Nutrieng Cycle Flashcards
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
Plants absorb a number of other nutrients from the soil including phosphates. Describe why phosphates are needed by a growing plant.
• production of phospholipids;
• in cell membranes;
• synthesis of ATP;
• production of DNA;
• production of RNA;
• production of NADP
Describe the process of eutrophication.
• Nitrates / Phosphates / Ammonium ions flushed into waterway
• Increased algal bloom
• Light blocked out
• Submerged aquatic plant unable to photosynthesise and die
• Increase in saprobionts so increases rate of aerobic respiration
• Saprobionts / aero.resp organismsn die as lack of oxygen (anoxic)
• Increase in anaerobic microorganisms
• Production of 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 ;
Outline the advantages of having Mycorrhizae
growth near plants
• Mycorrhizae help plants to defend themselves (causing an increase in crop yield);
• Mycorrhizae help plants to take up nitrates/phosphates (causing an increase in crop yield);
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 ;
Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested.
- amino acid/protein/ polypeptide/peptide;
- nucleic acid/nucleotide/base;
- DNA;
- RNA / pre-mRNA / mRNA / rRNA / tRNA
- ATP/ADP;
- NAD/NADP (reduced or not);
- Cyclic AMP/cAMP;
- Chlorophyll;
Describe how a lack of phosphates in the soil surrounding a plant can affect its growth
• (Required to) make ATP/glucose phosphate, so less respiration/less energy for growth;
• (Required to) make nucleotides, so less DNA/mRNA/tRNA for cell division/production of protein (for growth);
• (Required to) make RuBP/NADP, so less CO2 fixed/reduced into sugar;
• (Required to) make phospholipids for membranes;
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur.
• High concentration of carbon dioxide linked with night/darkness;
• No photosynthesis in dark/night / light required for photosynthesis/light-dependent reaction;
• (In dark) plants (and other organisms) respire;
• In light net uptake of carbon dioxide by plants/plants use more carbon dioxide than they produce/ rate of photosynthesis greater than rate of respiration;
• Decrease in carbon dioxide concentration with height;
• At ground level fewer leaves/less photosynthesising tissue/more animals/less light;
Describe the role of saprobionts in the nitrogen cycle.
• (use enzymes to) decompose proteins / DNA / RNA / urea;
• Producing / releasing ammonia / ammonium ions;
Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water.
Growth of algae / surface plants / algal bloom blocks light;
- Reduced / no photosynthesis so (submerged) plants die;
- Saprobiotic (microorganisms / bacteria);
- Accept: Saprobiont / saprophyte / saprotroph
- Neutral: decomposer
- Aerobically respire / use oxygen in respiration;
- Less oxygen for fish to respire / aerobic organisms die;
Scientists investigated the effect of a mycorrhizal fungus on the growth of pea plants with a nitrate fertiliser or an ammonium fertiliser. The fertilisers were identical, except for nitrate or ammonium.
The scientists took pea seeds and sterilised their surfaces. They planted the seeds in soil that had been heated to 85 °C for 2 days before use. The soil was sand that contained no mineral ions useful to the plants.
(a) Explain why the scientists sterilised the surfaces of the seeds and grew them in soil that had
been heated to 85 °C for 2 days
b) Explain why it was important that the soil contained no mineral ions useful to the plants.
The pea plants were divided into four groups, A, B, C and D.
- Group A – heat-treated mycorrhizal fungus added, nitrate fertiliser
- Group B – mycorrhizal fungus added, nitrate fertiliser
- Group C – heat-treated mycorrhizal fungus added, ammonium fertiliser
- Group D – mycorrhizal fungus added, ammonium fertiliser
The heat-treated fungus had been heated to 120 °C for 1 hour.
(c) Explain how groups A and C act as controls
d)fter 6 weeks, the scientists removed the plants from the soil and cut the roots from the shoots. They dried the plant material in an oven at 90 °C for 3 days. They then determined the mean dry masses of the roots and shoots of each group of pea plants.
(d) Suggest what the scientists should have done during the drying process to be sure
that all of the water had been removed from the plant samples.
f)The scientists determined the dry mass of the roots and shoots separately. The reason for this was they were interested in the ratio of shoot to root growth of pea plants. It is the shoot of the pea plant that is harvested for commercial purposes.
(f) Explain why determination of dry mass was an appropriate method to use in this investigation.
(a) 1. To kill any fungus / bacteria on surface of seeds or in soil;
- So only the added fungus has any effect.
b)So that only nitrate or ammonia / type of fertiliser affects growth.
c)So that effects of nitrate or ammonium alone could be seen;
2. So that effects of fungus can be seen.
d)Weigh samples at intervals during drying;
2. To see if weighings became constant (by 3 days).
f)(f) 1. Dry mass measures / determines increase in biological / organic material;
- Water content varies.
One environmental issue arising from the use of fertilisers is eutrophication.
Eutrophication can cause water to become cloudy.
You are given samples of water from three different rivers.
Describe how you would obtain a quantitative measurement of their cloudiness.
Principle is
- Named apparatus
- What is measured
- Standardisation of method
Accept any valid method, for example
- Use of colorimeter;
Reject calorimeter
- Measure the absorbance/transmission (of light);
Reject if samples are filtered unless filtering to remove debris
Accept descriptions
- Example of how method can be standardised eg same volume of water, zeroing colorimeter, same wavelength of light, shaking the sample;
Ignore references to calibration curves
