MS3
£3.00
WELSH JOINT EDUCATION COMMITTEE
CYD-BWYLLGOR ADDYSG CYMRU
General Certificate of Education
Tystysgrif Addysg Gyffredinol
Advanced Subsidiary/Advanced
Uwch Gyfrannol/Uwch
MARKING SCHEMES
SUMMER 2004
BIOLOGY
INTRODUCTION
The marking schemes which follow were those used by the WJEC for the 2004 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.
BIOLOGY
ASSESSMENT UNIT BI1
JUNE 2004
Question
Answer/Explanatory Notes
Protein
/
/
/
X
/
X
DNA
/
X
X
X
X
X
Marks
Available
Disaccharide Phospholipid
/
/
X
X
X
X
/
X
X
X
X
/
[6]
1
Carbon + Hydrogen + Oxygen
Nitrogen + Sulphur
Disulphide bonds
Glycosidic bonds
Peptide bonds
Ester bonds
1 mark per line
2
(a)
G = triose/glyceraldehydes
F = amylose
C = maltose
A = cellulose
D = alpha glucose
(b)
Insoluble (therefore do not affect osmotic potential)/coiled or compact/
glucose easily released or easily added or broken down easily
(Any 2)
2
(c)
Benedicts/boil/shows reducing sugar/brick red (precipitate)
(allow: green/yellow)
non-reducing sugar negative/stays blue in above/(heat with) acid/
neutralise/then gives positive with Benedicts
2 points for 1 mark
(not: hydrolyse)
3
1
1
1
1
1
3
[10]
(a)
Thymine
Cytosine
Adenine
Guanine
1
1
1
1
(b)
(i)
X = Nucleotide
1
(ii)
phosphoric acid/phosphate
organic base/nitrogenous base/cytosine
pentose (sugar)/Deoxyribose/5C sugar
(not: Pi/base/purine or pyrimidine)
1
1
1
(c)
Z = Hydrogen bond
1
(d)
deoxyribose and phosphate/deoxyribose and (nitrogenous) base
or named/pair of entities e.g. amino acids/sugars
(Any 1)
1
1
Question
4
Answer/Explanatory Notes
(e)
uracil/ribose/single strand/shorter/lower molecular weight/transcription
occurring
(Any 2)
2
[12]
(a)
hydrophilic/polar/phosphate head
hydrophobic/non polar/fatty acid tail
phospholipid
intrinsic protein/protein pore or other correct (not: protein unqualified)
extrinsic protein/carrier protein
glycoprotein/glycolipid
bilayer/drawn
cholesterol
glycocalyx/carbohydrate/polysaccharide
1 mark each if shown in correct position, max 5 if bilayer not shown
6
(b)
Fluid: phospholipids/molecules constantly moving/proteins move
Mosaic: proteins do not form a continuous layer/patchy or scattered
proteins/random pattern of proteins
(c)
Hydrophilic heads take up/attract aqueous 'stain',
(hydrophobic tails repel stain)
(d)
5
Marks
Available
Nucleus
mitochondria
chloroplast
(two correct 1 mark, three correct 2 marks)
1
1
1
2
[11]
(a)
Meiosis
1
(b)
A F B G D E H C [I]
all 8 = 3 marks, 6 = 2 marks, 4 = 1 mark
3
(DNA) replication/pairing of homologous chromosomes/bivalent
formation (not: crossing over/DNA duplication)
1
independent assortment/random assortment
crossing over
random fusion gametes/chromosome numbers halved
mutation
(Any 3)
3
(c)
(d)
(e)
metaphase takes twice as long/longer
2
1
[9]
Question
6
Answer/Explanatory Notes
(a)
Competitive inhibitor
similar shape as substrate/binds to/enters active site/
prevents normal substrate binding (not: competes)
Non competitive inhibitor
binds to enzyme but not at active site/distorts/denature active site
(not: denaturation (of enzyme))
End product inhibition
product of enzyme controlled reaction/
binds to enzyme (slowing down its own production)/
negative feedback
(not: ref. to binding to active site)
(b)
A and B
(kinetic) energy increases or molecules move faster
enzyme and substrate meet more frequently/more enzyme substrate complexes formed/
collision rate increases
Marks
Available
2
2
2
1
1
C and D
3D/globular/tertiary structure of protein affected/hydrogen bonds or equivalent
breaking down/active sites break down/denatured
2
(not: enzyme denatured unqualified)
(c)
To prevent damage to active sites/prevent enzyme being denatured;
enzymes/proteins would need to be constantly replaced;
accept to give some leeway.
