A2 Biology 4 Past Papers

Front 1

Oxygen is produced when water molecules are split in the process of

A analysis
B autolysis
C hydrolysis
D photolysis

Back 1

D photolysis

Front 2

Describe the structures in a chloroplast that are involved in the light-dependent reactions of photosynthesis.

Back 2

1, chloroplasts have a double membrane called the chloroplast envelop.
2, thylakoids are stacked up in the chloroplasts into grana. The grana are linked together by bits of thylakoid membrane called lamellae.
3, chloroplasts contain photosynthetic pigments. eg chlorophyll a, chlorophyll b and carotene. These are coloured substances that absorb the light energy for photosynthesis. The pigments are found in the thylakoid membranes. they are attached to proteins.
4, The protein and the pigment is called a photosystem.

Front 3

Suggest two advantages of growing crops of wheat in glasshouses with artificial lighting rather than growing them in open fields.

Back 3

Any two from
1. crops can be grown all year round
2. plants photosynthesise 24 hours a day
3. idea of less physical damage from weather /
animals
4. pest control easier
5. ref to control of other named factor, eg CO2,
temperature, humidity, water supply ;

Front 4

Explain how increases in carbon dioxide and methane, released into the atmosphere, may be contributing towards the estimated changes in mean
temperature

Back 4

1. carbon dioxide and methane both are greenhouse gases ;
2. absorb heat;
3. idea of reflected from Earth’s surface /
re-radiation ;
4. mean temperature of Earth’s surface increases

Front 5

Suggest why a higher estimate and a lower estimate were made.

Back 5

higher estimate assumes no change in
production of gases / lower estimate takes into
account reduction in carbon emissions

Front 6

Suggest how other animal populations on these islands might be affected by changes in the tuatara population.

Back 6

1. fewer prey eaten by tuataras
2. prey increase in number
3. other carnivores may increase
4. because less competition for food from tuataras
5. predator of tuatara might decrease / eat other
prey / migrate

Front 7

Explain how this piece of apparatus would be used to obtain the mean density of the two species of periwinkle in each area.

Back 7

1, put multiple frame quadrats on the ground at random points within the area you're investigating
2, random points can be choosen by random coordinates
3, Number of individuals of each species is recorded in each quadrat
4, mean density can be calculated using total count eg total number of each species divided by total area sampled.

Front 8

Suggest one abiotic factor and one biotic factor that may influence the distribution of the periwinkles on the seashore.

Back 8

(Abiotic)
light intensity / light duration / availability of oxygen(in
rock pools) / length of exposure (to air) / length of
submersion / temperature / presence of toxic chemicals/ height above sea level / slope/ aspect / wave action /
pH / any other suitable e.g. ;
(Biotic)
predators / availability of food organisms / disease /
parasites / competition for a named resource / any other suitable e.g. ;

Front 9

Gene mutation

Back 9

Gene mutations are changes in the base sequence of DNA that occur during DNA replication

Front 10

A population of Chlamydomonas was found in a pond in the centre of a developing forest of fast-growing trees. Suggest how the allele frequency for this mutation could change as the forest develops. Give reasons for your
answer.

Back 10

1. correct reference to change in frequency of
either allele e.g. mutant increases / normal
decreases ;
2. idea of reproductive success of the {mutant /
non-photosynthetic} individuals ;
3. (as trees develop) pond will be (more) shaded /
4. (less light means) less photosynthesis possible /
5. ref to photosynthetic individuals die / {nonphotosynthetic / mutant} individuals survive ;
6. pass on the {mutation / allele} for using organic compounds
7. more organic nutrients in pond ;

Front 11

iii) Suggest which of the suspects is most likely to have left the blood sample on the broken window pane. With reference to the theory used in DNA profiling,
explain how you came to this conclusion.

