WJEC 2019 Online Exam Review · 2019. 12. 6. · WJEC 2019 Online Exam Review GCE Biology Unit 3 - 1400U30-1 All Candidates' performance across questions Question Title N Mean S D

WJEC 2019 Online Exam Review

GCE Biology Unit 3 - 1400U30-1

All Candidates' performance across questions

Question Title N Mean S D Max Mark F F Attempt %

1(a)(i) 2479 0.8 0.8 2 39.5 99.1

1(a)(ii) 2465 0.7 0.6 2 35.1 98.5

1(b) 2500 3.4 1.6 5 67.7 99.9

1(c)(i) 2434 1.5 1.3 4 38.5 97.3

1(c)(ii) 2468 1.1 0.6 2 55 98.6

2(a) 2499 2.2 1 3 74.2 99.9

2(b) 2487 1.2 0.8 4 30.6 99.4

3(a) 2478 2.1 1.2 3 69.4 99

3(b)(i) 2451 1.5 1 3 51.5 98

3(b)(ii) 2498 1.9 0.9 3 65 99.8

3(b)(iii) 2499 0.5 0.5 1 45.2 99.9

3(b)(iv) 2491 1.2 0.7 2 59.4 99.6

4(a)(i) 2498 0.6 0.5 1 59.2 99.8

4(a)(ii) 2476 0.7 0.5 1 66.5 99

4(a)(iii) 2463 1 0.8 2 47.7 98.4

4(a)(iv) 2427 1.1 0.8 2 55.1 97

4(a)(v) 2408 0.7 0.8 2 37 96.2

4(a)(vi) 2488 1.1 0.7 2 56.5 99.4

4(b)(i) 2449 0.8 1 3 26.3 97.9

4(b)(ii) 2379 1.1 0.7 2 55.8 95.1

4(c)(i) 2387 0.7 0.9 2 34.9 95.4

4(c)(ii) 2475 1.6 0.7 3 52.7 98.9

5(a) 2499 1.6 1.1 5 32.9 99.9

5(b)(i) 2471 1.5 1.1 4 37 98.8

5(b)(ii) 2433 1.3 1.2 3 42.3 97.2

5(c) 2470 0.6 0.6 2 29.7 98.7

5(d) 2450 2 1 4 49.7 97.9

6(a) 2501 1.1 0.7 2 55.1 100

6(b) 2499 0.9 0.9 3 30.9 99.9

6(c) 2451 1.8 1.3 4 44.9 98

7 2486 3.6 2.2 9 39.5 99.4

39.535.1

67.738.5

5574.2

30.669.4

51.565

45.259.459.2

66.547.7

55.137

56.526.3

55.834.9

52.732.9

3742.3

29.749.7

55.130.9

44.939.5

0 10 20 30 40 50 60 70 80 90 100

1(a)(i)1(a)(ii)

1(b)1(c)(i)

1(c)(ii)2(a)2(b)3(a)

3(b)(i)3(b)(ii)

3(b)(iii)3(b)(iv)

4(a)(i)4(a)(ii)

4(a)(iii)4(a)(iv)4(a)(v)

4(a)(vi)4(b)(i)

4(b)(ii)4(c)(i)

4(c)(ii)5(a)

5(b)(i)5(b)(ii)

5(c)5(d)6(a)6(b)6(c)

7

Facility Factor %

Qu

est

ion

GCE Biology Unit 3 - 1400U30-1

1

6 © WJEC CBAC Ltd.

Question Marking Details Marks Available AO1 AO2 AO3 TOTAL Maths Prac

4 (a) i Number of bubbles ( in a minute for 5 minutes) 1 1 1 ii The glucose is used up (in respiration) /

{decrease in live population of yeast/ some yeast die}/ Build up of toxic waste NOT reference to oxygen

1 1 1

iii Bubbles vary in size(1) measuring volume of gas (1) OR Bubbles too fast to count (1) slow motion recording / measuring volume of gas (1)

1 1 2 2

iv Decrease/ become acidic (1) CO2 {dissolved in solution/released/ produced}/ carbonic acid produced (1) 2 2 1

v Sucrose is {a disaccharide/ made of glucose and fructose} (1) Has to be {hydrolysed/ broken down} (before it can be respired)/ 3 minutes was not enough time {to produce sucrase / for sucrase to act}/OWTTE (1)

2 2

vi Any two × (1) from: Can be used in all organisms (1) For {most/ all} reactions (1)

2 2

(b) i Any three × (1) from: Glucose is used in glycolysis takes place in the cytoplasm (1) Glucose cannot enter mitochondria/ pyruvate can enter the mitochondria(1) Pyruvate used in link reaction and takes place in the mitochondria (1) no enzymes for glycolysis in mitochondria/ ORA (1)

3 3

ii ADP required to generate ATP (1) Accept equation Oxygen is {final electron acceptor/termimal electron acceptor/ converted to water} (1)

2 2

7 © WJEC CBAC Ltd.