(i.e. idea of 'comfort zone' e.g. temperature fluctuation (1)
consequences e.g. denaturation and replacement (1)
2
[12]
3
Question
7
(a)
Answer/Explanatory Notes
Marks
Available
A.
diffusion with example
B.
down concentration gradient/from high to low concentration
C.
no energy required/passive
D.
facilitated diffusion (plus example)/cotransport and example
E.
qualification of facilitated diffusion/cotransport e.g. carriers, faster,
no energy (2 from 3)
F.
active transport (with example)/diagram
G.
qualification - energy, against concentration gradient, carriers
(2 from 3)
H.
osmosis water only
I.
definition - high  low water potential/concentration, SPM
J.
correct use of water terminology
L.
water potential qualified, accept equation/turgor pressure/
P opposes inward flow
M.
phagocytosis/endocytosis qual
N.
pinocytosis qual
O.
exocytosis/vesicles qual
P.
material injected bacteriophage
[10]
4
Question
(b)
Answer/Explanatory Notes
Marks
Available
A.
alginate beads, gel membrane, adsorbed onto nylon/inert
support
(not: inert casing)
B.
reuse of enzymes/easily separated
C.
stable - temperature/pH
D.
advantage of using enzymes, e.g. not poisonous therefore do not need
to be removed, heat stops action, no contamination of product.
E.
rapid.
F.
accurate/specific.
G.
detect/sensitive to low concentrations.
H.
glucose oxidase or any other e.g. monitoring blood sugar, pectinase
I.
transduction, converted into electrical output/electronic
current/colour change.
J.
restriction enzyme.
K.
separation of different size fragments.
L.
electrophoresis.
M.
probes, dyes, markers, radioactive tracers
N.
unique pattern of bands/unique DNA fingerprint for individual
(not: genetic fingerprint)
O.
use of technique, e.g. criminal investigation, paternity, defining
closeness of evolutionary links, identification.
6 marks for A-I
4 marks for J-O
10
[10]
5
BIOLOGY
ASSESSMENT UNIT BI 2
JUNE 2004
Question
1
Answers/Explanatory Notes
(a)
(b)
(c)
(d)
(e)
Marks
Available
succession
spirometer
emphysema
autotroph/producer
sino-atrial node
(not: abbreviation/pacemaker)
1
1
1
1
1
[5]
2
(a)
(b)
(c)
(i)
(ii)
(iii)
(d)
an organism that feeds off another organism
of a different species/host
harms host/doesn't kill host (not: cause disease)
(Any 2)
2
quick acting/cheap/localised use/more efficient/effective/
easy to apply/produce
(Any 1)
1
chemicals non-specific
(chemicals) would kill wasp
long residual effect on Encarsia
waste of money
(Any 2)
2
cooler climate;
wasp can't fly/little flying below 18C
would not fly to/reach more slowly, other infected plants in
field
whitefly would not be killed/crops remain infected
(not: fly away) (Any 2)
2
honeydew sticky wasps can't move/fly
1
can't achieve this/biological
levels/specific to whitefly
control
maintains
low
1
[9]
6
Question
3
(a)
Answers/Explanatory Notes
correct axes and labels
appropriate scale (over half of paper used)
correct plot
well drawn curve
Marks
Available
4
(b)
correct figure from graph (150 x 105  130 x 105)
(unit needed but consequential error in e)
1
(c)
690  105 cells
1
(d)
no/reduced levels of nutrients/increased competition (not:
competition)
accumulation of toxins
number of dying equals numbers produced
(not: resources/space/oxygen/food) (Any 2)
2
lag phase
log phase/exponential phase
2
(e)
(f)
(steep) decline in curve/death phase
decrease/decline/numbers drop
1
[11]
4
(a)
Vein
thin wall/little muscle in wall/large (volume) lumen
low pressure blood/large volume blood returning to heart