Back 11

1. (S/ suspect) 3 ;
2. (S3) matches {all / 9 of the bands in the sample ;
3. DNA profiling assumes every individual’s DNA is
unique / different
4. apart from identical twins
5. ref to DNA profiling analyses the {introns / noncoding
blocks / STR / short tandem repeats
6. non-coding DNA very variable / hypervariable
7. large number of {introns / non-coding blocks
8. many combinations at each locus)

Front 12

Explain why evidence from DNA profiles may not be absolutely conclusive.

Back 12

1. DNA profiling has several stages, contamination can arise at any stage ;
3. only small portion of DNA analysed
4. possibility of two identical profiles from unrelated individuals ;
5. identical twins / closely-related individuals may show same profile

Front 13

Suggest how DNA profiling could be useful to scientists who examine fossils of animals and plants.

Back 13

1. comparisons made between DNA from fossils and
other organisms ;
2. to find genetic relationships / how closely related
3. to used in {taxonomy / classification
4. to understand evolutionary lines / to determine
common ancestor

Front 14

State how the genetic material in HIV differs from the genetic material in the bacterium Mycobacterium tuberculosis that causes TB.

Back 14

HIV: RNA, linear nucleic acid, no plasmids
Bacterium: DNA, circular nucleic acid, plasmids

Front 15

One of the ways in which HIV may enter the blood is through the use of infected needles. Explain why unbroken skin is an effective barrier against HIV infection.

Back 15

Protein in skin surface forms a physical barrier against HIV infection.

Front 16

Describe the change in numbers of CD4 T-lymphocytes during the first 6 weeks after infection with HIV.2'

Back 16

1, numbers decrease
2, small decrease between weeks 4/5 and 6
3, large decrease between weeks 1/2 to 3
4, manipulated figures

Front 17

*(ii) Explain the change in numbers of CD4 T-lymphocytes during the first 6 weeks
after infection with HIV.
(5)

Back 17

1. glycoprotein on virus
2. binds with receptors
3. on (surface) membrane of lymphocytes
4. viral RNA enters the lymphocyte
5. viral RNA used to produce viral DNA (in
lymphocyte)
6. by action of reverse transcriptase ;
7. ref to formation of new viruses ;
8. lymphocyte destroyed when new viruses leave the cell
9. T killer cells destroy T helper cells

Front 18

(iii) Suggest one effect that this change would have on one other component of the infected person’s blood.
(1)

Back 18

B cells not activated thus fewer antibodies, T killer cells increase.

Front 19

(ii) Name two types of plant fibre that may be present in the material eaten by cattle.
(2)

Back 19

sclerenchyma (fibres) ;
xylem (vessels) ;
cellulose (fibre) ;

Front 20

The first stage in the decomposition of a cow pat is known as putrefaction.
Explain how carbon dioxide and ammonia are formed during this stage of decomposition.

Back 20

1, Microorganisms eg bacteria & fungi on and in the cow pat secrete enzymes that decompose the cow pat into small molecules that they can respire.
2, It converts organic compounds to carbon dioxide.
3, It converts nitrogen compounds/proteins/amino acids to ammonia.

Front 21

suggest why the time taken for a cow pat
to decompose changes at different times of the year.

Back 21

1. temperature effect ;
2. water availability ;
3. waterlogging reduces oxygen availability ;
4. frozen water ;
5. more insects / decomposers in summer ;
6. rate of growth of microorganisms
7. rate of metabolism / enzyme reactions
8. use of manipulated figures to support above
points e.g. {50 / 60} days faster in late summer ;

Front 22

(a) Explain what is meant by the terms bacteriostatic antibiotic and bactericidal antibiotic.
(3)

Back 22

1. antibiotic is used to kill bacteria ;
2. bacteriostatic prevent growth of bacteria;
3. bactericidal kill bacteria ;

Front 23

Suggest why the rate of MRSA infection in hospital D differs from the rates in the other hospitals.
(3)

Back 23

1. D has stricter hygiene practices
2. hand washing regimes for {doctors / nurses
/ medical staff / visitors} ;
3. particularly when dealing with open wounds
4. wearing suitable clothing ;
5. antiseptic (solutions) readily available ;
6. named antiseptic e.g. gels, pastes, alcohol rubs ;
7. isolation of suspected cases / screening of admissions
8. D {controls / monitors} use of antibiotics
9. fewer patients / visitors passing in and out ;