(c) i Released as heat (1) Keeps baby warm/ maintains body temp/ counteracts high surface area to volume ratio (1)

1 1 2

ii Higher number of capillaries (1) to supply the tissue with {oxygen / nutrients / named nutrient}/ remove carbon dioxide from the tissues (1) and distribute the produced heat throughout the body/ increased respiration rate/ produces more heat to maintain body temperature (1)

1

2 3

QUESTION 4 TOTAL 3 12 5 20 0 6

4ai: 1

4aii: 0

4aiii: 1

1

1

Sticky Note

In a minute would be better!

Sticky Note

Not sure where the oxygen in the air comes into this.

Sticky Note

The candidate has the way to measure the volume of gas released, but completely misses the point as to the limitation.

4aiv: 0

4av: 2

4avi: 0

1

1

Sticky Note

The candidate understands what a buffer does but does not answer how and why pH changes.

Sticky Note

The candidate gains the two marks for knowing that sucrose has to be broken down to fructose and glucose.

Sticky Note

Does not answer question

4ai: 0

4aii: 1

4aiii: 2

1

1

1

Sticky Note

There were many candidates who were unsure what a dependent variable is.

Sticky Note

That's enough for the mark, but it would be better to say why there's not enough.

Sticky Note

"Miscounting" bubbles is not enough. Why are they miscounted? This gains the mark for the different sizes.

4aiv: 2

4av: 0

4avi: 1

2

1

Sticky Note

Many candidates wrote about the number of carbon atoms.

4ai: 1

4aii: 1

4aiii: 2

1

1

1

1

Sticky Note

An excellent answer that explains why there is less glucose present.

Sticky Note

Different sized bubbles and the way to measure the volume is given.

4aiv: 2

4av: 2

4avi: 2

1

1

1

1

1

1

Sticky Note

A thorough answer.

Sticky Note

The reason is given and the fact that sucrose must be hydrolysed to glucose and fructose first is fully explained.

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4. (a) A group of students carried out the following experiment to investigate the effect of temperature on the rate of aerobic respiration in yeast.

A yeast suspension containing glucose, made up in pH 7 buffer, was added to a boiling tube. The apparatus was set up as shown below.

The boiling tube was placed in a water bath at 10 ºC. The apparatus was left for three minutes. The students then counted the number of bubbles released every minute for five minutes.

The students repeated the procedure at 5 ºC intervals from 15 ºC to 40 ºC, each time using fresh yeast suspension with glucose from the same batch. Oxygen was available to the yeast throughout the experiment.

(i) State the dependent variable in this experiment. [1]

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Explain why the number of bubbles may decrease if a fresh yeast suspension with glucose was not used for each repeat. [1]

(iii) When investigating the rate of respiration, counting the number of bubbles is a limitation.

Explain this limitation and suggest how it can be overcome. [2]

beaker of water

water

water bath

yeast suspension with glucose (20 cm3)

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(iv) State the effect of respiration at 30 ºC on the pH of the yeast suspension in the absence of a buffer. Explain your answer. [2]

(v) The students then carried out the procedure with sucrose replacing the glucose in the yeast suspension.

The initial rate of respiration was found to be lower when sucrose was used as the substrate instead of glucose. Suggest why this may happen. [2]

(vi) ATP is a more useful immediate energy source for cell metabolism than either glucose or sucrose. Explain why ATP is described as an universal energy currency.

[2]

Turn over.

140

0U

30

113

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5 (a) i Intraspecific (1) Space/ food (1)

1 1 2

ii Semibalanus could not survive in an area that experienced so much desiccation / extreme changes/ OWTTE Reject cannot survive at high tide level not qualified

1 1

iii Semibalanus is a more successful competitor in the lower zone/ Chthamalus is outcompeted in this area (1) There is interspecific competition normally/ A lack of interspecific competition after clearing (1)

2 2

(b) i A. Choose {same / random} {positions/ aspect} on each statue (1) B. Use of quadrat to count {number/ percentage cover} of barnacles

(1) C. Repeat 1) D. Calculate a mean (1)

3 1 4 3

ii Due to water potential in the cell being lower than the surrounding water (1) water would move in by osmosis (1) cells would lyse/ burst (1)

3 3

(c) i {Genetic/ DNA} {fingerprint/ profiling}/ DNA base sequencing/ DNA hybridisation

1

ii 2 correct answers for 1 mark from: UV light (Chemical) mutagen Ionizing radiation Errors in DNA replication NOT radiation alone

1

9 © WJEC CBAC Ltd.


