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Date November 2017 Marks available 9 Reference code 17N.2.SL.TZ0.4
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term To what extent Question number 4 Adapted from N/A

Question

Describe the role of primary producers in ecosystems.

[4]
a.

Explain the potential impact of ocean acidification on environmental systems and societies.

[7]
b.

To what extent do anthropocentric value systems dominate the international efforts to address climate change?

[9]
c.

Markscheme

producers are plants that convert light energy into chemical energy by photosynthesis;
photosynthesis/primary producers convert carbon dioxide and water into glucose/sugar and oxygen;
this conversion/glucose forms the raw material of biomass/the basis of food chains;
producers (thereby) provide food for consumers/energy in a form that can be passed along food chains;
the production of oxygen by producers is vital for the majority of ecosystems;
the absorption of CO2 maintains a balance of CO2 in atmosphere/reduces global warming;
primary producers may alternatively generate biomass through chemosynthesis;
chemosynthetic bacteria use chemical energy to produce food without using sunlight;
plants may also provide other resources/services for ecosystem eg habitats/soil conservation/cycling of matter;

Award [1] for each correct role described, up to [4 max].

a.

ocean acidification is caused by increased CO2 levels in atmosphere leading to more CO2 absorbed into ocean;
the CO2 reacts with the water forming an acid (carbonic acid)/decreasing the pH/changing pH from about 8.2 to 8.1;
macro-algae/seagrasses may benefit from higher CO2 conditions in the ocean;
some organisms are adapted to a narrow pH range/very sensitive to pH changes;
low pH/reduces ability of shelled organisms to maintain their shells/reduces reproductive ability in fish/shellfish;
producers eg phytoplankton/corals in ocean environments can be particularly sensitive to low pH;
corals are more prone to bleaching/less able to recover from damage in acidified water;
reduction in producers reduces the resilience of an ecosystem/impacts entire food webs/is a potential tipping point for marine systems/reduces biodiversity;
collapse of a natural ecosystem may lead to collapse of fisheries/collapse of aquaculture (eg oysters)/overfishing of diminishing fish populations;
loss of fisheries can lead to limited food supply for indigenous communities/need to import food;
decline in fishing/aquaculture would result in reduced employment/socio-economic hardship;
coral reefs support economically valuable ecotourism that may be lost/decline;
loss of corals will bring an aesthetic loss/infringe biorights of organisms;

Do not credit responses that mistakenly address acid deposition.
Award 2 max for describing process of acidification.
Award 5 max if impacts are limited only to ecosystems or only to societies.

Award [1] for each correct explanation, up to [7 max].

b.

The following guide for using the markbands suggests certain features that may be offered in responses. The five headings coincide with the criteria given in each of the markbands (although “ESS terminology” has been conflated with “Understanding concepts”). This guide simply provides some possible inclusions and should not be seen as requisite or comprehensive. It outlines the kind of elements to look for when deciding on the appropriate markband and the specific mark within that band.

Answers may include:

Please refer to paper 2 markbands, available under the "your tests" tab > supplemental materials

c.

Examiners report

Q4 was the most popular choice in Section B. Great majority were able to identify a couple of aspects of the role of primary producers but few went on to gain full credit.

a.

There were some excellently detailed answers in response to this question, though a great number confused ocean acidification with acid precipitation which have very different causes and impacts. Similarly, many mistakenly addressed contamination of food sources, bioaccumulation etc.

b.

Again there were some very impressive responses that correctly characterised the anthropocentric position and their role in many named international agreements developing a clear argument in contrast to other environmental value systems. A good deal of responses, however, portrayed a rather distorted version of anthropocentrism more along the lines of cornucopian values or climate change sceptics, so the argument became unbalanced or confused.

c.

Syllabus sections

Topic 1: Foundations of environmental systems and societies » 1.1 Environmental value systems
Show 29 related questions
Topic 7: Climate change and energy production » 7.3 Climate change—mitigation and adaptation
Topic 1: Foundations of environmental systems and societies
Topic 7: Climate change and energy production

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