C6 Nitrogen and Phosphorus Cycles!

What is eutrophication?

the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.) Leads to oxygen depletion

In how long will the availability of phosphate yields become severely restricting to agriculture?

50-100 years! It is considered a non renewable resource because the rate of turnover is so slow.

What is nitrogen converted to during nitrogen fixation?

Ammonia (NH3) becomes ammonium (NH4) when mixed with water and then can be used by plants

Which types of bacteria are able to 'fix' nitrogen?

Azotobacter: Lives freely in the soil Rhizobium: forms nodules within plant roots and supplies ammonia to the plant in exchange for carbohydrates

What is the only other natural way of nitrogen fixation?

Lightning

How does water logging impact the nitrogen cycle?

Loses nitrogen through denitrification and leeching (minerals are washed away)

Ammonification (what is it?)

Production of ammonia from the break down of organic material (mostly amino acids) Done by saphrotrophs

how are insectivorous plants adapted to grow in waterlogged soil (in bogs and moorlands)?

They obtain nitrogen by feeding on invertebrates e.g. venus flytrap has spines on the edges of its leaves which can be triggered to fold and form a cage, then it releases digestive enzymes.

List two sources of the ammonium in the forest soils apart from deposition in rainfall. (2)

a. activity of soil microorganisms / ammonification / nitrogen fixation b. urine/feces/other nitrogenous waste c. dead organisms d. fertilizers «on edge of forest

Nitrates ( - NO3 ) are components of the nitrogen cycle. Outline the possible conversions of - NO3 in the nitrogen cycle. [2]

a. assimilation by plants / conversion to amino acids ✓ b. denitrification to nitrogen gas / reduction to nitrogen «N2» by denitrifying bacteria ✓ c. reduction of nitrates to nitrites ✓

Suggest one reason why ammonium levels in the interior of a forest might be lower than the soil ammonium close to the edge. (2)

a. greater distance from an open field where they are applying fertilizer b. more ammonium absorbed/recycled c. less ammonium in rain reaches soil/trapped in treetops

The percentage of phosphorus in an ecosystem that is recycled per year is in most cases very small, and far smaller than the percentage of nitrogen that is recycled. Suggest reasons for this difference. [2]

a. largest store of phosphorus «in ecosystems» is in marine sediments and minerals/phosphate rock while nitrogen is in the atmosphere ✓ b. main source of release of phosphorous is by weathering of rocks «very slow process»/ nitrogen is by bacterial action ✓ c. high concentrations of nitrogen/low concentration of phosphorous «compounds» in living organism ✓ d. phosphorus is not a very soluble mineral ✓

Some scientists estimate that available phosphorus reserves in the Earth will be completely depleted within approximately 100 years. Discuss the implications of these estimates. [2]

a. production of fertilizers will decrease/price of fertilizers will rise ✓ b. less food production / increase in cost of foods c. development of alternative methods of agriculture ✓ d. Phosphate needed by living organisms for nucleic acids/ATP so lack will affect growth negatively ✓

how have farmers traditionally added phosphate to the soil

animal manure

Nitrosomas

convert ammonium ions into nitrites

Denitrification

denitrifying bacteria convert nitrates (NO3-) into nitrogen gas (N2) BAD FOR THE SOIL happens in the absence of oxygen reduces availability of nitrates to plants

How do humans fix nitrogen industrially?

haber process (to manufacture fertilizers)

how do humans add and remove phosphorous from the cycle?

mining to produce fertiliser adds to the cycle phosphorous is removed when crops are harvested (and waste is not recycled) While the application of fertiliser adds phosphorus at one site, it causes the depletion of phosphorus reserves at another site

Main difference between phosphorous and nitrogen cycles

phosphorous cycle has a much lower rate of turnover because a lot of it is stored in rock sediments (none in the atmosphere)

Nitrification

the conversion of ammonium ions into nitrites (NO2-) and nitrates (NO3-) by nitrifying bacteria in the soil

Nitrobacter

use oxygen to convert nitrites into nitrates

Main ways phosphorous is used and exchanged with the environment

weathering/mining of rocks used in living things for nucleic acids, phospholipids and ATP returned to the soil through organic waste