(d) Any four × (1) from: A. Could outcompete {native/ other} species (1) B. May not have a natural predator in this area (1) C. This will reduce the biodiversity (around the coast)/ impact on food

chains (1) D. Could cause damage to the {harbours/ boats} (more friction so more

fuel costs)/ boats use more fuel so higher economic impact (1) E. Economic impact of removal of barnacles from {boats/ harbour}/

prevention of barnacle growth (1) F. Introduction of disease (1)

4 4


5d: 2

C

1

F

1

Sticky Note

Along with the decrease in genetic variation this enough for the reduction in biodiversity mark.

Sticky Note

This is not explained.

Sticky Note

Spreading of disease gains a mark

5d: 4

1

1

C

1

F

1

D

A

Sticky Note

"damaging boats" is point D and a good economic concern.

Sticky Note

There are 3 excellent environmental concerns here which are all linked well.

5d: 3

1

A

1

F

1

E

Sticky Note

Introduction of disease is a good environmental concern

Sticky Note

Outcompeting gains a mark. However, the student could have gone on to say that this could reduce the biodiversity in the area, not just that the native barnacles may become endangered.

Sticky Note

A lot of candidates wrote about the local barnacles not surviving and so the barnacle harvesters would go out of business.

16

(1400U30-1)16 © WJEC CBAC Ltd.

5. Barnacles are marine animals related to crabs and lobsters. They have an external shell made of several plates. They live in shallow tidal waters and the adults are attached permanently to a hard surface. They feed by filtering particles from the water using their modified feathery legs. When they reproduce, they produce larvae which swim in the sea until they attach to a hard surface and begin to grow into adults.

Barnacles are commonly found on rocky shores around the coast of Wales. The two most common species are Semibalanus balanoides and Chthamalus stellatus.

A rocky shore was studied and the distribution of these species was found as shown in the diagram.

maximum high tide level

maximum low tide level

distribution of mature

adultsdistribution of

developing adults

sea

Semibalanus balanoidesChthamalus stellatus

Distribution of Chthamalus stellatus

Distribution of Semibalanus balanoides

Chthamalus stellatus

Semibalanus balanoides

(1400U30-1) Turn over.17

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(a) Near the maximum high tide level only Chthamalus barnacle larvae develop into adults.

(i) State the type of competition occurring in this area and what the mature adults could be competing for. [2]

(ii) Scientists removed Chthamalus from the upper area continually for several weeks and observed that Semibalanus did not colonise this area. Suggest a possible explanation why Semibalanus cannot colonise this area. [1]

(iii) Scientists then removed Semibalanus from the lower area continually for several weeks and observed that Chthamalus were found in this cleared area. Give an explanation for this observation. [2]

18

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In 2005, 100 life-sized human sculptures were installed, at different distances between low and high tide marks, on a sandy beach near Liverpool. A year later it was noticed that some of these structures had become covered in barnacles. All of the barnacles belonged to the species Austrominius modestus. The photographs below show one of the statues and a 0.1 m × 0.1 m quadrat being used on the statue.

Scientists selected sculptures to look at the distribution of the barnacles at different positions on the shore.

(b) (i) Describe the method by which reliable data would have been collected. [4]

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(ii) If there is decreased salinity in the surrounding water (e.g. in an estuary) Austrominius are able to carry out active transport to remove sodium ions from their cells. Explain why they would be unable to survive if this did not occur. [3]

(c) Two varieties of Austrominius were found on one of the sculptures.

(i) A sample of DNA was taken from each of the varieties. State the technique that could be used to show the relatedness of the two varieties of barnacles. [1]

(ii) State two possible causes of increased DNA mutation rate. [1]

20

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(d) Austrominius modestus is a species of barnacle that was found only in Australasia up to 100 years ago. The first recorded sighting of it in the UK was in 1946. In 2014, a survey of sixteen harbours in Wales found Austrominius in all of the harbours surveyed. It is now classified as an “invasive species”.

