| Date | May 2015 | Marks available | 3 | Reference code | 15M.3.SL.TZ2.19 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Discuss | Question number | 19 | Adapted from | N/A |
Question
Limpets (Helcion pectunculus) are marine molluscs that live in rock crevices (cracks and holes) in South Africa. In order to see whether the crevices protected the limpets from wave action, the force required to detach limpets in their natural habitat was measured. Once detached from the rocks, the area of the foot of each limpet was also measured.
State the force required to detach a limpet with an area of foot of 2 cm2 .
State the smallest area of foot necessary to resist a force of 50 N.
...................cm2
Outline the relationship between area of foot and the force required to detach the limpet.
Smaller limpets can only be found at the back of crevices. Discuss the reasons for this.
Limpets tend to live towards the high tide zone. State the method used to determine the distribution of limpets between the low and high tide lines.
Markscheme
42 (N) (allow answers in the range of 41 (N) to 43 (N))
2.6 (cm2) (allow answers in the range of 2.5 (cm2) to 2.7 (cm2))
Positive correlation / as area of foot increases so does force required.
a. back of crevice less subjected to action of waves;
b. (hypothesis supported as) small area of foot requires less force;
c. amount of predators/food could be affecting the distribution;
d. larger limpets may not fit in the back of the crevice;
e. less competition with larger limpets at the back of the crevice;
transect line / quadrat with transect line
Do not accept quadrat alone.
Examiners report
Option G data was a scatter graph showing the relationship between the area of the foot and the force required to detach limpets. The data was on the whole well answered.
Option G data was a scatter graph showing the relationship between the area of the foot and the force required to detach limpets. The data was on the whole well answered.
Option G data was a scatter graph showing the relationship between the area of the foot and the force required to detach limpets. The data was on the whole well answered.
Option G data was a scatter graph showing the relationship between the area of the foot and the force required to detach limpets. The data was on the whole well answered.
Option G data was a scatter graph showing the relationship between the area of the foot and the force required to detach limpets. The data was on the whole well answered.
