Question 1:
(a) Fig. 1.1 is a diagram showing parts of two organ systems that are active when a person sneezes.
(i) Sneezing is an automatic action that occurs in response to a stimulus in the nose.
State the name of this type of automatic action.
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(ii) Table 1.1 shows the names and functions of some of the parts of the human body that
are involved when a person sneezes, and the letters in Fig. 1.1 that identify these parts.
Complete Table 1.1.
(b) Fig. 1.2 is a diagram of a cell from the human nervous system.
(i) On Fig. 1.2, label two visible cell structures.
(ii) Draw an X on the cell in Fig. 1.2 to show where a receptor molecule for a neurotransmitter would be found.
(iii) Explain how the cell in Fig. 1.2 is adapted for transmitting impulses.
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(c) Describe how nervous communication differs from hormonal communication.
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▶️Answer/Explanation
Ans: 1(a)(i) reflex ;
1(b)(i) any two labels to correct structure on Fig.1.2:
nucleus ;
cell membrane ;
cytoplasm ;
AVP ; e.g. cell body / axon / dendrite
1(b)(ii) X drawn at any tip of left-hand side of the motor neurone ;
1(b)(iii) any two from:
1 axons / long, to transmit (impulse), over (long) distance /
fast / direct connection ;
2 (many) branches to connect to, other / relay, neurones /
cells / effector / muscle ;
3 mitochondria to (release energy), for, transmission of
impulse / protein synthesis / active transport / making or
releasing (neuro)transmitters ;
4 vesicles to, carry / hold / release, chemicals /
(neuro)transmitters (into synapse) ;
5 receptor (molecules), to ensure unidirectional transmission /
to allow signal to be received by next neurone ;
6 AVP ;
1(c) any three from:
nerve communication is:
1 faster / ora ;
2 shorter-lasting / ora ;
3 specific / one, target / location ;
4 electrical (and chemical) ; A uses impulses
5 conducted through cells / uses neurones / uses nerves / uses
CNS ;
6 AVP ;
Question 2:
(a) Digestive enzymes are secreted into the alimentary canal.
(i) As well as enzymes, other substances that are important for digestion are also secreted into the alimentary canal.
State the names of two of these other substances.
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(ii) Table 2.1 summarises some facts about the enzymes that are secreted into the alimentary canal.
Complete Table 2.1.
(b) The activity of the enzyme pepsin was measured at different temperatures.
The results are shown in Fig. 2.1.
Describe and explain the effect of temperature on the activity of pepsin.
Use the information in Fig. 2.1 to support your answer.
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(c) Lactase is another digestive enzyme, which is produced by human babies.
(i) Explain why lactase is important for the nutrition of young babies.
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(ii) Most people stop producing lactase when they become adults. If they drink milk, this may give them diarrhoea.
Describe the symptoms of diarrhoea.
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(iii) Cholera can also cause diarrhoea.
Explain how the cholera bacterium causes diarrhoea.
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▶️Answer/Explanation
Ans: 2(a)(i) any two from:
bile ;
(hydrochloric) acid ;
mucus / water / saliva ;
AVP ;
2(a)(ii)
2(b) any six from:
1 39 ± 2 oC is optimum temperature / AW ;
2 highest activity is 2500 U per mg (protein) ;
3 steep(er) decrease in activity after optimum / ora ;
4 no activity after 62 ºC ± 2 ;
5 (increased) temperature causes increased kinetic energy /
ora ;
6 increased frequency of (effective) collisions / ora ;
7 forming enzyme-substrate complexes / ora ;
8 denaturation occurs (at any temperatures above optimum
temperature) ;
9 active site changes shape ;
10 no longer, fit into substrate / complementary (to substrate) ;
11 idea that both enzyme and substrate are proteins and may
change ;
2(c)(i) any two from:
lactose is found in milk ;
lactase breaks down lactose ;
(young) babies are dependent on, lactose / milk (for their
nutrition) / AW ;
2(c)(ii) (loss of) watery faeces / AW ;
2(c)(iii) any three from:
(cholera bacterium) release toxins ;
causes chloride ions (to be secreted from the body) ;
(chloride ions) in small intestine / duodenum / ileum ;
ref to osmotic movement / lowers water potential (in gut) ;
water moves into gut or more water remains, in intestines / gut ;
Question 3:
Fig. 3.1 shows the estimated growth of the global human population between the 1860s and 2010s.
