ECF Saint Too Canaan College
Form 6 Biology
201516 Pre-Mock Exam Marking Scheme
Section A: Multiple-choice questions (36 marks)
15
ACDCD
610
BADDC
1115
CBACC
1620
ABACD
2125
ABCDA
2630
CABBB
3135
DDABD
36
B
Section B: Structured questions (84 marks)
1.
C
(1)
B
(1)
D
(1)
3
2.

the pressure of fluid A near the arterial end is higher than that of fluid B (1)

some of the plasma except large proteins, red blood cells and platelets (1) are forced through the thin
(3)
wall of the blood capillary to form fluid B (1)
3
3.
(a)

the protease works best at pH 2 (1)

it also works at pH 5 (1)

it does not work in alkaline medium, i.e. from pH 8 to 14 (1)
(3)
(b)
*stomach (1)
(1)
(c)
*pancreatic juice (1)
(1)
5
15-16 Pre-Mock Exam S.6 Biology Marking Scheme p.1
4.
(a)
*belt transect (1)
(1)
(b)

the abundance of a certain species at different positions along a transect (1)
(1)
(c)

it cannot be used for sampling organisms that move rapidly (1)
(1)
(d)

nitrogen fixing bacteria are present in the root nodules of Mimosa (1)

they can convert nitrogen gas in soil air to ammonium compounds (1) and then absorbed by the
(3)
plant for growth (1)
6
5.
(a)

drug X blocks / inhibits the action of pancreatic lipase (1) and prevent the digestion of fat (1)

unabsorbed / undigested fat is egested together with faeces (1)
(3)
(b)
fat-soluble vitamins / vitamin A / vitamin D (1)
(1)
(c)
cardiovascular disease / coronary heart disease (1)
(2)
diabetes (1)
6
6.
(a)
Any two set of the following:

rolled leave (1)

trap moisture inside the leave to maintain a humid internal environment / reduce concentration
gradient of water vapour between the leave and the environment (1)
OR
(4)

sunken stomata (1)

trap moisture inside the leave (1)
OR
(b)

stomata can only be found in the lower epidermis (1)

reduce direct exposure to dry air (1)

the leave contains lignified cells / xylem vessels / thick-walled cells (1) which provide support
to the leave by rigidity (1)

(3)
the mesophyll cells press against and support each other when they become turgid (1)
7
15-16 Pre-Mock Exam S.6 Biology Marking Scheme p.2
7.
(a)

(b)
(i)
the petals are large / brightly-coloured (1)
(1)
Advantage:

pollination does not depend largely on external agents (1)
Disadvantage:

(2)
the species is less adapted to changes in the environment as there are less genetic
variations in the offspring (1)
(ii)

remove / cover the anthers / cover the stigmas (1)
(1)
4
8.
(a)

both individuals 3 and 4 have blood group A therefore each of them must possess at least one
allele for blood group A (1)

one of their children (individual 12) has blood group O, that means at least one of the parents
must also possess one allele for blood group O (1)
(b)

at least one of the parents is heterozygous (1)

in a heterozygous condition, only the dominant allele will be expressed (1)

blood group A is dominant (1)
Defined symbols (1) e.g. :
(5)
Ia = allele for blood group A
Io = allele for blood group O
(2)
a o
individual 7: I I (1)
(c)
individual 4, 5, 6 and 7 (1)
(1)
(d)

discontinuous variation (1)

there are only few intermediates. / The blood groups cannot be changed by environment / diet /
(2)
habits (1)
10
9.
(a)
(b)
(c)
(i)
anaerobic respiration (1)
(1)
(ii)
carbon dioxide (1)
(1)

glucose was consumed quickly as a source of energy for the growth of the yeast (1)

therefore, the concentration of glucose decreased quicklyy (1)

ethanol was produced when glucose was being broken down during anaerobic respiration (1)

therefore the concentration of ethanol increased (1)

the density of the yeast cell suspension decreased as yeast cells died (1)

this is because ethanol is toxic to yeast cells (1)
(4)
(2)
8
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10.
(a)
*axon (1)
(b)
Any two of the following:
(c)
1

the myelin sheath protects and insulates the nerve fibres (1)

it prevents the transmission of nerve impulses to the surroundings (1)

it speeds up the transmission of nerve impulses (1)

nerve impulse transmission may slow down or even stop (1)
(d)
sensory
neurone
spinal cord
motor
neurone
(2)
(1)
(3)
stretch receptors
in leg muscle
leg muscle
(effector)
Correct drawing and labels of sensory neurone and motor neurone: 2 marks
Correct directions of arrows: 1 mark
7
11.
(a)
(b)

the lowest level of antibodies that is sufficient for protection can be reached faster (1)

no booster doses are required (1)

no injection is required so that the chance of infection can be reduced (1)

(3)
when a vaccine is introduced into the body, the antigen in the vaccine stimulates the body to
produce a primary response (1)

memory cells that remember the type of antigens are produced (1)

if the body is later invaded by the same antigen, the body will develop a secondary response (1)

a larger amount of specific antibodies and killer T cells are produced in a shorter time, and the
(4)
body will show enhanced immunity (1)
7
15-16 Pre-Mock Exam S.6 Biology Marking Scheme p.4
12.
(a)
Any two of the following:

the mutation does not occur on coding region (1)

codons are degenerative, mutation may not lead to change in protein structure produced (1)

the alternated proteins may not be metabolic significant / not involved in important metabolic
(2)
pathway (1)
(b)
(c)

both GCA and GCU code for alanine (1)

therefore this mutation would not change the protein structure (1)

cut the DNA fragment containing mutation 2 and a plasmid (1) with the same restriction
(2)
enzyme (1)
(4)

join the DNA fragment and the plasmid by using a DNA ligase (1)

the recombinant plasmid is then introduced into tomato plants to improve the tolerance (1)
8
13.
Phagocytes engulf foreign particles by phagocytosis (1), which is an active process. (1)
Max.
There are many mitochondria in the cytoplasm for releasing energy. (1)
(7)
The fluidity of the cell membrane allows the phagocyte to change shape to engulf foreign particles. (1)
There are many glycoproteins embedded in the cell membrane (1) for cell recognition / recognition of
foreign particles. (1)
There are many rough endoplasmic reticulum in the cytoplasm. (1)
They are the sites for producing enzymes for digesting foreign particles. (1)
Max.
Mark award for communication:
(3)
Mark
3
2
Clarity of expression and relevance to question

Answers are easy to understand.
They are
Logical and systematic presentation

Answers
are
well
structured
fluent showing good command of language.
showing coherence of thought

There is no or little irrelevant material.
and organization of ideas.

Language used is understandable but there is

some inappropriate use of words.

Answers are organized, but there
is some repetition of ideas.
Irrelevant material obscures some minor
ideas.
1


Markers have to spend some time and effort

Answers are a bit disorganized,
on understanding the answer(s).
but
paragraphing
is
Irrelevant material obscures some minor
Repetition is noticeable.
evident.
ideas.
0

Language used in incomprehensible.


Irrelevant material buries the major ideas
systematic.
required by the question.
attempt to organize thoughts.
Ideas
are
not
coherent
and
Candidates show no
10
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