Students must develop an understanding of the challenge posed by the need to provide food and forest resources for a growing human population without damaging the planet’s life support systems. The interaction of the production of biological resources with other areas of the subject should be emphasised, including with conservation of biodiversity, energy resources, pollution and the physical environment.
3.5.1 Agriculture
Students should understand that agriculture involves the control of food webs to divert photosynthetic energy into human food. This involves the control of abiotic and biotic factors to maximise production.
3.5.1.1 Agroecosystems
Content | Additional information |
|---|
The selection of species Suitability of the environment:- temperature
- light: intensity, day length
- water availability
- soil fertility
- topography
- relief
- pest problems.
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Technological factors:- availability of energy
- pesticides
- machinery/equipment
- irrigation
- transport infrastructure.
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The biotic factors that affect productivity. Pest control: predators, competitors, pathogens, eg insects, fungi, weeds, bacteria. | |
Cultural pest control: - crop rotation/cultivation management
- barrier crops
- companion crops
- predator habitats
- biological control: introduced predators/pathogens
- sterile male techniques
- pheromone traps
- genetic resistance.
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Pesticides | How the properties of pesticides influence their effectiveness and environmental impacts: - toxicity
- specificity
- persistence
- solubility in water/lipids
- mode of action: contact/systemic.
A comparison of insecticide groups to consider their relative advantages and disadvantages: - organochlorines
- organophosphates
- pyrethroids
- neonicotinoids.
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Antibiotics:- as growth promoters
- to prevent infection
- to treat infections.
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Pollinators:- controlled use of pesticides that harm bees and other pollinators
- introduction of bee hives to flowering crops.
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Nutrient supply: maintenance of soil biota: detritivores and decomposers. | |
Food chain energy losses: - control movement
- temperature control
- species selection: different food conversion ratios (FCRs).
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| The abiotic factors that affect productivity | Abiotic factors controlled in agroecosystems: - temperature
- light: intensity, day length
- water availability
- nutrient supply
- topography
- relief
- pH
- carbon dioxide
- soil fertility
- soil salinity.
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3.5.1.2 Manipulation of food species to increase productivity: the advantages and disadvantages of the methods that are available to improve crop and livestock gene pools
Content | Additional information |
|---|
Genetic manipulation: - selective breeding
- asexual reproduction/vegetative propagation/cloning
- genetic engineering/transgenics/GM.
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Agricultural energetics The ways in which agricultural energetics can be quantified and their applications: - productivity
- efficiency
- intensive/extensive systems
- energy subsidies: machinery, fertilisers, pesticides, transport, processing
- energy ratios and efficiency: a comparison of intensive and extensive systems.
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Manipulation of food species to increase productivity: - stocking/crop density
- monocultures: advantages and disadvantages.
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3.5.1.3 Environmental impacts of agriculture
Content | Additional information |
|---|
Habitat impacts:- habitat clearance
- wetland drainage
- ploughing of grassland
- reduced biodiversity
- genetic contamination
- soil degradation and erosion.
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Pollution- pesticides
- nutrients
- GHGs: methane, carbon dioxide, NOx .
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Changes to the hydrological cycle:- unsustainable irrigation
- changes in evapotranspiration.
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3.5.1.4 Social/economic/political factors which influence agricultural production
Content | Additional information |
|---|
Consumer choice: - social factors
- cultural factors
- religious factors
- ethical factors.
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Economic factors:- subsidies
- guaranteed prices
- quotas.
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Political factors:- trade controls
- economic controls
- subsidies
- guaranteed prices
- quotas.
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3.5.1.5 Strategies to increase the sustainability of agriculture
Content | Additional information |
|---|
Pest control. | |
Reduced use of chemical pesticides. | |
Reduced use of antibiotics. | |
Cultural pest control: - weeding
- mulching
- crop rotation
- barrier crops
- biological control
- predator habitats
- polyculture/companion crops.
| |
Integrated control. | |
Nutrient supplies: Use of natural processes: - nitrogen-fixing bacteria
- decomposition
- crop rotation.
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Increased use of natural processes to supply nutrients:- recycling of organic matter
- crop rotation
- permaculture
- growth of legumes
- conservation of soil biota.
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Energy inputs:- use of natural processes instead of artificial fertilisers
- low tillage techniques.
