2nd Edition
2nd Edition
The Discover Biology for GCE 'O' Level Science Workbook
(2nd Edition) is specially developed to complement the Discover Biology
for GCE ‘O’ Level Science (2nd Edition) textbook. Designed to support learning
with understanding, this workbook is written in line with the 2013 GCE Ordinary
Level Science (Biology) syllabus from the Ministry of Education, Singapore.
Its wide-ranging exercises build foundational knowledge and develop critical
higher-order thinking skills.
Workbook (Teacher’s Edition)
Reinforces concept development
• Concept mapping helps students review and integrate key concepts taught in
a chapter.
2nd Edition
Shapes independent learners and critical thinkers
• Self-evaluation tool at the end of every worksheet helps students monitor their
learning progress.
• A variety of context-based and data-based questions challenge students to train
up their higher-order thinking skills.
Builds skills and exam confidence
• Thought Process in worked examples guides students through essential points
to consider when answering free-response questions.
• A Model Examination Paper gives further practice and boosts exam confidence
by helping students familiarise with the exam format.
Lam Peng Kwan • Eric Y K Lam
Christine Y P Lee
Other components
• Practical Book
• Textbook
Lam Peng Kwan
Eric Y K Lam
Christine Y P Lee
ISBN 978-981-01-1730-6
Workbook
Teacher's Edition
(S)SciB_WB&TE Cover.indd 1
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2nd Edition
Workbook
Teacher's Edition
Lam Peng Kwan • Eric Y K Lam • Christine Y P Lee
Tittlepage TB-WB-PB-Sci.indd 3
8/29/12 10:23 AM
© 2007, 2013 Marshall Cavendish International (Singapore) Private Limited
© 2014 Marshall Cavendish Education Pte Ltd
Published by Marshall Cavendish Education
Times Centre, 1 New Industrial Road, Singapore 536196
Customer Service Hotline: (65) 6213 9444
E-mail: tmesales@mceducation.com
Website: www.mceducation.com
First published 2007
Second edition 2013
All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system
or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior permission
of the copyright owner. Any requests for permission should be
addressed to the Publisher.
Marshall Cavendish is a registered trademark of Times Publishing Limited.
ISBN 978-981-01-1730-6
Printed in Singapore
(S)SciBioWBTE_Imprint/Acknow.indd 2
12/12/16 9:55 am
ACKNOWLEDGEMENTS
The publisher would like to acknowledge the following who have kindly given permission
for the use of copyright material:
Cover Page Nudibranch © Kelpfish/Dreamstime.com; 3 ER & mitochondria © Don
W. Fawcett/Science Photo Library; 4 Plant cells © Kristian Peters - Fabelfroh(own
photo)/Wikimedia Commons/CC-BY-SA-3.0(http://commons.wikimedia.org/wiki/
File:Plagiomnium_affine_laminazellen.jpeg); 7 Red blood cells © Bobjgalindo(own photo)/
Wikimedia Commons/CC-BY-SA-3.0(http://commons.wikimedia.org/wiki/File:Reactive_
lymph.JPG); 47 Stomata © Yunxiang987/Dreamstime.com; 60 Blood cells © Mkkans/
Dreamstime.com; 103 Sarracenia flower © Noah Elhardt(own work)/Wikimedia Commons/
Public domain(http://commons.wikimedia.org/wiki/File:Englishtitles2-1.jpg)
While every effort has been made to contact copyright holders of material reproduced,
we have been unsuccessful in some instances. To these copyright holders, we offer our
sincere apologies and hope they will take our liberty in good faith. We would welcome any
information, which would enable us to contact the copyright holders/owners involved.
iii
(S)SciBioWB_Imprint/Acknow.indd iii
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Preface
This Workbook is written specially for students taking the GCE ‘O’ Level Science (Biology)
examination. To enhance learning and reinforcement, the topics in this Workbook are
arranged in the same sequence as the topics in the Textbook.
Connect It!
WORK ON IT!
Circle the question(
s) you have answered
incorrectly. Then,
textbook to strengthe
revisit the relevant
n your understanding
section(s) in the
of the key concept(
s).
Students fill in a concept map using keywords from
a chapter, in order to strengthen key concepts
taught in that chapter.
Date:
Class:
CONNECT IT!
Discuss with your
using keywords learnt in the chapter.
Complete the concept map below
can be extended.
classmates how the concept map
Organ
system
Red blood cell
specialised
cells
Cell
Tissue
Organ
Xylem
Root
Organism
This section helps students monitor
their progress in learning. Questions
are categorised based on the learning
outcomes in the Textbook. Students
are asked to circle the questions
they have answered incorrectly, and
refer to the relevant section in the
Textbook for further revision.
