Nutrient Cycles Questions Flashcards
Name the type of bacteria that convert nitrites into nitrates (1)
Nitrifying
Other than spreading fertilisers, describe and explain how one farming practice results in addition of nitrogen containing compounds to a field (2)
Allow cattle to graze
Add dung/urine
Purification ponds can be used in warm climates to break down sewage. Explain the advantage of having both algae and bacteria in a purification (4)
Breakdown of sewage by enzymes from bacteria
Nitrates used by algae to make proteins
Algae photosynthesise
Bacterial respiration uses O2
Increased reproduction of bacteria
Purification ponds can be used in warm climates to break down sewage. The ponds contain bacteria and green algae. The ponds only work efficiently when ey are shallow and warm. Explain why (4)
Sufficient light penetration for photosynthesis of algae
Warm leads to faster enzyme activity
Faster bacterial respiration
Faster photosynthesis
Increased growth of bacteria
Explain why the net production of an area does not represent the total amount of plant biomass formed per year by photosynthesis (2)
Biomass lost in respiration
Biomass lost as co2
Explain the role of bacteria in making carbon in dead plant remains available to plants (4)
Decomposers
Release enzymes and digest detritus
Substances found in detritus
Absorb producers of digestion
Explain how the activities of decomposers and nitrifying bacteria recycle the substances in fallen leaves for reuse by the trees (7)
Decomposers digest organic matter
Respiration
Release CO2
CO2 used in photosynthesis
Release nutrients
Nitrifying bacteria convert ammonium to nitrate
By oxidation
Nitrates used in protein synthesis
Explain how the felling and burning of trees on a large scale could affect the concentration of carbon dioxide in the atmosphere (2)
Burning release co2
Less co2 removed from atmosphere by trees
Both rapidly growing softwood trees and slow growing hard trees grow in tropical tai forests. The seeds of both kind of trees lie dormant on the floor of a mature forest and only germinate when exposed to light and warmth. However, the seedlings of many hardwood species grow more successfully beneath the protective canopy of the softwood tress. When a small area of trees has been cut down, it can return normally to tropical rainforest . Suggest and explain how reestablishment of the rainforest ecosystem may occur in such areas (6)
Cleared area tree seeds germinate/grow in light
Light for photosynthesis
Softwoods compete for light
Hardwoods can grow in low light
Canopy reduces impact of rainfall
Roots stabilise soil
Less leaching
Trees provide food for animal
Trees provide habitats
A large lake is surrounded by fields. These are separated from each other by hedges. One hundred years ago the lake was a habitat for many plants, invertebrates and fish. Today the lake has no fish and few plants or invertebrates. Explain how increased use of inorganic fertilisers on the fields may have led to these changes.
Leaching of nitrates
Leads to increased growth of algae
Competition for light
Deeper plants die
Increases food supply for Decomposers
Respiration of microorganisms uses up oxygen
Fish/animals die due to lack of oxygen
A large lake is surrounded by fields. These are separated from each other by hedges. Explain how the removal of hedges near the lake would increase the impact of fertilisers on the aquatic ecosystem (2)
Leads to soil erosion
Increase in run off carries more fertilisers
Soil (+fertilisers) blown into lake
What is the prices by which nitrates turn to nitrogen (1)
Denitrification
What is the process by which nitrogen turns to ammonia (1)
Nitrogen fixation
Explain how farming practices might be responsible for the change in nitrate concentration in the water near their fields (2)
Excessive use of fertilisers
Run off/leaching
Describe the effect of increased nitrate concentration in a river (5)
Growth of algae
Death of deeper plants due to less light reaching them
More Decomposers
Respiration
Decomposers remove oxygen
Animals die because of lack of oxygen
Explain why an outbreak of pests is more of a problem in monoculture than where a mixture of crops is grown (3)
Weeds left in soil
Plentiful supply of sane food source for pest
Rapid reproduction of pesticides
Need to really same pesticide - resistance developed
Hence lower yield
Other than resistance, give two disadvantages of using pesticides (2)
Kill beneficial organisms
Bioaccumulation
Residue left on crop
Can enter water/food chain
Microorganisms make the carbon in polymers in a dead worm available to cells in a leaf. Describe how (5)
Microorganisms are saprobionts
Extracellular digestion
Absorb products of digestion
Respiration produce co2
Co2 taken into leaves
Explain why deforestation reduces the diversity index of an area (2)
Removes many habitats/niches
Fewer species
Use your knowledge of the nitrogen cycle to explain the potential benefit of adding fertiliser containing ammonium nitrate rather than one containing Potassium nitrate (3)
Ammonium nitrate contains more nitrogen per molecule
Ammonium converted to nitrate
By nitrifying bacteria
Explain how high nitrate concentration increases the growth of algae (2)
More proteins
More nucleotides
Increased cell division
Suggest how increased growth of algae could lead to the death of submerged plants (2)
Reduced light
Less photosynthesis
Explain how the decay of dead plants results in reduced oxygen concentration and increased nitrate production (6)
Bacteria feed on dead matter saprobiotically
Bacteria multiply
Respiration uses oxygen
Converts proteins to amino acids
Then to ammonium compounds
Nitrifying bacteria
Convert ammonium compounds
Via nitrates
Describe how the reduced oxygen concentration of the water will change the composition of the communities in the river (2)
Lower species diversity
Species tolerant to low oxygen concentrations thrive
Heterocysts are thick walled cells that do not contain chlorophyll. Suggest how these features improve the process of nitrogen fixation (3)
Thick walls exclude oxygen
Contain no chlorophyll so do not produce oxygen
Do not produce oxygen
Oxygen would inhibit nitrogen fixation
In China the fern is cultivated and ploughed into fields to act as an organic fertiliser. Explain how ploughing the fern plants into the soil results in an improvement in the growth of rice crops in these fields (5)
Decomposers in fields
Convert organic nitrogen into ammonium ions
Ammonium ions converted to nitrite
Nitrite converted to nitrate
By nitrifying bacteria
Decomposers respire and release co2
Used in photosynthesis by rice
Describe the role of bacteria in making the nitrogen in dead leaves available to growing plants (5)
Saprobionts
Break down nitrogen containing substances
Extracellular digestion
Ammonium produced
Ammonia converted to nitrite to nitrate
By nitrifying bacteria
Clearing the forests and burning the vegetation affects the carbon dioxide concentration in the atmosphere. Describe how and explain why (4)
Co2 concentration increases
Less vegetation so less photosynthesis
Less co2 removed from atmosphere
Burning/combustion release co2
Name the type of bacteria which convert nitrogen in the air into ammonium compounds (1)
Nitrogen fixing