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Water management to ensure sustainable supplies. | |
| Social impacts: the control of environmental impacts on rural communities. | |
3.5.1.6 Opportunities for skills development and independent thinking
| Mathematical skill number | Opportunities for skills development and independent thinking |
|---|
| MS 1.3 | Students could construct tables on fish population data to draw conclusions on overfishing risks. |
| MS 1.9 | Students could use the Mann-Whitney U test to compare the effect of pest control methods on crop growth. |
| MS 1.10 | Students could calcuate the standard deviation of a data set, eg of crop yield for a given nutrient input. |
| MS 2.1 | Students could use symbols in assessing fish populations and fish catches. |
| MS 2.2 | Students could change the subject of equations when calculating energy efficiencies and energy ratios when comparing agricultural production systems. |
| MS 3.3 | Students could select an appropriate format for presenting data, on nutrient inputs and yield increase. |
Working scientifically
Students could plan activities in a range of broader environmental contexts related to food production systems, including ones where first-hand experience of practical activities may not be possible eg: monitoring how the use of GM fodder may affect energy ratios and food conversion ratios.
| Practical skill number | Opportunities for skills development and independent thinking |
|---|
| PS 3.1 | Students could plot and interpret graphs on the use of nitrate fertilisers and nitrate levels in aquifers. |
| PS 4.1 | The practical skills of using equipment within scientific studies are expanded, as appropriate, in detail in the selected methodologies and sampling techniques below. |
Opportunities to investigate the required methodologies of which students must have first-hand experience. Further details can be found in Appendix A: Working scientifically
| Methodology skill number | Opportunities for skills development and independent thinking |
|---|
| Me 2 | Students could plan a survey to assess the impact of livestock on soil compaction. |
| Me 6 | Students could use a t-test to assess the statistical significance of a yield change following the introduction of a new crop variety or fertiliser. |
Opportunities to investigate the required sampling techniques of which students must have first-hand experience. Further details can be found in Appendix A: Working scientifically
| Sampling technique skill number | Opportunities for skills development and independent thinking |
|---|
| ST 3 | Students could measure the soil moisture and organic matter content of fields with different management regimes. |
3.5.2 Aquatic food production systems
Students should understand that fishing is the last large-scale human hunting activity. While aquatic species are renewable resources, humans can easily exploit populations above the Maximum Sustainable Yield.
Aquaculture allows humans to control productivity of aquatic species but has not yet increased food supplies in the way that agriculture has on land.
3.5.2.1 Marine Productivity
Content | Additional information |
|---|
The role of nutrients in controlling biological productivity | Nutrient availability. Variations in light levels: photic/aphotic zones. |
A comparison of productivity in open oceans, coastal areas, areas with upwelling | Students should understand how light and nutrient supplies control productivity in different areas. |
3.5.2.2 Fishing
Content | Additional information |
|---|
| The advantages and disadvantages of the main fishing methods | Catch effectiveness, catch selectivity, energy inputs, environmental impacts: - pelagic trawling
- demersal trawling
- purse seining
- drift netting
- long lining
- shellfish traps.
|
| Environmental impacts of fishing | Population decline caused by overfishing. Changed age structure. By-catch. Ghost fishing. Damage to seabed, coral reefs, seagrass beds. Food web impacts. |
| The methods of estimating fish populations and Maximum Sustainable Yield | The relationship between biomass, recruitment, growth, mortality and catch. Population sampling from the commercial catch: - catch size
- catch per unit fishing effort
- mean fish size
- mean age.
Data from research: - breeding success – egg/larvae density/survival.
|
| Methods of reducing environmental impacts of fishing | Catch quotas. Net design: - mesh design
- mesh size
- escape panels
- acoustic deterrent devices (‘dolphin pingers’).
Restricted fishing effort. No-take zones/protected breeding areas closed-seasons. Minimum catch size. Maximum catch size/protected individuals. Captive rearing and release to boost wild populations. Biodegradable/radio tracked equipment to reduce ghost fishing. |
3.5.2.3 Aquaculture
Content | Additional information |
|---|
| The relative merits of extensive and intensive aquaculture | Productivity, energetics and environmental impacts. |
| Principles of aquaculture and their application to extensive and intensive systems | Species selection. Stock selection. Breeding/genetic control. Disease control. Control of competition. Control of nutrition. Control of abiotic factors: - temperature
- dissolved oxygen
- light levels
- water flow.
