Date | May 2013 | Marks available | 1 | Reference code | 13M.3.HL.TZ2.4 |
Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
Command term | Calculate | Question number | 4 | Adapted from | N/A |
Question
Investigators studied the behaviour of two species of small fish, the sand goby (Pomatoschistus minutus) and the black goby (Gobius niger), while they foraged for mud shrimps. The amount of food foraged by the gobies was measured after they had been fed or after they had been starved. The measurements were repeated when a predator of the gobies was introduced to the tank where they were feeding.
Calculate the decrease in mass of food foraged by fed sand gobies when a predator was introduced, giving the units.
Compare the effect that starvation had on both species of goby when no predator was present.
Describe the effect the predator had on the foraging of the gobies.
Suggest a reason for the effect of the predator.
Markscheme
2.6 mg (units required) (accept answers in the range of 2.5 mg to 2.7 mg)
No working required.
both foraged more after starvation;
black goby increased the amount of food foraged more than the sand goby;
a. predator present causes both to forage for less food;
b. fed black gobies showed little change in foraging (with predator present);
c. starved gobies foraged more than fed gobies (with predator present);
d. relative foraging remains similar between the two species / black goby always forages less than sand goby;
a. gobies may feed on smaller mud shrimps when predator present;
b. gobies may hide rather than forage when predator present / gobies may feed less efficiently if they are watching out for predators;
c. predator may also eat shrimp so less for gobies;
d. if predator eats gobies the total mass of food foraged is less / OWTTE;
Examiners report
Generally well done, although some answers were a bit unclear.
Generally well done, although some answers were a bit unclear.
Generally well done, although some answers were a bit unclear.
Generally well done, although some answers were a bit unclear.