1. B4h Recycling CO2 Carbon is one element that is recycled naturally
The Carbon Cycle
CO2
respiration
CO2
CO2
BURNING
CO2 released
Photosynthesis
Carbon compounds in plants
Useful products
feeding
death
Fossil fuels
Compaction ,000+ years
Carbon compounds in soil being decayed by bacteria

2. 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

3. B4h Recycling Complete the diagram of the carbon cycle
Atmospheric carbon dioxide
Green plants
Carnivores
Microorganisms
Respiration
Photosynthesis
Excretion, defaecation, death and decay
Feeding
Death and decay
Herbivores

4. B4h Recycling The Nitrogen Cycle Dead rabbit Denitrifying bacteria
Nitrogen fixing bacteria live in root nodules of some plants
Denitrifying bacteria
Nitrogen gas
Nitrates
Dead rabbit
Absorbed by plants and used to make amino acids
Plant gets nitrogen it can use to make proteins
The proteins in the rabbit are digested by fungi and bacteria
Nitrifying bacteria
Nitrates
ammonia
urea
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

5. 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

6. 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:
Warm, wet and anaerobic
Cold, dry and aerobic
Warm, wet and aerobic
Warm,dry and aerobic
An earthworm that fragments leaves is an example of a ?
Detritivore