| Date | November 2019 | Marks available | 7 | Reference code | 19N.2.SL.TZ0.6 |
| Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 0 |
| Command term | Explain | Question number | 6 | Adapted from | N/A |
Question
Outline the factors that contribute to total biodiversity of an ecosystem.
Explain how ecological techniques can be used to study the effects of human activities on the biodiversity of a named ecosystem.
To what extent are strategies to promote the conservation of biodiversity successful?
Markscheme
biodiversity includes the diversity of species, habitat and genes;
species diversity involves both the variety/number of species/richness and their relative proportions/evenness;
habitat diversity refers to the range of different habitats in an ecosystem or biome;
...which may vary due to environmental gradients/changing abiotic conditions/altitude/latitude/major disturbances (volcanic activity/landslides, etc);
habitat/niche diversification promotes species diversity;
genetic diversity refers to the range of genetic material/genes in a population/species;
...which is influenced by mutation/sexual reproduction/natural selection/speciation;
high primary productivity/insolation/precipitation/optimum abiotic conditions promote biodiversity;
succession promotes greater biodiversity by increasing length/branching of food chains / because it leads to improved abiotic conditions.
Credit can be gained through description of particular ecosystems eg. climax communities; hotspots; but the specific factors must be identified to gain credit.
Do not credit human impacts or any factor reducing biodiversity.
named ecosystem, eg shallow stream running through woodland;
studies should be made before and after human activity/in proximal and distal positions from activity;
Explanation: to provide evidence of human causation/correlation;
transects and quadrats may be used to sample area;
Exp: to reduce overall workload but be representative of area;
sampling should be repeated over time/distance;
Exp: to increase reliability;
abundance/biomass of biotic components may be measured;
Exp: to assess whether population size/productivity of populations/species have been affected.
numbers of motile organisms can be measured using Lincoln Index/mark–release–recapture;
Exp: because quadrats are ineffective if organisms are constantly on the move;
abiotic components may be measured using probes/thermometers/chemical tests, etc;
Exp: because human activity may alter prevailing abiotic conditions;
indicator species may be identified/quantified (using keys);
Exp: because their presence/abundance will indicate degree of human impact;
species diversity can be measured using a diversity index (eg Simpson’s);
Exp: because the index takes into account both species richness and equitability/distribution/relative abundance / can quantitatively compare different habitats/same habitat over time;
genetic & habitat diversity can be identified;
Exp: because these are also components of overall biodiversity.
Award [6 max] if no named ecosystem.
Award [4 max] if no explanations for use of techniques are given
There should be no credit given for extra detail of methods/techniques or for potential results of those methods. Focus of question is on purpose of techniques.
Refer to paper 2 markbands, available under “your tests” tab > supplemental materials
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 and terminology of the roles of organizations in conserving and restoring ecosystems and biodiversity; roles of international conventions on biodiversity; role of IUCN and Red List; CITES; captive breeding and reintroduction programmes; zoos, botanical gardens and seed banks; role of charismatic/flagship species vs keystone species; design of protected areas and impact of community involvement; genetic/species/habitat diversity; threats to biodiversity; impact of extinction/biodiversity loss; strategy approach depending on EVS; habitat vs species vs mixed approach; etc;
- breadth in addressing and linking a range of strategies for conservation to their relative success in addressing biodiversity as measured by a range of criteria (including measures of biodiversity; costs; resilience of systems; public popularity/engagement; rarity of protected species/habitats; etc;)
- examples can include a range of specific conservation measures / protected areas/zoos / means of assessing success / case-studies.
- balanced analysis of the extent to which conservation has or has not been successful in conserving biodiversity.
- a conclusion that is consistent with, and supported by, analysis and examples given eg ‘there are individual success stories, such as the observed increase in panda populations in Western China or increased counts of the tiger in India, and these are associated with increases in biodiversity to support these species, but the overall trend in biodiversity is down with massive percentages of species threatened by habitat degradation and climate change’;