It also shows the estimated number of people that were affected by famines between these dates.
(a) (i) State the final size of the estimated global human population shown in the 2010s in Fig. 3.1.
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(ii) Using the information in Fig. 3.1, calculate the percentage of the estimated global human population that was affected by famine during the 1860s.
Give your answer to one significant figure.
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(b) An increase in the size of the human population can cause famine.
(i) Describe other factors that could have caused famines since the 1970s.
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(ii) Chemical fertilisers have helped farmers to increase food production.
Discuss the negative impact on the natural environment of using chemicals, other than fertilisers, in modern farming methods.
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(iii) Crops are often grown as monocultures.
State what is meant by a monoculture.
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(iv) Scientists are developing crop plants that can produce antigens so that people gain immunity to different diseases such as hepatitis B.
State the process which can be used to develop crop plants that can produce proteins from other species.
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▶️Answer/Explanation
Ans: 3(a)(i) 7.6 billion / 7 600 000 000 / 7.6 × 10$^{9}$ ;
3(a)(ii) 0.3(%) ;;
3(b)(i) any three from:
(named crop) disease ;
war ;
drought / AW ;
flooding / AW ;
unequal distribution of food / AW ;
(widespread) poverty ;
AVP ;
3(b)(ii) any four from:
1 one named chemical (other than fertilisers) used in farming ;
pesticides / insecticides / herbicides:
2 kill / harm, non-target species (in natural environment) ;
3 example of specific impact from harm of non-target species ;
4 loss of biodiversity / disrupt food chains ;
5 bioaccumulation / bioconcentration / biomagnification ;
6 ref to resistant organisms or super, bugs / weeds ;
7 pollute / destroy / AW, non-target / named, area / habitat ;
8 (antibiotics cause) antibiotic-resistance ;
9 AVP ;
Question 4:
(a) Fig. 4.1 shows a dandelion plant, Taraxacum officinale, in a field. The flower stalk is called a scape.
(i) The scape of a dandelion responds to sunlight by growing upwards.
State the name of this growth response.
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(ii) The scapes of dandelions keep the plant upright without the need for structures such as bones.
Explain how cells in plant scapes and stems keep plants upright.
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(b) Fig. 4.2 is part of a cross-section through the scape of a dandelion.
Draw a line and add a label on Fig. 4.2 to identify one area of xylem tissue.
(c) Describe the function of phloem tissue.
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(d) A dandelion scape was cut into long strips for an osmosis investigation.
Immediately after the scape was cut, the pieces of scape bent outwards, as shown in Fig. 4.3.
Strips of dandelion scape were placed in four dishes, A, B, C and D, for 30 minutes.
Each dish contained a different concentration of salt solution.
Fig. 4.4 shows the appearance of the four strips of scape after 30 minutes.
Using the information in Fig. 4.3 and Fig. 4.4, deduce and explain which strip of scape was in the most concentrated salt solution.
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▶️Answer/Explanation
Ans: 4(a)(i) (positive) phototropism ;
4(a)(ii) any two from:
(plants have) cell walls ;
pressure of water pressing against cell wall / ref. to turgor ;
ref. to xylem (offering support) ;
AVP ;
4(b) label to xylem shown on Fig. 4.2 ;
4(c) any three from:
1 translocation ;
2 transport of, sucrose / amino acids / sugars ;
3 (transports nutrients) from (named) source to (named) sink ;
4 AVP ;
4(d) strip of stalk:
1 B ;
explanation, max two from:
2 shows greater degree of, bending / shrivelling / AW ;
3 because more water moves out (of the cells in the inner
surface of the scape) ;
4 (water moves) from high water potential to, lowest water
potential / lower water potential ;
Question 5:
(a) Researchers investigated water pollution in the centre of a lake for 11 days.
Fig. 5.1 shows researchers collecting samples of aquatic organisms from the lake with a net which was placed at a specified water depth.
Each day, the researchers collected 5dm3 of water from the lake. Fish and other large organisms were released back into the lake.
The researchers extracted the chlorophyll from all the microorganisms that were collected in the sample of lake water.
