Fig. 1 shows a rooftop garden with flowering plants, aphids, ladybirds and robins. The gardener notices that several leaves have been damaged by aphids. Tab...
Question 1 Report
Fig. 1 shows a rooftop garden with flowering plants, aphids, ladybirds and robins. The gardener notices that several leaves have been damaged by aphids. Table 1 gives estimated energy at each trophic level in one part of the garden.
| Organisms | Energy / kJ m-2 |
|---|---|
| flowering plants | 15 500 |
| aphids | 1400 |
| ladybirds | 155 |
| robins | 18 |
(a) Draw a food chain using all four groups of organisms. [2]
(b) What is the percentage energy transfer from aphids to ladybirds? [1]
(c) Describe the overall pattern shown by the energy values. [1]
(d) Give one reason why ladybirds do not receive all of the energy stored in aphids. [1]
Fig. 1 shows a cattle farm using anaerobic digesters. Cow manure enters a sealed tank. Microorganisms break down the material and methane is collected to heat farm buildings. Digestate is spread on fields.
(a) What gas is used as the fuel collected from the digester? [1]
(b) Describe why the digester must be sealed to maintain anaerobic conditions. [1]
(c) Give one energy transfer that occurs when methane is burned. [1]
(d) What happens to much of the chemical energy in manure that is not stored in methane? [1]
Answer Details
Labelled answer diagram:
Rooftop food chain
(a) A correct food chain is flowering plants → aphids → ladybirds → robins. [2]
(b) \[\left(\frac{155}{1400}\right)\times100=11.1\%\] Therefore the percentage transfer is 11.1%, or 11%. [1]
(c) Energy decreases at each successive trophic level. [1]
(d) Ladybirds do not receive all aphid energy because aphids use energy in respiration and movement, and may lose energy in waste. [1]
Anaerobic digester
(a) The fuel gas is methane. [1]
(b) The digester must be sealed to prevent oxygen entering, maintaining anaerobic conditions. [1]
(c) When methane burns, chemical energy is transferred to thermal energy, or heat. [1]
(d) Much chemical energy not stored in methane is released as heat during respiration by microorganisms. [1]
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