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WELSH JOINT EDUCATION COMMITTEE
CYD-BWYLLGOR ADDYSG CYMRU
General Certificate of Education
Tystysgrif Addysg Gyffredinol
MARKING SCHEMES
JANUARY 2005
AS/Advanced
BIOLOGY
INTRODUCTION
The marking schemes which follow were those used by the WJEC for the January 2005
examination in GCE BIOLOGY. They were finalised after detailed discussion at examiners'
conferences by all the examiners involved in the assessment. The conferences were held
shortly after the papers were taken so that reference could be made to the full range of
candidates' responses, with photocopied scripts forming the basis of discussion. The aim of
the conferences was to ensure that the marking schemes were interpreted and applied in the
same way by all examiners.
It is hoped that this information will be of assistance to centres but it is recognised at the
same time that, without the benefit of participation in the examiners' conferences, teachers
may have different views on certain matters of detail or interpretation.
The WJEC regrets that it cannot enter into any discussion or correspondence about these
marking schemes.
ASSESSMENT UNIT BI 1
JANUARY 2005
Question
1.
Answer/Explanatory Notes
Marks
Available
(a)
organic molecule
amino acid / starch
tissue
muscle
compound
NaHCO3
element
Magnesium
polymer
starch
5
(b)
(i)
starch and cellulose: starch alpha glucose, cellulose beta;
starch two polysaccharides, cellulose one;
Starch has 1-4 and 1-6 links, cellulose 1-4 only.
Starch has a branched structure within it, cellulose un-branched;
Amylose/starch coiled, cellulose (H) bonds/cross links between
adjacent mols.
2
(max 2) (Reference to both needed)
(ii)
Triglyceride and phospholipids: triglyceride three fatty acids,
phospholipids two;
Phospholipid: phosphoric acid/phosphate;
Phospholipids hydrophilic (head) and hydrophobic(tail) (Max 2) 2
(Comparison needed, except last point)
[9]
1
Question
2.
Answer/Explanatory Notes
(a)
(b)
Marks
Available
A = Golgi
1
B = Mitochondrion
1
C = (Smooth) Endoplasmic reticulum. (not: ER)
1
D = Cell membrane / cell surface membrane / plasmamembrane.
1
E = Cell wall.
1
F = Ribosome
1
Chloroplasts/grana/thylakoid;
Vacuole;
Starch grains;
Plasmodesmata;
Nucleus or associated structure e.g., nucleolus or chromatin;
RER/rough endoplasmic reticulum;
Tonoplast/vacuolar membrane
(Max. 2) (No consequential error allowed)
(c)
2
Vesicles; (labelled)
from golgi;
migrate to cell membrane; (movement indicated)
membranes fuse;
exocytosis; (term required)
(Max. 3) (Diagram needed; unlabelled diagram, max 2)
2
3
[11]
Question
3.
Answer/Explanatory Notes
(a)
Marks
Available
(i)
D
1
(ii)
B
1
(iii)
A
1
(iv)
F
1
(v)
C
1
(vi)
E
1
(Letters only; more than one answer, no mark)
(b)
4.
(i)
condensation
1
(ii)
water (allow correct formula)
1
[8]
(a)
Increased conc increased rate of reaction.
1
(b)
5.5; (allow : 5.6)
1
Fig. from graph (1.1 to 1.2)
1
Denature/boil enzyme
(not: no enzyme)
1
(c)
(d)
Enzyme has a pH optimum/does not work in acid pH
(allow: denatured not: destroyed/inhibited)
1
(e)
Faster (colour change) at start as temperature increases;
1
No further colour change after enzyme denatured.
1
rate drops/stops if all active sites blocked;
1
competes with normal substrate for active sites.
1
Biuret test/NaOH or any alkali plus CuSO4;
1
Purple/violet ring/colour develops if protein.
(linked marks)
1
[11]
(f)
(g)
3
Question
5.
Answer/Explanatory Notes
(a)
(b)
(c)
Marks
Available
(i)
E
1
(ii)
E and A
1
line 15N below 14N with labels;
1
line between two
1
Light;
1
Medium
(two bands only)
1
[6]
6.
(a)
(b)
(i)
Positive end, negative end/ unequal distribution of charge;
1
Hydrogen +ve, oxygen –ve;
1
(ii)
diagram of H linked to O of adjacent water.