At the time of the survey there were just a few Austrominius barnacles in each of the harbours.

State why the Welsh Government is concerned about the presence of Austrominius in the harbours. Your answer should include environmental and economic concerns. [4]

11 © WJEC CBAC Ltd.


7 Indicative Content PCT

• All glucose and some sodium ions (selectively) reabsorbed (back into the blood)

• Using co transport with Na+

• Lowers the water potential of the blood • So water out of filtrate into blood by osmosis • So less water in filtrate

Descending limb of loop of Henle

• Drop in water due to: • Permeable to water • Water moves out of filtrate by osmosis into {tissue/interstitial fluid} • Due to high concentration of Na+ ions there • Sodium ions increase in descending limb due to diffusion back in

from interstitial fluid / medulla Ascending limb of loop of Henle

• Impermeable to water • So water does not move out so levels stay same • Na+ actively transported out (into interstitial fluid) • So drop in ascending • Makes filtrate more concentrated with Na+ at bottom of loop /

reference to counter current multiplier 7-9 marks Detailed explanation of all three sections. Including correct reference to graph for 8-9 marks.

5 4

12 © WJEC CBAC Ltd.


The candidate constructs an articulate, integrated account, which shows sequential reasoning. The answer fully addresses the question with no irrelevant inclusions or significant omissions. The candidate uses scientific conventions and vocabulary appropriately and accurately. 4-6 marks Explanation of two areas or brief explanation of three areas The candidate constructs an account correctly linking some relevant points, such as those in the indicative content, showing some reasoning. The answer addresses the question with some omissions. The candidate usually uses scientific conventions and vocabulary appropriately and accurately. 1-3 marks Brief explanation of any of one area. The candidate makes some relevant points, such as those in the indicative content, showing limited reasoning. The answer addresses the question with significant omissions. The candidate has limited use of scientific conventions and vocabulary. 0 marks The candidate does not make any attempt to give a relevant answer worthy of credit.


Sticky Note

There is no need to write about ultrafiltration as it is not asked for in the question.

P

P

Sticky Note

There is just about some credit here, with water entering the blood by osmosis.

Sticky Note

Should really mention that it is all of the glucose molecules

Sticky Note

There is no mention of the loop of Henle so this cannot get above the bottom band. There are some credit worthy comments, but not many! 2 marks

P

P

P

P

A

D

A

D

D

Sticky Note

The credit here is for all of the glucose and some/most of the sodium ions being reabsorbed. This candidate has also referred to the figures on the graph which can put them in the highest band.

cliff

Sticky Note

This is good. The water potential in the blood is lowered and water is moving out by osmosis. To be excellent it would help if he candidate had written about water moving from higher to lower water potentials.

Sticky Note

Very few candidates explained the reason for sodium ions increasing in the descending limb.

A

A

A

cliff

Sticky Note

This is a good description of why the water level remains constant in this region and few candidates pointed this out.

Sticky Note

This is an excellent essay and is certainly in the top band. 8 marks

Sticky Note

Be careful. I don't think glucose wants anything!

D

A

A

P

P

D

A

Sticky Note

There's no need to write about adaptations of the proximal convoluted tubule cells. It's irrelevant to the question. Many candidates wrote a huge amount about this.

Sticky Note

Credit for reference to Co-transport in proximal convoluted tubule.

Sticky Note

For the first point the candidate must have all of the glucose going from the filtrate as well as a lot of the sodium ions.

Sticky Note

There is very little point summarising a short essay. If one of the points here contradicts what is written in the main body it will negate a mark.

Sticky Note

Middle Band 5 marks

24

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7. The kidneys have an important role to play in the removal of urea and homeostasis in the body. Along the length of a nephron there are mechanisms which regulate the balance of water and dissolved solutes in the blood.

The graph below illustrates the changes in the percentage of sodium ions, glucose and water remaining in the filtrate as it passes from the start of the proximal convoluted tubule to the end of the loop of Henlé.

0

40

80

100

60

20

Percentage of substance remaining in filtrate / %

Distance along nephron from glomerulus / au

Loop of HenléProximal convoluted tubule

Use the information from the graph to explain the changes in the filtrate as it passes through a nephron from the proximal convoluted tubule to the end of the loop of Henlé. [9 QER]

Key:

sodium ions

water

glucose

Documents

WJEC 2019 Online Exam Review · 2019. 12. 6. · WJEC 2019 Online Exam Review GCE Biology Unit 3 - 1400U30-1 All Candidates' performance across questions Question Title N Mean S D