Some students wanted to find the effect of sugar solution on onions. They cut slices of onion $2\text{ mm}$ thick from a whole onion as shown in Fig. 1.1A. One ring was separated and cut into two equal pieces as shown in Fig. 1.1B. One half of this onion ring was immersed in distilled water in a dish and the other half in a sugar solution in another dish. The shape of these two pieces at the start was recorded in Table 1.1. The dishes were left for 30 minutes under the same…

Biology 5090/61 — May/June 2014

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

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

Q115MExperimental ContextsObservations and MeasurementsPlanning Experiments and InvestigationsAnalysis, Conclusions and EvaluationFree sample

Some students wanted to find the effect of sugar solution on onions.

They cut slices of onion $2\text{ mm}$ thick from a whole onion as shown in Fig. 1.1A. One ring was separated and cut into two equal pieces as shown in Fig. 1.1B.

Fig. 1.1

One half of this onion ring was immersed in distilled water in a dish and the other half in a sugar solution in another dish.

The shape of these two pieces at the start was recorded in Table 1.1.

The dishes were left for 30 minutes under the same conditions and then the piece of onion ring in each dish was observed and its shape drawn in Table 1.1.

Table 1.1

(a)

(i)

Describe the changes that are visible in the two pieces of onion after 30 minutes.

(ii)

Explain what has happened to cause the changes in the two pieces of onion.

(b)

(i)

State one factor that was kept the same in this investigation and explain why it was kept the same.

(ii)

Some students decided to find out the effect of using a range of different concentrations of sugar solution on pieces of onion.

Describe two other factors that would need to be controlled.

______
______

(iii)

Explain how you could measure the effect of using a range of different concentrations.

(c)

In one of the sugar concentrations the shape of the onion remained unchanged.

Suggest an explanation for this.

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Q2Microscopy and Biological Drawing · Experimental Contexts · Observations and Measurements · Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials · Planning Experiments and Investigations25M

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