| Date | May 2017 | Marks available | 3 | Reference code | 17M.3.SL.TZ2.17 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Discuss | Question number | 17 | Adapted from | N/A |
Question
The fire ant (Solenopsis geminata) is an effective colonizer and has become invasive in a number of ecosystems. Sometimes, efforts to eliminate this species have had an unexpected impact on community structure. It is argued that S. geminata can play a beneficial role in corn production. The graph shows how the presence of S. geminata
can impact insect diversity in areas where crops of corn are grown.
State the impact of S. geminata on insect species diversity.
Discuss whether S. geminata might play a positive role in corn production.
Researchers have argued that S. geminata is a keystone species in the corn agricultural system. Outline what is meant by a keystone species.
Markscheme
reduction in number of species/richness/diversity
a. biological control of/reduction in corn pests
b. reduction in the use of pesticides
c. damage on beneficial species OWTTE
d. reduction in insect diversity can have broad ecosystem negative impact
OR
example of negative effect
e. long-term effects unknown
definition
a. keystone species is one in which presence has a disproportionate impact on the ecosystem
impact
b. removal often leads to significant changes
OR
valid example