Cell membrane
Cytoplasm
Nucleus
which
which
which
surrounds
Contains
chromatin
(DNA)
Mitochondria
Ribosomes
Energy source
for cells
Synthesise
proteins
© 2013 Marshall Cavendish International
Is partially
permeable and
encloses the
cytoplasm
contains
organelles
such as
(Singapore) Private Limited
Vacuoles
Store
substances
within the cell
Chloroplasts
(in plant cells)
Site of
photosynthesis
Worksheet 1
are classified
(d) Describe the characteri
stics of
enzymes
FreeResponse
Textbook
section(s)
5.1
5.1
2
3
4, 5, 7
1, 3, 5
5.1
2
5.2
5
3, 6, 7
1, 2, 4
2
5.2
1
5.2
Work On It!
vessel
hair cell
Cell wall
plants )
(only in
made up of
Structured
1
1
Link to the Textbook chapter
for easy reference.
for Chapter 2
Cells
MultipleChoice
enzymes
(e) Describe the mode
of enzyme action
based on the ‘lock-and-k
ey’ hypothesis
(f) Explain how conditions
such as
temperature and pH
can affect the rate
of an enzyme-catalysed
reaction
Worksheet 1
)
(
Name:
Questions
Learning objectives
(a) Define an enzyme
(b) State the function
of
(c) Explain how enzymes
1
© 2013 Marshall Cavendish
International (Singapore)
Private Limited
Worksheet 4
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Learn & Apply
A worked example and related practice
questions show students how to answer
essay-type and structured questions.
TEST IT!
Test It!
A variety of questions
with different difficulty
levels is provided.
-Choice Questions
Section A: Multiple
in the brackets provided.
Choose the correct answer,
Enzymes are
1.
A
B
C
D
2.
3.
and write its letter
.
up in chemical reactions
proteins that are used
any temperature
chemical reactions at
proteins that catalyse
living organisms
chemical reactions in
substances ( C )
proteins that catalyse
compounds into simpler
the breakdown of complex
proteins that speed up
would be the most
to remove stains. Which
biological washing powders
Enzymes are added to
chocolate milk stains?
effective enzymes in removing
Amylase and catalase
A
B Amylase and maltase
( D )
C Protease and catalase
D Protease and lipase
temperatures.
out in water at different
experiment that was carried
The diagram shows an
(d)
Name two conditions
or factors that had to
Any two of the following:
be kept constant in this
Temperature / pH / Amount
experiment.
of enzyme used
water
LEARN & APPLY
mixture of amylase and
starch in a Visking tubing
nse Questions.
try to answer the Free-Respo
example below, then
Go through the worked
sugar at 30-second
the presence of reducing
The water was tested for
detected most rapidly?
would reducing sugar be
A
B
C
D
intervals. At which temperatur
10°C
20°C
40°C
100°C
e
is
note that the question
Thought Process
It is important to take
to answer the questions.
Giving examples will help
asking for plants.
( C )
Answer
Points to cover
in plants.
speed up chemical reactions
complete.
1. Enzymes help to
will take a long time to
these reactions.
many reactions in plants
enzymes to speed up
2. Without enzymes,
esis and respiration require
stored starch into glucose
3. For examples, photosynth in seed germination. Enzymes will digest the
important
4. Enzymes are also
and grow.
for embryo to germinate
© 2013 Marshall Cavendish
28
Worked Example
of enzymes in plants.
Explain the importance
International (Singapore)
Section B: Struc
tured Questions
Private Limited
Answer the followi
Worksheet 4
ng questions
1.
in the spaces
provided.
X is an unknow
n substance extract
the ability of X
ed from a living
to bring about
organism. A studen
the hydrolysis
boiling water
t was required
of starch. She
(100°C) and the
to investigate
set up two water
other contain
ing water at 36°C.
baths, one contain
ing
The student used
the water baths
• Test tube 1:
1 cm3 of X (pre-tre and set up the reaction mixture
• Test tube 2:
ated
s as follows:
at 100°C for
1 cm3 of X (pre-tre
1 minute) + 9
• Test tube 3:
ated at 36°C
cm3 of distille
for 1 minute)
1 cm3 of X (pre-tre
d
water
+ 9 cm3 of distille
• Test tube 4:
ated at 100°C
d water
1 cm3 of X (pre-tre
for 1 minute)
3
+
9
• Test tube 5:
ated
cm
of
at
starch
36°C for 1 minute
1 cm3 of distille
) + 9 cm3 of starch
d water + 9 cm3
of starch
The reaction mixture
s were placed
the student
tested the mixture in the water bath that contain
ed water
Benedict’s test.
in
Her observations each test tube for the presen at 36°C. After 15 minute
s,
were as follows
ce of reducin
:
g sugar using
Test tube
Observation for
Benedict's test
1
Mixture remain
ed blue
2
Data-based questions are provided
to prepare students for the current
examination format. The questions
involve various kinds of data, to
provide practice in interpreting
and manipulating different kinds
of data.
