IB ESS SL Topic 1 Foundation Question Bank

Marking guidance:

Award [ 2 m a x ] for an outline of Gaia hypothesis:
compares Earth to a living organism;
in which feedback mechanisms maintain equilibrium/homeostatic state; an approach which sees the Earth as a global ecosystem (Daisyworld);
Award [2 max] for suggestions on how traditional views differ.
Traditional views: tend to break up/fragment the Earth into smaller systems/ecosystems; or see the Earth in a more static way;
or see the Earth as something which just supplies us with resources; give more significance/centrality to the role of humans;
allow for possibility that humanity could irreversibly destroy life-supporting conditions of the planet (Gaia suggests Earth will continue despite us); it is possible to have a systems approach to the Earth without believing that the Earth is alive;

Marking guidance:

Award [1] for a flow diagram which shows a clear causal/feedback link where the change itself causes or leads to a reversal/inhibition of that change (it is not sufficient to simply show an increase/decrease being followed by a decrease/increase).
A graph with oscillation is acceptable if it is annotated in sufficient detail to identify the causal link.

Award [1 max] for written definition of negative feedback. feedback that tends to damp down/neutralize/counteract any deviation from an equilibrium/promotes stability;

Award [4 max] for examples of complete negative feedback loop (credit non

ecosystem examples).
e.g. more $\mathrm{CO}_{2}$ in atmosphere leads to increased temperatures and more evaporation;
which creates more cloud cover, reducing rates of incoming solar insolation and reducing temperatures; e.g. increase in predator population will increase consumption of prey species making them more scarce; which in turn will represent a limiting factor for predator species allowing prey numbers to recover;

Award [4 max] if diagram is inadequate or absent. Do not credit both examples if they are too similar.

Credit different interpretations of what is meant by "bigger" in this context e.g. bigger can refer to the scale/number of effects, or to how immediate/frightening/concrete the threat may seem, or in terms of whether the threat is to humans or to living systems in general.

Marking guidance:

Award [1] for a explicit statement of their view on which is the bigger threat. global warming is a bigger threat than biodiversity; biodiversity is a bigger threat than global warming;
Do not credit if the viewpoint is only implied in the response.
Award [8 max] for relevant arguments for why one issue is a bigger threat than the other.
Award [4 max] if response is simply a description of the threat/effects not a comparison with the other threat. e.g. global warming is the bigger threat because:
it will have big effects e.g. melting ice caps/shifting biomes/changing the world's weather/flooding land;
its effects will be more widespread than biodiversity/every country will be affected; whereas the loss of diversity in, e.g. a tropical rainforest, may have little direct impact on people elsewhere;
larger numbers of people will be affected e.g. Bangladeshi delta region low-lying and densely populated affected by sea level rises;
it will affect a bigger range of human activity, such as food supply/living space, health/disease;
it will lead to biodiversity loss as well (whereas loss of diversity will not cause global warming);
many biodiversity hotspots are particularly vulnerable e.g. coral reefs; it has a higher public/global profile;
it can lead to significant social consequences e.g. wars / mass migrations; is harder to solve than biodiversity loss which can be helped by e.g. seedbanks; current rate of warming is unprecedented, whereas there have been mass extinctions in the past and the biodiversity has recovered;
it may lead to positive feedback loops/potentially devastating tipping points/exponential change;
> e.g. biodiversity is the bigger threat because:
> biodiversity provides/ensures key essential ecological services; e.g. a balance of atmospheric $\mathrm{O}_{2}$ and $\mathrm{CO}_{2}$ /soil preservation/mineral cycles; without these there would be no life-supporting conditions on the planet; once biodiversity is lost it is gone forever; and whereas global warming may be mitigated by negative feedback mechanisms there are no feedback mechanisms to maintain diversity; to restore biodiversity it can take very long periods of time; whereas climatic variations are reversible/happen in cycles (and have occurred in the past);
> from a human point of view, loss of biodiversity may mean loss of critical resources;
> biodiversity provides many forms of natural income, e.g. aesthetic, economic, ecological services;
> at a point in human population growth where resources are possibly limiting; it is biodiversity that gives living systems the ability to adapt to change; and the more it is reduced, the lower the chances of adapting to change; biodiversity is being lost now/threats seem more immediate to people; there are some positive benefits of global warming but no benefits to biodiversity loss;

