Fig. 7.1 A student placed cress seedlings in the covered box shown in Fig. 7.1, which had a single hole cut in one side to let in light from a lamp. Each da...
Question 1 Report
Fig. 7.1
A student placed cress seedlings in the covered box shown in Fig. 7.1, which had a single hole cut in one side to let in light from a lamp. Each day the student measured the angle, in degrees, by which the shoots had bent towards the hole, measured from the vertical. The results are shown in Table 7.1.
| Day | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| Angle of bending / ° | 0 | 10 | 18 | 24 | 28 | 30 |
(a) Measure, from Table 7.1, the angle of bending on day 3. [1]
(b) Name the characteristic of living organisms shown when the shoots bend towards the light. [1]
(c) Name the type of response of a shoot growing towards light. [1]
(d) State the independent variable and the dependent variable. [2]
(e) Describe the trend shown by the results. [2]
(f) Explain how bending towards the light is an advantage to the seedlings. [2]
(g) A second box was set up with the seedlings lit equally from all sides. Explain the purpose of this box. [2]
(h) Name a suitable instrument for measuring the angle of bending. [1]
(i) State two variables that should be kept constant. [2]
(j) Describe one way to improve the reliability of the results. [1]
(k) Name one characteristic of living organisms, other than sensitivity, shown by the seedlings, and give one observation. [1]
Answer Details
(a) From Table 7.1 the angle of bending on day 3 is 24 °. [1]
(b) Bending towards the light shows sensitivity (response to a stimulus), one of the characteristics of living organisms. [1]
(c) Growth of a shoot towards light is (positive) phototropism. [1]
(d) The independent variable is time / the number of days [1]; the dependent variable is the angle of bending [1].
(e) The angle of bending increases each day [1]; the increase is large at first and then slows down / levels off towards day 5 [1] (from 0° to 30°, with the daily gain falling from 10° to 2°).
(f) Bending is an advantage because it turns the shoot towards the light [1], so that more light reaches the leaves for photosynthesis and more food is made [1].
(g) The evenly-lit box is a control [1]: with light coming equally from all sides there is no single direction to bend towards, so any lack of bending shows that the bending in the first box was caused by the direction of the light [1].
(h) A suitable instrument for measuring the angle is a protractor. [1]
(i) Any two kept constant: the temperature; the size of the hole; the type or number of seedlings; the distance of the lamp. [2]
(j) Improve reliability by repeating with several boxes and averaging the angles (or using more seedlings). [1]
(k) Any one other characteristic with an observation, for example growth - the seedlings increased in height over the days. [1]
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