Transcript Chapter 3part2

Chapter 3: How
Ecosystems Work
Section 3.2: The Cycling of
Materials
In ecosystems resources are used
over and over again: otherwise, they
would soon be gone, and life could
no longer exist.
There are three cycles that allows
materials to be reused:
• The Water Cycle
• The Carbon Cycle
• The Nitrogen Cycle
Water Cycle
• Water is essential to life.
• Although water is destroyed in photosynthesis
and created during cellular respiration, the
overall amount on Earth stays the same.
• The sun provides the energy that drives the
water cycle.
• As water vapor cools in the atmosphere, it
condenses to form tiny droplets in clouds.
Water Cycle cont.
• When the clouds meet cold air, the water returns
to the Earth again in the form of precipitation.
• The precipitation that falls onto land may just
evaporate again.
• Some collects into streams and rivers – flows
into the ocean
• Some absorbs into the ground.
Water Cycle cont.
• Water that soaks into the soil may be used
immediately by plants, or it may seep down into
the soil and rocks until it can’t travel further.
This layer of
underground
water is called
groundwater.
Carbon is essential component
of the proteins, fats and
carbohydrates necessary for
life.
Carbon Cycle
• Carbon enters an ecosystem when producers
take in carbon dioxide from the atmosphere
during photosynthesis.
• When consumers eat the producers, they obtain
carbon.
• As the consumer breaks down food particles
during cellular respiration, the carbon is released
back into the atmosphere, as carbon dioxide.
Humans effect on carbon
cycle
• Fossil fuels are essentially stored
carbon left over from the remains
of organisms.
• When we burn fossil fuels, we
release this carbon into the
atmosphere as CO2.
All
organisms
need
nitrogen to
build
proteins.
Nitrogen is around
us in large
quantities;
nitrogen composes
78% of the
atmosphere
Nitrogen cycle
• The only organisms that can use nitrogen
directly from the atmosphere are a few bacteria
known as nitrogen-fixing bacteria.
• All other organisms are dependent on these
bacteria for nitrogen.
• Nitrogen fixing bacteria live within the roots of
legumes such as peas, beans, and clover.
Nitrogen cycle
• The bacteria use sugars produced by the plants
and, in exchange, produce nitrogen containing
compounds.
• The excess nitrogen is released into the soil.
• Some nitrogen-fixing bacteria live freely in the
soil.
• Plants that do not have this type of bacteria get
nitrogen from the soil.
Nitrogen Cycle
• Animals get nitrogen by
eating plants or other
animals.
• The nitrogen is returned
back into the atmosphere by
decomposers breaking
down wastes such as urine,
dung, dead organisms.