1
(i)
used for transport (in blood/phloem)/chemical reactions occur in
solution/allows gaseous exchange (reference to organisms
needed).
1
(ii)
Used for cooling body (sweating)
1
(iii)
Stops large fluctuations in temperature of water, helps aquatic
organisms/organisms large percentage water therefore prevents
large temperature fluctuations.
1
(iv)
prevents heat loss, insulating layer/allows organisms to live
below it.
1
(v)
light can pass through, aquatic organisms can photosynthesise. 1
[8]
4
Question
Answer/Explanatory Notes
7.
12 single structures (chromosomes);
1
Separated from each other;
1
Labels: centrioles, spindle fibres, centromere, chromosomes
Max 2 for labels.
2
(a)
(b)
Marks
Available
replication DNA;
Centrioles replicate;
Organelles e.g. mitochondria produced;
Protein synthesis;
RNA / nucleotide synthesis;
High rate respiration/ATP synthesis;
Energy store
AVP. e.g. Two chromatids formed.
3
(Max. 3) (not: growth)
[7]
5
Question
8.
(a)
Answer/Explanatory Notes
Marks
Available
A. Gene must be identified;
B. Using e.g. gene probes/nucleotide/amino acid sequence;
C. Gene is cut out/isolated using restriction enzymes;
(not: extracted)
D. or made from RNA using reverse transcriptase;
E.
DNA polymerase to produce double strand from cDNA
F.
Suitable vector used, e.g. plasmid;
G. Vector DNA cut using same restriction enzyme;
H. Complementary base pairing;
I.
Original joined to vector DNA using ligase;
J.
Reference to blunt or sticky end;
K. Recombinant DNA formed;
L.
Vector DNA inserted into bacterial cell;
M. Vector may be identified using antibiotic markers;
N. Growth of bacteria in (industrial) fermenter to produce metabolic
products, e.g. insulin;
O. Growth/cloning of bacteria to express new gene i.e., multiplication;
P.
Purification of protein
(Max. 10)
[10]
6
Question
8.
(b)
Answer/Explanatory Notes
Marks
Available
A.
Primary structure, sequence of amino acids;
B.
Linked by peptide bonds;
C.
Secondary structure described;
D.
Hydrogen bonds / ionic bonds;
E.
Tertiary structure described;
F.
As shown by globular proteins;
G.
Disulphide bridges / covalent;
H.
Ionic, salt bridges, hydrogen, hydrophobic bonds, Van der Waals;
(Any 2)
Quaternary structure described;
(reference to polypeptide chains, not proteins)
I.
J.
Enzymes with an example;
K.
Antibodies or hormones;
L.
Connective tissue/keratin is a resistant protein in skin cells helps prevent entry of pathogens/structural or fibrous/muscle;
M.
AVP Carrier molecules in active transport/facilitated diffusion;
N/O Any two from:
AVP Secondary source of energy;
AVP Albumin - water potential;
AVP Transport of oxygen-haemoglobin;
AVP Histones;
AVP Fibrinogen - blood clotting;
AVP Allow one other function if described.
6 marks for structure 4 for function.
7
[10]
ASSESSMENT UNIT BI 2
JANUARY 2005
1.
2.
(a)
Unicellular Organisms/single celled. (not: examples/description)
(b)
Thin/Moist. (not: good blood supply/thin walled/permeable)
(a)
118 (mm Hg)
(b)
Aortic/Semilunar/valves at the beginning of
(not: bicuspid/pocket)
close under aortic pressure, (preventing backflow).
(c)
1
2
[3]
1
the
aorta;
1
1
The ventricle relaxes increasing its volume.
(allow: muscle, not: heart)
The volume increases more rapidly than it is being refilled/
decreases pressure.
1
(d)
Much lower pressure/no or less rhythmical fluctuation in pressure.
2
(e)
(i)
Loss of fluid to tissues/much larger diameter of veins
1
(ii)
Massaging effect of muscles/presence of venous/pocket
valves. (not: semi lunar valve)
1
1
[9]
3.
(a)
(b)
(i)
A.
B.
C.
D.
Epiglottis
Cartilaginous rings/cartilage
Diaphragm
Bronchioles
1
1
1
1
(ii)
A. (Closes entrance to trachea) to prevent inhalation of
food.
B. Prevent collapse of air passages (as pressure falls to
draw in air).
