Distinguish between the terms niche and habitat with reference to a named species.

Suggest the procedures needed to collect data for the construction of a pyramid of numbers for the following food chain:

Quantitative models are frequently constructed to show the flow of energy and cycling of matter in natural systems.

To what extent can these models be useful in assessing the sustainability of named food production systems?

habitat is the kind of (biotic and abiotic) environment in which a species normally lives;
eg lions are found in tropical grasslands;
whereas its niche refers to all its interactions with its (biotic and abiotic) environment;
eg the prey that it eats / its vulnerability to parasites / access to fresh water;
habitat may be shared by many species / niche is more limited to a single species;
eg different cat species inhabit tropical grasslands but only lions hunt in groups and so tend to take larger prey.

Award [2 max] if no examples are given. “Role of species within ecosystem” would be acceptable as definition of species, but not “job” which is anthropomorphic and only addresses impact of species on system, not the mutual relationship.
Accept any relevant/valid/equivalently detailed examples to those given.
Award [1] for each correct answer, up to [4 max].

quadrats can be used for counting/sampling snail/plant populations;
need to be randomly distributed within area of system;
total estimated by multiplying mean of samples by total area/sample area;
mark–release–recapture/Lincoln index can be used for bird/snail species;
individuals are caught using traps/nets/bait;
individuals marked by some means that is indelible/harmless/easily visible to investigators;
individuals released/allowed to redistribute before resetting traps;
ratio of marked : unmarked in recapture is recorded and used to estimate total population;
bird populations may be estimated by aerial photographs/birdsong recordings that allow capture/recapture analysis;
bars/histograms proportional to each total population are drawn.

Award [1] for each correct suggestion, up to [7 max].
Accept alternative procedures of equivalent validity.

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 demonstrate:

• understanding concepts & terminology of models; energy flow through trophic levels; mineral cycles; sustainability; gross and net productivity; sustainable yield; natural capital and income; stock; storages; energy loss; harvesting; depletion of minerals; desertification; inorganic fertilizers; run-off; eutrophication; irrigation; leaching; etc
• breadth in addressing and linking models of energy flow and cycles of matter with balance of inputs and outputs; sustainability; agricultural strategies/activities; impacts related to energy flow / mineral cycles; other impacts; limitations of models; etc
• examples of a food production system; associated agricultural practices (sustainable and unsustainable); impacts addressed by models of energy flow / mineral cycles; other impacts; etc
• balanced analysis of ways in which models of energy flow and mineral cycles reveal sustainability of the food production system or fail to address them accurately, acknowledging relevant counter-arguments/alternative viewpoints;
• a conclusion that is consistent with, and supported by analysis and examples given eg these models are very effective at quantifying certain aspects of food production related to balancing inputs and outputs but there are many peripheral unsustainable aspects such as soil erosion, transport, use of pesticides that they do not address. NB This is only an example of a possible conclusion. Candidates’ conclusions do not have to agree.

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

Question 5 was the least popular choice. In part (a) the majority could distinguish “habitat” and “niche”. Although “role in an ecosystem” is an acceptable synonym for niche, “job” is less so …being somewhat anthropomorphic and only focusing on the impact of the species rather than its mutual relationship with the environment. A good number of candidates spent unnecessary time distinguishing fundamental and realised niches while failing to address specific requirements of question.

Majority of candidates had a sound understanding of quadrat sampling and mark–release–recapture methodologies, though generally lacked sufficient detail to gain more than 5 of the available 7 marks.

Majority of responses were very superficial. Firstly, few candidates were able to link energy flow and mineral cycles with food production, and secondly, few demonstrated any sound grasp of sustainability in this context. The relationship of sustainability and sustainable yields with e.g. steady state equilibria, balanced inputs and outputs, cycling, transfer efficiency were rarely addressed. It was as if candidates had only explored ecosystem models, food production and sustainability in isolation from one another and were unable to make appropriate links.