Topic 1 Revision - Year 9

A student found four different worms in a sample of soil and drew diagrams of them.

The diagrams were drawn with different magnifications.

Which worm had the longest actual length?

• worm A: Length of diagram is 60mm and its magnification x3

• worm B: Length of diagram is 70mm and its magnification x1

• worm C: Length of diagram is 100mm and its magnification x2

• worm D: Length of diagram is 120mm and its magnification x5

Answer explanation

The working shows worm B specimen has the longest actual length.

Scientists investigated the effect of different concentrations of sodium chloride solution on the

germination and growth of marram grass.

After 20 days, the lengths of the seedling roots were measured with a ruler.

The results of the investigation described are shown in Table 2.1.

If you want to construct a graph using the results from the Table 2.1, state which data will be on the y-axis of your graph and state the unit clearly.

Answer explanation

Tips for Drawing Graphs in Biology:

(i) 1 mark for knowing which data is going to be the x-axis and y-axis of your graph.

*Just copy exactly the headings from the table and the units when labelling your graph.

(ii) 1 mark for having a good linear scale for the graph.

*Check the data table for the lowest value and highest value fill at least half of each axis.

**Choose a scale that is easy to work with.

Examples include: "0, 2, 4, 6...." or "0, 5, 10, 15.... for each big square on the graph.

(iii) 1 mark for clear and accurate plotting using the data from the table.

(iv) Follow instruction: ruled lines or a best fit line.

*Sometimes, the question demands that you draw a "Line (or curve) of best fit" then you do just that. Do take care to balance the points about the line you draw - not too many points above or below the line drawn. There is no need to force the line to pass the origin as well.

**Strictly NO extrapolation unless told to do so. That means, you do not extend the line before or beyond the first and last plots respectively.

The diagram shows a cross-section through two guard cells of a leaf.

Which labelled structures would also be found in an animal cell?

• W and X

• X and Y

• Y and Z

• Z and W

Answer explanation

The diagram is of guard cells, which are plant cells.

So the only structures that will be shared by both plant cell and animal cell are a nucleus (W) and cell surface membrane (X).

Figure shown is a photomicrograph of a section through part of a marram grass leaf, Ammophila arenaria.

Draw a large diagram of the section of marram grass leaf shown in the space below it.

Do not draw individual cells!

Answer explanation

BIOLOGICAL DRAWING TIPS: [4 marks]

(i) 1 mark for drawing with clean, neat and

unbroken lines.

(ii) 1 mark for an appropriate size drawing

(drawing must be at least twice as big as

sample figure given OR make use at least

3/4 of the drawing space given.)

(iii) 2 marks for drawing accurate details AND in correct proportion.

• *Details could be recognizable tissue cells

• e.g. vascular bundle or external features e.g. projections or hairs etc.

• *Details do NOT mean drawing all

• individual cells!

Continue practising to hone your skills in drawing biological diagrams! The effort will pay off! • ᴗ•

The length of line PQ on Fig. 2.2 is 112mm.

Calculate the actual diameter of the marram grass leaf using the magnification formula.

   Give your answer to one decimal place and state the unit clearly.

There are several ways a scientific investigation could be improved to give more reliable results.

Select the TWO (2) options which improve the reliability of the results of an investigation?

• Increase sample size: Increasing the number of samples can give a more reliable and accurate results.

• 1. Small sample size: A small sample may not represent the overall population accurately.

• 1. No repetition of experiments: Without repetitions, it is difficult to establish the reliability of the findings.

• 1. Repeat the experiments: This involves repeating the same experiments multiple times to ensure that the results are consistent and not due to chance.

Answer explanation