Front 24

Explain what the data indicates about the reliability of using core temperature to estimate the time of death.

explain data trend and get conclusion

Back 24

1. Standard deviation measures range of data; (what data means)
2. most readings are within {+ 1 x SD / + 2 x SD} e.g. approx 60% readings within (+ )1 x SD / approx 90% readings within (+) 2 x SD ;(general trend with manipulated data)
3. as length of time increases, SD increase (trend)
4. more variability (in temperature) as time increases (general trend/differences)
5. change in reliability of time of death with time
6. estimate (of time of death) can only be
within a {4 / 5 / 6 / 7} hour period ;
7. use of manipulated data ;

Front 25

factors that could influence the rate at which a body cools after death.

Back 25

{(body) mass/ BMI / weight / eq}
{(subcutaneous) fat /eq}
surface area,
{ambient / eq } temperature
immersion in water
age (of person at death)
skin colour
thickness of hair
gender
clothing
blood loss
humidity
air movement
{core / body} temperature at time of death

Front 26

why light hitting the surface of a leaf is not 100% used
by the chloroplasts?

Back 26

1. reflection ;
2. incorrect wavelength / colour / frequency
3. not hitting the chloroplast / chlorophyll / it is transmitted ;
4. light being in excess e.g. at max. photosynthesis so more light can be used ;

Front 27

J m–2 year–1.

Back 27

{joules / energy} per {square metre / metre squared
/(unit) area} per {year / unit time} ;

Front 28

With reference to the structures in a chloroplast, explain how the energy from light is made available in ATP molecules for the synthesis of organic materials.

Back 28

1, thylakoid membranes are stacked together to form grana, which is the photosystem. It is linked by electron carriers.
2, light energy excites electrons in chlorophyll, thus it is released from photosystem and move to a higher energy level.
3, As the excited electrons move out, they must be replaced. thus light energy splits water into protons (H + ions), electrons and oxygen.
4, Energy level falls as the excited electrons move along the electron transport chain.
5, Energy is used to transport protons into thylakoid, thus thylakoid has a higher concentration of protons than stroma, which forms a proton gradient across the membrane.
6, Protons move down concentration gradient, into the stroma, via an enzyme called ATP synthase. The energy from this movement combines ADP and Pi to form ATP.
7, light energy absorbed by PSI and excites the electrons again, electrons are transfered to NADP, with a proton(H +) to form reduced NADP.
8. involvement of pigments

Front 29

Put a cross in the box next to the structure that would not be found in a cell from the strand of a filamentous alga.
A lysosome
B mitochondrion
C plasmid
D ribosome

Back 29

C plasmid

Front 30

what's the effect of increasing temperature on the rate of growth?

Back 30

1. rate of growth increases as temperature
increases {between 13oC and 22oC / up to
22oC} ;
2. rate of growth decreases {between 22oC and
25oC / above 22oC} ;
3. use of manipulated data to support above
e.g. increases by {0.7 (a.u.) / 4.5 times},
decreases by 0.1 (a.u.) ;
4. enzymes involved in growth ;
5. molecules move about more / have more
kinetic energy, as temperature increases ;(therefore) {enzyme and substrate molecules collide more / rate of enzyme-substrate complexes formation increases as temperature increases ;
6. denaturation of some enzyme / protein molecules when temperature is above 22c ; (therefore) rate of growth / reactions decreases as fewer enzyme molecules available ;

Front 31

Suggest why it was important that this investigation was carried out at a high light intensity.

