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TIME1 hour 30 minutes.
INSTRUCTIONS TO CANDIDATESWrite your Centre Number and Candidate Number in the spaces provided at the top of this page.You must answer the questions in the spaces provided. Do not write outside the boxed area on each page or on blank pages. Complete in black ink only. Do not write with a gel pen.Answer all eight questions.You are provided with Photograph 2.5 for use with Question 5 in this paper. Do not write your answers on this photograph.
INFORMATION FOR CANDIDATESThe total mark for this paper is 75.Section A carries 60 marks. Section B carries 15 marks.Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question.You are reminded of the need for good English and clear presentation in your answers.Use accurate scientific terminology in all answers.You should spend approximately 20 minutes on Section B.You are expected to answer Section B in continuous prose.Quality of written communication will be assessed in Section B, and awarded a maximum of 2 marks.
ADVANCED SUBSIDIARY (AS)General Certificate of Education
2017
BiologyAssessment Unit AS 2assessing
Organisms and Biodiversity
[AB121]TUESDAY 6 JUNE, AFTERNOON
Centre Number
Candidate Number
*AB121*
*AB121*
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Section A
1 Using the key below, identify the five kingdoms of living organisms labelled A–E.
DNA is usually linear
noyes
noyes
noyes
noyes
Most members are unicellular
Cells may have several nuclei
Feeding is always heterotrophic
A
ED
C
B
A _________________________
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2 (a) Many farmers apply chemicals to their fields to kill weeds. An investigation was carried out into the effect of one of these chemicals on biodiversity. The results are summarised in the graph below. (Simpson’s index is a measure of biodiversity.)
Simpson’sindex
Increasing concentration ofchemical applied
0
1
(i) State the term used for a chemical that kills weeds.
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(ii) Describe and explain the relationship shown in the graph.
Description
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Explanation
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(b) Government regulations are in place to ensure that farmers manage theirhedgerows in a way that promotes biodiversity. One such regulation states thathedgerows should only be cut at certain times of the year.
Suggest when farmers should cut hedgerows and explain how this wouldpromote biodiversity.
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3 (a) Fick’s Law states that the rate of diffusion increases if the concentration gradient is high and/or the diffusion distance is short.
(i) With reference to the mammalian respiratory system, describe how a highconcentration gradient is maintained between the alveolus and the blood.
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(ii) Describe how a short diffusion distance is created between the alveolus andthe blood.
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(iii) According to Fick’s Law, a third factor contributes to an increased rate ofdiffusion across an exchange surface. Identify this factor and describe howit is achieved in the lungs.
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(b) Special cells around the alveoli secrete a substance called surfactant. Somepremature babies cannot produce enough of this substance and therefore needassistance to breathe.
State the function of surfactant and suggest, with reference to Fick’s Law, how alack of it would result in poor gas exchange in premature babies.
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4 The Audus apparatus shown below was used to measure the volume of oxygen produced by a shoot of pondweed (Elodea) over 15 minutes in each of three different light intensities. This data could be used to indicate the rate of photosynthesis in this aquatic plant.
(a) (i) State the function of the syringe in this apparatus.
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(ii) Describe how the independent variable could have been changed.
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(iii) Name one variable, other than time, that would need to have been kept thesame. Explain how this variable would be controlled.
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(b) The experiment was carried out three times in each light intensity and the resultsare shown in the table below.
Light intensity Volume of oxygen collected in 15 minutes/cm³
High 10.5 10.5 9
Medium 6 5.5 4.5
Low 2 3 1.5
(i) Calculate the average rate of oxygen collection per hour at high lightintensity.
(Show your working.)
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(ii) Suggest why the volume of oxygen collected would be less than the totaloxygen produced by this shoot.
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(c) Using the diagram of the apparatus provided, suggest how the accuracy of theresults could be improved.
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5 Photograph 2.5 is a photomicrograph of a transverse section through the root of a buttercup (Ranunculus repens).
(a) In the space below, draw a block diagram to show the tissues present in theroot, as shown in the photomicrograph. Label your diagram to identify fourtissues.
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Some of the tissues shown in the photomicrograph are involved in the transport of water and minerals in the plant.
(b) Describe concisely how water is transported up a stem according to thecohesion-tension theory.
