Transcript 3 - Matter Cycles

Science 20 Unit D – Living Systems
Recycling of
Matter
Matter Cycles
Matter is recycled,
but energy is
not.
Ex) Even when
trees die from a
fire, their seeds
do not and plant
new seedlings.
Recycling happens through
biogeochemical cycles: the
movement of
elements/compounds between
abiotic and biotic parts of the
environment.
We will look at three types of matter
cycles:
The Carbon and Oxygen cycle
• Plants perform photosynthesis (carbon
dioxide + light  glucose + oxygen)
• Animals/plants perform cellular
respiration (oxygen +glucose carbon
dioxide and energy).
• Soil organisms (bacteria) decompose
dead organisms and return carbon.
• Reservoirs of carbon = carbon sinks.
Fossil fuels – part of the
carbon cycle
• Dead organisms are
compressed into fossil fuels;
when it is burned, it releases
carbon into the atmosphere.
• Added Carbon disrupts natural
cycling, leading to climate
change.
• The Greenhouse effect: CO2
traps energy in the atmosphere
and increases the temperature
of the Earth.
Greenhouse effect
Nitrogen cycle
• Includes four processes:
• Nitrogen fixation
• Ammonification
• Nitrification
• Denitrification.
Nitrogen is an important
component of all proteins and
nucleic acids (think DNA).
Most organisms can’t use
nitrogen directly; it must be
put into soil by:
•Volcanic action.
•Lightening.
•Nitrogen- fixing bacteria.
Nitrogen fixation and
Ammonification
• Nitrogen fixation: bacteria
(90%)/lightening (10%) convert
atmospheric nitrogen into roots of
plants (legumes).
• Fertilizers increase this amount.
• Ammonification: Decomposers
convert nitrogen products (from
tissues) into ammonia (NH3).
Nitrification and Denitrification
• Nitrification: process changing
ammonium ions into nitrates (NO3),
performed by nitrifying bacteria.
• Absorbed by plants, used to make
amino acidss: absorbed by consumer
when eaten.
• Denitrification: Bacteria convert
ammonia into Nitrogen, which returns
to atmosphere.
Pesticides
• Pesticides have had the largest
impact on food webs
• Pesticides benefit society
– reduce the number of pests (weeds,
molds, insects, birds, etc.) to
increase crop production
– Reduce the spread of disease
(malaria, West Nile)
Pesticides have also negatively affected
ecosystems:
Eliminating an insect species on small
island using DDT reduced the spread of
malaria, however, the entire food web of
the island was affected: other insects
disappeared - then lizards - then cats increasing rat population – outbreak of
disease = more problems!!!
Biological amplification/ magnification – the
buildup of toxins as you move up a food
chain.
Therefore, the higher the trophic level, the
greater the concentration of toxins.
Toxins affect the environment in unexpected
ways. Example: DDT accumulation in the
Peregrine Falcon creates thin shells,
therefore breaking easily. The numbers of the
species in Canada decreased so dramatically,
that they were close to extinction.
DDT interfered with
Calcium deposition
Soluble in water,
Collects in fatty tissue
Human use of
Pesticides
Time magazine in 1947
Assignment
• Read: 453-462