Biology 5090 · O Level · Coordination and response in plants
Coordination and response in plants — practice question
A student examined how gravity affected germinating seeds. Eight pea seeds were used.\n\nAs germination began, the pea seeds first formed radicles (roots). The radicle length can be measured between the dotted lines, as shown in Fig. 1.1.\n\nThe student fixed four of the seeds with germinating radicles to the cork base on each of two electric motors, as shown in Fig. 1.2. The cork was kept wet throughout the investigation and the apparatus was kept in the dark.\n\nThe student then switched on motor A so that the cork base turned very slowly for two days, in the direction shown by the arrow.\n\nMotor B was left switched off, so the cork base did not turn.\n\nFig. 1.3 shows the pea radicles after 2 days.\n\nAnother student investigated the growth of the shoots (plumules) of germinating pea seeds for eight days. The student’s results are shown in Table 1.1.
(a(i))[4]
In the space below, create a table to record your measurements from A and the student’s measurements from B.
(a(ii))[2]
Measure and enter in your table the lengths of the radicles from A in Fig. 1.4.
(a(iii))[1]
Enter the student’s measurements for the radicles from B in Fig. 1.5 into your table.
(a(iv))[2]
Calculate the mean lengths of the radicles from A and B, and record each to 1 decimal place.\n\nA mean length ................................ mm\n\nB mean length ................................ mm
(a(v))[3]
Use Fig. 1.3 together with the mean lengths in (iv) to suggest what conclusion the student should reach about how radicles respond to gravity.
(b)[2]
Suggest why the student should repeat the investigation several times to obtain results for more pea seeds.
(c)[2]
Suggest why the apparatus was kept in the dark throughout the investigation.
(d(i))[4]
Construct a graph from the data in Table 1.1 on the grid below. Join the plotted points with ruled straight lines.
(d(ii))[3]
Use your graph to estimate the mean height of the pea shoots on day 5.\n\nShow your working on the graph.\n\nmean height ................................
Worked solution & mark scheme
This 23-mark question has a full step-by-step worked solution and mark scheme. One marking point: “One table only, with rows and columns shown by ruled lines” …