agriculture
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Explain why intensive agricultural systems have higher energy inputs (3 marks)
• Use of fertilisers • requires irrigation -manufacturing/use of machinery • control of abiotic factors eg use of artificial lighting
Explain how factors that limit productivity may be managed to increase the sustainability of crop production (6 marks)
• Insects can be controlled using biological control or insecticides. • low nutrient availability can be controlled through organic manures/nitrogen fixing bacteria • crop rotation • drip irrigation • multi-cropping
The food samples collected were individually wrapped before being sent for analysis of pesticide levels. Why is this less important for samples containing systemic pesticides than contact pesticides? (1 mark)
Systemic pesticides will be retained within the food.
Suggest why pesticide residue levels in samples of a single type of food may show high variability (4 marks)
• types of pest may vary • seasonal changes/species life cycles affect abundance (requiring different application rates) • different methods/timing of application affect concentrations Variation after application • rainfall • time before harvest • increase in mass causes dilution • storage/treatment method
Describe three advantages of using pyrethroids (3 marks)
• does not remain in the environment for a long period of time/low persistence • (as it) degrades quickly • not liposoluble/do not bioaccumulate/ biomagnify • high specificity/high insect toxicity/low mammal toxicity /fewer non-target species are killed • insoluble in water/low mobility • not carcinogenic
Describe three indirect affects of pesticides on living organisms (3 marks)
1) loss of potential food source 2) loss of an ecosystem service eg seed dispersal or pollination. 3) Some species become more abundant as predators have been removed.
Barrier crop
Crop rotation
eg Lupin plants hosting nitrogen-fixing bacteria are cultivated to improve soil fertility
Genetic modification
eg Plasmid containing DNA code for antifreeze protein inserted into young strawberry plants
Introduced pathogen Introduced predator
Leguminous crop
eg Introduction of Phytoseiulus persimilis mite that feeds upon Two-spotted Spider Mites, Tetranychus urticae, which would reduce strawberry crop yields
Mulching
the practice of covering the soil surface with a layer of material, typically organic matter, to protect plants and improve soil health.
Pheromone traps
They work by using synthetic sex pheromones (or attractants) to lure male moths (or both male and female beetles) into traps. This allows farmers to monitor pest populations, determine the timing of treatments, and even reduce pest numbers
Weeding
Explain why neonicotinoids are less likely to build up in soil than in aquifers (3 marks)
Any three from: * More suitable conditions for decomposers/bacteria * Suitable temperature: rate of decomposer activity, kinetic energy for chemical reactions * No light for photodegradation * Less water * Lower mobility/dispersal
Suggest possible causes, other than the use of neonicotinoids, of the decline in the bee population. (3 marks)
• Changed farming practice • Other pesticide • Weather/climate change • Change in inter-dependent species
Explain how the total amount of pesticide used may be reduced by using seed coatings of persistent systemic pesticides rather than aerial spraying of nonpersistent contact pesticides. (3 marks)
Any three features that reduce the amount used, from: * Accurate positioning (on seed) (because seed coating rather than aerial) * Translocation throughout plant (because systemic rather than contact) * Longer presence (because persistent) * Reduced need for reapplication (because persistent/systemic) * No spray drift (because seed coating rather than aerial)
Plagioclimax
Habitat where human activity has prevented the ecosystem from developing
Define the term ‘vegetative propagation’. (1 mark)
Production of genetically identical offspring/asexual reproduction
Explain how transferring the potato plants to the field as a monoculture may affect the yield. [2 marks]
• all plants have same pests • specific pesticides make pest control easier, increasing yield or • increased risk of pest infestation, greater risk of yield loss OR • all plants have same disease resistance • specific pesticides make disease control easier, increasing yield or • increased risk of disease, greater risk of yield loss OR • all plants have the same nutrient needs • specific fertilisers may be used to increase yields or • increased competition for the same nutrients/ reduction in soil fertility may reduce yields
Explain how one method of gene manipulation is used to increase crop yields. [2 marks]
• genetic modification/transgenics/ gene editing/ selective breeding (or description of method) • named trait (to increase yield) e.g. pest resistance, drought resistance, frost resistance, salinity tolerance
Explain why systemic pesticides do not impact non-target species that land on crops. [1 mark]
• Pesticide inside plant tissue
Explain how the use of pesticides can reduce the availability of soil nutrients. [4 marks]
• death of detritivores/decomposers • reduces breakdown of organic matter • death of nitrogen fixing/nitrifying bacteria • reduces nitrate availability [A ammonium] • death of burrowing organisms/worms • reduces oxygen for decomposition/ nitrogen fixation/nitrification • reduces drainage increasing denitrification • death of mycorrhizal organisms • reduces nutrient uptake.
What is hydroponics?
The growth of crops in a nutrient solution rather than a solid growth medium