| Date | May 2017 | Marks available | 3 | Reference code | 17M.3.HL.TZ2.7 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Suggest | Question number | 7 | Adapted from | N/A |
Question
The shore crab (Carcinus maenas) preys on mussels (Mytilus edulis). M. edulis vary in size. The frequency distribution of the numbers of each length of M. edulis eaten by a population of C. maenas per day is shown in the graph.
State the most common length of M. edulis eaten by the C. maenas population.
Suggest reasons for the length you stated in (a) being the most common length of M. edulis that C. maenas eat.
Markscheme
17.5 mm OR 15 mm to 20 mm
a. larger mussels too much effort to open OWTTE
OR
best ratio between effort and energy return
b. smaller mussels means more individuals have to be eaten for the same return on effort
c. greater time/predator exposure spent during foraging to obtain required daily energy
d. it «may be» the most common size available
OR
«correct mussel» size favoured by natural selection
e. the claws are best adapted to prey on mussels of this size
Examiners report
Syllabus sections
-
20N.3.HL.TZ0.8b:
Explain how natural selection can cause mate selection behaviour patterns to develop in a species such as eastern bluebirds.
- 20N.3.HL.TZ0.8c: Another type of behaviour is altruistic behaviour. Outline an example of altruistic behaviour.
- 17N.3.HL.TZ0.06a: State the effect of simulated ship noise on foraging behaviour.
- 17M.3.HL.TZ2.7a: State the most common length of M. edulis eaten by the C. maenas population.
-
18M.3.HL.TZ1.7c:
Distinguish between innate behaviour and learned behaviour in the development of birdsong.
- 19N.3.HL.TZ0.7a: Courtship behaviour leads to mate selection. Describe innate behaviour.
-
18M.3.HL.TZ2.8:
Compare and contrast innate behaviour and learned behaviour.
-
20N.3.HL.TZ0.8a:
Evaluate the hypothesis that females prefer to mate with males whose feathers are a brighter blue.
- 19N.3.HL.TZ0.7b: Explain the implications of courtship behaviour in natural selection.
-
19M.3.HL.TZ2.6a.i:
Suggest a reason for the plateau in the graph when only one crab is present in the cage.
- 19M.3.HL.TZ2.6b: Outline the role of natural selection in animal behaviour.
-
19M.3.HL.TZ2.6a.ii:
Determine whether foraging by crabs is dependent on number of prey (mussels) or number of predators (crabs).
-
17N.3.HL.TZ0.06b:
Predict the consequences on C. maenas of increasing noise related to human activity.
-
18M.3.HL.TZ1.7d:
Outline an example of a change in animal behaviour as a result of natural selection.
-
18N.3.HL.TZ0.7:
The drawing shows male and female Emperor birds of paradise (Paradisaea guilielmi ) found in Papua New Guinea.
Suggest how the external features and courtship behaviour of these birds of paradise affect reproductive success.