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Mixture remain
ed blue
3
International (Singapore)
35
Private Limited
ed blue
Mixture turned
from blue to orange
-red
Mixture remain
ed blue
(a) Based on
the
X breaks down
student's observ
ations, what is
starch (a non-red
ucing sugar) into
(b) What eviden
ce
X is specific in
(test tube 3),
Worksheet 4
© 2013 Marshall Cavendish
Mixture remain
4
5
suppor ts that
action. That is,
substance X
it hydrolyses
it does not change
the action of
a reducing sugar
on starch?
(maltose).
contains an enzym
e?
only starch. /
When X is pre-trea
ted at 100°C
starch to maltose
. This shows
at high temper
substance X
8/25/12 5:24 PM
atures.
that X is an enzyme
, and is denatu
red
(c) Suggest
two experiments
that the studen
an enzyme.
t could perform
to find out if substa
nce X contain
The student could
s
either
change the pH
student could
use the Biuret
of the reaction
test to check
© 2013 Marshall
mixture to see
if X contains protein
if X is sensitiv
e to pH, or the
, since all enzyme
of proteins.
Cavendish Internatio
s are made
nal (Singapore)
Private Limited
Worksheet 4
(S)SciBioWB_04.indd
31
31
The Worksheets emphasise contextual learning, information handling and
problem-solving skills. It is hoped that these emphases will stimulate students’ interest
in Biology and in the application of the subject to everyday life.
iv
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Contents
Acknowledgements
iii
Preface
iv
Terms Used in Examination Questions
vi
A Guide to Essay Writing
vii
Worksheet 1
Cells
Worksheet 2
Movement of Substances
11
Worksheet 3
Nutrients
21
Worksheet 4
Enzymes
27
Worksheet 5
Nutrition in Humans
39
Worksheet 6
Nutrition in Plants
45
Worksheet 7
Transport in Humans
57
Worksheet 8
Transport in Plants
67
Worksheet 9
Respiration in Humans
79
Worksheet 10
Coordination and Response
89
Worksheet 11
Reproduction in Plants
99
Worksheet 12
Reproduction in Humans
107
Worksheet 13
Heredity and Molecular Genetics
115
Worksheet 14
Ecology and Our Impact on the Ecosystem
125
Model Examination Paper
1
135
v
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Terms Used in Examination Questions
Below is a list of terms that are used in examination questions. It is important that you
familiarise yourself with these terms and what is expected in your answers when such
terms are encountered.
Term
vi
What is expected in your answer
Analyse
Interpret data to reach conclusions.
Annotate
Add brief notes to a diagram, drawing or graph.
Apply
Use an idea, equation, principle, theory or law in a new situation.
Calculate
Find an answer using mathematical methods (show working unless
instructed otherwise).
Compare
Give an account of similarities and differences between two (or more)
items, referring to both (or all) of them throughout your account.
Construct
Represent or develop information in a graphical form (include a legend
or key).
Deduce
Reach a conclusion from the information given.
Define
Give the precise meaning of a word or phrase as concisely as possible.
Derive
Manipulate a mathematical equation to give a new equation or result.
Describe
Give a detailed step-by-step account, including all relevant information.
Design
Produce a plan, model or simulation.
Determine
Find the only possible answer.
Discuss
Give an account including, where possible, a range of arguments,
assessments of the relative importance of various factors or
comparisons of alternative hypotheses.
Distinguish
Give the differences between two or more different items or concepts.
Draw
Illustrate by means of pencil lines (add labels unless told otherwise).
Estimate
Find an approximate value for an unknown quantity, based on the
information provided and prior scientific knowledge.
Evaluate
Assess the consequences and limitations.
Explain
Give a clear account including causes, reasons or mechanisms.
Identify
Find an answer from a number of possibilities.
List
Give a sequence of names or other brief answers, with no elaboration.
Each point in your sequence should be clearly separated from the rest.
Measure
Find a value for a quantity (include units as well).
Outline
Give a brief account or summary (include essential information only).
Predict
Give an expected result.
Solve
Obtain an answer using algebraic and/or other numerical methods
(show working unless instructed otherwise).
State
Give a specific name, value or other brief answers (no supporting
argument or calculation is necessary).
Suggest
Propose a hypothesis or an alternative answer.
(S)SciBioWB_Frontmatter.indd vi
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A Guide to Essay Writing
Essay questions are designed to test your ability to describe and explain biological
processes, principles and concepts. Marks will be awarded according to the
points presented.
It is important to read the essay question carefully before attempting to answer it.
