Question 19M.3.HL.TZ1.c
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.HL.TZ1.c |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | c | Adapted from | N/A |
A leafy shoot was cut from a plant and connected to a potometer to measure the transpiration rate. The length of the air column in the glass tube was measured using the ruler.
[Source: © International Baccalaureate Organization 2019]
One criticism of the experiment is that it only measured the rate of transpiration indirectly. Explain how the experiment is an indirect measurement of transpiration.
[2]
a. transpiration is water evaporating from «the leaves of» a plant ✔
b. what is being measured is water uptake to the plant ✔
c. assumes no water used for other processes/photosynthesis ✔
This is not about water loss from apparatus
This item was rarely answered well, with many candidates simply describing what would happen in a potometer. An ability to outline limitations, assumptions and possible errors shows the ability to evaluate, and is one of the objectives of the DP Biology course. A similar question on the limitations of the potometer last year was also answered poorly.