C. Lowered by muscles to increase volume of
thorax/lowers pressure. (not: contracts to change
volume/moves up and down for inspiration)
1
(i)
Bigger vital capacity. (not: description; term needed)
1
(ii)
Flow rate decreased as air is expelled/(more difficult to
breathe out)/reference to time. (not: reference to height of
peaks)
1
(iii)
Constriction/inflammation (of the lining) of the bronchii
restricts flow. (not: ref. to trachea)
1
1
1
[10]
8
Question
4.
5.
Answer/Explanatory Notes
Marks
Available
(a)
A. Epidermis
B. Palisade/Mesophyll Tissue
1
1
(b)
(i)
II
1
(ii)
Thicker Cuticle and Sunken Stomata. (not: reference to air
spaces)
2
(c)
I
1
(d)
(i)
Peak around midday.
Low at night.
Rapid rise at dawn.
1
1
1
(ii)
Reference to malate/CO2/ATP etc.
Influx of potassium ions
Explanation of guard cell opening e.g. asymmetric walls
1
1
1
(iii)
Temperature/humidity. (not: wind speed)
1
[13]
(a)
Fresh leaves require time for establishment of numbers of
decomposers. (not: adapting)
1
(b)
(i)
Rapid growth of population of decomposers/change in
population numbers.
1
(ii)
Winter temperatures slow decomposition or converse.
(not: reference to lack of resources)
1
(c)
(90% - 30%) = 60% loss from starting value
(60% of 0.6  50g = 0.6  30) = 18g.
1
1
(d)
Saprophytes/saprobionts/saprotrophs. (not: decomposers/detritivores)
1
(e)
(i)
Ammonia/ammonium ions or compounds. (not nitrate)
1
(ii)
Nitrifying bacteria
Convert it first to nitrite and then to nitrate.
1
1
(iii)
Leaching/washed out of soil by rain and drainage.
Activity of denitrifying bacteria converts it to atmosphere
nitrogen. (not: denitrification unqualified)
1
1
Waterlogged soils suffer oxygen depletion.
Much slower rate of decomposition.
Bacteria mainly responsible are aerobic/bacteria show greater
denitrifying activity.
1
1
1
(f)
[14]
9
Question
6.
(a)
(b)
Answer/Explanatory Notes
(i)
Death/defaecation.
2
(ii)
W
W contains 900 - 10 - 290 = 600KJ:
X must contain <10kJ (not: description)
1
(i)
1
Reflected/passes through leaves/wrong wavelength/raises
temperature.
1
Inedible material (bark/tannin)/out of reach (roots/
heartwood)/heat loss
1
(i)
Y = carnivorous animals/predators/secondary consumer.
1
(ii)
Z = Respiration.
1
(iii)
Z.
1
(ii)
(c)
Marks
Available
(d)
((10/900)  100 = 100/90) = 1.1%
(e)
Heat
1
1
[11]
10
Question
7.
(a)
Answer/Explanatory Notes
(i)
Marks
Available
A.
Each sieve tube has a companion cell alongside.
1
B.
At each end of the sieve tube are perforated sieve
plates.
1
C.
Cell cytoplasm/protein strands continuous through
sieve plates.
1
D.
Companion cells contain organelles (nuclei/
mitochondria)
1
Nuclei which are lost/absent in sieve tubes/few
organelles.
1
Companion cells are connected to sieve tubes by
plasmodesmata.
1
E.
F.
[Four marks may be awarded from the six available]
(ii)
G.
Phloem transports sucrose in the plant.
1
H.
Transported from source to sink.
1
I.
Example of sources (leaves) and sinks (growing
points, fruit, seeds, bulbs) or explanation of
sources and sinks.
1
J.
Loading of sucrose (active transport).
1
K.
High concentration (lower WP) in sources, water
taken up.
1
L.
Hydrostatic pressure drives organic solution to
sink.
1
M.
Removal of solutes at sink (raises water potential).
1
N.
One example of problem with hypothesis (bidirectional movement, ATP consumption/no
function for sieve plate/ barrier.)
1
O.
Some mention of an alternative or additional
hypothesis (cytoplasmic streaming, electrosmosis).
1
[Six marks can be awarded from the nine available for (b)]
[10]
11
Question
7.
(b)
Answer/Explanatory Notes
(i)
A.
B.
(Lag phase) - numbers and therefore rate of
reproduction low.
