Fig. 1.1 shows a drawing of a dicotyledonous leaf. A student was asked to make an accurate scale drawing of the leaf at half its size. The actual sizes of s...
Question 1 Report
Fig. 1.1 shows a drawing of a dicotyledonous leaf. A student was asked to make an accurate scale drawing of the leaf at half its size. The actual sizes of some features of the leaf are given in Table 1.1.
| Feature | Actual size / mm | Size at x0.5 / mm |
|---|---|---|
| Leaf length | 80 | |
| Leaf width | 30 | |
| Petiole length | 20 |
(a) Measure the length of the leaf shown in Fig. 1.1, from the tip to the base of the leaf blade, in mm. [1]
(b) The scale drawing is to be made at x0.5. Calculate the length the leaf should be in the scale drawing, in mm. [1]
(c) Draw a scale drawing of the outline of the leaf at half its size (x0.5). [3]
(d) Measure the length of your finished scale drawing, in mm, to check it. [1]
(e) State the magnification of your scale drawing. [1]
(f) Complete Table 1.1 by calculating the size, in mm, of each feature in the x0.5 scale drawing. [3]
(g) Describe two rules a student should follow when making a biological scale drawing. [2]
(h) Explain why a scale drawing is more useful than a freehand sketch when comparing the sizes of specimens. [2]
(i) A second drawing of the same leaf measured 120 mm long. Calculate the magnification of this drawing. Show your working. [2]
(j) A student's drawing measured 36 mm instead of 40 mm. Suggest one reason for this difference. [2]
(k) State the actual length of the leaf if a x0.25 drawing of it measured 20 mm. Show your working. [2]
Answer Details
Labelled answer diagram:
This question is about making an accurate scale drawing and working with magnification. A scale of \( \times 0.5 \) means every real length is drawn at half its true size; magnification is always \( \dfrac{\text{drawing size}}{\text{actual size}} \).
(a) Measure the length of the leaf blade in Fig. 1.1 from tip to base with a ruler; the reading is 80 mm (accept 79-81 mm). [1]
(b) At \( \times 0.5 \) the drawing length should be
\[ 80 \times 0.5 = 40\ \text{mm} \]
[1]
(c) The scale drawing of the leaf outline at half size (drawn 40 mm long, single clear lines, no shading):
Marks: outline drawn 40 mm long [1]; correct shape and proportions [1]; clear single continuous lines with no shading [1]. [3]
(d) Measure your finished drawing to check it: it should read 40 mm (accept 39-41 mm). [1]
(e) The magnification of your scale drawing is \( \times 0.5 \) (half size). [1]
(f) Each feature at \( \times 0.5 \) is half its actual size. The completed Table 1.1:
| Feature | Actual size / mm | Size at \( \times 0.5 \) / mm |
|---|---|---|
| Leaf length | 80 | 40 |
| Leaf width | 30 | 15 |
| Petiole length | 20 | 10 |
[3]
(g) Two rules for a biological scale drawing (any two): use a sharp pencil; draw clear single continuous lines; do not shade or colour; draw to scale using a ruler; use straight ruled label lines. [2]
(h) A scale drawing is more useful than a freehand sketch because it keeps the correct proportions and relative sizes [1], so real sizes can be worked back out and specimens compared fairly [1]. [2]
(i) If a drawing of the same 80 mm leaf measures 120 mm, the magnification is
\[ \frac{120}{80} = \times 1.5 \]
working [1], answer [1]. [2]
(j) One reason a drawing measured 36 mm instead of 40 mm (any one, developed): the length was measured or drawn inaccurately [1], for example a blunt pencil, a parallax error, or not using a ruler [1]. [2]
(k) If a \( \times 0.25 \) drawing measures 20 mm, the actual length is
\[ \frac{\text{drawing size}}{\text{magnification}} = \frac{20}{0.25} = 80\ \text{mm} \]
working [1], answer [1]. [2]
Examination tip: for any scale problem, arrange \( \text{magnification} = \dfrac{\text{drawing}}{\text{actual}} \) and rearrange for the unknown; a magnification less than 1 means the drawing is smaller than the real specimen.
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