| Date | November 2016 | Marks available | 4 | Reference code | 16N.1.SL.TZ0.3 |
| Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | Suggest | Question number | 3 | Adapted from | N/A |
Question
Figure 3: The number of plant species present on the slopes of two volcanoes, which erupted in the 1880s. Measurements were taken in 1930, 1975 and 2015.
[Source: Data courtesy of Roger del Moral]
State the ecological processes illustrated by the data in Figure 3.
Describe a method for measuring the abundance of plant species in volcanic areas.
Suggest two reasons why there are differences in the number of plant species found on Krakatau and Tarawera.
Markscheme
(primary) succession / colonisation (of islands)/lithosere.
Do not accept ‘secondary succession’.
[2 max]
select sample areas representative of the area / select sampling sites using random sampling method / use aerial photographs of the area;
do quadrat/transect based sampling to collect data;
record the number of individual plants of each species / proportion of cover;
calculate abundance as % frequency / % cover / using ACFOR scale in the quadrats;
extrapolate for the whole volcano;
record during different seasons.
[3 max]
presence of ash increases plant diversity/different type of volcanic surfaces affects speed of colonization/weather differently;
... ash is plant ready whereas lava has to weather before it can support plants;
...having plants in ash will speed up weathering of adjacent lava;
...ash can be nutrient rich enhancing plant growth/diversity;
...plant roots can more easily penetrate ash than lava surfaces thereby contributing to greater plant diversity;
differences in climate/latitude: one is in tropics and experiences high rainfall/and temperature/insolation / one is in temperate latitudes with lowerrainfall/temperatures/insolation;
...plants in tropical rainforest biome grow rapidly all year / conditions can support a wide range of plant species;
...plants in temperate latitudes/with less insolation/rainfall/lower temperatures grow more slowly /conditions support a narrower range of plant species;
the level of biodiversity from nearby areas that are the source of the colonising species varies;
…there is a high level of biodiversity near Krakatau;
…there is a lower level of biodiversity near Tarawera;
direction of prevailing winds determine from which areas seeds/species are introduced from;
…Krakatau is downwind of areas which are rich in biodiversity;
…Tarawera is downwind of areas which have lower levels of biodiversity;
development of tourism/human activity in one area could reduce the number of species;
...building of infrastructure/roads/houses/amenities could result in removal of some species.
2 max for identifying 2 factors and 2 max for explanation of these factors.
Do not accept ‘volcanic eruption happened earlier in Krakatau’ or difference in latitude/climate without specifying which factors e.g. higher rainfall.
[4 max]
Examiners report
A significant proportion of candidates did give the correct response. A common mistake was to state volcanic eruption or zonation as the process.
Most candidates achieved some marks for this question, with many correctly suggesting the use of random sampling strategy and quadrats. Many answers incorrectly included Lincoln Index or Simpson Diversity Index and confused determining abundance of species with species diversity.
Marks varied widely between 0 and 4 for this question. Some responses were too vague e.g. referred to climate without linking how higher/lower levels of sunlight/rainfall/temperature would affect plant diversity at each specific location.
