As Biology With Stafford Unit 3 Workbook Answers

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  • Marking scheme for AS Biology with Stafford, Unit Three Practical Workbook. Book available at http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2 +Bi ology +with+ stafford

    AS Biology with Stafford. Unit Three: Practical Workbook answers / Unit three paper BIO7 Page 1

    Marking schemes for

    Advanced Level Biology

    AS Biology with Stafford Unit Three: Practical Workbook

    Paper reference: 6BIO7

    The book is available at the following link

    http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2+Biology+with+stafford

    A copy of this marking scheme and many other resources can be downloaded from the

    following link

    http://www.facebook.com/groups/biologywithstafford/

    and

    www.staffordeducationalservices.com

  • Marking scheme for AS Biology with Stafford, Unit Three Practical Workbook. Book available at http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2 +Bi ology +with+ stafford

    AS Biology with Stafford. Unit Three: Practical Workbook answers / Unit three paper BIO7 Page 2

    Copyright Stafford Valentine Redden

    Unauthorized duplication contravenes applicable laws.

    Typeset & layouts by : Mohamed Sobir

    Cover designed by : Mohamed Sobir

    Printed in Maldives by : Copier Repair

    Published by : Author publisher

    All rights reserved.

    No part of this publication may be

    Reproduced, stored in a database or

    retrieval system, or transmitted in any

    form or by any means, electronic,

    mechanical, photocopying, recording,

    or otherwise, without the prior

    written permission of the author

    ISBN: 978-81-910705-2-1

    Note: A few graphs have been drawn to give students an idea on how to find the scale and plot range or variability. Other graphs have not been drawn as students need to practice the graph drawing. Do post your graphs on my FB group and I can give a

    feedback on the graphs. Any other queries on any aspect of the practical paper can be clarified on my FB group http://www.facebook.com/groups/biologywithstafford/

    I have also included additional notes on referencing, citation or bibliography at the end of the document. Evaluation of references is also dealt with in detail. Cheers and all the best. Stafford Valentine Redden (M.A; M.Sc.; M.Ed.; (Ph.D))

    Head of Department (Biology)

    Villa International School,

    Male, Republic of Maldives Email: staffordv@yahoo.com Mobile: +960 7765507

  • Marking scheme for AS Biology with Stafford, Unit Three Practical Workbook. Book available at http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2 +Bi ology +with+ stafford

    AS Biology with Stafford. Unit Three: Practical Workbook answers / Unit three paper BIO7 Page 3

    SAQ1. a. (i) Correct mean calculation; consistency with decimal places;

    Relative Caffeine concentration (%)

    Heartbeat rate of daphnia in beats per minute

    Daphnia 1 Daphnia 2 Daphnia 3 Mean

    0 (pond water) 82 90 87 86.3

    1.56 83 87 89 86.3

    3.12 88 91 94 91.0

    6.25 96 97 102 98.3 12.5 97 98 106 100.3

    25 140 142 146 142.7

    50 150 156 154 153.3

    100 (pure Red Bull) 181 184 183 182.7

    (ii) Relative caffeine concentration; (1) (iii) Heartbeat rate of daphnia; (1) (iv) Use Daphnia of the same size, as size or surface area to volume ratio could influence the rate of absorption of caffeine into the body; it is not possible to measure the size or

    surface area of Daphnia, but Daphnia of similar size can be selected for the experiment by simple observation and judgement; Do not keep the Daphnia on the cavity slide for too long after removing it from the water bath, as the temperature could change and thereby influence the heartbeat rate; This can be controlled by counting the heartbeat rate 30 seconds as soon as the

    Daphnia is transferred to the cavity slide; The concentration of dissolved oxygen in each caffeine soultion; this can be controlled by aerating the solutions by passing air through it to saturate the solution with oxygen; (b) Refer to graph 1, on page 2. Axes labelled and correctly oriented with units; scale more than 50% of graph covered; points clearly indicated with a cross or dot and circle

    at the accurate position on the graph; single neat line drawn either with a ruler from point to point or freehand curve / no extrapolation; range bars plotted accurately; (c)Tap water contains chlorine, which could be toxic to daphnia. A beaker containing tap water can be left open overnight to allow chlorine to evaporate.

    (d) Metabolic activity is slowed down at low temperatures due to lack energy as respiratory enzymes have low kinetic energy. The aeration ensures that the water gets saturated with oxygen and metabolic activity is not limited by lack of oxygen for respiration. (e) As the caffeine concentration increases there is a corresponding increase in the

    mean heartbeat rate of daphnia. The increase is not linear. (f) Blind counting means that the person who is counting the heartbeat rate is not aware of the caffeine concentration that the daphnia has been exposed to. This can help to reduce bias while counting.