Do highlight key terms and words in the question. Many students misunderstand the
question and as a result, their essays are inappropriate. Sometimes an essay question
consists of two or more parts. Ensure that you have answered every part.
Before starting to write, plan the essay. Here is how an essay may be planned:
1.
2.
3.
4.
Note the topics involved.
Write down all the relevant points and ideas.
Organise these points and ideas so that a logical sequence is formed.
Develop an introduction, followed by the sequence of points and a conclusion.
While writing, keep referring to the essay plan to stay on track. Avoid using long
sentences in your essay.
A few examples are given below to illustrate some key points that should be taken
note of while writing your essay.
Example 1
Describe the functions of each of the following in the nutrition of a mammal:
(a) hydrochloric acid
(b) liver
[2]
[3]
This is considered a ‘recall’ or ‘knowledge’ question. Note that the question requires a
description of functions that relate to nutrition in a mammal. Care must be taken when
writing so that the essay does not include items that are out of point. This is especially
true for the functions of the liver. Although there are several functions of the liver listed
in the Textbook, the essay must only mention the functions that relate to nutrition
in mammals.
Example 2
Compare nutrition in mammals with nutrition in green plants.
[5]
A common mistake, which most students make, is to state only the differences.
An appropriate answer requires both similarities and differences to be stated.
vii
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(S)SciBioWB_Frontmatter.indd viii
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Class:
Worksheet 1
(
Name:
)
Date:
Cells
for Chapter 2
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Organ
system
Organ
specialised
cells
Cell
Tissue
Red blood cell
Xylem
vessel
Organism
Root
Cell wall
(only in plants )
made up of
Cytoplasm
Nucleus
Cell membrane
which
which
surrounds
Contains
chromatin
(DNA)
Mitochondria
hair cell
which
Is partially
permeable and
encloses the
cytoplasm
contains
organelles
such as
Ribosomes
Vacuoles
Chloroplasts
(in plant cells)
Energy source
for cells
Synthesise
proteins
© 2013 Marshall Cavendish International (Singapore) Private Limited
(S)SciBioWB_01.indd 1
Store
substances
within the cell
Site of
photosynthesis
Worksheet 1
1
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
For questions 1, 2 and 3, refer to the diagram shown below.
4
1
2
5
6
3
1.
2.
What are the numbered parts of the cell?
1
2
3
A
Cell surface membrane
Cell wall
Cytoplasm
B
Cell wall
Cell surface membrane
Cytoplasm
C
Cytoplasm
Cell surface membrane
Cell wall
D
Cytoplasm
Cell wall
Cell surface membrane
Which structure traps light energy?
A
B
C
D
3.
3
4
5
6
1
1
2
2
Worksheet 1
(S)SciBioWB_01.indd 2
( B )
Which structures are found in both plant and animal cells?
A
B
C
D
2
( B )
and
and
and
and
2
3
3
4
( C )
© 2013 Marshall Cavendish International (Singapore) Private Limited
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4.
The electron micrograph of a section of a liver cell taken from an animal is shown below.
X
What is the function of structure X?
A
B
C
D
5.
( C )
An animal cell had its nucleus removed by means of a fine glass tube. The cell was not otherwise
damaged. It was put in a solution that induces cell division. It continued to survive for a day, but did
not undergo cell division. An intact cell, used as a control, divided twice in that time. What can you
conclude from this experiment about the role of the nucleus in the cell?
A
B
C
D
6.
Contains enzymes for the breakdown of unwanted organelles
Controls the synthesis of proteins
Releases energy for use by the cell
Transports molecules such as proteins, lipids and steroids
The
The
The
The
nucleus
nucleus
nucleus
nucleus
controls the normal activity of the cell.
is essential for cell division.
is essential for life.
is the only part of the cell that contains DNA.
( B )
The diagram below shows a three-dimensional view of a plant cell with some of its internal
structures revealed.
A
B
C
D
The diagram below shows a section of the cell (viewed from above) after it has been sliced along a
plane. At which plane, A, B, C or D, has the cell been sliced?
( D )
© 2013 Marshall Cavendish International (Singapore) Private Limited
(S)SciBioWB_01.indd 3
Worksheet 1
3
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7.
The diagram below shows plant cells observed under a microscope.
What is the likely function of these plant cells?
A
B
C
D
8.
Carry out photosynthesis
Carry out respiration
Provide support to the plant
Transport water in the plant
( A )
The diagram below shows four types of cells that are not drawn to scale.
1
2
3
4
Which cells are involved in the transport of substances in a living organism?
A
B
C
D
4
1 and 2
1 and 4
2 and 3
3 and 4
Worksheet 1
(S)SciBioWB_01.indd 4
( D )
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9.
Which of the following correctly relates these specialised cells to their functions?