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(c) In mammals, blood is involved in both transport and defending the body againstdisease. Some of the white blood cells involved in defence are shown below.Complete the table by naming the three types of white blood cell shown andstating the function of each.
Diagram Name Function
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6 In the UK the peppered moth (Biston betularia) has two distinct forms, a light peppered form and a dark melanic form, as shown in the photographs below. Before the UK became industrialised, the light form was more common and the dark form was rare.
Light form Dark form© Photographs of Biston betularia taken by Olaf Leillinger, June 2006. Published by
Colourpoint Educational “AS Biology for CCEA”. Licenced under https://creativecommons.org/licenses/by-sa/2.5/deed.en
(a) (i) State the genus of the peppered moth.
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(ii) Despite the different appearance, the two forms are classified as the samespecies. Define the term ‘species’.
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(b) During the day, the moths rest on lichen-covered tree branches and trunkswhere they are vulnerable to predation by a range of birds.
As a result of the Industrial Revolution, smoke pollution increased significantlyin the UK, and tree trunks in many areas became blackened by soot. In the1950s controls were put in place to reduce air pollution. The graph below showspollution levels and the relative number of each form of moth between 1950and 2010.
Key
Numberof
mothsSmoke
pollutionlevel
1950 1960 1970 1980 1990 2000 2010
Smokepollutionlevel
Light Form
Dark Form
Year
(i) Estimates of the numbers of the two forms were made by samplingthe moths found on tree trunks. Suggest how this may result in anunderestimation of numbers.
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(ii) Name the type of selection demonstrated by the data and explain thechange in numbers of the light form from 1970 to 2010.
Type of selection
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Explanation
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(c) The diagram below represents the caterpillar of the peppered moth attached to atwig. Suggest how the caterpillar avoids predation.
Peppered mothcaterpillar
Twig
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7 The heart contains several structures which are necessary for its function of pumping blood in one direction. The photograph below shows the left side of the heart when dissected.
Atrium wall
Ventricle wall
A
B
Forceps
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(a) (i) Name the structures labelled A and B.
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(ii) Explain how structures A and B ensure that blood flows through the heart inone direction.
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(iii) Explain the difference in thickness of the atrium and ventricle walls asshown in the photograph.
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(iv) Semi-lunar valves also have a role in maintaining the blood flow through theheart. Explain what causes these valves to open during ventricular systole.
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(b) The sinoatrial node (SAN) is often referred to as the pacemaker of the heart.
(i) State precisely the location of the SAN in the heart.
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(ii) Describe how a wave of excitation, which originates in the SAN, eventuallyresults in ventricular systole.
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(c) Sick Sinus Syndrome (SSS) is a condition where the SAN malfunctions. TheECGs below are from a healthy individual and an individual with SSS.
ECG from a healthy
person
© Science Source / Science Photo Library
ECG from an individualwith SSS
© Science Source / Science Photo Library
Symptoms of this condition include tiredness and fainting. Using the information in the ECGs, suggest a reason for these symptoms.
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Section B
Quality of written communication is awarded a maximum of 2 marks in this section.
8 Marram grass (Ammophila arenaria) is a plant species found in the sand dune system at Murlough Nature Reserve in County Down. After sampling the sand dunes, A. arenaria was found to be most abundant in the dunes closest to the shore, where water retention by the soil is very poor.
(a) Describe how the abundance of A. arenaria could be sampled along the sand dune system. [4]
(b) Describe and explain the environmental factors that affect the rate of transpiration in a plant and suggest two adaptations the leaves of A. arenaria may have to survive in a sand dune habitat. [9]
Quality of written communication [2]
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(a) Describe how the abundance of A. arenaria could be sampled along the sand dune system.
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(b) Describe and explain the environmental factors that affect the rate of transpiration in a plant and suggest two adaptations the leaves of A. arenaria may have to survive in a sand dune habitat.
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Permission to reproduce all copyright material has been applied for.In some cases, efforts to contact copyright holders may have been unsuccessful and CCEAwill be happy to rectify any omissions of acknowledgement in future if notified.
Examiner Number
For Examiner’suse only
QuestionNumber Marks
1 2 3 4 5 6 7 8
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10751.02/1
GCE Biology Advanced Subsidiary (AS)Assessment Unit AS2Organisms and BiodiversitySummer 2017
Photograph 2.5(for use with Question 5)
© CCEA
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