    (Total 20 marks)

  • Marking scheme for AS Biology with Stafford, Unit Three Practical Workbook. Book available at http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2 +Bi ology +with+ stafford

    AS Biology with Stafford. Unit Three: Practical Workbook answers / Unit three paper BIO7 Page 4

    Graph 1 (Total 20 marks)

    SAQ 2 a. Duration since exposure to caffeine / time; b. mean heartbeat rate of daphnia; c. i. This is a random error. All other readings lies close to the expected values and

    follow a trend. Only this value lies away from the trend and is unexpected. A systematic error will lead to the entire set of data devaiting from the actual trend. ii.

    Duration since exposure to caffeine / minutes

    Heartbeat / beats per minute

    Flea 1 Flea 2 Flea 3 Mean 0 184 180 185 183

    2 220 222 224 222

    4 232 234 230 232

    6 246 240 120 243

    8 242 240 238 240

    10 230 232 234 232

    iii. Axes labelled and correctly oriented with units; scale more than 50% of graph covered; points clearly indicated with a cross or dot and circle at the accurate position on the graph; single neat line drawn either with a ruler from point to point or freehand curve / no extrapolation;

  • Marking scheme for AS Biology with Stafford, Unit Three Practical Workbook. Book available at http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2 +Bi ology +with+ stafford

    AS Biology with Stafford. Unit Three: Practical Workbook answers / Unit three paper BIO7 Page 5

    d. The heartbeat rate of 182 beats per minute without caffeine is the control. All results from caffeine treatment must be compared with the control to make any conclusions about caffeine exposure and heartbeat rate. The mean heartbeat rate increases with time as more caffeine is absorbed into the body from the solution as time increases. So the

    greater caffeine concentration in tissues increases the heartbeat rate. However, after 8 minutes the heartbeat rate begins to decerase, maybe because diffusion stops or caffeine begins to be excreted from the tissues. e.

    f. Use a microscope fitted with a video camera and integrate timer to record the heartbeat rate. Then replay the video in slow motion and count the number of heartbeats

    in one minute as shown on the integrated timer. g.

    Daphnia has reduced awareness of pain because of the lack of a well developed nervous system.

    It is transparent and its heart is visible without the need for dissection. Daphnia is abundant in nature and there is no threat to it or its dependent species (food

    chains). Some people also feel that it is bred for fish food and will thus die anyway. Daphnia can reproduce asexually and may be clones, therefore there is no loss of

    genetic variation. (Total 20 marks)

    SAQ3 a. i. Concentration of nitrogenous fertilizer used

    ii.) Vitamin C concentration of the oranges iii.) concentration of other fertilizers in the soil; Volume of water provided to each plant; Edaphic factors / Soil type / Humus content of soil; Pest control strategy and application;

    b. i.) Blue ii.) Colourless iii.) Risk: The DCPIP solution could stain clothes and skin. This could be minimized by using rubber gloves / wearing a laboratory coat / using a pipette to transfer DCPIP; c. i. And ii.

    CB = (VA x CA) / VB

    = (8 x 0.1) / mean volume First example (8 x 0.1) / 28 = 0.029

  • Marking scheme for AS Biology with Stafford, Unit Three Practical Workbook. Book available at http://www.amazon.com/gp/aw/s/ref=is_s_?k=AS+A2 +Bi ology +with+ stafford

    AS Biology with Stafford. Unit Three: Practical Workbook answers / Unit three paper BIO7 Page 6

    Plot Number

    Mass of fertilizer

    used / kg

    Volume of orange juice needed to reach the end point / cm

    -3

    Concentration of Vitamin C in the oranges / mg cm

    -3 Orange 1 Orange 2 Mean

    1 0 29 27 28.0 0.029

    2 2 27 30 28.5 0.028

    3 4 25 23 24.0 0.033

    4 6 23 21 22.0 0.036

    5 8 20 19 19.5 0.041

    6 10 17 17 17.0 0.047

    7 12 16 17 16.5 0.048 8 14 17 18 17.5 0.045

    9 16 15 16 15.5 0.052

    10 18 12 18 15.0 0.053

    c. iii. Due to the orange colour of the juice, it is difficult to accurately observe the point at which the DCPIP becomes colourless;

    d. Axes labelled and correctly oriented with units; scale more than 50% of graph covered; points clearly indicated with a cross o