Back 31

1. each temperature has same light intensity ;
2. must be above threshold / compensation point ;
3. (below which) no net photosynthesis takes
place
4. so light is not limiting factor / so temperature is the limiting factor;
5. photosynthesis produces material needed for growth ;

Front 32

Suggest two abiotic factors, other than light intensity, that would need to be controlled in this investigation.
(2)

Back 32

1. {wavelength / colour / frequency} of light ;
2. CO2 concentration ;
3. pH of solution ;
4. mineral ;

Front 33

Inflammation caused by a chemical released by white cells in connective tissue.
(1)
A Histamine
B Interferon
C Lysozyme

Back 33

A Histamine

Front 34

Explain why the processes shown in the flow diagram will only happen in response to some types of bacteria.

Back 34

1. protein nature of {antigens / antibodies} ;
2. antigens are specific to each bacteria ;
3. antibodies need to be complementary /
specific to the antigen ;
4. binding can take place ;
5. some bacteria have different antigens ;
6. this is a primary infection ;
7. mucus / slime} {coat /capsule} (of bacterial cells) ;
8. some bacteria are inside body cells;
9. antibodies already present e.g. from passive immunity or breast feeding ;

Front 35

Polymer formed
from a single strand
of nucleotides

DNA/RNA?

Back 35

RNA

Front 36

Pentose present in the nucleotides

DNA/RNA?

Back 36

Both

Front 37

Adenine, cytosine, guanine and thymine present

DNA/RNA?

Back 37

DNA

Front 38

Nucleotides linked by phosphodiester bonds

DNA/RNA?

Back 38

Both

Front 39

The formation of mRNA during transcription in the nucleus (3)

Back 39

1. DNA strands separate / unzip ;
2. one DNA strand used as template to form mRNA)
3. from free nucleotides ;
4. complementary base pairing ;
5. hydrogen bonding ;
6. RNA-polymerase / DNA helicase ;
7. credit correct sequence of bases on {mRNA /
DNA} ;

Front 40

The translation of mRNA into the sequence of amino acids in a ribosome (3)

Back 40

1. specific amino acid attachment to tRNA ;
2. anticodon on tRNA binds to the codon / triplet
on mRNA ;
3. example quoted using the information in the
diagram e.g. tRNA with alanine has CGA
anticodon which binds to GCU on mRNA ;
4. two tRNA held in ribosome (at any one time) ;
5. formation of peptide bonds between adjacent amino acids ;
6. peptidyl transferase ;

Front 41

Suggest why the final triplet of nucleotides, on the strand of mRNA involved in the
synthesis of this sequence of amino acids, did not correspond with any anticodon
on tRNA.

Back 41

1. stop codon ;
2. used to end the sequencing / further
attachment of tRNA ;
3. release of the polypeptide / ribosome

Front 42

why: varieties within the same species rather than as two separate species?

Back 42

1. individuals of a species can interbreed;
2. to produce fertile offspring ;
3. the offspring can flower and produce viable seeds

Front 43

genetic diversity

Back 43

variety of alleles in a gene pool

Front 44

Explain why there is likely to be a greater genetic diversity in the hybrid plants than in either of the two separate species.
(2)

Back 44

1. different alleles in each of the two populations ;
2. each population is adapted to live in different environmental conditions
3. there will have been different mutations in
each population ;
4. alleles from different species will mix / hybrids receive alleles from both species ;

Front 45

*Explain how the two different species may
have evolved from a single population of an ancestral species.

Back 45

1. original population increasing in size and spreading into a wider diversity of habitats ;
2. mutations ;
3. leading to diversity in flowering times ;
4. (and) other plant features ;
5. reproductive isolation ;
6. restriction in gene flow ;
7. between extremes of population ;
8. different environmental factors in each region ;
9. each region has different selection pressures ;
10. plants adapted to a region ;
11. survival and breeding ;
12. change in allele frequencies over time;
13. leads to differences between gene pools

Front 46

Suggest how insects are involved in the recycling of carbon.

