Question 19N.3.SL.TZ0.12
| Date | November 2019 | Marks available | [Maximum mark: 7] | Reference code | 19N.3.SL.TZ0.12 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Discuss, Distinguish, Outline | Question number | 12 | Adapted from | N/A |
The blackberry (Rubus fruticosus) is a plant that grows in deciduous woodlands in many parts of the world. A 30 m transect was laid out in a woodland to investigate the relationship between light intensity and blackberry growth. The percentage cover of blackberries and the light intensity were measured at 26 positions along this transect.
Outline how these results indicate that blackberry distribution is limited by light intensity.
[2]
a. as light level changes so does the percentage cover «of blackberry» ✔
b. distribution is higher at intermediate/moderate light intensities ✔ Accept appropriate numerical values
c. little growth at low light intensities
OR
little growth at high light intensities ✔ Accept appropriate numerical values
d. distribution is bell shaped ✔
Distinguish between the transfer of matter and energy in closed ecosystems.
[1]
only energy can be lost/gained/exchanged/transferred «with the exterior»
OR
only matter is constant/recycled ✔
A pyramid of energy represents the amount of energy taken in by each trophic level per unit time and per unit area. Discuss the advantages and disadvantages of the use of pyramids of energy as models of energy flow in an ecosystem.
[4]
Advantages:
a. can show the energy loss/transfer between trophic levels ✔
b. permits a ‹quantitative› comparison between ecosystems ✔
c. shows change over time ✔
Disadvantages:
d. are difficult to produce accurately ✔
e. require destructive methods to obtain the data ✔
f. do not show all the interactions/food chains/feeding relationships «between different members of the community» ✔
g. cannot represent organisms that feed at different trophic levels ✔
Award [3 max] if only one side of the argument is given.
