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Water and Life. The Hydrologic Cycle. Water cycles through both biotic and abiotic cycles 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….

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Presentation Transcript
the hydrologic cycle
The Hydrologic Cycle
  • Water cycles through

both biotic and abiotic

cycles

  • 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….

chemical properties
Chemical Properties

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.

the universal solvent
The Universal Solvent

Water dissolves more polar substances than other liquid and all without reacting to them!

  • Ions like Ca+, Fe+; necessary for nerves, muscles
  • Ionically bonded substances like NaCL
  • Organic molecules like sugars, that are required for the processes of life…
physical properties
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.

density
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…

temperature
TEMPERATURE

One of the most important roles of water is the ability to retain enormous amounts of 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 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.

dissolved oxygen
Dissolved Oxygen

One negative effect of higher water temperatures is that it holds less dissolved oxygen. 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. The cooler the water the more oxygen it can hold.

WHY?

Cooler water traps dissolved O2

whereas warm water allows more

spaces where dissolved O2 can

escape into the atmosphere.

cohesion
COHESION

As stated earlier, water is a polar molecule.

As a result water is attracted to itself.

When water molecules are attracted to water molecules the force that results is called COHESION. Water is highly cohesive. WHY?

When water comes in contact with the

atmosphere the attraction between the

molecules becomes uneven so they ‘pull’

together more, drawing the molecules in

tighter forming a sphere.

BUMBLE BEE

surface tension
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.

adhesion
ADHESION

As water molecules cohere to each other, they also are attracted to different polar materials.

When water molecules are attracted to polar molecules of different substances the force that results is called ADHESION.

capillarity
CAPILLARITY

Capillarity occurs due to the forces of cohesion and adhesion. 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 to the walls is stronger than the cohesive forces between the liquid 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?

capillary action in living systems
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

http://www.arkive.org/thorny-devil/moloch-horridus/video-10.html

Capillary Action, as well as, the unique properties of water allow materials to be dissolved and transported without the cell, or organism, expending ENERGY!

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