Experimental Contexts

Make a large drawing in the space below of the pea seedling as it appears in Fig. 2.1.

The leaves of the pea shoot are green.

Describe how you would prepare a leaf from the shoot and then carry out a test on it to show that it contains starch.

State and explain which individual is healthy.

State and explain which individual has diabetes.

The pH of urine in healthy humans is normally 6.5. The pH of urine can be measured using universal indicator paper strips.

A scientist wants to determine whether the pH of human urine is affected by the volume of water drunk. For her investigation she selects 20 healthy female volunteers of similar age and weight.

Plan a method the scientist could use for her investigation.

The sample contained three different plant species.

The student counted the number of plants of each of these species in this sample.

One plant was not fully within the square frame. Suggest and explain what you would do about this plant.

______

Count the number of plants of species E in Fig. 2.1, taking into account your answer to (a).

Record your answer in Table 2.1.

Table 2.1

The whole field measured $10\text{ m} \times 20\text{ m}$.

Use the sample in Fig. 2.1 to estimate the number of plants of species E in the whole field and record this value in Table 2.1.

Show your working.

Explain why the student counted the numbers of plants in samples of the field instead of counting the number of plants in the whole field.

______

Suggest two reasons why taking several samples would improve the accuracy of the estimate for the number of plants in the whole field.

1. ______

2. ______

Use the data in Table 2.1 to construct a bar chart to show the estimated number of plants of species C, D and E in the whole field.

Count the numbers of woodlice in each area of choice chamber C and record them in the table.

Calculate the mean number of woodlice in each of the four areas of the choice chamber to the nearest whole number. Record these results in the table.

Construct a bar chart on the grid provided to show the mean number of woodlice (to the nearest whole number) found in each area of the choice chamber.

Using the data in the table and your bar chart, state which area of the choice chamber the woodlice preferred.

______

Suggest where the student should have placed the 10 woodlice when she first put them into the choice chamber. Explain your answer.

______

Suggest two ways in which the results of this investigation could be made more reliable.

1. ______
2. ______

Another student says that it would be a good idea to make some holes in the lid of the choice chamber. Suggest one advantage and one disadvantage of doing this.

advantage = ______
disadvantage = ______

Suggest a method that he could use to determine this volume of milk.

When he added protease to the milk, it digested the casein. As a result, the milk became colourless after five minutes and he could see the X through it.

A fruit contains a protease enzyme. Not all protease enzymes can digest casein.

Using a method similar to the one above, design an investigation to find out whether this fruit protease will digest casein.

Suggest why the student being tested kept her eyes closed.

______

Describe the results obtained when her finger was placed in water at $20\,^\circ\text{C}$ after having been in the three different temperatures of water in beaker E.

______

Suggest what the results show about the sensitivity of skin compared to the sensitivity of a thermometer.

______

Use this information to complete the table, including the column heading.

Explain what the student could conclude about the digestion of protein from these results.

Suggest a suitable temperature for the water in the water bath and explain why that temperature should be used.

Suggest a suitable piece of apparatus:

for measuring the volume of enzyme solution = ______
for adding the pH solution = ______

Explain why distilled water was added to test-tubes A, B and C.

______

Giving full experimental details, design an experiment based on test-tube D to investigate the effect of different pH values on the action of this enzyme.

State and explain one safety precaution that should be taken when this experiment is carried out.

Describe how she could measure her pulse rate.

On the grid below, construct a graph to show the student's results. Join your points with ruled, straight lines.

Describe how the student's pulse rate changes following her exercise.

In the space below, make a drawing of the cell labelled Q in Fig. 2.1, magnified $\times 2$.
You do not need to label your drawing.

Identify cell P and cell Q.

P = ______
Q = ______

Use Fig. 2.1 to describe how the appearance of cell Q differs from that of cell P.

Fig. 2.2 shows a plant cell as seen using a light microscope.

Complete Table 2.1 to compare cell Q in Fig. 2.1 and the plant cell in Fig. 2.2.

Table 2.1