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The extent to which aquaculture can replace fishing | Food requirements. Trophic level efficiency. |
Methods of reducing environmental impacts of aquaculture | Fish farm location. Control of organic wastes. Lower stocking density. Control escapes. Control of species and methods of collecting food for fish. Reduced use of pesticides/antibiotics. Feeding control. |
3.5.2.4 Opportunities for skills development and independent thinking
| Mathematical skill number | Opportunities for skills development and independent thinking |
|---|
| MS 0.1 | Students could convert between different units when estimating changes in total biomass, mean mass, fecundity and growth rates when assessing MSY. |
| MS 1.3 | Students could construct tables on fish population data to draw conclusions on overfishing risks. |
| MS 1.6 | Students could calculate or compare the mean, median and mode of a set of data, eg of yields of fish farmed under different conditions or fish from commerical catches. |
| MS 2.1 | Students could use symbols in assessing fish populations and fish catches. |
| MS 2.2 | Students could use and manipulate an equation to estimate the maximum sustainable yield of a fish population. |
3.5.3 Forest resources
Trees are a renewable resource but their slow growth rate and the need for land for other purposes has caused a significant reduction in global forest area.
3.5.3.1 The resources and life-support services gained from forests
Content | Additional information |
|---|
Resources:- timber
- fuel
- food
- fibres
- medicines.
| |
Ecosystem services: - atmospheric regulation
- habitat and wildlife refuge
- regulation of the hydrological cycle
- climate regulation
- soil conservation
- recreation/amenity uses.
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3.5.3.2 The relationship between forest productivity and biodiversity
Content | Additional information |
|---|
The impacts on productivity and biodiversity of: - growth of non-indigenous species
- single-species plantations
- close planting
- simple age structure.
| |
3.5.3.3 Deforestation
Content | Additional information |
|---|
| The causes of deforestation | Exploitation above the MSY. Clearance for alternative land use. |
The effect of deforestation on resources, biodiversity, hydrology, soil and climate | Loss of resources: - timber, fuel, fibres, medicines
- reduced biodiversity
- loss of species
- fragmentation of remaining forest areas.
|
Changes to hydrology: - reduced interception and transpiration
- increased runoff.
| |
Impact on soil:- less dead organic matter
- increased soil erosion
- less protection of soil by vegetation and leaf litter
- reduced root binding.
| |
Climate impacts:- increased albedo
- reduced carbon sequestration and carbon reservoir
- reduced rainfall downwind.
| |
| Sustainable forest management | Mixed species plantations. Indigenous species. Mixed age structure. Selective logging. |
3.5.3.4 Opportunities for skills development and independent thinking
| Mathematical skill number | Opportunities for skills development and independent thinking |
|---|
| MS 0.3 | Students could use data on percentage forest clearance to estimate changes in area, biomass and carbon storage. |
| MS 0.4 | Students could estimate changes in forest area using satellite images. |
| MS 1.4 | Students could use mean tree mass and tree spacing to estimate biomass and carbon storage per hectare. |
| MS 1.9 | Students could use the t-test to compare the timber yield of two tree species. |
Working scientifically
Students could plan activities to investigate environmental issues related to forestry which they could carry out eg:- the effect of tree cover on the abiotic factors that affect wildlife in the woodand
- the effect of tree species diversity on the biodiversity of wildlife.
Students could plan activities in a range of broader environmental contexts related to forestry, including ones where first hand experience of practical activities may not be possible eg: the use of aerial survey data to monitor changes in forest area.
| Practical skill number | Opportunities for skills development and independent thinking |
|---|
| PS 2.2 | Students could evaluate the methods used to estimate tree biomass and assess potential inaccuracies. |
| PS 2.3 | Students could identify the other variables that may affect a study of humidity within a forest. |
| PS 3.1 | Students could construct a graph to show changing abiotic factors along a transect into a woodland. |
| PS 4.1 | The practical skills of using equipment within scientific studies are expanded, as appropriate, in detail in the selected methodologies and sampling techniques below. |
Opportunities to investigate the required methodologies of which students must have first hand experience. Further details can be found in Appendix A: Working scientifically
| Methodology skill number | Opportunities for skills development and independent thinking |
|---|
| Me 5 | Students could assess the effect of sample timing on a survey of abiotic factors in a forest. |
Opportunities to investigate the required sampling techniques of which students must have first hand experience. Further details can be found in Appendix A: Working scientifically
| Sampling technique skill number | Opportunities for skills development and independent thinking |
|---|
| ST 1 | Students could use light meters, temperature data loggers, humidimeters and anemometers to measure abiotic factors within a forest. |
| ST 3 | Students could investigate the impact of different management systems or tree types on soil organic matter content. |
