B4h Recycling
Carbon is one element that is recycled naturally
The Carbon Cycle
CO2
Carbon compounds
in plants
CO2 released
BURNING
CO2
CO2
respiration
Useful
products
Fossil fuels
Compaction
100,000+ years
feeding
death
Carbon compounds in soil being decayed
by bacteria
B4h Recycling
The processes which remove materials are balanced by the
processes which return materials. The materials are constantly
cycled
The constant cycling of carbon is called the carbon cycle. In the carbon
cycle:
• carbon dioxide is removed from the air by green plants for
photosynthesis; they use it to make carbohydrates, fats and proteins
which make up the body of plants;
• some of the carbon dioxide is returned to the atmosphere when green
plants respire;
• when green plants are eaten by animals, some of the carbon
becomes part of the carbohydrates, fats and proteins which make
up their bodies;
• when animals respire some of this carbon becomes carbon
dioxide and is released into the atmosphere;
• when plants and animals die, some animals and microorganisms
feed on their bodies; carbon is also released into the atmosphere
as carbon dioxide when these organisms respire
B4h Recycling
Complete the diagram of the carbon cycle
Atmospheric carbon
dioxide
Respiration
Photosynthesis
Microorganisms
Respiration
Respiration
Respiration
Excretion,
defaecation, death
and decay
Green plants
Feeding
Feeding
Death and
decay
Herbivores
Carnivores
B4h Recycling
The Nitrogen Cycle
Nitrogen gas
Dead rabbit
Denitrifying
bacteria
Absorbed by
plants and used
to make amino
acids
Nitrates
Plant gets nitrogen it can
use to make proteins
Nitrogen fixing
bacteria live in
root nodules of
some plants
The proteins in the rabbit are
digested by fungi and bacteria
urea
Nitrates
ammonia
So, on Monday a nitrogen molecule could be in the eye of a rabbit. By the
following Sunday, it is in the leaf of a plant
B4h Recycling
Nitrogen fixation is performed by nitrogen-fixing bacteria which can
reduce nitrogen gas from the air spaces of the soil to synthesize
ammonia and ammonium compounds. Some nitrogen-fixing bacteria
live freely in the soil. Others live in the swollen root nodules of
leguminous plants, ( e.g. clover, beans, peas)
Denitrification is performed by denitrifying bacteria which operate in
cold, water-logged, oxygen deficient soils. These bacteria gain
energy by reducing soil nitrates to nitrogen gas which then escapes into
the atmosphere. Thus they reduce soil fertility
B4h Recycling
Quick Quiz
What is a saprophyte?
An organism that feeds on dead and decaying material
The conversion of nitrogen into ammonia by bacteria is called?
Nitrogen fixation
Denitrification is the conversion of nitrates and ammonium compounds
into?
Nitrogen
To speed up composting conditions should be:
A. Warm, wet and anaerobic
B. Cold, dry and aerobic
C. Warm, wet and aerobic
D. Warm,dry and aerobic
An earthworm that fragments leaves is an example of a ?
Detritivore