Absorption of water
and mineral salts
Conduction and
support
Transport of oxygen
A
Red blood cell
Xylem
Root hair cell
B
Root hair cell
Xylem
Red blood cell
C
Xylem
Red blood cell
Root hair cell
D
Xylem
Root hair cell
Red blood cell
10. The stomach is considered as an organ, because
A
B
C
D
it
it
it
it
consists of a group of cells working together to digest food
consists of different tissues working together to digest food
is a basic unit of life
produces digestive enzymes to digest food
( B )
.
( B )
11. Which of the following correctly lists the organs in flowering plants?
A
B
C
D
Flower, leaf, stem, root
Flower, leaf, stem, root hair cell
Leaf, stem, root, root hair cell
Stem, root, root hair cell
© 2013 Marshall Cavendish International (Singapore) Private Limited
(S)SciBioWB_01.indd 5
( A )
Worksheet 1
5
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The diagram below shows the structures visible in a plant cell, when it is examined under an
electron microscope.
H
A
G
B
F
C
E
D
(a) Identify the parts labelled A to H.
A:
Nucleus
E:
Cell wall
B:
Ribosome
F:
Cytoplasm
C:
Chloroplast
G:
Vacuole
D:
Cell surface membrane
H:
Mitochondrion
(b) State one function each for A, B, G and H.
A controls cell activities.
B is needed to synthesise proteins in the cell.
G is used to store water and food substances.
H is the site of aerobic respiration.
(c) What feature(s) in this cell indicate(s) that it can photosynthesise?
The presence of chloroplasts
(d) State one structural difference between structures D and E.
D is partially permeable, while E is fully permeable. / D is made up of mainly phospholipids, while E
is mainly made up of cellulose.
6
Worksheet 1
(S)SciBioWB_01.indd 6
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2.
The diagram below shows some normal blood cells, when they are viewed under a microscope.
(a) Name the type of blood cells shown, and state the function of these cells.
Red blood cells
To transport oxygen from the lungs to all the cells in the body
(b) Explain how a red blood cell is adapted for its function.
The red blood cell does not have any nucleus; instead it has haemoglobin that carries oxygen. Its
biconcave shape increases surface area to volume ratio for more efficient absorption of oxygen. As it is
elastic, it can squeeze through capillaries easily.
© 2013 Marshall Cavendish International (Singapore) Private Limited
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Worksheet 1
7
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3.
(a) Complete the table below.
Cells
A
B Tissue
endothelial layer
muscle
Organ
C
liver
(b) Arrange A, B, and C in increasing order of complexity.
Least complex
A
8
Worksheet 1
(S)SciBioWB_01.indd 8
Most complex
B
C
© 2013 Marshall Cavendish International (Singapore) Private Limited
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Section C: Free-Response Questions
Answer the following questions.
1.
Explain how the structure of a root hair cell is adapted for its function.
A root hair cell absorbs water and dissolved mineral salts from the soil into the plant.
It has a long, narrow extension (the root hair) that increases surface area to volume ratio for
water absorption. There is also a large number of mitochondria in the cell to provide energy for active
transport.
2.
Compare the structural differences between a typical animal cell and a typical plant cell.
The cell wall is present in a plant cell, but not in an animal cell.
Chloroplasts are present in a plant cell, but not in an animal cell.
A plant cell has a large central vacuole, but an animal cell has many small vacuoles.
3.
The human skin is composed of many structures such as blood vessels, epidermal cells, nerves
and sweat glands. Explain whether we should classify the skin as a tissue or an organ.
A tissue is a group of cells that work together to perform a specific function.
An organ is made up of different tissues working together to perform a specific function.
Skin has structures or tissues like blood vessels, epidermal cells, nerves and sweat glands.
These structures work together to contribute to the functions of skin.
Therefore, the skin is an organ.
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Worksheet 1
9
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
Structured
FreeResponse
1, 2, 3, 4,
5, 6
1
–
2.1
8, 9
2
1
2.2
(c) Compare the structures of typical animal
and plant cells
–
–
2
2.1
(d) Differentiate between cell, tissue, organ
and organ system
10, 11
3
3
2.2
7
–
–
2.1
(a) Identify cell structures in diagrams
or micrographs, and state the functions of
organelles
(b) State the relationship between cell
structure and function
(e) Examine and identify typical plant and
animal cells under a microscope
10
Textbook
section(s)
MultipleChoice
Worksheet 1
(S)SciBioWB_01.indd 10
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Class:
Worksheet 2
(
Name:
)
Date:
Movement of Substances
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Movement
rate affected by
Diffusion
Osmosis
Net movement of particles
from a region of
higher concentration
to a region of
lower concentration
Net movement of water molecules
from a solution of higher
water potential to a solution of
lower
water potential, across
a partially permeable membrane
affected by
affected by
Concentration gradient
Swell
(may burst)
animal
cells
Turgid
plant
cells
Cells in solution
of higher water
potential
for Chapter 3
CONNECT IT!
