Biology · Oct / Nov 2022 · Paper 62 · Question 2

single clear unbroken outline ;

drawing at least 78 mm wide ;

Detail 1: minimum of eight vascular bundles drawn ;

Detail 2: square-shaped indent at the top ;

one vascular bundle labelled ;

PQ = 78 ±1 (mm) ;

(x) 3 ;;

total of six from:

independent variable:

1

at least two different air temperatures ;

dependent variable:

2

time for dye to reach the leaves or a set distance

/ distance moved by dye (in set time) / counting number of sections cut 3 + 4 detail of method – max two from ;;

method of maintaining (two) air temperatures

idea of equilibration time for the celery and / or dye before celery is put in the dye

(idea of) cutting, sections of stalk (to see the distance moved by the dye) / down the middle / cut in half

cut stems under water (if used a potometer)

5 + 6 + 7 variables kept constant – max three from ;;;

wind-speed

humidity

light intensity

length of stalk

number of leaves / surface area of leaves

species / type (celery) / age / health / plant

same dye / concentration of dye

set period of time (in dye) / time stated (if not the dependent variable) same thickness of cut sections

8

two or more repeats at each temperature / repeat the investigation at least two more times ;

9

safety precaution ; e.g. cutting sections on flat or stable surface / cut away from body

any three from:

ref. to preparation of tissue sample ;

add Benedict’s (solution / reagent) ;

heat ;

reducing sugars present / positive result, if sample becomes,

yellow / green / orange / brown / red ;