Back 46

1. carbon / organic compounds in plant material ;
2. digestion provides respiratory substrates ;
3. carbon dioxide released from respiration ;
4. this carbon dioxide is available for
photosynthesis ;
5. insects eaten / decompose ;

Front 47

Suggest two examples of abiotic factors that might influence the behaviour and distribution of species

Back 47

1. wavelength / colour / frequency of light ;
2. light intensity / shading ;
3. temperature ;
4. moisture content of air / substratum / humidity ;
5. pH / chemical composition of substratum ;
6. air currents / wind ;
7. texture of substratum ;
8. oxygen / carbon / methane ;

Front 48

Suggest why taking photographs is a suitable method to count

Back 48

1. if they move about thereforedifficult to count;
2. some might be counted more than once /
missed out ;

Front 49

Explain why it would be difficult to determine which abiotic factor is influencing the behaviour and distribution

Back 49

1. for results to be (scientifically) valid, only one factor needs to be varied, other factors need to be kept constant ;
2. many / biotic factors in a complex environment, these factors are difficult to control ;
3. difficult to set test factor values

Front 50

Enclosed by outer smooth membrane;inner membrane folded forming cristae

name?
prokaryotic cells only (P), eukaryotic cells only (E) or both types of cell (B)?

Back 50

Mitochondrion /mitochondria

E / eukaryotic

Front 51

Long strand-like structure extending out from the cell
Used for locomotion?

name?
prokaryotic cells only (P), eukaryotic cells only (E) or both types of cell (B)?

Back 51

Flagellum / flagella

B / both

Front 52

Small, circular loop of doublestranded DNA

name?
prokaryotic cells only (P), eukaryotic cells only (E) or both types of cell (B)?

Back 52

plasmid

P / prokaryotic

Front 53

State the term used to describe antibiotics, such as vancomycin, that kill bacterial cells.

Back 53

bactericidal

Front 54

how bacterial cells are killed?

Back 54

1. cell wall weaker thus cannot form properly
2. cell wall bursts easily ;
3. during division

Front 55

Explain why doctors have been advised to limit the prescription of antibiotics.
(2)

Back 55

1. antibiotic acting as selective pressure ;
2. some bacteria resistant to antibiotic ;
3. resistant bacteria survive and reproduce / pass on resistance / pass on gene ;
4. antibiotic no longer effective ;
5. some infections cannot be treated with antibiotics ;

Front 56

how you could investigate the effect of different antibiotics on bacteria.

Back 56

1. bacteria distributed evenly / description of technique e.g. lawn spreading ;
2. description of method used to apply different
antibiotics at known positions e.g. multidisks,
wells in agar ;
3. control of antibiotic concentration ;
4. sterile / aseptic technique ;
5. incubation at a suitable temperature ;
6. how effect is assessed e.g.
measure {clear area / inhibition zone ;
7. replication with same bacterium ;
8. repetition with different bacteria ;

Front 57

Suggest why the development of corn cobs, suitable for producing cereal products, depends on the rate of carbon fixation in maize plants.

Back 57

1. carbon fixation produces GP;
2. product is converted to starch / sugar
3. faster C-fixation means faster sugar / starch production ;
4. rate of growth / development depends on rate of carbon fixation ;
5. increased GPP of crop ;

Front 58

temperature & enzyme

Back 58

1. effect of temperature change on kinetic energy of
molecules;
2. therefore this effects number of collisions /
enzyme-substrate complex

Front 59

Feature: Glycogen granules

Bacteria only /Viruses only /Both bacteria and viruses?

Back 59

bacteria

Front 60

Feature: Nucleic acids

Bacteria only /Viruses only /Both bacteria and viruses?

Back 60

both

Front 61

Feature: Protein coat (capsid)

Bacteria only /Viruses only /Both bacteria and viruses?

Back 61

virus

Front 62

Suggest why medications, other than antibiotics, are needed to treat the most severe cases of BRD

Back 62

1. viruses (and bacteria) involved ;
2. (usually) antibiotics are only effective
against bacteria / do not affect viruses
3. thus other medication needed to deal
with viruses

Front 63

Suggest why it might be advisable to change the antibiotic being used, in the treatment of these cattle, once the pathogen has been identified.

Back 63

1. antibiotic used is most effective against the known bacterium ;
2. none of the antibiotics is 100% effective / some bacteria will still survive;
3. some bacteria are resistant/ resistant strain develops / prevented ;

Front 64

chemical nature of cellulose.