Surface area to
volume ratio
Water
potential
gradient across a partially
permeable membrane
Cells in solution
of lower water
potential
animal
cells
Shrink in
size
e.g. red
blood cells
plant
cells
Flaccid,
shrink in size
Crenation
Cell membrane
and cytoplasm
pull away from
the cell wall
Plasmolysis
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
The two gas jars shown below were left for a long time to let oxygen and carbon dioxide molecules
diffuse through them.
oxygen
molecule
carbon dioxide
molecule
gas jar
How would the molecules be arranged after a long time?
A
B
C
D
( A )
For questions 2 and 3, refer to the diagram below, which shows the appearance of a typical plant cell
after it was placed in concentrated sugar solution for 15 minutes.
1
2
3
4
2.
Which of the numbered structures are partially permeable?
A
B
C
D
3.
( C )
Which of the following occupies the region labelled X?
A
B
C
D
12
1 and 2
1 and 4
2 and 3
2 and 4
Air
Cell sap
Sugar solution
Water
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( C )
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4.
The diagram shows the results of an experiment after 3 hours. The liquid in the glass tube rose to
point X from initial level.
X
initial level
Visking tubing
(partially
permeable)
container
0.4 mol/dm3 sucrose
0.2 mol/dm3 sucrose
In a second experiment, what change could be made to cause the liquid to rise higher than
point X after 3 hours?
A
B
C
D
5.
( C )
Which of the following statements is true of these cells, assuming that both cells have the same
thickness?
A
B
C
D
Y
Cell X is specially adapted for active transport, and Y for diffusion.
Cell X has a greater surface area to volume ratio than Y.
Cell Y is modified for absorbing materials into the cell.
Diffusion of oxygen into cell Y occurs at a higher rate than X.
( D )
Dissolved gases move between the blood and body cells in our system by a certain process.
What is this process known as?
A
B
C
D
Absorption
Diffusion
Osmosis
Respiration
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.
diffusion
filtration
osmosis
phagocytosis
X
7.
( D )
The process by which water enters the root hair cell is called
A
B
C
D
6.
A larger container with the same volume of liquid
A smaller container with the same volume of liquid
Change the sucrose solution in the Visking tubing to water.
Change the sucrose solution in the container to water.
( B )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
In an experiment, a peeled potato was cut into half, and wells were created as shown in the diagram
below. One potato half was boiled before the experiment.
Both potato halves were soaked in 10 cm3 of distilled water, before their wells were filled with
5 cm3 of 10% salt solution.
peeled raw
potato
10% salt
solution
peeled
boiled
potato
distilled
water
(a) Predict what will happen to
(i)
the levels of the solution in the well of the peeled raw potato, and distilled water in the
dish after 24 hours.
The level of the solution in the well rises/increases, while the level of distilled water in the dish
drops/decreases.
(ii) the levels of the solution in the well of the peeled boiled potato, and distilled water in
the dish after 24 hours.
The level of the solution in the well drops/decreases, while the level of distilled water in the dish
rises/increases.
(b) Explain your answer in (a)(i) using your knowledge of diffusion and osmosis.
Cells in the peeled raw potato have partially permeable cell membranes. Water potential of
distilled water is greater than the water potential of cell sap, which is in turn greater than the water
potential of 10% salt solution. Water moves into the cells first, then to the 10% salt solution down a
water potential gradient by osmosis to achieve equilibrium.
14
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2.
Six identical cylinders of fresh potato (A to F), each weighing 10 g, were immersed in salt solutions of
different concentrations for two hours. They were removed and reweighed. The change in mass of
each cylinder was recorded in a bar graph as shown.
Change in mass of
potato cylinder/g
12
11
10
9
8
7
6
5
4
3
2
1
E (6)
A (4)
B (3)
F (1)
0
–1
–2
–3
–4
–5
–6
–7
Fresh potato
cylinder
D (–2)
C (–6)
(a) Which cylinder has been immersed in salt solution with:
(i)
the highest concentration?
(ii) the lowest concentration?
C
.
E
(iii) a concentration closest to that of the potato cells?
.
F
.
(b) Explain the changes in the cells of potato cylinder D.
The potato in cylinder D was placed in a solution that had a lower water potential than the cell
sap. Water moved from the cells into the solution by osmosis, down a water potential gradient (from a
region of higher water potential to a region of lower water potential). Hence, the cells lost water and
shrank in size, causing the mass of the potato in cylinder D to decrease.
(c) Calculate the percentage increase in mass shown by potato cylinder A.
