| Chemical energy stores | - GPP (Gross primary production)
- NPP (Net primary production) |
| GPP (Gross primary production) | - The amount of light energy converted into chemical energy, per unit area |
| NPP (Net primary production) | - The amount of energy converted into chemical energy that is available to consumers |
| How primary production is expressed as rate | - Typical units might be kJ ha-1 year-1 (kilojoules per hectare per year) |
| NPP equation | net primary production = gross primary production - respiratory loss |
| Net production of consumers | - Consumers also store chemical energy in their biomass
- Get energy by ingesting other organisms
- However not all chemical energy stored in the consumers food is transferred to the next trophic level
- Around 90% of the total available energy is lost is various ways |
| Where the energy is lost to | - Egested as faeces + urine
- Respiration
- The energy that's left after all this is stored in the consumers biomass, is available to the next trophic level |
| Net production equation | N = I - (F + R)
N = Net production
F = Chemical energy lost in faeces and urine
I = Chemical energy in ingested food
R = Energy lost through respiration |
| Two ways in which farming increases the amount of energy available for human consumption | - The energy lost to other organisms e.g. pests, can be reduced
- The energy lost through respiration can be reduced |
| The energy lost to other organisms e.g. pests | - Farmers can reduce pest numbers using chemical pesticides + biological agents, so crops lose less energy + biomass
- Increasing efficiency of energy transfer to humans
- Combined effect of using both can reduced pest no. even more than either method alone, so NPP is increased even more |
| The energy lost through respiration can be reduced | - Controlling the conditions that they live on
- So that more of the energy is used for growth + less is lost through respiration
- This means that more biomass is produced + more chemical energy can be stored
- Increasing NP + efficiency of energy transfer to humans |
| Productivity in animal farming | - High protein diet, decreases faeces, increase absorption
- Kill animals are 1 year, when productivity is highest
- Antibiotics in feed, prevent loss of biomass due to disease
- Movement restricted, less muscle contractions, less respiratory losses
- Kept at 25c, less energy used for thermoregulation |