valve/prevents backflow of blood
Capillary
thin wall/endothelium/wall one cell thick
exchange of materials/formation of tissue fluid/short
distance for diffusion
Artery
thick wall/muscle/elastic tissue
high pressure blood (not: to pump blood)
(b)
valve/pocket valve
(not: if valve given in table or specific valves)
2
2
2
1
[7]
7
Question
5
(a)
Answers/Explanatory Notes
(i)
denitrification
1
(ii)
bacteria/fungi/saprophytes
1
combined with products of photosynthesis
to form amino acids
to form proteins
growth of new cells/tissues
to form nucleic acids
(Any 3)
3
nitrite concentration increases then decreases
use of figures (amount and days)
nitrate concentration increases
after increase in nitrate concentration
use of figures (amount and days)
(Any 3)
3
(b)
(c)
Marks
Available
(i)
(ii)
excretion/waste produced by goldfish/decayed (surplus)
fish food
(iii)
converted/oxidised
to nitrite
by bacteria
(Any 2)
2
nitrite converted to nitrate/
nitrate not converted into other products/no plants to
absorb nitrates
(Any 1)
1
(iv)
(v)
water changed/partially changed/water added/tank cleaned/
vigorous plant growth/new plants put into tank/algal bloom
8
1
1
[13]
Question
6
(a)
Answers/Explanatory Notes
(i)
Leaf B
thicker cuticle
sunken stoma/(deep) air chamber
2
reduced loss through epidermis/cuticle (not: prevents)
traps water vapour/reduces diffusion gradient
2
hairs
traps water vapour
curled leaf
traps water vapour
stomata open at night
vapour can't escape during hot part of day
leaves reduced to spines/leaf area reduced
less surface area/fewer stomata
(Any 2)
2
(i)
xeromorph/xerophytic
1
(ii)
low (environmental) temperature
(high) humidity (not: damp)
decrease in/low wind speed
dark day/low light intensity
(Any 2)
(ii)
(iii)
(b)
7
Marks
Available
2
[9]
(a)
sucrose
(not: sugar(s)/water)
1
(b)
14
C at top of stem/14C in roots
but absorbed at leaf halfway up stem
1
1
growing point/growth
active process/ATP required/energy required
respiration
carbohydrate in respiratory substrate
(Any 2)
2
(c)
(i)
(ii)
sinks;
1
[6]
9
Question
8
(a)
Answers/Explanatory Notes
A
unicellular organisms use diffusion
B
multicellular organisms are large
C
metabolically more active
D
substances need to travel distances/around the body
E
diffusion only efficient over short distance/too great
for diffusion
F
diffusion too slow
H
ref. surface area to volume ratio being too small in
multicellular organisms
I
for uptake of nutrients/named nutrient
J
oxygen
K
removal of waste products
L
carbon dioxide/urea
M
system/lungs/gills required to distribute/absorb
substance/named substance
N
quickly
O
in sufficient quantities due to large surface area
P
so processes/named processes operate efficiently
Maximum 10 marks
Marks
Available
10
10
Question
(b)
Answers/Explanatory Notes
A
enters root hair
B
by osmosis
C
water potential of root hair increases/becomes
higher than surrounding cells
D
water moves into these cells
E
movement via symplast/symplasm/cytoplasm to
cytoplasm
F
via plasmodesmata
G
via vacuolar pathway, vacuole to vacuole
H
down a water potential gradient
I
across cortex/cortical cells
J
via apoplast pathway/apoplasm, along cell walls
K
until endodermis
L
casparian strip prevents movement of water
M
redirected into symplasm
N
water moves up in root xylem
O
reduces water potential in xylem of root
P
water enters xylem (from surrounding cells)
Q
active transport of salts into xylem
Maximum 10 marks
Marks
Available
10
[10]
11
BIOLOGY
ASSESSMENT UNIT BI4
JUNE 2004
Question
1.
