Topic: Term Two 2021 Holiday Homework

Subject: Biology Form Two

Teacher: Mr. F. Moyo
Week: Week 1

1. A student investigated osmosis. They used a model cell made from dialysis tubing.
Dialysis tubing is permeable to water but is not permeable to larger molecules such as
sucrose, which is a type of sugar.

Step 1 One test-tube was labelled DW and a second test-tube was labelled S.

Step 2 Two dialysis tubing bags were made by knotting lengths of dialysis tubing at one
end.

Step 3 A syringe was filled with 10 cm3 of sucrose solution.

Step 4 The 10 cm3 of sucrose solution was transferred from the syringe to a dialysis tubing
bag, as shown in Fig. 1.1.

Figure 1.1:

Step 5 A ruler was used to measure the distance from the knot to the meniscus of the
sucrose solution in the bag, as shown in Fig. 1.2.

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 Figure 1.2:

Step 6 The dialysis tubing bag was placed into test-tube S and secured with an elastic band.

Step 7 A measuring cylinder was used to pour 30 cm3 of distilled water into test-tube S, as
shown in Fig. 1.3.

Figure 1.3:

Step 8 The student filled the second dialysis tubing bag with 10 cm3 of distilled water.

Step 9 The student measured the distance from the top of the knot to the bottom of the
meniscus of the distilled water in the dialysis tubing bag.

Step 10 The dialysis tubing bag containing distilled water was then placed into test-tube
DW and secured with an elastic band. 30 cm3 of distilled water was poured into

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 test-tube DW.

Step 11 Test-tubes S and DW were left for 15 minutes.

Step 12 At 15 minutes the dialysis tubing bags were removed from test-tubes S and DW.

(a) Fig. 1.4 shows the dialysis tubing bags at 0 minutes and at 15 minutes.

Figure 1.4:

(i) Measure the distance from the top of the knot to the bottom of the meniscus …/3
at 0 minutes and 15 minutes for the dialysis tubing bags from test-tubes S and
DW.
Prepare a table and record these measurements in your table.

(ii) Calculate the change in distance from the knot to the meniscus of the liquids in …/2
the dialysis tubing bags in test-tubes S and DW.

(iii) Explain why it is important to take the measurements from the same place on …/1
the dialysis tubing bags shown in Fig. 1.4.

(iv) State a conclusion for the results of this investigation. …/1

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 (v) Only one set of results was collected during this investigation. …/1
Explain why it is better to collect several sets of results.

(b) Another student repeated the investigation but their results were not the same. The …/1
student only used one syringe during the investigation and did not wash it.
Suggest why the results of their investigation were not as expected.

2. A balanced diet contains seven different groups of substances.

Three of these groups of substances are fats, fibre (roughage) and vitamins.

(a) State the names of three other groups of substances in a balanced diet. …/3

(b) The boxes on the left contain the names of conditions that can develop if the diet is …/4
not balanced for a long period of time.
The boxes on the right contain descriptions of how these conditions may be caused.
Draw one straight line from each box on the left to a box on the right to link the
condition to its cause.

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 Topic: Term Two 2021 Holiday Homework
Subject: Biology Form Two
Teacher: Mr. F. Moyo
Week: Week 2

1. (a) Sucrose can be broken down into reducing sugars. …/3

Describe how you would test for the presence of reducing sugars.

(b) Students investigated the effect of sucrose concentration on the mass of potato
cylinders.

* A potato was cut into cylinders.

* The potato cylinders were all cut to 2 cm in length.

* The initial mass of each potato cylinder was measured and recorded.

* Each potato cylinder was put into a different concentration of sucrose solution.

* The potato cylinders were left in the sucrose solutions for one hour.

* The potato cylinders were removed from the sucrose solutions and the final mass
of each potato cylinder was measured and recorded.
(i) State two variables that were kept constant in this investigation. The results …/2
of the investigation are shown in Table 1.1.

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 Table 1.1:

(ii) Calculate the percentage change in mass of the potato cylinder that was …/3
immersed in 1.00 mol per dm3 sucrose solution.
Give your answer to one decimal place.

