Biology 5090/32 — May/June 2021

Cambridge O-Level · Practical Test · worked solutions for every part, with the mark scheme

questions

marks

minutes

Topics Observations and Measurements · Experimental Contexts · Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials · Planning Experiments and Investigations · Microscopy and Biological Drawing

Q127MObservations and MeasurementsAnalysis, Conclusions and EvaluationExperimental ContextsUse of Techniques, Apparatus and MaterialsPlanning Experiments and InvestigationsFree sample

You are provided with a dish of seedlings that have germinated and then grown for 3–5 days.

You are going to measure the heights of six seedlings and calculate their mean height.

(a)

(i)

In the space below, construct a table to record your results.

Select six seedlings from the dish and measure the height of each stem to the nearest millimetre.

Enter your results in the table.

Calculate the mean height and record it in your table.

(ii)

State two possible sources of error in measuring the seedlings.

______
______

(iii)

Use the apparatus provided to cut or crush some of the seedlings. Add drops of iodine solution to the cut or crushed seedlings.

Record your observations and conclusion from this test.

observations ______

conclusion ______

(b)

In another investigation, some students calculated the mean heights of some seedlings as they grew. They recorded their results.

Grown for 6 days mean height $8\,\text{mm}$ .

Grown for 10 days mean height $23\,\text{mm}$ .

Grown for 12 days mean height $27\,\text{mm}$ .

Grown for 15 days mean height $32\,\text{mm}$ .

Grown for 20 days mean height $36\,\text{mm}$ .

Grown for 23 days mean height $37\,\text{mm}$ .

(i)

On the grid construct a line graph to show the relationship between time and mean height for these seedlings. Join your points with ruled lines.

Fig. 1.1

(ii)

Use the graph to describe the growth of these seedlings.

______

(iii)

Use the graph to state the time period during which the rate of growth of the seedlings was greatest.

______

(iv)

Use the data and your graph to calculate the rate of growth of the seedlings for the five days from day 15 to day 20.

rate = ______

(v)

State two variables that need to be controlled whilst growing these seedlings and explain why they need to be controlled.

variable 1 ______

variable 2 ______

explanation ______

(c)

The seeds needed water to germinate and for the seedlings to grow.

Design an investigation to determine the effect of the pH of water on the growth (mean height) of seedlings. You should use seedlings grown in Petri dishes in a laboratory.

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