(a)
(b)
(c)
Answer/Explanatory Notes
(i)
palisade (mesophyll)
1
(ii)
Calvin cycle/light independent stage/dark stage
1
(iii)
Ribulosebi(s)phosphate/RuBP
1
to absorb light (energy)/act as a transducer/convert light energy into
chemical energy/high energy electrons/harvest or trap light
1
absorption spectrum: the (quantity of) light absorbed (by plant
pigments) at different wavelengths.
1
action spectrum: the quantity/rate of photosynthesis at each
wavelength.
2.
(a)
(b)
(c)
Marks
Available
1
[6]
(i)
amylase
1
(ii)
amylose/starch is broken down to maltose.
(not: maltose and glucose)
1
(i)
there is no amylase/starch digesting enzyme in stomach tissue. 1
(not: ref. to acid/pH; allow consequential error from (a) (i)
(ii)
duodenum tissue does not secrete amylase, pancreas does.
1
5cm3 starch suspension + 2cm3 deionised/distilled water/boiled tissue 1
[5]
12
Question
3.
Answer/Explanatory Notes
Marks
Available
Natural active immunity
When an individual produces antibody;
and memory cells;
as a result of natural infection.
Artificial active immunity
When an individual produces antibody;
and memory cells;
as a result of vaccination/immunisation or description
Natural passive immunity
When an individual receives antibody produced by another individual/mother;
There are no memory cells;
It is short-lived immunity;
(Maternal antibodies transferred to the foetus) over the
placenta/to the offspring in breast milk/colostrum.
Artificial passive immunity
When an individual is injected with pre-synthesised antibody;
There are no memory cells;
It is short-lived immunity;
Tetanus antitoxin/rabies/rubella antibodies/ any suitable disease
[8]
4.
(a)
(b)
(c)
A
Gram positive
bacillus/rod
B
Gram negative
Coccus
4
Gram +ve have a thicker cell wall (not: larger)
made of murein/peptidoglycan (not: lipopolysaccharide)
which retains the crystal violet/purple stain
or converse
Red stained/Gram negative bacteria have extra layers in the/
more complex cell wall
which protect/give resistance to lysozyme/penicillin/antibiotics
(not: prevents osmotic lysis)
3
2
[9]
13
Question
5.
Answer/Explanatory Notes
Marks
Available
(a)
Salmonella/bacteria
1
(b)
Indicate organisms with the same/similar antigens on the surface
Sub-groups or strains of a microbial species/bacteria (which may be
used to trace infections)
Identified by antibodies from serum
1
(c)
Poisonous substances/toxins produced by the bacteria
1
(d)
May already be dehydrated/immune systems may be unable to combat
infection/weakened immune system
1
(e)
Bacteria are at a higher temperature if food is not refrigerated and so
multiply (eq) more rapidly/undercooked meat from barbecue
(f)
Thorough cooking of meat/poultry/eggs (not: food)
storage in cold conditions/fridge
separate cooked and raw meat
prevent contamination (of food) by carriers/washing hands before
handling food
(Any 1)
1
1
[6]
6.
