| Date | November 2011 | Marks available | 3 | Reference code | 11N.3.HL.TZ0.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 11 | Adapted from | N/A |
Question
In 1988 a fire destroyed large portions of forest in Yellowstone National Park, USA. Photograph A was taken soon after the fire and photograph B one year later. The photographs are of the same area.
Identify, with a reason, the type of succession that has taken place.
Outline a method that could be used to sample the plant population shown in photograph B.
Yellowstone National Park was the first national park in the world and is a designated biosphere reserve site. Outline the biogeographical features of nature reserves that promote conservation of diversity.
Markscheme
secondary succession as some plants/organic components were present before fire
describe method for ensuring random placement of quadrats in a grid; (do not accept transect)
different species present in quadrat identified and counted;
used to estimate species density/frequency/abundance/cover;
size:
large nature reserves usually promote conservation better than small ones;
large areas needed for far-ranging animals (e.g. grizzly bear);
larger areas have proportionally smaller perimeters/less affected by edges;
edge effect:
ecology of edges of ecosystems is different from central areas due to edge effects;
fragmentation (of forests) leads to increase in edges which will favour some species over others;
habitat corridor:
habitat/movement/wildlife corridors allow organisms to move between different parts of fragmented habitat;
To award [3] responses must refer to size, edge effect and habitat corridor.
Examiners report
A good number of answers compared the two photos and made no reference to "before the fire‟, which was not strictly needed.
Similarly here, a question that could produce an essay for the answer. Answers generally referred to the fact that a single large herbivore appeared to be better for plant community due to higher and abundance. The rest of the answer tended to lack the clarity for the other marking points. Also some candidates took the question to mean a single plant species/population (understandably) therefore not evaluating what would happen when multiple large herbivores are present.
There were some very good answers including examples of all 3 requirements but most candidates wrote vaguely about pollution and avoiding humans. Some answers about natural reserves were also too vague, about "good nutrition and absence of predators".