Back 64

1. polysaccharide ;
2. unbranched / straight chain ;
3. {beta / β} glucose ;
4. (1-4) glycosidic bonds (between glucose
molecules) ;
5. intermolecular hydrogen bonds ;

Front 65

Name a plant tissue that could be the main source of the lignin

Back 65

xylem / sclerenchyma

Front 66

Describe the role of microorganisms in the recycling of the carbon from these compounds.

Back 66

1. decomposition by microorganisms ;
2. respiration ;
3. releases carbon dioxide for photosynthesis;
4. methane released in anaerobic conditions;
5. methane available as fuel

Front 67

Suggest one reason why some countries may decide to drain their marshy peatlands for the production of biofuels.

Back 67

1. increased income
2. in order to export fuel
3. more jobs
4. reduce imports of (fossil / bio) fuels /
5. biofuels renewable / sustainable
6. fossil fuels finite
7. reduce use of / as alternative to fossil fuels /reference to meeting carbon targets
8. no loss of farmland

Front 68

*Suggest why the continued draining and clearance of peatlands may contribute towards global warming even though they may be used to produce biofuels.

Back 68

1. combustion of biofuels releases carbon dioxide recently removed from atmosphere, therefore there is no (net) increase in carbon dioxide in atmosphere ;
2. carbon dioxide is a greenhouse gas that absorbs heat / long-wave radiation reflected from Earth’s surface ;
3. prevents heat / long-wave escaping into space, (therefore) mean temperature of Earth’s surface increases ;
4. carbon in peat(land) was trapped a long time ago
5, peatland clearance releases carbon
dioxide ;
6. there is a (net) gain of carbon dioxide in the atmosphere ;
7, removal of plants (during clearance) reduces photosynthesis ;
8, carbon dioxide released from (clearance) machinery

Front 69

characteristic symptom of TB other than coughing.

Back 69

tubercules, bloody sputum, (general)body tissue
wastage ;

Front 70

Describe how bacteria are taken up by macrophages.

Back 70

1. bacterium recognised as non-self ;
2.labelling of bacteria by B cells ;
3. phagocytosis / phagocytic / phagocyte ;
4. descriptive detail of phagocytosis involving bacterium
5. formation of vacuole

Front 71

Ingesting food containing these organisms is unlikely to lead to the development of TB. Give an explanation for this.

Back 71

1. kills bacteria in stomach / mouth / saliva / gastric juice ;
2. by hydrochloric acid / lysozyme ;

Front 72

*Discuss how far the data in the graphs support the following hypothesis.
The increase in HIV infection in central Africa has led to an increase in TB infection.

Back 72

Supporting the hypothesis:
1. both HIV and TB infection rates rise and
then fall ;
2. both HIV infection and TB infection increase
{from 1990 to 2000 / for the first 10 years}

Not supporting the hypothesis:
3. TB infection falls from 2000 onwards but HIV
continues to rise (until 2004) ;
4. different {parameters /measures / variables
/ eq} for the two infections ;

General points:
5. more data / information is needed / other factors (may be) involved need for statistical analysis
6. such as correlation data / test / named example
7. there is no data that links HIV infection
with TB infection / shows that people with
HIV also have TB / shows causal relationship ;

Front 73

Suggest why the quadrats were divided up into 25 smaller sections.

Back 73

1. make it easier to {estimate / measure / calculate / count} ;
2. more precise ;
3. each section would be 4% ;

Front 74

Suggest why the students were not able to draw valid conclusions about the effect of saturation of the soil by water on the distribution of the five plant species.

Back 74

1. {saturation / eq} not measured / depth of
water does not give saturation data / eq ;
2. no data on other {factors / variables /
conditions} ;
3. other {factors / variables / conditions}
may be {affecting distribution / not
controlled / confounding} ;
4. named example ;
5. only one set of data taken ;

Front 75

Transcription takes place in the?

