Transcript ENVIRONMENTAL SCIENCE

ENVIRONMENTAL SCIENCE
Chapter 5 How Ecosystems Work
5.2 The Cycling of Materials
5.2 The Cycling of Materials
Objectives
• List the three stages of the carbon cycle.
• Describe where fossil fuels are located.
• Identify one way that humans are affecting the
carbon cycle.
• List the three stages of the nitrogen cycle.
• Describe the role that nitrogen-fixing bacteria
play in the nitrogen cycle.
• Explain how the excess use of fertilizer can affect
the nitrogen and phosphorus cycles.
The Carbon Cycle
• The carbon cycle is the movement of carbon from the
nonliving environment into living things and back.
• Carbon is an essential component in the four major
molecule types that make up living things –
carbohydrates, lipids, proteins, and nucleic acids.
• Carbon is cycled between land, air, atmosphere, and
living things.
• Carbon may enter into a short-term cycle or a longterm cycle.
• A “sink” is a reservoir where something may be stored
for some time.
The Carbon Cycle
• Producers convert atmospheric carbon dioxide
into carbohydrates during photosynthesis.
• Consumers contain carbon from the
carbohydrates in the producers they eat.
• During cellular respiration, some of the carbon
is released back into the atmosphere as
carbon dioxide.
• Some carbon is stored in limestone – one of
the largest carbon sinks on Earth.
The Carbon Cycle
• Carbon may also be released into the soil as
organisms die and decompose.
• The carbon and hydrogen from the remains of
buried organisms can form coal, oil, or natural
gas – fossil fuels.
• Fossil fuels store the hydrocarbons left over
from the remains of organisms that died
millions of years ago.
The Carbon Cycle
• When we burn fossil fuels, carbon is released back into
the atmosphere – mostly as carbon dioxide.
• In 2000, one third of all the carbon dioxide emitted in
the U.S. came from motor vehicles.
• When the carbon emitted from the burning of fossil
fuels is added to the carbon emitted from other
sources, the amount of atmospheric carbon increases.
• Carbon dioxide is a greenhouse gas and may contribute
to global warming – an overall increase in average
temperatures around the world.
http://www.ei.lehigh.edu/learners/cc/car
bon/carbon3.html
http://whyfiles.org/211war
m_arctic/
The Nitrogen Cycle
• The nitrogen cycle is the process in which
nitrogen circulates among the air, soil, water,
and organisms in an ecosystem.
• All organisms need nitrogen for building
proteins – the building blocks of cells.
• Nitrogen makes up 78% of gases in the
atmosphere.
• Nitrogen must be “fixed” before it can be used
by organisms.
The Nitrogen Cycle
• Only a few species of bacteria – nitrogen-fixing
bacteria – can convert atmospheric nitrogen (N2)
into a more useable form (such as ammonia –
NH3).
• Nitrogen-fixing bacteria live within the roots of
legumes such as beans, peas, and clover.
• The bacteria use sugar provided by the legumes
to produce nitrogen containing compounds like
nitrates (NO3-).
• Excess nitrogen fixed by the bacteria is released
into the soil.
The Nitrogen Cycle
• Nitrogen stored within organisms is returned
to the nitrogen cycle as decomposition occurs.
• After decomposers return nitrogen to the soil,
bacteria transform a small amount of the
nitrogen into nitrogen gas, which then returns
to the atmosphere.
http://www.waikato.ac.nz/wfass/subjects/geography/people/max
/ConceptDiagrams.shtml
The Phosphorus Cycle
• The phosphorus cycle is the movement of
phosphorus in different chemical forms from the
environment to organisms and then back to the
environment.
• Phosphorus is an essential component of nucleic
acids as well as many other important molecules
to organisms.
• Plants get phosphorus from the soil and water.
• Animals get their phosphorus by eating plants or
animals that have eaten plants.
The Phosphorus Cycle
• Phosphorus may enter soil and water when rocks
erode and may even move into the soil in small
amounts in the form of phosphate (PO4)3-.
• Plants absorb phosphates in the soil through their
roots.
• Some phosphorus washes off the land and ends
up in the ocean.
• Phosphate salts are not soluble in water and will
sometimes sink to the bottom and accumulate as
sediment.
The Phosphorus Cycle
• Fertilizers used to stimulate and maximize plant
growth contain nitrogen and phosphorus.
• Excessive amounts of fertilizer can enter
terrestrial, marine, and aquatic ecosystems
through runoff.
• Excess nitrogen and phosphorus can cause rapid
algae growth – an algal bloom.
• As massive amounts of rapidly produced algae
begin to die off and settle, oxygen depletion
becomes a problem for any organism relying on
oxygen.
http://oceanclassrooms.com/ms101_u3_
c1_sc_1
http://www.toxipedia.org/display/toxipedia
/Algal+Bloom
Acid Precipitation
• When fuel is burned, large amounts of nitric
oxide is released into the atmosphere.
• In the air, nitric oxide can combine with
oxygen and water vapor to form nitric acid.
• Nitric acid then falls as acid precipitation.
http://perstoremyr.net/2011/01/10/cleopatras-needleegyptian-concern-about-the-nyc-obelisk/