| Date | May 2021 | Marks available | 2 | Reference code | 21M.1.SL.TZ0.7 |
| Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | Outline | Question number | 7 | Adapted from | N/A |
Question
Figure 8(c): Example of a Siberian food web
[Source: [Reindeer] Natalia Kollegova/Pixabay [Siberian tiger] Pixabay [Wild boar] Pixabay [Arctic hare] Pixabay [Wolf] Pixabay [Siberian larch] Pixabay [Siberian wheatgrass] USDA PLANTS Database [Bearberry] Arctostaphylos uva-ursi, Sten Porse https://en.wikipedia.org/wiki/Bearberry#/media/File:Arctostaphylos-uva-ursi.JPG CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0/.]
Outline the impact that a reduction in the tiger population may have on other populations in the food web shown in Figure 8(c).
Outline why a reduction in the Siberian tiger’s population may increase its probability of extinction.
Markscheme
it is likely to lead to an increase in its prey populations/ reindeer/hare/wolves/lemming/boar;
…which in turn may lead to decreases in their prey/food populations/hares/reindeer/lemming/plants/larch/wheatgrass/bearberry;
…causing fluctuations in population size/instability/reduced resilience throughout web;
Do not accept ‘collapse in food chain’.
smaller population will reduce its gene pool/genetic diversity;
…reducing its resilience / making it more vulnerable/less adaptable to changes in environment/disease/resource availability;
harder to find a mate / reduce successful pairing/mating/reproduction/favourable gender ratios;
increase rarity in tiger population may result in an increase in demand/market/trade value (increasing probablity of extinction);
Do not accept 'tigers do not reproduce fast'.
Examiners report
This question was very well answered by most candidates.
Although most students were able to give one reason, such as "not being able to find a mate", few gave a second reason required to achieve the full two marks.
