Transcript Cycles in Nature - Holy Family Regional School

“Cycles”
KEY CONCEPT:
Matter cycles in and out of an
ecosystem.
The Water Cycle
The water cycle is the circular pathway of
water on Earth.
The Water Cycle
The movement of water between the oceans,
atmosphere, land, and living things is
known as the water cycle.
How Water Moves
During evaporation, the sun’s heat causes
water to change from liquid to vapor.
In the process of condensation, the water
vapor cools and returns to a liquid state.
The water that falls from the atmosphere to the land
and oceans is called precipitation. Rain, snow,
sleet, and hail are all forms of precipitation.
Most precipitation falls into the ocean.
The precipitation that falls on the land and flows
into streams, rivers, and lakes is called runoff.
Groundwater is precipitation that seeps into the
ground and is stored between or within rocks.
Groundwater slowly flows back into the soil,
streams, rivers, and oceans.
Oxygen Cycle:
Plants make food by photosynthesis
They use carbon dioxide (CO2) to make
oxygen (O2)
Animals breathe out carbon by respiration
They use oxygen (O2) and breathe out
carbon dioxide (CO2)
–By the way … humans are animals too
Water and Life
Without water, there would be no life on
Earth. All organisms, from bacteria to
animals and plants, are composed mostly of
water.
Water helps transport nutrients and waste
within an organism.
Water helps regulate temperature.
All water taken in by an organism is
eventually returned to the environment.
Example: Oxygen Cycle:
oxygen
photosynthesis
respiration
carbon
dioxide
Carbon Cycle
Carbon is the building block of life.
a. The carbon cycle moves carbon
from the atmosphere, through the
food web, and returns to the
atmosphere.
b. Carbon is emitted by the burning
of fossil fuels (like oil, gasoline,
and coal)
Carbon Cycle: notice photosynthesis and respiration are
back … they both involve CO2 (now we’re looking at the C
for carbon)
carbon
dioxide
in air combustion
respiration
photosynthesis
respiration
decomposition
of organisms
fossil fuels
photosynthesis
carbon dioxide
dissolved in water
The Carbon Cycle
Besides water, the most common molecules in living
things are organic molecules, or molecules that
contain carbon.
The exchange of carbon between the environment
and living things is known as the carbon cycle.
Decomposition and Combustion
The breakdown of substances into simpler molecules
is called decomposition.
For example, when fungi and bacteria decompose
organic matter, carbon dioxide and water are
returned to the environment.
Combustion is the process of burning a substance,
such as wood or fossil fuels. Combustion of organic
matter releases carbon.
The Nitrogen Cycle
Living things need nitrogen to build
proteins and DNA.
The movement of nitrogen between the
environment and living things is called the
nitrogen cycle.
The nitrogen cycle mostly takes place underground.
Some nitrogen
fixing bacteria
live in
nodules on the
roots of plants;
others live
freely in
the soil.
Converting Nitrogen Gas
Although about 78% of the Earth’s atmosphere is
nitrogen gas. Most organisms cannot use nitrogen
gas directly.
Bacteria in the soil are able to change nitrogen gas
into forms that plants can use. This process is called
nitrogen fixation.
Other organisms get the nitrogen they need by
eating plants or animals that eat plants.
Passing It On
When organisms die, decomposers break down the remains.
Decomposition releases a form of nitrogen into the soil that
plants can use.
Certain types of bacteria in the soil convert nitrogen to a
gas, which is returned to the atmosphere.