DP Biology (last assessment 2024)
Question 18M.3.HL.TZ1.14
| Date | May 2018 | Marks available | [Maximum mark: 3] | Reference code | 18M.3.HL.TZ1.14 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Outline | Question number | 14 | Adapted from | N/A |
14.
[Maximum mark: 3]
18M.3.HL.TZ1.14
(a)
The sea star Pisaster ochraceus is identified as a keystone species in the Pacific Ocean.
Outline the characteristics of keystone species in an ecosystem.
[1]
Markscheme
a. keystone species has a strong/disproportionate effect on a community/food web/ecosystem
b. absence of keystone species would completely alter the ecosystem
(b)
Outline one example of mutualism.
[2]
Markscheme
a. example of mutualistic species
b. description of mutualism
Accept commonplace names for organisms in (a)
Examples:
a. oxpecker (bird) and therhinoceros/zebra
b. oxpeckers/bird on rhinos/zebras eat parasites getting food while rhino/zebra get pest control
OR
a. hummingbird hawk-moth and Dianthus
b. (hummingbird hawk) moth gets nectar from flower while it pollinates the flower