User interface language: English | Español

Date November 2019 Marks available 9 Reference code 19N.2.SL.TZ0.6
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term To what extent Question number 6 Adapted from N/A

Question

Outline the factors that contribute to total biodiversity of an ecosystem.

[4]
a.

Explain how ecological techniques can be used to study the effects of human activities on the biodiversity of a named ecosystem.

[7]
b.

To what extent are strategies to promote the conservation of biodiversity successful?

[9]
c.

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.

 

a.

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.

b.

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:

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Topic 3: Biodiversity and conservation » 3.3 Threats to biodiversity
Show 37 related questions
Topic 3: Biodiversity and conservation » 3.4 Conservation of biodiversity
Topic 3: Biodiversity and conservation

View options