CAIE IGCSE Biology 22 Assessed Scientific Skills

Practise handling biological information, planning and evaluating investigations, and applying the mathematical skills assessed across CAIE IGCSE Biology.

[Maximum number: 2]

Some students set up the apparatus shown in Fig. 6.1 to compare transpiration in two sets of leaves.

Set A was kept in a transparent bag and set B was left in the open air.
All other conditions were kept constant.
The mass of the leaves in each set was measured at the start of the investigation and after five hours.

Fig. 6.1

The students needed two additional pieces of apparatus to take measurements so that they could calculate the rate of transpiration from their results.

State the two additional pieces of apparatus the students needed to take the measurements.

1

2

[Maximum number: 5]

(a)

A student investigated the effect of different wavelengths of light on the rate of photosynthesis of the water plant, Cabomba.

The student used the apparatus shown in Fig. 6.1.

Fig. 6.1

The student collected the gas produced by the plant for five minutes. The results are shown in Table 6.1.

Table 6.1

Describe the effect of wavelength of light on the rate of photosynthesis as shown in the student's results in Table 6.1.

You will gain credit if you use data from the table.

[ 3 ]

as wavelength increases, rate (of photosynthesis) decreases and increases ;

high rates in, blue and violet and red / 400-475 nm and 675 nm ; low(est) rate in, green and yellow $/ 550-600 \mathrm{~nm}$ ;

either

Marking guidance:

maximum rate $=0.9 \mathrm{~cm}^{3}$ , at $675 \mathrm{~nm} / \mathrm{red}$ or minimum rate $=0.2 \mathrm{~cm}^{3}$ , at $550 \mathrm{~nm} /$ green ;

[max 3]

units must be used once in the answer
A volume of gas for rate

(b)

State how the student would calculate the rates of photosynthesis from the results in Table 6.1.

[ 1 ]

(c)

State why the student:

[ 1 ]

(i)

kept the lamp at the same distance during the investigation,

[ 1 ]

[Maximum number: 5]

Scientists measured the rate of photosynthesis in the leaves of a sunflower plant, Helianthus annuus.

The scientists used the apparatus shown in Fig. 3.1 to measure the rate of photosynthesis.

Fig. 3.1

(a)

The apparatus in Fig. 3.1 maintains a constant temperature and a constant humidity.

[ 2 ]

(i)

The apparatus was left for 15 minutes.

Explain how the scientists would use the readings for the concentration of carbon dioxide in chambers 1 and 3 to calculate the rate of photosynthesis.

[ 2 ]

(b)

The scientists carried out another investigation using the same apparatus at different temperatures.

They measured the rate of uptake of carbon dioxide in the light and then they measured the rate of release of carbon dioxide in the dark.

The results are shown in Fig. 3.2.
rate of carbon dioxide uptake and release $/ \mu \mathrm{g}$ per hour per $\mathrm{cm}^{2}$ of leaf

Fig. 3.2

[ 3 ]

(i)

Use the information in Fig. 3.2 to complete Table 3.1.

Table 3.1

[ 2 ]

$\mathrm{CO}_{2}$ uptake: 136 ;

$C O_{2}$ release: 20 ;

(ii)

Explain why the results in Table 3.1 are expressed as 'per $\mathrm{cm}^{2}$ of leaf' rather than 'per leaf'.

[ 1 ]

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Covered syllabus points

22. Assessed scientific skills question 1

22. Assessed scientific skills question 2

Question (a)

Question (b)

Question (c)

Question (i)

22. Assessed scientific skills question 3

Question (a)

Question (i)

Question (b)

Question (i)

Question (ii)