▶️ Answer/Explanation
(a)(i)
(5 \text{ mm})
(a)(ii)
Based on Fig. 7.1, the changes can be described as follows:
- Microplastics: The mass increased steadily from 1950, reaching a peak in 2000, before decreasing in 2010.
- Macroplastics: There was little to no mass recorded until 1970; it then increased slowly until 2000, followed by a sharp/rapid increase between 2000 and 2010.
- Comparison: Microplastics had a higher mass than macroplastics from 1950 to 2000, but in 2010, the mass of macroplastics exceeded that of microplastics.
(b)
Two ways plastics harm animals:
- Ingestion: Animals eat plastic mistaking it for food, which can block the digestive system, cause internal injuries, or lead to starvation due to a false sense of fullness.
- Entanglement: Animals can get trapped in plastic debris (e.g., fishing nets, six-pack rings), which restricts movement, causing drowning, injury, or inability to feed/escape predators.
(c)
One other source of pollution:
- Untreated sewage.
- Excess chemical fertiliser (leading to eutrophication).
- Insecticides/Herbicides (agricultural runoff).
- Oil spills (marine pollution).
Part (a)(i): Unit Conversion
The syllabus requires candidates to convert between units, including cm and mm. Since (1 \text{ cm} = 10 \text{ mm}), the calculation is (0.5 \times 10 = 5 \text{ mm}).
Part (a)(ii): Data Interpretation
This question assesses the ability to interpret bar charts and describe trends (AO2: Handling information). Candidates must note the rise and fall of microplastics versus the late surge in macroplastics.
Part (b): Effects of Plastics
The syllabus explicitly includes the description of the “effects of non-biodegradable plastics, in both aquatic and terrestrial ecosystems.” In the ocean, this primarily manifests as physical harm through ingestion and entanglement.
Part (c): Aquatic Pollution
The syllabus lists several other aquatic pollutants. Key examples include “untreated sewage and excess fertiliser” and “freshwater and marine pollution” associated with habitat destruction.