Biology 0610 | Paper 5 Mock 01 | Practical Test

Labelled answer diagram:

This question tests observation, classification of arthropods, and building a dichotomous key. First the completed feature table:

(a) and (b) Measure the body length of animal A and of animal D along the line shown, in mm, reading each with a ruler on the printed figure [1] + [1].

(c) Counting the legs in Fig. 2.1: animal A has 6 legs; animal C has many legs (more than 15) [2], as entered in the table above.

(d) Animal A is an insect [1] because it has 6 legs and 3 body parts [1].

(e) Animal B is an arachnid [1] because it has 8 legs and 2 body parts [1].

(f) Any two distinguishing features: an insect has 3 body parts while a myriapod has many segments; an insect has 6 legs while a myriapod has many pairs; an insect may have wings and a myriapod does not [2].

(g) Dichotomous key. Each numbered couplet gives two contrasting, observable choices that lead either to an animal or to the next couplet:

Award for a workable key using contrasting observable features [2] that correctly separates all four animals [2] [4].

(h) Any three features shared by all arthropods: jointed legs (paired jointed appendages); a hard exoskeleton; a segmented body; bilateral symmetry [3].

(i) Divide the length of C by the length of A using your own measured values, for example \( \frac{\text{length of C}}{\text{length of A}} \). Method mark for dividing [1], answer mark for the number of times [1] [2].

(j) A labelled drawing can show only the key structures clearly and can be labelled, removing background clutter that a photograph would include [1].

Exam tip: a good dichotomous key uses only features you can actually see and count, such as number of legs or body parts, never colour or size, because those vary between individuals.

Labelled answer diagram:

This question is about the structure and function of a capillary and how it is adapted for the exchange of substances between the blood and the tissues.

(a) Measure the internal (lumen) diameter of the capillary on Fig. 3.1 with a ruler; a typical reading is about 2-3 mm (accept 1-4 mm; mark your own reading). [1]

(b) Measure the width of one red blood cell in the same way; a typical reading is about 10 mm (accept 8-12 mm as drawn). [1]

(c) At a magnification of \( \times 1500 \) the actual width of a red blood cell is

\[ \frac{\text{measured width}}{\text{magnification}} = \frac{10\ \text{mm}}{1500} = 0.0067\ \text{mm} \]

and since 1 mm = 1000 µm,

\[ 0.0067\ \text{mm} \times 1000 = 6.7\ \mu m \]

(accept 6-8 µm): correct division [1], unit conversion [1], answer [1]. [3]

(d) Two ways the capillary is adapted for exchange (any two, plus development): its wall is only one cell thick, giving a very short diffusion distance [1]; the lumen is very narrow so cells move slowly in single file, allowing time for exchange [1]; the capillary network has a very large total surface area [1]. [3]

The single-file arrangement and thin wall are shown here:

(e) The completed comparison Table 3.1:

[4]

(f) The cells pass in single file because the lumen is only just wider than one red blood cell [1], so the cells cannot pass side by side [1]. [2]

(g) One substance that passes out of the blood into the tissues (any one): oxygen, glucose, water, or amino acids (carbon dioxide passes the other way, into the blood). [1]

(h) The thin wall gives a short diffusion distance [1], so substances are exchanged quickly between the blood and the tissues [1]. [2]

(i) An outline of two of the red blood cells as they appear in Fig. 3.1:

Marks: two biconcave-disc shapes drawn [1]; neat single outlines of correct relative size [1]. [2]

(j) A capillary joins a vein (or venule) to return blood towards the heart. [1]

Examination tip: a capillary is defined by a wall one cell thick and a lumen barely wider than a red blood cell, which together make it perfect for exchange but useless for carrying blood at high pressure.

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:

[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.