Nutrient Cycles Flashcards
What are the 4 processes of the nitrogen cycle
Nitrogen fixation
Ammonification
Nitrification
Denitrification
What happens in nitrogen fixation
One way is some organisms can directly take up nitrogen from atmospheric nitrogen gas
Or
The nitrogen fixing bacteria in the soil convert nitrogen gas into ammonia
What happens in ammonification
Decomposers (saprobionts) hydrolyse N containing compounds to release ammonia in the soil
What happens in nitrification
Nitrifying bacteria convert ammonia to nitrites (NO2-)
Nitrites to nitrates (NO3-)
By oxidation
What happens in denitrification
Nitrates can be converted to N2 gas by denitrifying bacteria. This only occurs in waterlogged, anaerobic conditions. A way to prevent leaching.
What is erosion
Once the rock has been weakened (phosphate ions trapped inside rocks) and broke by weathering erosion happens.
This is when rocks and sediments are picked up and moved to another place by ice, water, wind or gravity.
Phosphate containing compounds
ATP
NADP
Phospholipids
Nucleic acids
What happens in the phosphorus cycle
- Phospholipids, RNA and DNA from dead organisms into phosphate ions
- Decomposed by saprobionts
- Phosphate ions also found in waste and remains
- Phosphate ions transported by streams, rivers, lakes and oceans
- Form sedimentary rock
- Weathering and erosion of rocks helps phosphate ions dissolve into oceans, lacks and soils
- Phosphates become available for absorption by plants to incorporate into biomass
What happens in eutrophication
Nitrates washed into water
Increased algal bloom
Algae block light and less photosynthesis
Algae die
Plants that can’t photosynthesis under the surface die off
Increase in saprobionts increases anaerobic respiration
Reduces O2 concentration of water
Increase in toxins
Explain what is meant by the term carbon sink.
• Takes up / locks up / stores carbon / carbon dioxide (for a long time) / eq ;
• Named example e.g. peat / coal / limestone / trees / fossil fuel / chalk / shells ;
Explain what is meant by the term global warming.
• Increase in {temperature of earth’s surface / mean global temperature / eq};
• Carbon dioxide is a greenhouse gas / due to an increase in greenhouse gases ;
• (Which) {trap / reflect back} {heat / long wave / infra red} (in the atmosphere) ;
• Reference to an {increased / enhanced} greenhouse effect ;
• Reference to valid {effect / consequence} e.g. melting ice caps, flooding, climate
• change ;
Describe the role of saprobionts in the nitrogen cycle.
• (use enzymes to) decompose proteins / DNA / RNA / urea;
• Producing / releasing ammonia / ammonium ions;
Explain how carbon-containing compounds present in the pine leaves that fall from the trees are absorbed and used for growth by saprobionts/fungi that live in the soil.
• extracellular digestion;
• by secretion of enzymes;
• absorption of digested/soluble products;
• synthesis of structural compounds/named compound;.
• respiration provide energy for growth
Nitrogen compounds in the plants are made available for the main crop after ploughing in spring.
Describe the role of microorganisms in this process.
• proteins/amino acids broken down;
• deamination/ammonification/ release of ammonium compounds;
• By saprophytes/saprobionts/decomposers;
• conversion to nitrates via nitrites;
• by nitrifying bacteria/named bacterium;
• nitrates absorbed into roots via active transport
The scientists used units of μg g−1 for the concentration of ammonia in soil.
Suggest why, in this investigation, the scientists used these units.
• (μg because) very little ammonia (in soil);
• (μg because) avoids use of (lots of) decimal places (in their results) / avoids the use of powers of 10 / avoids the use of standard form /makes numbers more manageable / Accept makes easier to plot graph
• (g-1) to allow comparisons (between samples);
