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Pine processsionary moths lay eggs that develop into larvae and then into caterpillars, as shown in the diagram - OCR Gateway - GCSE Biology - Question 20 - 2022 - Paper 1
Question 20
Pine processsionary moths lay eggs that develop into larvae and then into caterpillars, as shown in the diagram. The caterpillars are a major pest, eating and killi... show full transcript
Worked Solution & Example Answer:Pine processsionary moths lay eggs that develop into larvae and then into caterpillars, as shown in the diagram - OCR Gateway - GCSE Biology - Question 20 - 2022 - Paper 1
Step 1
Draw a labelled pyramid of biomass for these feeding relationships showing the organisms at each level.
Answer
The pyramid of biomass should include the following trophic levels:
- Pine Trees (base level)
- Caterpillars (second level, feeding on pine trees)
- Cuckoos and Fungi (top level, predators of caterpillars and parasites respectively). Each level should be labelled clearly.
Step 2
Explain how natural selection may have resulted in all cuckoos having the sticky membrane.
Answer
Natural selection may have favored cuckoos that possess a sticky membrane in their guts because this trait increases their survival rate. Cuckoos that can effectively consume caterpillars without irritation from the caterpillar's hairs have a higher chance of survival and reproduction. Over time, the allele for the sticky membrane becomes more common in the population, resulting in all cuckoos eventually exhibiting this adaptation.
Step 4
Step 5
Calculate the percentage increase in the death of larvae on the pine trees compared to in the laboratory for the control treatment.
Answer
To calculate the percentage increase:
- Deaths in the laboratory: 13
- Deaths on the pine trees: 22
- Percentage increase = rac{22 - 13}{13} imes 100 = 69.23%.
Step 6
Suggest one reason why more larvae die in the natural environment of the pine trees than in the laboratory for all treatments.
Answer
One reason could be that the larvae in the natural environment are exposed to more predators and environmental stressors than those kept in a controlled laboratory setting.
Step 7
Evaluate the use of the two plant oils in the control of the larvae.
Answer
The laboratory results show that ginger oil (712 deaths) is significantly more effective than rosemary oil (300 deaths) in killing larvae. However, in the natural environment, both oils yield a lower effectiveness, with ginger showing 874 deaths compared to rosemary's 761. This suggests variables in the natural environment may reduce the effectiveness of these oils, requiring further research into their application in field settings.