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Natural Cycles
What materials are cycled through
the Earth’s ecosystems?
How do living things get the
materials they need?
Earth’s Resources
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Ecosystems depend
on energy from the
sun and different
natural cycles.
The Water Cycle
The Carbon-DioxideOxygen Cycle
The Nitrogen Cycle
The Water Cycle
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The movement of water
through Earth’s
ecosystems is the water
cycle.
Water falls to Earth as
precipitation and is used
by plants and animals.
Animals return the water
as waste.
Plants absorb the water
through their roots and
dismiss the water through
their leaves (transpiration).
The Water Cycle
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Energy from the sun
causes the water to
change from liquid to
vapor (evaporation).
Water vapor changes
from gas to liquid
through condensation.
Precipitation returns
water to the Earth.
Precipitation that goes
into the ground is
called groundwater.
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Groundwater used by
the plants is called
transpiration.
The Carbon Dioxide-Oxygen Cycle
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The Carbon DioxideOxygen cycle is powered
by the sun.
Photosynthesis occurs in
plants because plants take
in carbon dioxide and
release oxygen.
Gases are balanced in the
air.
Decomposers use oxygen
and produce carbon
dioxide.
Some animals produce
carbon dioxide as waste.
The Nitrogen Cycle
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The movement of nitrogen
through the ecosystem is
called the nitrogen cycle.
Nitrogen makes up 78% of
the air.
Nitrogen is used and
returned by living things.
Bacteria converts nitrogen
into compounds that can
be used by organisms to
build proteins.
Summary
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The water cycle is powered by the energy of the
sun.
Water evaporates and then condenses forming
clouds. Clouds return the water as precipitation.
In the carbon dioxide-oxygen cycle,
photosynthesis uses carbon dioxide and produces
oxygen.
The nitrogen cycle depends on bacteria that
convert nitrogen to nitrogen compounds that are
used by organisms.