Air & Water
Lesson 2
Chapter 6
Conserving Our Resources
Objectives
Summarize
Describe
the importance of air.
the water cycle.
Main Idea
Living things use air and water
to carry out their life processes.
Vocabulary
atmosphere
– the layer of gases
that surround Earth
ozone
layer – a layer of ozone gas
in Earth’s atmosphere that
screens out much of the Sun’s
ultraviolet rays
water
cycle – the continuous
movement of water between
Earth’s surface and the air
precipitation
– water that falls
from clouds to the ground in
the form of rain, sleet, hail, or
snow
watershed
– the region that
contributes water to a river or a
river system
water
table – the upper surface of
the groundwater that lies between
topsoil and tightly packed rocks
precipitation
watershed
water
table
aquifer
reservoir
How is air useful?
Air
makes life possible.
Air
is part of the atmosphere
which consists of nitrogen and
oxygen, also water vapor,
argon gas, and other gases.
It
protects us from meteors and
radiation.
It
is also a source of energy.
Oxygen
Carbon Dioxide Cycle
Oxygen
is necessary for respiration,
the breaking down of food to
produce energy.
Carbon
dioxide is a waste
product of respiration.
Plants
need carbon dioxide to use
in photosynthesis.
Oxygen
is a byproduct.
Earth’s Atmosphere
Plants
need nitrogen to make
proteins.
Nitrogen
is converted into a
chemical form by bacteria which
is usable by plants.
Consumers
eat the plants and
produce waste or die, releasing it
back into the atmosphere or soil.
Clouds
in the atmosphere block
sunlight during the day and trap
heat during the night which
protects life from extreme
temperatures.
Earth’s
atmosphere contains the
ozone layer.
It prevents 99% of the sun’s
ultraviolet rays.
Wind
is a source of energy.
Wind
moves the blades of a
windmill driving a wind turbine, a
machine that generates
electricity.
Wind
is also used in recreation.
Quick Check
Summarize
Describe how Earth’s atmosphere
sustains life.
The atmosphere contains oxygen
and carbon dioxide for respiration
and photosynthesis.
It regulates air temperature and
blocks UV rays.
Critical Thinking
What might happen to the
atmosphere if the number of
plants on Earth declined
significantly?
Carbon dioxide would build up in
the atmosphere and the
atmosphere would contain less
oxygen.
Where do we find water?
Water
is one of Earth’s most
important resources but only a
small fraction of Earth’s water is
usable.
Fresh water is constantly renewed
by the water cycle.
Water Cycle
Water
evaporates from bodies of
water on land.
The
water vapor rises, as it cools it
condenses into clouds of tiny droplets.
When
the droplets are heavy enough,
they fall to the land as precipitation.
Groundwater
seeps into the land
(infiltration), runoff moves downhill
and enters streams and rivers.
Watersheds
Watersheds
are generally bordered
by landforms similar to mountain
ridges.
Quick Check
Summarize
Identify the
steps in the
water cycle.
evaporation, condensation,
precipitation, runoff
Critical Thinking
Why is the water cycle so important
to living things?
The water cycle provides organisms
with fresh water that is needed to
carry out life processes. It is also the
habitat for water dwelling organisms.
How is water useful?
More
than 97% of the Earth’s water is
salt water.
The
salt in the oceans, halite or rock
salt, and other materials are left
behind when the water evaporates.
The
ocean levels will remain about the
same even though water evaporates
because new water is being added
by precipitation and rivers.
Ocean
water contains almost every
element and mineral.
Producers
use carbon dioxide and
sunlight to make food.
Consumers
eat the producers
containing those elements and
minerals.
Desalination
is the process of turning
salt water into fresh water by boiling
and evaporating the salt water. The
evaporated water is collected and
condensed as fresh water.
Global currents circulate warm water
from the equator and cold water
from the polar regions. These currents
help form weather patterns on land.
Using Fresh Water
Rain,
snow, and groundwater seeps
into the ground and fills in among
the rocks and soil.
The
top of this water filled space is
the water table. The depth varies.
A spring is where groundwater comes
out of the ground; this is where the
water table meets the surface.
Wells are holes that are dug below
the water table.
Some
wells go into an aquifer and
need a pump.
A
confined aquifer is squeezed
between tightly packed layers of
rock.
An
artesian well extends down
into a confined aquifer and does
not need a pump.
Quick Check
Summarize
Describe some of the places where
people find fresh water.
People find fresh water where the
water table reaches the surface
(such as ponds, lakes, rivers, and
streams), in wells (ordinary and
artesian), and in reservoirs.
Critical Thinking
Why
is it important to conserve
fresh water?
Conserving fresh
water is
important
because fresh
water represents
only about 3
percent of the
water on Earth.
What are droughts and floods?
A
drought is a lack of precipitation
over an extended period of time.
The “dust bowl” occurred in the
southern Great Plains during the
1930’s when the topsoil blew
away and the crops failed.
To help minimize erosion farmers
used contour - plowing methods
and planted trees as windbreaks.
Floods
occur when there is more water
than can be held by its banks. They
occur during the wet seasons and
during the spring snow melt.
Scientists
try to
predict floods
by studying the
land and the
amount of
water in rivers
and lakes.
Quick Check
Summarize
How can people protect the land
from soil loss due to wind?
We can protect soil loss by planting
windbreaks and contour-plowing.
Critical Thinking
Why is predicting when floods
might occur important?
Floods can cause widespread
damage and loss of life. It allows
people to prepare and/or evacuate.