. This results in the many unique physical characteristics of water that enable life to exist.

9. DENSITY
Density is the amount of matter in a given space. Water is the only substance who’s solid state is LESS dense than its liquid state. As a result, ice floats! WHY? As water freezes the polar molecules form a lattice shape which increases its volume, but, decreases its density. This is why water pipes crack in winter! Ice layers help to insulate the water beneath allowing life in temperatures well below freezing, floating ice sheets moderate climate by reflecting heat back into the atmosphere…

10. TEMPERATURE
One of the most important roles of water is the ability to retain enormous amounts of heat energy with only a little change in its own temperature. WHY?
As water absorbs heat energy
its molecules increase in motion, only
until all the H bonds between the
molecules are broken will water
change phase, and that takes time.
As a result…
Large bodies of water retain large amounts of heat moderating climate which ensures the survival of marine life.
Chemical reactions and solubility rates increase.
Internal temperatures of organisms remain more stable even when external temperatures vary…
which means ENERGY does not have to be expended by the cell or organism to maintain homeostasis.

11. Dissolved Oxygen
As atmospheric temperatures increase water temperatures also increase…one negative effect of higher water temperatures is that it holds less dissolved oxygen. The cooler the water the more oxygen it can hold. WHY? Cooler water traps dissolved O2 whereas warm water breaks H bonds allowing more trapped O2 to escape into the atmosphere. Even though the water molecule is composed of the element oxygen, this is not what the organisms that live in water use… they need dissolved free oxygen, so cool to moderate water temperatures are best.

12. COHESION As stated earlier, water is a polar molecule.
As a result water is strongly attracted to itself.
When water molecules are attracted to water molecules the force that results is called COHESION. Water is highly cohesive. WHY?
Where water molecules come in contact with the atmosphere
the attraction between the water molecules becomes uneven
The polarity ‘pulls’ them together tighter
drawing the molecules in
toward center… this is why
water drops are spheres.
COCONUT

13. Surface Tension
The cohesive force of water is high where water comes in contact with the atmosphere. This results in the phenomenon; surface tension. The surface of the water is slightly “thicker” than the water below. WHY?
The molecules at the surface do not have
other water molecules on all sides of them
and consequently they cohere more strongly
to those directly below and to the sides.

14. ADHESION
As water molecules cohere to each other, they are also highly attracted to different polar materials and surfaces. When water molecules are attracted to polar molecules of different substances the force that results is called ADHESION.

15. CAPILLARITY The height to which capillarity will
Capillarity occurs due to the interaction of cohesive and adhesive forces. Adhesion of water to the walls of a vessel will cause an upward force on the liquid at the edges resulting in a meniscus. Capillary action occurs when the adhesion of water molecules to a curved surface is stronger than the cohesive forces between the water molecules.
The height to which capillarity will
take water in a uniform circular
tube is limited by surface tension
and, of course, gravity.
Why is this important to life?

16. Capillary Action in Living Systems
Allows water to move high into trees.
Blood to continue to flow great
distances from heart
Moss to ‘wick’
moisture into cells
Lizards to ‘drink’ without moving
All of the unique properties of water enable materials to be dissolved and transported, heat to be conserved and all without the cell, or organism, expending ENERGY to do it!