A2 Biology - Nutrient cycle

ALL NUTRIENT CYCLES HAVE ONE SIMPLE SEQUENCE THEY ALL FOLLOW; 

• NUTRIENTS TAKEN UP BY PRODUCERS (PLANTS) AS SIMPLE INORGANIC MOLECULES
• PRODUCER THEN INCOORPORATES THE NUTRIENT INTO COMPLEX ORGANIC MOLECULES
• WHEN PRODUCER IS EATEN THE NUTRIENT PASSES TO CONSUMER
• IT PASSES ALONG FOOD CHAIN 
• WHEN THESE CONSUMERS/PRODUCERS DIE, SAPROBIOTIC ORGANISMS BREAK DOWN COMPLEX MOLECULES AND RELEASE THEM AS SIMPLE INORGANIC MOLECULES
• CYCLE STARTS AGAIN 

CARBON - COMPONENET OF ALL MAJOR MACROMOLECULES 

BASIC BUILDING BLOCK OF LIFE 

CARBON DIOXIDE - ONLY TAKES UP 0.04% OF AIR 

GLOBALLY CO2 LEVELS HAVE INCREASED BECASUE OF HUMAN ACTIVITIES ....

• COMBUSTION OF FOSSIL FUELS - COAL, OIL
• DEFORESTATION - LESS PHOTOSYNTHESIS 

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
3. Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxideformed during respiration. The animals and plants eventually die.
4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

Air is about 78% nitrogen. Nitrogen is needed for life. It is an important part of proteins, DNA, and RNA.

FOUR MAIN STAGES OF NITROGEN CYCLE 

• AMMONIFICATION 
• NITRIFICATION
• NITROGEN FIXATION 
• DENITRIFICATION 

EACH INVOLVE SAPROBIOTIC ORGANISMS 

AMMONIFICATION IS WHEN NITROGEN COMPOUNDS FROM DEAD ORGANISMS OR THEIR WASTE IS TURNED INTO AMMONIUM COMPOUNDS BY DECOMPOSERS

WHEN NITROGEN GAS FROM THE AIR IS TURNED INTO AMMONIA BY A BACTERIA 

2 TYPES OF BACTERIA 

• FREE LIVING NITROGEN FIXING BACTERIA - REDUCE NITROGEN GAS TO AMMONIUM SO IT CAN MAKE AMINO ACIDS 
• MUTUALISTIC NITROGEN FIXING BACTERIA - LIVE ON NODULES ON THE ROOT OF THE PLANT AND THEY OBATAIN CARBOHYDRATE FROM THE PLANT WHILST GIVING THE PLANT AMINO ACID.

NITRIFICATION WHEN AMMONIUM COMPOUNDS IS TURNED INTO NITROGEN COMPOUNDS 

• NITRIFYING BACTERIA CHANGES AMMONIUM COMPOUNDS INTO NITRITES 
• MORE NITRIFYING BACTERIA CHANGE NITRITES TO NITRATES - WHICH CAN BE USED BY PLANTS 

WHEN SOILDS ARE WATERLOGGED - OXYGEN IS ABSENT 

THIS MEANS THERE ARE LESS AEROBIC NITRIFYING BACTERIA, SO THERE IS AN INCREASE IN THE ANAEROBIC DENITRIFYING BACTERIA 

THESE CONVERT SOIL NITRATES INTO GASEOUS NITROGEN 

2 TYPES OF FERTILISER

• NATURAL (ORGANIC) - CONSIST OF DEAD AND DECAYING REMAINS OF PLANTS AND ANIMALS AS WELL AS WASTE - POO
• ARTIFICAL (INORGANIC) - MINED FROM ROCKS AND DEPOSITS AND CONVERTED INTO A SOLUTION TO AID LANT GROWTH.

• REDUCES SPECIES DIVERSITY - NITROGEN RICH SOILD FAVOUR GROWTH OF CERTAIN SPECIES WHICH WILL OUT COMPETE OTHER SPECIES
• LEACHING - NUTRIENTS ARE REMOVED FROM THE SOIL - EXCESSIVE RAINWATER CARRIES NUTRIENTS LIKE NITRATES DEEP INTO THE SOIL SO IT CANNOT BE USED BY PLANTS - THIS COULD LEAD TO POLLUTION OF WATER SUPPLIES 
• EUTROPHICATION 

• IN LAKES AND RIVERS - NATURALY VERY LITTLE NITRATES - THIS IS THE  LIMITING FACTOR FOR THE GORWTH OF PLANT AND ALGAE
• AS LEACHING OCCURS - THE BUILD UP OF NITRATES LEADS TO EXPONENTIAL PLANT GROWTH 
• ALGAL BLOOM - ALGAE COVER THE SURFACE 
• DENSE SURFACE ABSORBS LIGHT AND PREVENTS IT GOING TO BOTTOM
• LIGHT THEN BECOMES A LIMITING FACTOR FOR PLANTS AT LOWER DEPTHS AND THEY DIE 
• LACK OF DEAD PLANTS FOR SAPROBIOTIC ORGANISM IS NO LONGER A LIMIING FACTOR SO THEY GROW 
• SAPROBIOTIC BCTERIA REQUIRE OXYGEN FOR RESPIRATION 
• CONCENTRATION OF OXYGEN IN THE WATER IS LESS 
• OXYGEN IS THE LIMITING FACTOR FOR ORGANISMS AEROBIC -  DEATH
• ANAEROBIC ORGANISMS POPULATIONS RISE