Cambridge International A Level Biology Revision Guide

Cambridge International AS Level Biology
Answers to end-of-chapter questions
lines continuous, not sketchy and sharp
pencil used;[4]
ii LP plan drawn showing vascular bundles
only and no cell detail;
sclerenchyma, xylem and phloem drawn in
outline;[2]
iii no. of squares of graph paper covered by
lignified tissue in root counted;[1]
iv no. of squares of graph paper covered by
whole root section counted;[1]
v % squares occupied by lignified tissue in
root calculated correctly from student’s
answers to iii and iv; (answer should be
greater than for root) [1]
vi no. of squares covered by lignified tissue in
stem counted;
no. of squares covered by whole stem
counted;
% squares occupied by lignified tissue in
stem calculated correctly; (answer should
be around 1%) [3]
vii
stem needs more support than root;
because upright in air and needs support
to prevent it falling over / collapsing; AW[2]
c roots subjected to tugging / pulling pressure
from parts above ground;
roots spread out, so like a series of guy ropes;
stem a single column;
greater strength from a ring of rods than from
one central rod;
ring of rods provides greater resistance to
compression from above than a single central
rod;
AVP; accept any reasonable suggestion(s)
which are based on different stresses to
which roots and stems are subjected.[max. 2]
[Total: 20]
5 a i ‘Temperature / °C’ on x-axis and ‘Enzyme
activity / mean number of carbon dioxide
bubbles released per minute’ on y-axis;
suitable scales on both axes – range from
10 or 15 to 40 on x-axis and 0 or 5 to 20 on
y-axis, in intervals of 2 or 5;
all points plotted accurately, using crosses
or encircled dots;
thin, clear, best-fit line drawn or points
joined with ruled lines – no extrapolation;
[4]
ii correct reading from graph, including unit
(mean number of bubbles per minute);[1]
iii accuracy:
use water bath to change independent
variable;
control of significant named variable plus
method of control (e.g. use same type of
yeast);
use named apparatus (e.g. gas syringe) to
collect gas (for measurement of dependent
variable);
reliability:
increase number / range of temperatures;
repeat each temperature three times and
calculate mean; [max. 3]
b hypothesis is supported;
quote figures for change in mean number
of bubbles between any two temperatures
between 15 °C and 40 °C;
reference to no data below 15 °C or above 40 °C;
so cannot tell if hypothesis is also supported
outside this range; [max. 2]
[Total: 10]
6 a x-axis is ‘Time / minutes’, y-axis is ‘Number of
individuals’;
scales on both axes with suitable range and
interval;
all bars plotted accurately or points plotted
accurately (using a cross or an encircled dot);
all lines neat and thin, plus key;[4]
b on both days, minimum time taken is 35 min
and maximum time taken is 55 min;
on both days, number of individuals is
greatest near the centre of the range;
on day 1, greatest number of individuals
take 45 minutes to digest starch, but on day
2 greatest number of individuals take 40
minutes to digest starch;
mean time is greater on day 1 than on day 2;
[max. 3]
c temperature may have been higher on day 2;
animals on day 2 may have eaten recently
and so had more saliva / amylase in their
mouths; [max. 1]
Cambridge International AS and A Level Biology © Cambridge University Press 2014