(a)
infection/pathogen will not be destroyed by the antibiotic if it is
resistant or converse
the infection/bacteria will be destroyed most rapidly by antibiotics having
the greatest effect (not: greatest effect unqualified)
the patient will recover more quickly with correct antibiotic treatment
(not: some organisms are resistant) (Any 2)
2
(b)
A or A and C (not: C)
this antibiotic gives the largest clear area/area free of bacteria;
most bacteria are killed by this antibiotic/stops growth better/most
effective at killing
(not: it has the greatest effect) (Any 1)
1
(c)
Bacteriostatic antibiotics prevent growth;
bactericidal antibiotics kill bacteria
Which antibiotic has which action must be clear
1
1
(d)
resistance arises by (random) mutations (occurring in populations)/
transfer of resistant gene from another resistant bacterium
1
1
by natural selection this confers a selective advantage in the presence
of that antibiotic/removes competition/kills non-resistant organisms
1
(e)
MRSA/VRSA/TB/Staphylococcus aureus
(not: Staphylococcus)
(f)
(in animal feed) to promote growth/prophylactic or preventative
use (eq).
(not: treat sick animals/better yield/prevent disease in meat)
1
1
[10]
14
Question
7.
Answer/Explanatory Notes
(a)
Krebs cycle
(b)
Glucose cannot/too big to enter mitochondria/is not a substrate
that mitochondria can break down/no enzymes present to break
down glucose
(Any 1)
Marks
Available
1
1
(c)
Pyruvate/pyruvic acid/any Krebs cycle intermediate
(Any 1)
1
(d)
(Inorganic) phosphate/P(i)/creatine (phosphate)
1
(e)
Oxygen is the (final) electron acceptor (in the respiratory chain/ETC);
Oxygen combines with H+ and electrons to form water;
Thus oxygen levels fall as ATP is synthesised;
2
(Any 2)
(f)
Oxygen levels are too low/no oxygen, so the ETC ceases;
No more ATP can be synthesised by the mitochondria unless oxygen
is supplied.
(not: no oxygen left unqualified) (Any 1)
(g)
Oxygen enters mitochondria/CO2 leaves mitochondria by diffusion/
the pathway must be as short as possible for efficient diffusion.
15
1
1
[8]
Question
8.
Answer/Explanatory Notes
Marks
Available
(a)
Axis - correct way round and scale over half grid
Axis labels plus units
Correct plot with line, no extrapolation
(b)
(i)
At the closest distance/5cm the rate of photosynthesis/O2
evolved is at its highest
At 10cm the rate of P/S or O2 evolved
falls rapidly from 5cm to 10cm/correct ref. to figures and pattern
At distances of 20cm and greater the rate of P/S is very low/
no change over 60cm
(Any 2)
2
(ii)
At the closest distance/5cm there are (maximum)/more (photons of)
light falling on the leaf/chloroplast/photosystems;
more electrons emitted from photosystems causing
photolysis/splitting of water; (not: hydrolysis)
which includes oxygen as a by-product (linked to points 1 or 2)
(Any 2)
2
(iii)
there are insufficient readings to enable the relationship between
light intensity/distance from plant and evolution of oxygen to
be plotted accurately;
additional readings at high light intensity are required
measure light intensity e.g. luxmeter rather than distance
use heat shield to prevent temperature increase due to lamp
(not: take more readings or wider range of
readings unqualified)
1
(c)
the oxygen given off/evolved must have come from the water.
(d)
(i)
1
1
1
1
It is formed by the photolysis/splitting of water
(in the thylakoid cavity)
1
(ii)
NADP
1
(iii)
Photolysis/Photosynthesis does not occur in the
dark/without light/needs light
Photolysis/Photosynthesis only occurs very slowly at 5C
Photolysis/Photosynthesis proceeds more quickly at a
temperature of 25C
(not: ref. to limiting factors/high temperatures/
photosynthesis affected by light) (Any 2)
16
2
[13]
Question
9.
(a)
Answer/Explanatory Notes
Marks
Available
A
GALP/Triose phosphate/glucose and oxygen.