Valid factors: greater diversity of components/species increases resilience;
complexity of interactions/developed food webs increase resilience; establishment of keystone species increases resilience;
larger storages/stores / more abundant/productive resources (nutrients, water, sunlight, reproductive rates, biomass etc) increase resilience (NB for credit, there must be indication of abundance in these resources, and if multiple examples are given like those in brackets, there is still only [1 max] allowed for this MP);
larger size of the system increases resilience; strong negative feedback systems increase resilience; strong positive feedback mechanisms may decrease resilience; human impact degrading structure/diversity/abundance will decrease resilience;
a steady state equilibrium/balanced inputs and outputs (as in climax communities)
increases resilience; systems being close to a tipping point decrease resilience;

Marking guidance:

Accept converse statements.
Award [1] for each correct factor identified, up to [4 max].
If valid factors are identified, but their effect on resilience is not, award [1] for each TWO factors up to [2 max] (ie FOUR factors). Eg identifying TWO factors and their effect on resilience, along with TWO factors but no specified effect would score [2+1=3] total OR eg TWO factors and their effect, along with ONE with no effect would score $[\mathbf{2} \boldsymbol{+} \mathbf{0} \boldsymbol{=} \mathbf{2}]$ total OR eg FOUR factors with no effect ([1+1=2] total).

A community of trees in a woodland has the following features of a system: individuals/species of trees are the components of the system; these components are interrelated/interdependent/form an integrated whole; eg may regulate populations through competition / contribute to succession of community;
it has flows/transfers of matter/energy between components/storages; eg leaf fall may provide nutrients through decomposition to other trees / pollination/genes/food storage in seeds / glucose is transported from leaves around tree;
components carry out processes/transformations; eg photosynthesis/respiration/growth;
it is an open system exchanging matter and energy with surroundings;
eg absorption of solar energy / provision of nutrients for non-tree species (NB mark for either example of matter or energy, not both);
it has feedback mechanisms to maintain equilibrium/balanced inputs and outputs; eg more seed production → more competition between seedlings → fewer viable offspring / death of trees → more light entering canopy → more tree growth;

Marking guidance:

Award [1] for each correct suggestion, up to [7 max].
Award [4 max] for identifying relevant generic features of system (given above) and [4 max] for examples of these within a tree community (beware of responses that are looking at entire woodland ecosystem as a system rather than the tree community alone). Credit alternative examples of equivalent validity/relevance and detail.

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:
- understanding concepts \& terminology of greenhouse gases; global warming; thermal expansion; rising sea-level; melting ice caps; salinity; ocean acidification; ozone depletion; UV radiation; global productivity; tropospheric ozone; acid rain (worth noting here that acid rain is NOT a significant cause/contributor to ocean acidification); etc
- breadth in addressing and linking impacts on atmospheric systems (increased $\mathrm{CO}_{2}$; global warming; ozone depletion; tropospheric ozone; acid rain; etc) with disturbances in marine systems (rising sea level; ocean currents; fish migration; acidification; destruction of coral reefs; phytoplankton / marine food chains; etc)
- examples of relevant atmospheric pollutants/disturbances; ocean currents; coral communities; migratory fish; marine food chains; etc
- balanced analysis of the extent to which each atmospheric disturbance causes disturbance in marine systems whether significant, minimal or none at all, acknowledging relevant counter-arguments/alternative viewpoints;
- a conclusion that is consistent with, and supported by analysis and examples given e.g. generally, the statement is valid regarding large scale disturbances to the atmosphere such as global warming and ozone depletion but more localized disturbances like tropospheric ozone and acid rain have fairly minimal impact; NB This is only an example of a possible conclusion. Candidates' conclusions do not have to agree.

Please see markbands on page 21.