farming

give 4 farming practices which increase GPP/NPP:

• pesticides - insecticides and herbicides

• biological agents - parasites and pathogenic bacteria/viruses

• integrated systems (pesticides and biological agents)

• keeping animals in pens

explain how using pesticides increases GPP/NPP:

• killing of pests simplifies food web

• insecticides - kill insect pests os less biomass lost from crops ∴ NPP greater

• herbicides - kill weeds, removing direct competition for solar energy and removes insect pests’ habitat/food source

explain how biological agents increase GPP/NPP:

• reduces no. of pests so simplifies food web

• crops lose less energy and biomass, increasing efficiency of energy transfer to humans

• parasites - live in/lay eggs on pest insect, killing it/reducing its ability to function

• pathogenic bacteria/viruses also kill pests e.g. by secreting toxins

explain how integrated systems increase GPP/NPP:

• combination of pesticides and biological agents

• has greater effect on reducing pest numbers, further increasing NPP

explain how keeping animals in pens increases GPP/NPP:

• restricts movement and increases warmth (indoors) - decreases rate of respiration ∴ less energy wasted via movement/thermoregulation

• increases biomass production and chemical energy storage, further increasing NPP and efficiency of energy transfer to humans

• BUT ethical concerns - may cause distress to animals as they cannot exhibit natural behaviour

describe and explain the process of eutrophication:

1. soluble nutrients e.g. nitrates/phosphates washed out of soil, into water

2. increased nitrates/phosphates increase plant growth, causing algal bloom

3. plants cover surface and lock out light, meaning that aquatic plants cannot photosynthesise, causing them to die

4. death of aquatic plants initiates increase in saprobionts which decompose plants and respire aerobically, using up oxygen

5. less oxygen is available to aquatic animals, so they are unable to respire and die

what is leaching?

the process in which water soluble compounds e.g. fertilisers are lost from soil and washed off into bodies of water

give 2 factors which make leaching more likely:

• fertiliser applied just before heavy rainfall

• inorganic ions in artificial fertilisers - soluble so more likely to leach if not immediately used

give 2 factors which make leaching less likely:

• N/P in organic fertilisers less likely to leach as contained in organic compounds, making their release into soil more controlled

• phosphates less soluble than nitrates so leaching less likely

compare natural and artificial fertilisers:

how does productivity differ between natural and artificial ecosystems?

• relatively low in natural ecosystems

• increases in agricultural ecosystems due to additional energy input and exclusion of other species via pesticides/herbicides, reducing competition for abiotic factors

compare and contrast natural and agricultural ecosystems: