3.5.1 Agroecosystems

Question 1

Sustainability of environment

Answer 1

• temperature
• light: intensity, day length
• water availability
• soil fertility
• topography
• relief
• pest problems.

Question 2

Technological factors

Answer 2

• availability of energy
• pesticides
• machinery/equipment
• irrigation
• transport infrastructure.

Question 3

Cultural pest control

Answer 3

• crop rotation/cultivation management
• barrier crops
• companion crops
• predator habitats
• biological control: introduced
predators/pathogens
• sterile male techniques
• pheromone traps
• genetic resistance.

Question 4

Pesticides

Answer 4

• toxicity
• specificity
• persistence
• solubility in water/lipids
• mode of action: contact/systemic.

Question 5

Food chain energy losses

Answer 5

• control movement
• temperature control
• species selection: different food
conversion ratios (FCRs).

Question 6

Abiotic controlling agroecosystems

Answer 6

• temperature
• light: intensity, day length
• water availability
• nutrient supply
• topography
• relief
• pH
• carbon dioxide
• soil fertility
• soil salinity.

Question 7

Manipulation of food species: genetic manipulation

Answer 7

• selective breeding
• asexual reproduction/vegetative
propagation/cloning
• genetic engineering/
transgenics/GM.

Question 8

Agricultural energetics

Answer 8

• productivity
• efficiency
• intensive/extensive systems
• energy subsidies: machinery,
fertilisers, pesticides, transport,
processing
• energy ratios and efficiency: a
comparison of intensive and extensive systems.

Question 9

Increasing productivity

Answer 9

• stocking/crop density
• monocultures: advantages and
disadvantages.

Question 10

Agricultural impacts on habitats

Answer 10

• habitat clearance
• wetland drainage
• ploughing of grassland
• reduced biodiversity
• genetic contamination
• soil degradation and erosion.

Question 11

Enviro impacts: pollution

Answer 11

• pesticides
• nutrients
• GHGs: methane, carbon dioxide,
NOx.

Question 12

Enviro impacts: hydro cycle

Answer 12

• unsustainable irrigation
• changes in evapotranspiration.

Question 13

Social economic political factors influencing agriculture production

Answer 13

Consumer choice:
• social factors
• cultural factors
• religious factors
• ethical factors.
Economic factors:
• subsidies
• guaranteed prices
• quotas.

Political factors:
• trade controls
• economic controls
• subsidies
• guaranteed prices
• quotas.

Question 14

Strategies increasing sustainability

Answer 14

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.
Increased use of natural processes to supply nutrients:
• recycling of organic matter
• crop rotation
• permaculture
• growth of legumes
• conservation of soil biota.

Energy inputs:
• use of natural processes instead of artificial fertilisers
• low tillage techniques.
Water management to ensure sustainable supplies.
Social impacts: the control of environmental impacts on rural communities.