Section D: Case-Based Questions

Question 29: A study was conducted to observe the effects of pollution on aquatic life in a lake over a year. The concentration of various pollutants and their impact on the fish population were recorded. Based on the data:

• (a) Describe the observed relationship between pollutant concentration and fish population size.
• (b) If one type of pollutant was found to reduce oxygen levels in water, explain how this affects the fish population.
• (c) Given that certain algae species flourished with increased nutrient pollution, leading to algal blooms, discuss the potential long-term impacts on the lake’s ecosystem.

OR

• (c) If measures were implemented to reduce the inflow of nutrients into the lake halfway through the study, hypothesize the subsequent changes observed in the algal population and overall water quality.

Question 30: Researchers introduced a genetically modified crop designed to resist a common pest in agricultural fields. The crop produces a toxin that targets the digestive system of the pest, reducing crop damage. The effectiveness of the crop was monitored by comparing it with non-modified crops in adjacent fields.

• (a) Evaluate the effectiveness of the genetically modified crop based on the observed levels of pest activity and crop yield.
• (b) Discuss the implications of widespread use of genetically modified crops for pest resistance on local biodiversity.
• (c) Considering the potential development of resistance in pests to the genetically modified crop, suggest strategies that farmers could use to manage pest resistance effectively.

OR

• (c) If the genetically modified crop also showed unexpected effects on non-target insect species beneficial to the ecosystem, describe the potential ecological consequences and recommend measures to mitigate these impacts.

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