Biology

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Hong Kong Diploma of Secondary Education Examination

Integrated Science

School-based Assessment Sample Tasks

Teachers may use the sample tasks for non-profit making educational and research purposes with proper acknowledgement.

© 2009 Hong Kong Examinations and Assessment Authority All Rights Reserved 2009

TABLE OF CONTENT

Task C1 C2 C4 C5 C6 C7 C8 E3

Title Osmosis in Living Tissue Catalytic Activity of Enzyme Action of Electricity on Substances Encountered in Daily Life Do All Conductors Obey Ohm’s Law? Composting Bioreactor Sunglasses’ Protection from Ultraviolet (UV) Radiation Extracting DNA from Fruits How Cross-linking Changes the Properties of a Polymer

Integrated Science Sample SBA Task

Practical Related Task – C1 Osmosis in Living Tissue Student Handout (Version 1) Purpose To determine the water potential of potato tissue. Background When two solutions with different concentrations are separated by a selectively permeable membrane, osmosis takes place. Water will pass from the side with higher water potential to the side with lower water potential. When a plant tissue is immersed in a solution of higher water potential, water will enter its cells by osmosis. As the plant cells swell and become turgid, the plant tissue will increase in size. On the other hand, when the plant tissue is placed in a solution of lower water potential, water will leave its cells by osmosis. In this case, the plant tissue will decrease in size as the plant cells shrink upon losing water. For this activity, you are required to design and perform an experiment to determine the water potential of potato tissue using sucrose solutions of different concentrations. The water potential of potato tissue will be expressed in terms of the concentration of sucrose solution.

Apparatus and Materials 1 ml pipette 10 ml pipette Pipette filler Cork borer 6 boiling tubes Petri dish Blotting paper Sealing film Razor blade Ruler Stopwatch 1.0 M sucrose solution Student Handout – C1 (Version 1) page 1 of 2

Integrated Science Sample SBA Task

Distilled water Fresh potato

Safety Precaution Handle the cork borer and razor blade with great care.

Tasks 1. 2. Use the given sucrose solution and distilled water to prepare a series of sucrose solutions of various concentrations. Devise and conduct an experiment to determine the water potential of the potato tissue.

Guidelines for designing the experiment 1. 2. 3. 4. 5. 6. 7. 8. 9. What biological process is being investigated in this experiment? What is the independent variable in this investigation? How would you manipulate it? What is the dependent variable? How would you measure it? What other variables need to be controlled? What are the precautions for this experiment? What are suitable ways of recording the experimental results? What further treatment of data is needed to find out the water potential of the potato tissue? What assumptions are made in the determination of the water potential of the potato tissue? What are the sources of error in making the measurements? Suggest ways of improvement.

Student Handout – C1 (Version 1)

page 2 of 2

Integrated Science Sample SBA Task

Practical Related Task – C1 Osmosis in Living Tissue Student Handout (Version 2) Purpose To determine the water potential of potato tissue. Background When two solutions with different concentrations are separated by a selectively permeable membrane, osmosis takes place. Water will pass from the side with higher water potential to the side with lower water potential. When a plant tissue is immersed in a solution of higher water potential, water will enter its cells by osmosis. As the plant cells swell and become turgid, the plant tissue will increase in size. On the other hand, when the plant tissue is placed in a solution of lower water potential, water will leave its cells by osmosis. In this case, the plant tissue will decrease in size as the plant cells shrink upon losing...
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