Nutrient Cycles Flashcards
Why is nitrogen needed in organisms?
Manufacture proteins, amino acids ad other nitrogen-containing compounds
What is ammonification?
The production of ammonia from urea or amino acids
What breaks down waste and dead organisms?
Saprobiotic microorganisms that release the ammonia as ammonium ions in the soil
What is nitrification?
The conversion of ammonium ions to nitrite and nitrate ions
How are ammonium ions converted into nitrates?
By free-living soil microorganisms called nitrifying bacteria
That require oxygen
What do free-living nitrogen-fixing bacteria do?
Reduce gaseous nitrogen to ammonia which are used to manufacture amino acids
What do mutualistic nitrogen-fixing bacteria do?
Obtain carbohydrates from the plant and in return provides the plant with amino acids
Live in nodules on the roots of legumes
What occurs during denitrification?
Soil becomes short of oxygen
There are fewer aerobic nitrifying and nitrogen fixing bacteria
There are more anaerobic denitrifying bacteria that convert nitrates to gaseous nitrogen
Reduces the availability of nitrogen containing compounds for plants
How do fertilisers increase productivity?
Nitrates are readily available
Plants are likely to develop earlier
They grow taller with a greater leaf area
Increases the rate of photosynthesis
What is leaching?
The process by which nutrients are removed from the soil
Rain water dissolves the soluble nutrients and may drain into watercourses
Eutrophication
Leaching means nitrogen is no longer the limiting factor causing algal blooms
Prevents light reaching lower depths stopping photosynthesis and so the plants die
Saprobiotic bacteria grow and use up remaining oxygen
Oxygen is limiting factor and fish die
Anaerobic organisms decompose dead material releasing more nitrates making water putrid