They determined the concentration of chlorophyll by measuring the mass of chlorophyll extracted from each dm3 of lake water.
Fig. 5.2 shows a researcher lowering a Secchi disc on a long string into a lake from a boat.
A Secchi disc is a plastic disc which is divided into black and white sections. It is used to measure the transparency of water in lakes, rivers and oceans.
The researcher recorded the maximum water depth at which the Secchi disc was still visible.
The results of the investigation are shown in Fig. 5.3.
(i) State the type of microorganism that contains chlorophyll.
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(ii) The researchers collected 5dm3 of water from the lake each day. Using this information and the information in Fig. 5.3, calculate the total mass of chlorophyll in the sample on day 1.
Include the appropriate units with your answer.
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(iii) Suggest why the researchers determined the concentration of chlorophyll rather than counting the number of microorganisms in the sample.
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(iv) Using the information in Fig. 5.3, identify the day when the water was the most transparent.
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(v) Explain why the transparency of the water is important for organisms that contain chlorophyll.
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(b) (i) Heavy rainfall in nearby fields caused ions from fertilisers to wash into the lake on day 1 of the investigation.
State which ions can cause an increase in the number of organisms that contain chlorophyll in the lake.
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(ii) Many of the organisms that contain chlorophyll died on day 2 of the investigation.
Explain the consequences of the death of these organisms to the lake ecosystem.
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(c) The researchers monitored the water in the lake for pollution.
Outline how sewage should be treated so that the water it contains is safe to put into the lake.
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▶️Answer/Explanation
Ans: 5(a)(i) (some) protoctists / algae ;
5(a)(ii) 15 ;
mg ;
5(a)(iii) any one from:
(organisms) too small / difficult, to count ;
AVP ;
5(a)(iv) (day) 8 ;
5(a)(v) any two from:
to absorb / receive, (enough) light (energy) ;
(light) is necessary for photosynthesis ;
(for the organisms) to make sugars / starch / to convert light
(energy) into chemical energy ;
5(b)(i) any one from:
nitrate / NO$_{3}$
AVP ;
5(b)(ii) any three from:
1 eutrophication ;
2 increase in, decomposition / number of (named)
decomposers ;
3 decomposers respire aerobically ;
4 decomposition causes a reduction in (dissolved) oxygen ;
5 (reduced oxygen) causes death of fish / (named aquatic)
animals / AW ;
6 (death of producers means) less food for consumers / loss
of biodiversity / knock on effect further along food chain ;
5(c) any five from:
1 screening / removal of, large pieces of waste ;
2 flocculation / coagulation / clump suspended particles / AW ;
3 settling of, (insoluble) particles ;
4 digestion / decomposition by, (aerobic) bacteria / fungi /
decomposers / microorganisms ;
5 (with) aeration (tank) / trickle filter / activated sludge ;
6 sludge treated with anaerobic decomposers / anaerobic
digestion ;
7 (water) treated with, chlorine / ozone / UV (light) ;
8 distillation / collection of water from evaporator ;
Question 6:
Plants can be classified according to the position and shape of the structures in their flowers.
(a) Fig. 6.1 shows sections of flowers from six different plant species.
(i) Use the key to identify each species. Write the letter of each species (A to F) in the correct box in the key.
(ii) The large petals of the flowers shown in Fig. 6.1 indicate that they are pollinated by insects.
List four other structural adaptations of insect-pollinated flowers.
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(b) Flowering plants are distinguished from ferns because they all produce flowers.
State one other morphological feature that can be used to distinguish flowering plants from ferns.
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(c) The fruit of a pear tree, Pyrus communis, is often used to make juice.
State what protein biotechnologists will use to increase the volume of juice produced from pear fruit.
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▶️Answer/Explanation
Ans: 6(a)(i)
6(a)(ii) any four from:
nectary / nectar ;
sticky / spiky / AW, pollen ;
sticky stigma ;
stigmas / style / carpel, within flower / AW ;
anthers / stamens, within flower / AW ;
colourful petals ;
AVP ;
6(b) features of flowering plants
any one from:
pollen ;
ovule(s) ;
(named part of) seed ;
fruit ;
leaves ;
aerial stems ;
AVP ;
6(c) pectinase ;