(Log/exponential phase) - Abundant resources and
exponential rate of increase/no limiting factors/
birth rate exceeds death rate.
Marks
Available
1
1
C.
(Stable/stationary phase) - carrying capacity
reached or definition.
1
D.
Competition for
1
E.
limiting factor/resource e.g.
1
F.
Decline phase - depletion of resources,
accumulation of toxins, etc. (not: resources/
limiting)
1
G.
(In stable population) Birth rate = Death rate
1
H.
Emigration = Immigration
1
[Six marks can be awarded from the eight available for part (a)]
(ii)
I.
Human activity increasing birth rate - one example
such as NO2 pollution, algal blooms,
eutrophication.
1
Mention of two distinct human activities which
increase death rate (decrease birth rate).
Overfishing,
hunting,
habitat
destruction,
deforestation, pollution.
1
K.
One named example.
1
L.
Human activities, decreasing death rate protection, conservation, predator destruction,
game keeping, fish quotas etc.
1
Activities affecting immigration - introduction of
exotics, garden escapes, biological control agents.
1
N.
One example.
1
O.
Example of habitat alteration on migrants.
1
J.
M.
[Four marks can be awarded from the seven available, of
which one must be either M, N or O.]
[10]
12
ASSESSMENT UNIT BI4
JANUARY 2005
Question
1.
(a)
(b)
Answer/Explanatory Notes
pregnancy testing/drug targeting or cancer treatment/disease
diagnosis;
(not: vaccination/treating disease)
(i)
Marks
Available
1
over-use of (prescription) antibiotics / use of antibiotics
in agriculture;
1
(not: mutation)
(ii)
(c)
via plasmids conjugation or sexual reproduction;
(not: breeding/plasmid unqualified)
they would act as a reservoir/reference to carriers/herd effect;
1
1
[4]
13
Question
2.
Answer/Explanatory Notes
Marks
Available
(a)
Active
natural
Active
artificial
Passive
natural
Passive
artificial

Exposure to measles

Receiving MMR vaccine

Receiving anti-rabies injection
Transfer of antibodies from mother to
child in breast milk

1 mark per row, any additional ticks, no mark.
(Alternative for welsh medium, line 3, active or passive)
4
(b)
immune system not stimulated/no memory cells remain (in circulation);
1
injected antibodies do not last/are broken down;
1
(c)
(i)
clonal selection;
B lymphocytes/B cells;
Each one specific to one antigen/selecting correct lymphocyte from
many ;
Antigen binds to lymphocyte/antibody
3
(not: reference to active site);
(Max. 3) (Reference to T lymphocytes, max 2)
(ii)
clonal expansion/mitosis; (not: replicate/divide)
of appropriate B cell/from stage 1;
plasma cells;
plasma cells produce antibodies;
memory cells;
4
(Max. 4)
[13]
14
Question
3.
(a)
(b)
Answer/Explanatory Notes
Marks
Available
(i)
mouth/buccal cavity and stomach;
1
(ii)
increases surface area (of food) for enzyme action/
chemical digestion;
1
(i)
fats converted to fatty acids;
1
(ii)
emulsify / breakdown fat droplets into smaller droplets;
1
increase surface area of lipid for activity of lipase/enzyme;
1
(iii)
neutralise stomach acid / excretion of bile pigments /
form micelles for absorption of vitamins;
1
(not: ensures correct pH for enzyme action/neutralisation)
(c)
glucose / monosaccharides/disaccharides into capillaries;
amino acids into capillaries;
fatty acids + glycerol into lacteal;
some fatty acids and glycerol enter capillaries;
lymphatic system to thoracic duct;
correct reference to active transport;
correct reference to diffusion;
correct reference to mechanics of fat transport.
5
(Max. 5)
(d)
(xs) lipid and (xs) carbohydrate stored as fat/adipose tissue;
1
(xs) amino acids deaminated and enter carbohydrate metabolism/
stored as fat.
1
(not: reference to glycogen)
[13]
15
Question
4.
(a)
Answer/Explanatory Notes
(i)
Marks
Available
sugar + base + 3 phosphates or correct names;
ATP to ADP + Pi releases energy/exergonic or description;
ADP + Pi to ATP needs energy/endergonic or description;
easily reversible;
transfers energy from place of release/one molecule
to energy-requiring reactions;
provides energy in 'small packets'/figure e.g. 30.6 or 31.
