Name: ____________________________

Revision

A student decided to investigate respiration in algae. Figure 1 shows how she set up her apparatus.
Figure 1

[pic]

The student completed the whole experiment in a dark laboratory. The student placed the algae in the boiling tube, filled it with water and placed the boiling tube in a water bath. Bubbles of gas were released from the algae, slowly at first then steadily. Once the release of bubbles became steady she placed the bung in the boiling tube and the drop of coloured liquid moved.

Answer all questions in the spaces provided.

1 (a) (i) Name the gas in the bubbles released by the algae.

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1 (a) (ii) Which way did the liquid move? Explain your answer.

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(2 marks)

1 (a) (iii) What measurements would the student need to make to compare the rate of respiration of different algae?

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1 (b) What is the syringe used for?

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1 (c) Explain why the student placed the boiling tube in the water bath.

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1 (d) Explain why the student waited for the release of bubbles to become steady before placing the bung in the boiling tube.

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2 The student completed the whole experiment in a dark laboratory.

Explain how the results would have been affected if the student had carried out the experiment in a light laboratory.

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(2 marks)

3 Another student only had the apparatus in Figure 2

Figure 2
[pic]

3 The student decided to count the number of bubbles of gas produced to measure the rate of respiration in the algae.

Explain why counting the number of bubbles of gas produced would be a suitable method.

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4 Which of the students’ methods would have given more accurate results? Explain why.

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(2 marks)

5 The students’ teacher told them that they needed to now investigate the effect of two temperatures on the rate of respiration in algae using the apparatus in figure 2. They were told to do this by using a thermostatically controlled water bath. All other variables needed to be controlled.

Complete the figure 3 to outline three variables the students should have controlled.

Figure 3

|Variable to control |Method of controlling variable |Reason why control of variable is needed |
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(3 marks)

6 The students’ results from the experiment in question 4 can be seen in figure 4.

Figure 4

|Temperature/oC |Number of bubbles of gas released by the algae in one minute |
| |Trial number |
| |1 |
|10 |8 (+/- 1.3) |
|20 |23 (+/- 2.4) |
|30 |37 (+/- 0.9) |
|40 |29 (+/- 1.7) |
|50 |15 (+/- 0.8) |

8 (a) (i) Calculate the percentage increase in number of bubbles of gas released by the algae in one minute at 30oC compared to 10oC. Show your working.

(2 marks)

8 (a) (ii) The teacher told the students that there was a significant difference in the number of bubbles of gas released by the algae in one minute at all temperatures.

Do you agree with what the teacher told the students?

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8 (b) The teacher asked the students to draw a graph of the data in figure 5. Describe the type of graph the students should have drawn.

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(2 marks)
9 Figure 6 shows the absorption of different wavelengths of light by three photosynthetic pigments in a red seaweed.

Figure 6
[pic]

9 (a) (i) Describe what the Figure 6 shows about the properties of chlorophyll a.

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9 (a) (ii) Describe the part played by chlorophyll in photosynthesis.

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(3 marks)

9 (b) The red seaweed lives under water at a depth of 2 metres. Water absorbs wavelengths of light in the red part of the spectrum. Suggest an advantage to the red seaweed of having other pigments in addition to chlorophyll a.

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(2 marks)

9 (c) Different oceans have varying temperatures and varying levels of nutrients.

Suggest how this may cause an increase in the amount of chlorophyll a found in red seaweeds from warmer oceans that contain more nutrients.

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9 (d) A student studying the graph in figure 6 and the information in 9(b) came up with two theories.

Theory 1: Phycoerythrin helps red seaweed absorb light when underwater.

Theory 2: Chlorophyll a prevents red seaweed from dying when water levels are low.

9 (d) (i) Which theory does figure 6 provide evidence for?

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9 (d) (ii) Explain your answer to 9(d)(i).

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(2 marks)

9 (d) (iii) Suggest one further piece of evidence you would need to support the theory you have chosen in 9(d)(i).

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10 The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur.

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(5 marks)