WETLAND, FOREST & OTHER BIOMES

BIOMES: "A major community of living or-
ganisms; a complex of climax communities
of plants and animals in a major region."
"A major life zone, biotic formation."
"A major ecological community type."

HYDROLOGICAL CYCLE
The water cycle--the unique story of water in all its forms and functions. 2 programs. One completely revised 1999. 31 slides and guides.
EP #173X SLIDES
$54.95

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SAVE OVER $12.00 ON 2 SLIDE SET BUNDLE ORDER EP #173X...........$54.95
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THE WATER CYCLE---EARTH, AIR & LIVING SYSTEMS Order #173..........$42.50
(Revised 1999)

Provides a comprehensive overview of the hydrologic cycle. Details the relative
amounts of water available from various sources, special properties of water, energy flow
as water evaporates, condenses and precipitates, cloud and dew formation, infiltration,
underground water and cave formation, how plants use water, erosion, dams and their
effects, causes of flooding and flood control. Revised text now contains pictures of the
slide images for easy reference. 20 slides and guide.

CONTENT SAMPLE: 27350 The reverse of evaporation is condensation, in
which water changes from the vapor to the liquid phase. Condensation occurs when water
molecules lose kinetic energy, such as when air is cooled. Familiar examples of condensation
include the formation of dew on plants and soil when the air cools at night, or the condensation on
the outer surface of a cold glass.

At any given temperature, air can hold only a certain amount of water vapor, and warm air
can hold more than cool air. Relative humidity is a measure of how close the air is to containing
all the water vapor it can hold at a given temperature. Air is said to be saturated when the relative
humidity is 100 per cent. At saturation no more water vapor can be added to air; any extra
condenses into liquid. This is what happens when air cools, such as when the sun goes down.
Then the atmosphere becomes fully saturated and can no longer hold its burden of water vapor,
the vapor condenses back into a liquid, forming droplets of water.

When this happens at ground level because the saturated air is in contact with colder
objects, dew forms as it did on this spider web. When it happens in the atmosphere, clouds form.
When condensation occurs, the latent heat stored in the water vapor is released into the
surrounding atmosphere.

For any given water concentration, the temperature at which air becomes saturated is
called the dew point. If the dew point for a particular air mass is above 0° C (the melting point of
water), excess water vapor will collect as a liquid, or dew. Condensation from air at a temperature
below 0° C yields frost crystals. Condensation requires something solid on which the water
molecules can collect. Dew and frost form on solid surfaces, but in the atmosphere microscopic
particles of dust, smoke and sea salts serve as nuclei for condensation.

Clouds are caused by the condensation of water vapor on such nuclei. They form when
an air mass is cooled to its dew point. Clouds may remain in the air for considerable periods of
time when a balance exists between the water molecules leaving and those joining their
component droplets.

Eventually clouds are destroyed in one of two ways: an increase in temperature raises
the dew point and the cloud evaporate into water vapor. Or a decrease in temperature causes
more water to condense into cloud droplets. When the droplets get so heavy they can no longer
float in the air, precipitation results. They then fall to the ground as rain, sleet, snow or hail.

REVIEWS: "The content of the script which accompanies the slides is the best this
reviewer has seen in years." Previews.
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THE HYDROLOGICAL CYCLE Order #SS-0900S .............$24.95

Earth is unusual because water exists here in solid, liquid and gaseous phases.
This program traces the cycling of water and soluble minerals through the hydrosphere,
atmosphere and lithosphere. Water and minerals are necessary for life and living
systems have evolved biological cycling mechanisms that mimic the geochemical
cycles. 11 frames and guide. (Filmstrip order #SS-0900F ..............$15.00.)

CONTENT SAMPLE: 7. Green plants synthesize carbohydrates from water and carbon
dioxide using sunlight as an energy source. Actively growing plant tissues have high water
contents, as much as 85-95% of their weights, while dormant seeds may contain only 5-10%
water. The water within plant cells gives them their characteristic turgor (i.e., distention and
resiliency) and acts as a medium for the exchange of materials between cells. Sap is a watery
solution that circulates throughout the plant, carrying inorganic materials from the roots to the
leaves and organic molecules from the leaves to the roots. Water is also the medium through
which plants obtain minerals from their environments. Aquatic plants absorb these nutrients
through their general body surface from the surrounding water. Land plants absorb water and
minerals through their roots.

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RELATED PROGRAMS WORTH NOTING
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WATER, WATER EVERYWHERE Order #C-3100P.........$19.95

Featuring a breakthrough technology that makes CD-ROM-type programs and
images available on a 3.5 in. floppy disk!

An elaborate and detailed presentation on all aspects of the hydrological cycle.
Covers the recycling of water as water vapor and precipitation, weather factors, ground
water, water use by plants and animals and the cycling of minerals from the sea. Very
comprehensive text and 29 images. Additional projects and references. Runs easiest on
IBM PC with Windows 3.1 or higher. HTML format to run under a web browser available
on special order at no extra charge (content complete but some features non-functional).
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~1874-008~ Condensation on spider web. photo by Charles R. Belinky, Ph.D.

Copyright (c) MCMXCVII Educational Images Ltd., Elmira, NY, USA. All rights reserved.

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