4
(Max 4)
(ii)
(b)
(c)
two of synthesis/muscle contraction/active transport/other
e.g. nerve impulses/photosynthesis etc.;
(not: movement/growth)
1
(i)
X
Y
H (atom)/reduce NAD/reduced FAD;
oxygen; (not water)
1
1
(ii)
X
Y
chlorophyll/photosystem I or II;
chlorophyll/NADP/photosystem I;
1
1
(electron) fuels proton pump;
across membrane/into intermembrane space;
H+/protons diffuse/flow down concentration gradient;
Through ATP synthetase/stalked particles (not: ATPase);
Chemiosmosis;
Membrane impermeable to protons;
(Max 4)
4
[13]
16
Question
5.
Answer/Explanatory Notes
Marks
Available
(a)
Stage
Name of process
Precisely where it occurs
A
glycolysis
Cytoplasm
B
link reaction
matrix (of mitochondrion)
C
Krebs cycle
matrix (of mitochondrion)
One mark per box
(b)
(i)
carbon dioxide;
1
(ii)
acetyl CoA;
1
(c)
dehydrogenase;
1
(d)
(i)
32 / 38 / 34 / 36 ;
1
(ii)
C (allow: Krebs)
1
(iii)
only glycolysis/no Krebs cycle/stops at link reaction;
so net production of 2 ATP/4 made and 2 used;
no electron transport chain;
no final electron acceptor/O2 to accept H+;
no recycling of NAD;
pyruvate/ethanal acts as H accepto/energy remains in
pyruvate;
3
(Max 3)
[14]
17
Question
6.
(a)
Answer/Explanatory Notes
Marks
Available
mostly peptidoglycan/thick murein layer;
carbohydrate/polysaccharide with amino acid side chains;
(b)
no lipoprotein/lipopolysaccharide;
2
(i)
each cell produces 1 colony/cells separate;
1
(ii)
underestimate/doesn't allow for clumping;
1
(c)
include dead bacteria;
1
(d)
calculation of dilution factor 10-2;
1
counting of colonies 7;
1
multiplication 700;
1
(allow: consequential error)
[8]
18
Question
7.
(a)
Answer/Explanatory Notes
Marks
Available
A
exploit weak points in transmission/life cycle;
1
B
prevent mosquitoes biting;
1
C
netting/clothing and repellants;
1
D
control mosquito population;
1
E
insecticide/DDT for adults or insects;
1
F
fish to eat larvae;
1
G
bacteria to infect larvae;
1
H
sterilisation of/infertile males;
1
I
drain/cover standing water;
1
J
spray oil/detergent on water;
1
K
very few points to attack parasite/only when 'free'
1
in bloodstream
L
spends much of its time inside body cells;
1
M
cannot be targeted without damaging host;
(not: reference to side effects)
1
N
parasite mutates/antigenic types;
1
O
Ref. vaccine as alternative e.g. vaccine difficult to develop
because of different antigenic types.;
1
(A maximum of 10 marks may be awarded from the 15 available)
[10]
19
Question
7.
(b)
Answer/Explanatory Notes
Marks
Available
A
photosynthesis is affected by more than one factor/list given;
1
B
rate will be limited by factors nearest its minimum value/in short
supply;
1
C
if the value of this factor changes then so will rate (direction needed);
1
D
increasing light intensity will increase rate;
1
E
energy source for reaction;
1
F
at low intensities light is limiting;
1
G
at high intensities light is not limiting/other factors become
1
limiting;
H
suitable graph of rate v light intensity/description;
1
I
carbon dioxide concentration;
1
J
carbon dioxide used in Calvin cycle/light independent reaction; 1
K
temperature;
1
L
influences enzymes activity in Calvin cycle;
1
M
suitable graph of rate v carbon dioxide concentration/
1
Description;
N
suitable graph of rate v temperature/description/collision theory and
denaturation;
1
O
Ref. to nutrients (e.g. Mg)/water qualified;
(not: reference to wavelength)
1
(A maximum of 10 marks may be awarded from the 15 available)
[10]
GCE M/S Biology (January 2005)/ME
20
Welsh Joint Education Committee
245 Western Avenue
Cardiff. CF5 2YX
Tel. No. 029 2026 5000
Fax. 029 2057 5994
E-mail: [email protected]
website: www.wjec.co.uk/exams.html