Nutrient Cycles 5.4 Flashcards
Explain what is meant by the term carbon sink (1)
- Stores carbon / carbon dioxide (for a long time)
Named example = peat, coal, limestone, trees, fossil fuels, chalk, shells
Explain what is meant by the term global warming (5)
- Increase in temperature (of Earth’s surface / global temp) ;
- Increase in CO2 greenhouse gases;
- (which) trap heat / reflect long wavelengths (infrared) (in atmosphere) ;
- Increased/enhanced greenhouse effect;
- REF to consequence e.g flooding, climate change, melting ice caps, etc.
Describe the role of saprobionts in the nitrogen cycle (2)
- (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 (4)
- extracellular digestion (of leaf);
- by secretion of enzymes;
- absorption of digested/soluble products (e.g nitrate ions);
- synthesis of structural compounds (e.g use P for ATP)
- respiration provides 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 (4)
- proteins/amino acids broken down;
- ammonification/release of ammonium ions (NH3+)
- by saprobionts/decomposer organisms;
- nitrification/conversion to nitrites then to nitrates;
- by nitrifying bacteria;
- nitrates absorbed into roots via active transport.
The scientists used units of ug (microgram) g-1 for the concentration of ammonia in soil.
Suggest why, in this investigation, the scientists used these units (3)
- (ug because) very little ammonia in soil;
- avoids use of many decimal places/standard form/powers/makes numbers more manageable/makes easier to plot graph
- (g-1) to allow comparisons (between samples).
Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested (2)
ANY 2 FROM:
- amino acids/proteins/polypeptides;
- nucleic acids/nucelotides/DNA;
- (if prokaryotic) RNA/pre-mRNA/mRNA/rRNA/tRNA;
- ATP/ADP;
- NAD/NADP (reduced or not);
- Cyclic AMP/cAMP;
- chlorophyll
Plants absorb a number of other nutrients in the soil including phosphates.
Describe why phosphates are needed by a growing plant (1)
- production of phospholipids (for cell membranes);
- synthesis of ATP;
- production of DNA/RNA/NADP.
Describe how a lack of phosphates in the soil surrounding a plant can affect its growth.
phosphates required to make:
- ATP/glucose phosphate -> so less respiration/energy for growth;
- nucleotides -> so less DNA/mRNA/tRNA for cell division/protein synthesis for growth;
- RuBP (regenerated) /NADP -> so less CO2 fixation/reduced to sugar for growth;
- phospholipids -> so less cell membrane production so less growth (of cells).
Outline the advantages of having Mycorrhizae growth near plants (2)
- Mycorrhizae help plants to defend themselves;
OR Mycorrhizae help plants to take up nitrates/phosphates; - causing an increase in crop yield.
You are given samples of water from three different rivers. Describe how you would obtain a quantitative measurement of their cloudiness (3)
- use of a colorimeter;
- measure the absorbance of light;
- standardise the method e.g same volume of water, zeroing/calibrating colorimeter to zero, same wavelength of light, shaking the sample.
Describe the process of Eutrophication (5)
- Excess nitrates/phosphates/ammonium ions washed into waterway/lake/pond/river;
- (High conc of ions) increases agal bloom/biomass on surface;
- Aglae block light so less photosynthesis;
- Submerged aquatic plants/algae die;
- More/larger population of saprobionts decompose dead biomass;
- (so) more/higher rate of aerobic respiration;
- Bacteria/saprobionts use up/decrease oxygen dissolved in water;
- (so) death of aerobic organisms (anoxic) as increase in anaerobic respiration leads to putrification.
