Nutrient Cycling Flashcards
What is ammonification?
Decomposes excrete proteases and deaminases to decay dead organisms. Proteases digest proteins. Deaminases remove NH2 groups from amino acids and reduce them to NH4+.
What is nitrification?
Ammonium ions are converted to nitrites and nitrates.
Nitrosomonas convert ammonium to nitrite
Nitrobacter convert nitrite to nitrate.
Why does nitrification require aerobic conditions?
It is an reduction reaction as oxygen is gained.
What is denitrification?
The loss of nitrogen from the soil. Psuedomonas convert nitrates to nitrogen. It requires anaerobic conditions as it is reduction.
What is nitrogen fixation?
The conversion of nitrogen to ammonium ions. Azotobacter is a nitrogen fixing bacteria and rhizobium in plant nodules also does this.
Why is leg-haemoglobin in root nodules?
Nitrogen diffuses into the nodules and nitrogenase catalyses the reaction to form NH4+. It requires ATP so needs aerobic conditions. The reaction is poisoned by oxygen, so the oxygen immediately binds to the leg-haemoglobin.
How does rhizobium enter root nodules?
Radicles and rhizobium secrete chemo attractants. Radicles grow towards rhizobium and rhizobium use flagella to move towards radicle. Rhizobium invade cortex and the rapid reproduction makes the swelling which is the root module.
What non-biological processes have an impact on the nitrogen cycle?
Fertilisers
Lightning
Leaching of minerals remove nitrogen from the soil
Give 5 ways humans impact the nitrogen cycle.
- Ploughing soil
- Draining land - air can enter soil
- Artificial nitrogen fixation - haber process
- Animal waste - releases N2 compounds into soil
- Planting fields of legumes - encourages nitrogen fixation
Why is animal waste beneficial to soil?
- Improves soil structure
- Improves soil fertility
- Encourages microbial activity
- Improves plant nutrition
Why does ploughing soil affect the nitrogen cycle?
Aerated the soil so favours nitrogen fixers, nitrifying bacteria and plants roots can aerobically respirate to make ATP.
Describe the process of eutrophication. (6)
- Algal bloom
- Sun can’t get to plants so plants die
- Decrease in animal diversity because no plants
- Algae die. Saprobiontic fungi decompose them, they are aerobic so create a biochemical oxygen demand.
- Upper layers of water become deoxygenated, fish die
- Anaerobic bacteria flourish. Release gases
How do farmers reduce quantities of nitrates?
- Restrict amount of fertiliser
- Only apply fertiliser when crops are actively growing
- Leave a small strip at least 10m wide next to watercourses
- Dig drainage ditches.
How do drainage ditches decrease the effect of eutrophication?
The minerals concentrate in them and eutrophication happens there, so natural watercourses aren’t disturbed.
What has caused the increase in CO2 in the air?
- Burning fossil fuels releases CO2 previously locked up in them
- Deforestation removes photosynthesising biomass that would remove it
What are the 3 major biological processes in the carbon cycle?
Respiration - adds it to the air
Photosynthesis - removes it
Decomposition - dead remains of plants and animals acted upon by detritivores and sapropbionts in the soil which releases CO2 into the atmosphere
What happens to CO2 in aquatic systems?
As HCO3- Ions. Incorporated into magnesium and calcium carbonate in mollusc shells and arthropod exoskeletons which sink after animals death. Carbonates become components of chalk limestone and marble. If eroded, CO2 is released again.
What are the 6 components of atmospheric and aquatic carbon cycles and what component is extra in aquatic cycles?
CO2 in atmosphere/ HCO3- in seas C in producers C in consumers Death C in decomposers C in fossil fuels
+ extra = c in chalk, limestone and marble.
What are the 5 human impacts on the carbon cycle?
Deforestation Climate change The greenhouse effect Global warming Carbon footprint
What are the 2 ways deforestation impacts the carbon cycle?
Cutting down forests reduced how much carbon dioxide is taken from the air
When trees are cut down they may be burned or left to decay which releases carbon dioxide.
What has caused the huge rise in carbon dioxide, causing climate change?
Human activity and increases in other greenhouse gases. Causes changes in temperature wind patterns and rainfall.
What are the two major reasons for the increase in carbon dioxide?
Burning fossil fuels: increase in industrialisation and global transport
Deforestation
What are some examples of greenhouse gases?
Carbon dioxide Methane Nitrous oxide CFCs Ozone Water vapour.
Briefly describe the greenhouse effect.
- High energy short wavelength radiation passes through to the earths surface which warms it up and is absorbed
- It is then re-radiated at a lower energy and a longer wavelength.
- Absorbed and trapped by greenhouse gases in the atmosphere so gases re radiate in all directions and energy re-radiated back to earth is absorbed again, causing the planetary surface to warm up.
Define global warming.
The enhanced greenhouse effect caused by High concentrations of greenhouse gases.
What are the consequences of global warming?
- Flooding due to melting polar ice
- Increased extreme weather conditions like droughts
- Increased forest fires
- Decreased water availability in tropical areas = more deserts
- Plants may be driven to extinction as evolutionary adaptation to the heat is slow; animals dependent on these plants may die
- Fishing areas and crop-growing belts may move
- Increased crop yields, but increased pest populations
- Food production may decrease - economic and political consequence
- Increasing CO2 decreases oceans pH which threatens organisms eg fish secreting mucus not allowing gas exchange.
What are the 5 problems associated with global warming for farmers and what are their sources?
- Carbon dioxide - decomposition of organic soil matter
- Methane - digestive activity of farm animals and decomposition of wet souls
- Nitric oxide and nitrous oxide - waterlogged and anaerobic soils
- Low+fluctuating water supplies - low rainfall; high temp
- Raised sea level - cultivated land inundated by sea water
5.
How can the issue of decomposition of soil matter causing CO2 be addressed?
Improve soil quality by conservation tillage (leave crop residues on soil to reduce erosion), cover cropping (eg clover to clover soil to protect and improve it between crops enhancing soil structure) and crop rotation (reduces pests)
How can the issue of methane through animals digestive activity and decomposition in wet soils be addressed?
Reduced dietary intake of meat and dairy, high sugar grasses, oats etc reduce methane they release
Use rice varieties that grow in drier conditions; select varieties w a higher yield, ammonium sulphate can favour non-methane producing microorganisms
How can the issue of nitric/nitrous oxide from waterlogged and anaerobic soils be addressed?
Improving drainage
How can low and fluctuating water supply due to low rainfall and high temps be addressed?
Use drought tolerant crops
How can the issue of raised sea level from cultivated land inundated by salt water be addressed?
Salt tolerant crops.
Define carbon footprint.
A way of measuring a contribution to the greenhouse gases in the atmosphere - the equivalent amount of CO2 generated by an individual, product or service in a year.
How do crops cause indirect sources of carbon dioxide?
Production of farming tools
Production of insecticides; herbicides; fungicides and fertilisers
Farm machinery powered by fossil fuels
Transport of produce.
What do the 3 R’s - reduce reuse and recycle - recommend?
Recycle packaged material Drive less Use less air con and heating Choose a diet to reduce animal protein Avoid food waste Plant trees in deforested regions