B
GALP/Triose phosphate is converted to glucose.
C
Oxygen used by mitochondria/aerobic respiration.
D
Glucose used as a respiratory substrate/for ATP synthesis (in
regions of cell division/growth/root/shoot tip).
E
may be converted to starch and stored as starch grains in choroplasts
(temporarily)/specialised areas/underground stems/potatoes/seeds/
fruits eq.
(not: food store)
F
converted to fructose/fructose combined with glucose to
form sucrose/sucrose is synthesised for transport.
G
Glucose is converted to cellulose to form plant cell walls.
H
amino acids can be synthesised, providing there is a nitrogen/
nitrate source/using nitrogen
I
amino acids from glucose via metabolic pathway can be
used to synthesise protein.
J
lipids can be synthesised for storage/phospholipids/cell membranes.
K
with a Magnesium source, chlorophyll can be synthesised.
L/M
mention of any other 2 products
Nucleic acids/DNA/RNA/ATP/ADP/Vitamins/
xanthophylls/anthocyanins/carotenes
N
all organic materials in the plant must be made from the
intermediates and products of photosynthesis.
(Maximum 10 marks)
10
[10]
17
(b)
A
Glucose is phosphorylated/ATP is added.
B
to form Hexose (di)phosphate.
C
this is split into 2 3C/triose phosphate molecules.
D
these are converted to pyruvate.
E
with a net gain of 2 ATP (stated unambiguously).
F
and 2 reduced NAD.
G
it occurs in the cytoplasm of all cells/does not require oxygen.
H
in the absence of oxygen, (the Krebs cycle and) ETC cannot occur/no
oxygen to act as the final electron acceptor at the end of the ETC.
I
Pyruvate is converted to lactate/lactic acid in animal cells/humans
(not: ref. to CO2)
J
or ethanol in plant and/or fungal (cells)/or yeast
K
and carbon dioxide in plant and/or fungal (cells).
L
using the reduced NAD to reduce the pyruvate/transferring the
hydrogen to pyruvate (in the process).
M
Anaerobic respiration (only) yields a total of 2 ATP
(i.e. ref. to overall yield)
N
because a lot of energy is still tied up/contained in the lactate/ethanol
(i.e. ethanol high in calories)
Maximum 10 marks
10
[10]
18
BIOLOGY
ASSESSMENT UNIT BI 5
JUNE 2004
SECTION A
Question
1
(a)
(b)
Answers/Explanatory Notes
Marks
Available
(i)
vas deferens/sperm duct
1
(ii)
micropyle
1
(iii)
prolactin/oxytocin
1
(iv)
anther
1
(i)
self-pollination, pollen is transferred/pollination between
(from anther to stigma of) flower on same plant. Crosspollination, pollen is transferred to stigma on different
plant. (must refer to both) (not: ref. to different flowers)
1
intra specific is (competition) between (members of) same
species (allow: ref. to populations)
inter specific is (competition) between (members of)
different species
1
(ii)
[6]
2
(a)
(b)
(c)
animalia, plantae, fungi, monera/prokaryotae, protoctista
- all five for 2 marks, 1 wrong or more than 5 for 1 mark
(not: protist/protozoa)
(i)
phylum, class, order, family, genus
(1 mark for order, 1 mark for size)
2
(ii)
meat eating (predator)/large canine/carnassial
powerful jaws/vertical movement of jaw
(not: carnivore/feeds on other animals)
(iii)
shortened muzzle/retractile claws/fewer teeth than canidae
(not: fewer teeth unqual; (ii) and (iii) independent marks)
Genus and Species, 1 for each
(i)
(ii)
2
teeth/
avoids confusion of local common names/different
languages i.e. ref. to naming or identifying
(not: Latin understood by all)
1
1
2
1
[9]
19
Question
3
(a)
Answers/Explanatory Notes
(i)
Marks
Available
Parents'
phenotypes:
black, agouti
X brown, nonagouti
