Outline why top carnivores are vulnerable to non-biodegradable toxins.

Explain two factors which lead to a loss of marine (ocean) biodiversity.

Evaluate one possible pollution management strategy for solid domestic waste.

Please note: although "quality of expression" marking is no longer used in exams, this question from a past syllabus may still be useful for student practice.

organisms lower down food chain/plants absorb small/non-lethal amounts of toxin (into their fatty tissue/biomass);
as the toxin is non-biodegradable it stays in the organism’s body/is not broken down/is persistent, it accumulates over time (bioaccumulation);
toxin is then passed on to further trophic levels through feeding;
because non-toxic biomass is lost (through respiration/metabolism) along food chain but the mass of toxin is not, its concentration increases (biomagnification);
so concentration of toxins increases as it passes up the food chain / concentration increases by an average of 10 times per level (assuming an ecological efficiency of 10%);
...so impact on health of top carnivores is more severe/lethal than lower trophic levels. 

Do not credit the response that “higher trophic levels eat more than lower trophic levels”.

[4 max]

Please note: although "quality of expression" marking is no longer used in exams, this question from a past syllabus may still be useful for student practice.

Factor (F): global warming;
Explanation (E): leads to higher ocean temperatures to which many marine species are sensitive;
Explanation (E): some species cannot adapt/evolve/migrate quickly enough / compete successfully, leading to loss in biodiversity/extinction;
Explanation (E): changing temperatures may reduce productivity by phytoplankton leading to loss of diversity throughout the food chains;
Explanation (E): higher temperatures may lead to coral death/bleaching affecting whole food webs/ecosystem;

Factor (F): ocean acidification;
Explanation (E): leads to coral bleaching (especially at higher ocean temperatures);
Explanation (E): most marine organisms have a very narrow band of tolerance for pH (shells won’t develop) leading to possible extinction and loss of biodiversity;

Factor (F): pollution from plastic;
Explanation (E): tiny pieces of plastic ingested by organisms may carry associated persistent organic pollutants(POPs)/toxins that can be absorbed and passed along food chains;
Explanation (E): marine organisms become entangled in plastic and unable to feed/suffocate;
Explanation (E): marine organism/scavenging birds ingest plastic causing suffocation/starvation;

Factor (F): pollution from oil spills;
Explanation (E): oil spills will take long time to degrade, having a long term negative impact on ecosystems and biodiversity;
Explanation (E): oil leading to animals losing their protection to cope with cold/waterlogging/drowning;

Factor (F): overfishing/unsustainable fishing methods/hunting of keystone species;
Explanation (E): some fishing methods (e.g. bottom trawling, electrocution/poison/explosives) are indiscriminate and take all organisms leading to the loss of all organisms from an area;
Explanation (E): some fishing methods destroy the habitats (e.g. scallop dredgers or bottom trawlers) leading to local loss of diversity;
Explanation (E): if fish populations are harvested at rates greater than replacement then loss of numbers will lead to possible (functional) extinction;
Explanation (E): nets and fishing lines can entangle seabirds (especially Cormorants) and marine mammals (e.g. fur seals in Sub-Antarctic);
Explanation (E): Hunting top carnivores e.g. shark can disturb food webs leading to loss of diversity. 

Award [4 max] if only one factor explained.
Do not give credit for more than 2 factors. Only credit “eutrophication” as a factor if it is specifically identified in the context of estuarine/shallow water/coastal waters (it is not relevant to oceans/marine systems at large).

[6 max]

Please note: although "quality of expression" marking is no longer used in exams, this question from a past syllabus may still be useful for student practice.

Answers may include: recycling, incineration, landfill, composting, altering behaviour e.g. Recycling:

Strengths:
in general recycling reduces the amount of energy and resources required for a product;
e.g. the amount of energy saved when recycling aluminium is 95 %
e.g. plastic is usually made from oil which is a non-renewable resource and thus recycling saves a valuable resource;
recycling reduces air pollution and carbon emissions in comparison to a pollutionmanagement strategy (PMS) such as incineration;
recycling can be managed in many ways, such as a doorstep mixed collection, household sorting, drop-off at recycling points, and in less developed countries, by individuals picking through discarded rubbish/trash;

Limitations:
at the moment recycling is often not economical as it is cheaper to produce items from new raw materials;
recycling may not encourage a change in behaviour towards reducing rubbish/trash/garbage;
recycling is challenging for plastics as there are many grades of plastic and you can’t “upcycle” poorer grade plastics;
people may not want to sort their trash when recycling is only available through separation by households;
it is not possible to recycle all products due to poor packaging design. 

Conclusion should be a clear evaluative statement of the named pollution management strategy that is justified by evidence given in the response.
[1 max]

e.g. recycling is a particularly effective management strategy because, unlike landfill/incineration/composting, it not only reduces waste but also reduces demand on natural resources;
e.g. recycling is a very effective way of reducing the impact of waste on the environment, but since it depends on altering human activity it will only become really successful with a shift to more ecocentric value systems;

Award [7 max] if no clear conclusion regarding relative strengths or weaknesses.
Award [5 max] if only strengths or limitations discussed.

[8 max]

Expression of ideas [2 max]

Candidates usually earned one or two marks, but only a handful of candidates could demonstrate a true understanding of biomagnification. Very few scored the maximum 4 marks as there is confusion on the terms bioaccumulation & biomagnification.

This question was handled well by many candidates. They could usually identify two factors easily, with at least one explanation for each, but few achieved the full marks since they lacked depth.

Most students identified a couple of advantages and disadvantages for their chosen strategy. Q4 was the most popular. Similarly, the case on Pollution Management Strategy’s (Q4c); most achieved 3-5 marks. Some excellent responses. Lacking detail, thorough explanation of the content.