Original mass of A = 10 g
Change in mass of A = 4 g
Percentage increase = 4 × 100%
10
= 40%
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(d) Suggest how the experiment can be extended to find the concentration of the potato cells.
Step 1: Prepare 5 solutions with varying concentrations of salt (e.g. 10%, 5%, 2%, 1%, 0%).
Step 2: Put three identical cylinders of fresh potato in each salt solution. After 30 minutes to an hour,
record the change in length. Step 3: Plot the graph of change in length against concentration of salt
solution. Where the line cuts through the x-axis, the value of the salt concentration will be equal to the
concentration of the potato cells since there is no change in length at that point.
3.
In an experiment, six potato strips of equal mass were cut and placed in separate test tubes as
shown in the diagram below. Each test tube contained sugar solution of a different concentration.
A
B
C
D
E
F
After six hours, the potato strips were removed from the test tubes and dried carefully using a paper
towel. They were then weighed again. Some of the potato strips had gained in mass, while some had
lost in mass. The changes in mass are shown in the table below.
16
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Test tube
Amount of sugar in g in
100 cm3 of solution
Change in mass in g,
increase (+) or decrease (−)
A
18
− 0.40
B
14
− 0.02
C
12
+ 0.20
D
10
+ 0.30
E
6
+ 0.60
F
2
+ 0.90
© 2013 Marshall Cavendish International (Singapore) Private Limited
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(a) Draw a graph to show the results of the experiment.
Graph of change in mass of potato strips against concentration
of sugar solution
Change in
mass/g
1.0
×
0.8
0.6
×
0.4
×
0.2
×
0
2
4
6
8
10
12
×
14
16
18
20
Concentration/g/100 cm3
−0.2
−0.4
×
−0.6
(b) Which test tube contains sugar solution with the highest concentration? Explain your answer.
Test tube A contains sugar solution with the highest concentration, because the decrease in mass is
the largest.
(c) Use the graph to estimate a value for the sugar concentration in the potato cells.
13.6 g/100 cm3
(d) Explain why the potato strip in test tube F had increased in mass.
The water potential of the sugar solution in test tube F is higher than the water potential of the
cell sap. Water moves from the region of higher water potential (sugar solution) to the region of lower
water potential (potato cells) by osmosis. Hence, there is an increase in mass.
(e) Suggest two ways to increase the accuracy and reliability of this experiment.
Firstly, the difference in concentration between the sugar solutions could be decreased. Secondly, we
can use more than one potato strip for each sugar concentration, and calculate the average change in
mass of each strip.
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4.
A student carried out an experiment to find out the effect of sugar concentration on chilli strips.
Three chilli strips of equal length were cut and placed in Petri dishes labelled 1, 2 and 3. Each
Petri dish contained different concentrations of salt solution –– 1% salt solution, 0.5% salt solution
and 0.1% salt solution. The diagram below shows the appearance of the chilli strips initially and
after 60 minutes.
outer surface
(cuticle)
dish containing
salt solution
At the start
of the experiment
outer surface
(cuticle)
outer surface
(cuticle)
outer surface
(cuticle)
After 60
minutes
dish 1
dish 2
dish 3
(a) Based on the appearance of the strips after 60 minutes, deduce the concentration of the salt
solution in each of the Petri dishes.
Dish 1: 1% salt solution
Dish 2: 0.1% salt solution
Dish 3: 0.5% salt solution
(b) Explain how the change in the chilli strip in dish 2 was brought about.
The salt solution in dish 2 had a higher water potential than the cell sap in the chilli strips. Water
from the salt solution moved into the cells near the inner surface of the chilli strip by osmosis. Thus,
the cells increased in size. However, the cells near the outer surface of the chilli strip are protected
by the inelastic waterproof cuticle that does not allow water to pass through. Hence, there is
differential expansion of the cells, with the cells near the outer surface not expanding as much as the
cells near the inner surface. This results in the chilli strip curving towards one side.
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Section C: Free-Response Question
Answer the following question.
1.
Write a short paragraph to explain why the child with a bleeding leg wound, shown in the diagram, is in
danger of being bitten by the piranhas.
blood
piranhas
When the blood from the open wound enters the water, a diffusion gradient is set up.
The blood molecules will move from a region of higher concentration (boy’s leg) to a region of lower
concentration (near the piranhas).
As the blood diffuses into the water, the piranhas will be attracted to the blood and will attack the boy.
WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
(a) Define diffusion, and state its
importance in nutrient uptake and gas
exchange in organisms
(b) Define osmosis, and describe the effects
of osmosis in plant and animal tissues
MultipleChoice
Structured
FreeResponse
1, 6, 7
1
1
2, 3, 4, 5
1, 2, 3, 4
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Textbook
section(s)
3.1
3.2
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Class:
Worksheet 3
(
Name:
)
Date:
Nutrients
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
for Chapter 4
CONNECT IT!