1
Parents'
genotypes
Bb,Aa
X bb.aa
1
Gametes
B,A or B,a or b,A X b,a
or b,a
1
Fertilisation
Gametes
BA
Ba
bA
ba
ba
Bb,Aa
Bb,aa
bb,Aa
bb,aa
2
(Position of gametes (1), cross (1); allow consequential
error except F1 genotypes and F1 phenotypes)
(b)
(c)
F1 genotypes
Bb,Aa or Bb,aa or bb, Aa or bb,aa
1
F1 phenotypes
black agouti,
black non-agouti
1
brown, agouti,
brown non-agouti
(ii)
(Genotypes and phenotypes, independent marks)
2
1
(i)
mm
1
(ii)
mutation
1
(iii)
mutagen
1
(i)
I
all the alleles/all the genes in a population/species in
a specific place (not: species unqual)
1
II
Chance/random change in the gene/allele frequency
or because population is small (1 from 2)
1
(white mice more easily seen in dark) owls select against
albino allele or prevent alleles being passed on
1
(black mice more easily seen in daylight) hawks select
against B or prevent it being passed on
1
(ii)
(iii)
(iv)
phenotypes are selected against, recessive alleles can hide
in heterozygotes; dominant alleles are selected against in
both homozygous dominants and heterozygotes
20
2
[17]
Question
4
(a)
(b)
(c)
Answers/Explanatory Notes
Marks
Available
(i)
spermatogenesis
1
(ii)
oogenesis
1
(iii)
A-spermatids
B-secondary spermatocytes
C-primary spermatocytes
D-spermatogonia
all correct for 2, 1 wrong -1
2
(i)
labels from top down DCBA all correct for 2, 1 wrong -1
2
(ii)
sertoli cell
1
(iii)
nutrition of (sperm cells)/gives O2/removes waste/other
correct
(not: protection unqualified/energy)
1
(i)
meiosis (allow: reduction division)
1
(ii)
two pairs drawn, each made of two chromatids
centromeres either side of equator
3 correct labels from chromatids, equator, centromeres,
centriole, chromosome, spindle (fibres)/poles/aster
1
1
(iii)
1
halves chromosome number (prior to fertilisation)/
produces haploid cells or gametes
causes variation
2
[14]
21
Question
5
(a)
Answers/Explanatory Notes
A
correct order anterior to posterior,
cerebral hemispheres, hypothalamus, cerebellum,
medulla (award in diag./or description)
B
hypothalamus ventral to cerebellum dorsal (award
in diag.)
C
labelled diagram - minimum 3 correct labels
D
hypothalamus controls autonomic system/ref. to
homeostasis/example
E
link with pituitary
F
and some basic behaviour patterns/drives
G
cerebellum coordinates muscles, movement/gives
find control
H
posture and/or balance/ref. to ear/proprioceptors
I
medulla controls
activities
J
for example heart rate/breathing rate/blood pressure
swallowing/coughing/peristalsis
K
cerebral hemispheres/cerebrum are centres of
conscious/voluntary activity
L
contains sensory areas and motor areas
M
association areas e.g. visual cortex
N
memory/imagination/intelligence/personality
O
Specific functions of left and right cerebral
hemispheres
Marks
Available
reflex/autonomic/involuntary
Any 10 of available 15
[10]
22
Question
(b)
Answers/Explanatory Notes
A
in plant tissue culture plants are grown from parts
of a plant/cuttings/suitable example
B
reference to term tissue culture/micropropagation
C
(explants) placed in sterile, (aerated) medium
D
cells divide (by mitosis)
E
to form callus
F
callus is differentiates into plantlet
G
plantlets transplanted into (sterile) soil when big
enough/eq. e.g. grown on
H
in animals a nucleus/DNA may be removed from
diploid/somatic/udder/body/undifferentiated cell
I
transferred to an exnucleated egg cell/egg cell with
no nucleus
J
or an embryo split before differentiation/at early
stage
K
the embryo allowed to develop in a surrogate
