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Cycles of Life
Science 10
Unit 1: Sustainability of Ecosystems
G.Burgess
Sept.2006.
Water Cycle
• All fresh water begins as
precipitation
• Rain, sleet, snow, hail, mist, fog
• ONLY 3% of the world’s water is fresh
water
• fresh water begins as rain falling on
mountain tops creating run-off and
forms streams, rivers.
• It temporarily collects in ponds and
lakes, but will ultimately be
collected by the oceans and seas.
• All life on our planet depends on
water and much of it depends on
the amounts of available fresh
water.
Water Cycle
• Accumulation: collecting
of water in form of
ice/snow in glacial sheets
and as liquid in ponds,
lakes, seas, and oceans.
• Condensation: changing
of water vapor into liquid
• Evaporation: changing of
liquid water into vapor
• Precipitation: falling of
water as solid or liquid
from atmosphere
• Runoff: movement of
water from site of
precipitation to ocean
• Transpiration: water
vapor given off by living
organisms.
ga.water.usgs.gov/edu/watercycle.html, accessed Sept.19, 2006.
Carbon Cycle
• Carbon is the base element of all living
things on planet Earth.
• All living organism requires energy.
• Living organisms (all producers and
consumers) require sugar (glucose) to
produce energy.
• Producers (green plants) create the sugar
when the sun is out.
• The world’s first mass extinction (long
before the dinosaurs) is said to have
happened because the bacteria on our
planet produced large quantities of
oxygen as a waste product and made
the atmosphere toxic.
Carbon Cycle
• Living organisms convert sugar into
useable energy by the process of cellular
respiration.
• Cellular respiration requires oxygen from
the atmosphere to release the energy by
‘burning’ the sugar.
• ‘Burning’ of sugar releases water vapor
and CO2 into the atmosphere
• Producers take the CO2, from the
atmosphere, and water, from the soil and
atmosphere, to create sugar by the
process of photosynthesis
Carbon Cycle
C6H12O6
Photosynthesis
CO2 + H2O
Cellular Respiration
**The carbon cycle occurs on land and in
the water. Wherever there is life.
http://fig.cox.miami.edu/Faculty/Dana/carboncycle.gif, accessed Sept.19, 2006.
Nitrogen Cycle
• Agriculturalists use fertilizers to ensure that
their crops have enough nitrogen, and
other elements.
• All living things have proteins (DNA is a
type of protein)
• Proteins, unlike other organic molecules,
contain nitrogen.
• Plants take in the nitrogen from the soil to
create proteins.
• Consumers eating the plants change the
plant proteins in to proteins they can use.
• These nitrogen compounds are not only
found in soil but also in the atmosphere
and in the water.
Nitrogen Cycle
• producers package nitrogen from the soil
and air by nitrogen fixation. They change
the nitrogen gas to useable chemical
forms.
• Consumers must eat the plants or other
consumers to obtain the nitrogen.
• as consumers die or leave organic waste
material, decomposers (bacteria and
fungi) release the nitrogen into the soil as
ammonia (NH4) or as nitrate (NO3)
• Denitrifying bacteria release the nitrogen
from the nitrate as nitrogen gas
• The gas is then picked up by the
producers
• **Nitrogen released in water will be
absorbed by producers in the water
Nitrogen Cycle
http://www.epa.gov/maia/images/nitro.jpg, accessed Sept.19,2006.
Nitrogen Cycle
• Nitrification: process of converting
ammonia into nitrate.
– Performed by nitrifying bacteria
• Denitrification: process of converting
nitrate into nitrogen gas
– Performed by denitrifying bacteria
Human impacts on Nitrogen
Cycle
• Artificial fertilizers: the production of
fertilizer increased the amount of nitrogen
being fixed by more than half that which
was done naturally. This increased the
amount of nitrogen available in the
natural environment.
• Burning of fossil fuels increases the
amount of nitrogen in the atmosphere
• Excess nitrogen = nitrogen overload
Impacts of Nitrogen in Nature
• Atmosphere: acid rain (nitric acid)
• Fresh water ecosystem: eutrophication,
when the build up of nutrients causes the
population of producers to increase to a
point that harms the natural population
balance of the ecosystem
Impacts of Nitrogen in Nature
• Marine Ecosystem: all the nitrogen flowing
into rivers and streams ends up in the
oceans.
• An increase nitrogen in the oceans may
cause algal bloom (an explosion in the
algae population)
– Algae will grow in layers covering parts
of the lake and not allow oxygen to
enter the water.
– Bacteria decomposing the algae use
up the oxygen and release carbon
dioxide.
– Organisms normally requiring oxygen
will die of carbon dioxide poisoning
Resources
• Atmospheric Composition, Explores!
http://www.met.fsu.edu/explores/atmcomp.h
tml, accessed Sept.19, 2006
• Science Power 10, McGraw-Hill Ryerson, 2001.