A Golgi apparatus
B lysosome
C nucleus
D ribosome

Back 75

C nucleus

Front 76

A triplet of bases that could not be found in mRNA is

A Adenine Adenine Guanine
B Adenine Thymine Guanine
C Adenine Cytosine Guanine
D Adenine Uracil Guanine

Back 76

B Adenine Thymine Guanine

Front 77

The sequence of triplets on a section of DNA used to form a strand of pre-mRNA is a

A cistron
B codon
C neutron
D photon

Back 77

A cistron

Front 78

Describe how free nucleotides are bonded together in the correct sequence in pre-mRNA, at stage A.

Transcription

Back 78

1. sequence of {bases / nucleotides} on DNA determines sequence on (pre-) mRNA ;
2. complementary base pairing / stated example e.g. AU / CG / GC / TA (DNA: mRNA) ;
3. formation of bonds by condensation reaction ;
4. phosphodiester {bonds / links} ;
5. RNA-polymerase

Front 79

Explain the function of the codons at each end of a strand of mRNA, during the process of translation.

Back 79

1. start codon needed to begin polypeptide synthesis
2 stop codon needed to end polypeptide synthesis

Front 80

Suggest why a variety of different protein structures could be formed from the polypeptides synthesised using the mRNA molecules from a single gene.

Back 80

1.difference / variations /of {exons / mRNA} ;
2. different {primary structure / sequence of amino acids} ;
3. secondary / tertiary structure of proteins depends on primary structure / sequence
4. due to change in / different bonds ;
5. {hydrogen / ionic / disulphide} bonds ;
6. different 3D shape

Front 81

Allele frequency

Back 81

the proportion of / number of times occurring / for one allele within a gene pool /population

Front 82

Suggest why scientists classify the mainland and Sardinian wild boar as two sub-species rather than as two separate species.

Back 82

1. if allowed to interbreed ;
2. sub-species could (probably) produce
fertile offspring

Front 83

*(Suggest how the two sub-species, Sus scrofa meridionalis and Sus scrofa scrofa,
have developed from a single ancestral population.

Back 83

1. a few (ancestral) boar reaching the island ;
2. two populations geographical separation / separated by the sea / volcanic eruptions ;
3. populations cannot interbreed ;
4. gene flow between populations prevented / restricted ;
5. only a small number (on island) of other
boar for breeding / reference to founder
effect ;
6. restricted / limited variety of alleles ;
7. mutations ;
8. different {environmental conditions /
selection pressures on island different from mainland ;
9. changes in allele frequencies;
10. (leads to) {phenotypic / physiological /
physical / behavioural} changes ;
11. possibility of (allopatric) speciation ;

Front 84

Explain how the results of DNA profiling of tissue samples from the two sub-species could be used to provide evidence that they share common ancestry.

Back 84

1.bands produced ;
2. bands at certain positions ;
3. common bands contain similar DNA fragments
4, the more similar the patterns the {closer the relationship / more likely to have recent common ancestor} ;
5. very few differences if still a sub-species ;

Front 85

Produced following vaccination using antigen
A - artificial active
B - artificial passive
C - natural active
D - natural passive

Back 85

A - artificial active

Front 86

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium. When it enters the blood it can stimulate the production of several different clones of plasma cells. These produce a variety of antibodies (polyclonal antibodies).
Suggest an explanation for this.

Back 86

1. (bacterium) is made of many different
{polymers / chemicals / eq} / eq ;
2. which can act as antigens ;
3. B cells;
4. individual B-lymphocytes recognise specific antigens / antibodies are specific ;
5. activation of Blymphocytes by T cells ;
6. mitosis in B-cells to form genetically identical plasma cells ;

Front 87

Suggest the advantage of using monoclonal antibodies, rather than polyclonal antibodies, in the detection of antigens in the blood.

Back 87

1. specific antigen / virus / pathogen / bacterium can be identified ;
2. specific / monoclonal antibody binds to specific / only one antigen ;
3. specific treatment can be given ;
4. avoids unnecessary use of drugs /treatment
5. more likely to be effective