(uterus)
L
reference to totipotent/stem cells/pre differentiation
in either
[maximum 8 from available 12]
M
advantages: maintain genetic stocks/gene library
more quickly than seed propagation/rapid increase
in nos./standardisation for transport/ref. to cost
qualified
N
disadvantages: in mammals unforeseen long term
effects e.g. premature ageing/giantism
O
no variation/disease/entry of pathogens may be a
problem
[maximum 1 for advantage and 1 for disadvantage]
Max 10 from 15
Marks
Available
[10]
Total for Section A - 56 marks
23
SECTION B
Question
6
Answers/Explanatory Notes
(a)
(b)
(c)
(d)
Marks
Available
sarcomere
1
(i)
myosin
1
(ii)
actin
(i)
P - H zone Q - A band/anisotropic band
1
(ii)
P - shorter Q same length
1
(i)
(number and) sequence of amino acids (in polypeptide
chain)
1
(ii)
 - helix
1
(iii)
 - helix remains elongated cross-linked with others to
form rope like threads, in enzymes  - helix is folded to
form globular molecules/other correct examples
(not: ref. active sites)
1
[7]
7
(a)
(b)
A - Bowman's capsule
B - glomerulus/glomerular capillaries
(not: knot of capillaries)
C - afferent arteriole
D - efferent arteriole
All correct for 2, 1 wrong - 1 mark
(i)
2
podocyte above lower basement membrane with minor
processes touching it; epithelial cells beneath and touching
lower basement membrane (i.e. both types of cells (1),
relationship with capillary (1) (label if mirror image) or
layer of epithelium on basement (1), label (1))
2
(ii)
plasmamembrane/cell membrane/nuclear membrane
1
(iii)
drawing of fluid mosaic model, phospholipid bilayer heads
out and tails in
intrinsic proteins embedded in bilayer
3 correct labels from phospholipid (bilayer), intrinsic
protein, extrinsic protein, hydrophobic tail, hydrophilic
head, glycocalyx/carbohydrate/glycoprotein
24
1
1
1
Question
(c)
Answers/Explanatory Notes
(i)
(ii)
(d)
Marks
Available
the smaller (the radius) the more of the substance passes
through or converse
pores of a certain size will allow small molecules to pass
through but will prevent larger molecules from passing
through or only pores of a certain size will allow small
molecules to pass through
1
1
(iii)
28.5  35.5 Å (allow 36 if explanation given)
1
(i)
afferent arterioles
1
(ii)
blood (slows as) passes from one large to many small
vessels/greater friction against walls of vessels/increased
cross-sectional area
1
(iii)
glomerular capillary
1
(iv)
hydrostatic pressure is high/greater than
pressure/O.P. low (not: increasing/decreasing)
osmotic
1
[15]
8
(a)
(b)
synapses/synaptic cleft (not: cleft)
1
(i)
choline acetyltransferase and acetylcholinesterase
1
(ii)
Ca2+, Na+, K+ or named
1
labelled drawings to show vesicle moving towards
(presynaptic) membrane
vesicle fusing with membrane
vesicle opening to release transmitter
1
1
1
depolarisation/local currents only needs to happen at nodes
impulse can leap from node to node/saltatory conduction
sheath extends distance over which local current operates
(2 from 3)
2
(c)
(d)
(e)
(i)
(ii)
it will prevent breakdown/slows hydrolysis
acetylcholine/neurotransmitter
or therefore there will be a smaller deficit
neurotransmitters/more present
of
1
of
enzyme active site is specific shape
(substrate and inhibitor molecules have shapes) which both
fit active site/similar shape
bound inhibitor prevents substrate binding/competes with
substrate to bind
1
1
1
[12]
[34]
GCE M/S (June 2004)/Biology/JD
25
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