(iii) Plot a line graph on the grid of the concentration of sucrose solution against …/4
the percentage change in mass. One axis has been started for you.
Include a curved line of best fit on your graph.

(iv) Estimate the concentration of sucrose solution at which there was no per- …/1
centage change in the mass of the potato cylinder.

(v) Explain why the percentage change in mass is more useful than the change …/1
in mass when analysing the results in Table 1.1.

(c) State the name of the solution that is used to test for the presence of starch and …/2
give the result of a positive test.

2. Describe the pathway of water from outside the root to the xylem vessels at the centre …/6
of the root.

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 Topic: Term Two 2021 Holiday Homework
Subject: Biology Form Two
Teacher: Mr. F. Moyo
Week: Week 3

1. Metabolic reactions in cells produce toxic chemicals which can be converted to harmless
or less toxic chemicals.
Hydrogen peroxide is broken down using the enzyme catalase which is found in most cells.
Fig. 1.1 shows this reaction.

Figure 1.1:

A student investigated the effect of alcohol (ethanol) on the activity of catalase found in
potato, using three pieces of potato cut to the same size.
Fig. 1.2 shows these pieces of potato.

Figure 1.2:

(a) (i) Measure the length, width and height of one of these pieces of potato. …/3
Copy and record your results in Table 1.1.

Table 1.1:

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Step 1 The student labelled six test-tubes, 1, 2, 3, 4, 5, and 6 and used a syringe
to add 10 cm3 of hydrogen peroxide solution to each of the test-tubes.

Step 2 They cut potato piece A to obtain two slices of similar size.

Step 3 The student placed the free end of a delivery tube into a large test-tube
containing water.

Step 4 They placed one of the slices of potato piece A into the hydrogen peroxide
solution in test-tube 1.

Step 5 The student immediately placed the rubber bung attached to the delivery
tube into test-tube 1 and pushed it in as tightly as possible, as shown in Fig.
1.3.

Figure 1.3:

Step 6 They counted the number of bubbles released from the delivery tube in 3
minutes.

Step 7 The student repeated steps 4–6 for the second slice of potato piece A using
test-tube 2.

Step 8 They repeated steps 2–7 for potato piece B using test-tubes 3 and 4.

Step 9 They repeated steps 2–7 for potato piece C using test-tubes 5 and 6. The
student used a tally to count the number of bubbles. Fig. 1.4 shows their
tally count.

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 Figure 1.4:

(ii) Prepare a table to record the student’s results. Your table should show: …/5
• the numbers of bubbles produced by each slice of potato in 3 minutes

• the mean number of bubbles produced by each of potato piece A, B and C.

Complete your table using the results from Fig. 1.4.

(b) (i) Suggest why the free end of the delivery tube was placed in the water before …/1
adding the potato slice to the hydrogen peroxide solution and connecting the
test-tube to the bung of the delivery tube.

(ii) Explain why the bung of the delivery tube must fit tightly into the test-tube. …/2

2. Teeth can develop dental decay.

(a) Explain how dental decay is caused. …/6

(b) Describe four ways to avoid dental decay. …/4

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 Topic: Term two 2021 Holiday Homework
Subject: Biology Form Two
Teacher: Mr. F Moyo
Topic: Week 3

1. A potometer is used to measure water uptake by a plant. Fig. 1.1 shows the stem and
flower of a plant in a potometer. As water is taken up, the bubble moves in the direction
shown.

Figure 1.1:

(a) Name the parts A, B, C and D. …/4

(b) Describe the pathway taken by water as it moves from the potometer, through the …/3
plant stem and into the surrounding air.

(i) In an experiment, the bubble moved a distance of 60 mm in 10 minutes. …/2

Calculate the average rate at which the bubble moved in mm per min.

(ii) The experiment was repeated in an area of lower light intensity. …/3
Predict and explain what would happen to the rate at which the bubble moved.

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2. (a) State where and how water normally enters a plant. …/1

(b) Describe how water is lost from a plant by transpiration. …/4

(c) State the name of the tissue that transports water to the leaves. …/1

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