Nutrients
Minerals
Organic
Inorganic
Water
Carbohydrates
Fats
Proteins
broken
down by
consist of
Hydrolysis
Amino acids
Fatty acids
may be
Glycerol
linked
by
Peptide
bonds
forming
Polypeptides
Monosaccharides
Disaccharides
Polysaccharides
formed by
Fructose
Maltose
Cellulose
Galactose
Sucrose
Starch
Glucose
Lactose
Glycogen
Condensation
reaction
formed by condensation reaction
Reducing sugars
(except sucrose)
Food test
Benedict's
Brick-red
solution
precipitate
(large amounts of
reducing sugar)
Food test
Iodine
test
Blue-black
coloration
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Food test
Food test
Ethanol emulsion test
Biuret
Cloudy white emulsion
and heat is given off
coloration
test
Violet
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Which statement correctly describes one of the roles of water in the human body?
A
B
C
D
2.
( A )
Which form of carbohydrate is usually stored in the human body?
A
B
C
D
3.
As a solvent to dissolve some substances
As a source of energy
As an insulating layer for the body
As material for the build-up of muscles
Glucose
Glycogen
Glycerol
Starch
( B )
The diagram below shows the breakdown of three types of organic molecules.
X
Y
Z
What are the identities of X, Y, and Z?
22
X
Y
Z
A
Carbohydrate
Fat
Protein
B
Carbohydrate
Protein
Fat
C
Protein
Carbohydrate
Fat
D
Protein
Fat
Carbohydrate
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( B )
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4.
A student was given three test tubes, each containing two food substances. The student was asked
to identify the food substances present in each test tube. The table below shows the results of the
student’s tests.
Reagent added
Test
tube
Biuret solution
Benedict’s solution
Iodine solution
X
Solution remains blue
Orange-red precipitate formed
Blue-black colour observed
Y
Violet colour observed
Orange-red precipitate formed
Solution remains brown
Z
Violet colour observed
Solution remains blue
Blue-black colour observed
Which conclusion is consistent with the results?
A
B
C
D
5.
Egg white and maltose are present in test tube X.
Egg white and starch are present in test tube X.
Egg white and starch are present in test tube Z.
Starch and maltose are present in test tube Y.
( C )
Food tests are carried out on four solutions. Which solution contains only glucose and proteins?
( indicates a positive reaction; indicates negative result.)
Solution
Benedict’s test
Biuret test
Ethanol emulsion test
A
B
C
D
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( C )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
2.
A student conducted food tests on a solution given to him. Complete the table to show the
conclusions which can be drawn from the tests.
Food test
Observation
Conclusion
Sample mixed with Benedict’s
solution and boiled
Orange-red precipitate formed
Reducing sugar is present.
Sample mixed with sodium
hydroxide and 1% copper
sulfate, drop by drop
Violet colour observed
Protein is present.
Sample mixed with iodine
solution
Blue-black colour observed
Starch is present.
Sample mixed with ethanol and
then water
White emulsion formed
Fat is present.
(a) Name the type of reaction by which amino acids are linked together.
Condensation
(b) Name the product formed when many amino acids are linked together.
Polypeptide
3.
The table below refers to three organic molecules. Complete the table.
Carbohydrates
Elements present in
the molecule
Basic units
Type of reaction to
convert complex
form to simpler form
Two functions of the
molecules in a living
organism
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C, H, O
Proteins
C, H, O,
C, N
H, O, N
maybe
P
S S
maybeand
P and
Monosaccharides
Amino acids
Hydrolysis
Hydrolysis
Any two of the
following: Energy
source / Production of
mucus / Constituent
of cellulose cell wall
Any two of the
following: Synthesis of
enzymes / Production
of hormones /
Production of
antibodies / Growth
and repair
Fats
C, H, O
Fatty acids and glycerol
Hydrolysis
Any two of the
following: Energy
source / Solvent for
fat-soluble vitamins /
Insulating layer
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Section C: Free-Response Question
Answer the following question.
1.
David is given a slice of cucumber and a slice of tomato. He is curious to find out if the food samples
contain reducing sugars, proteins or fats. Outline the experiments that he should conduct to test the
food samples for reducing sugars, proteins and fats.
1. Cut the cucumber into small pieces. Divide the cucumber pieces into three portions.
2. Add 1 cm3 of distilled water to each portion. Mix well and decant.
3. Do the following tests:
(i) Reducing sugar test — Benedict’s test + observations
(ii) Protein test — Biuret test + observations
(iii) Fat test — Ethanol emulsion test + observations
4. Repeat for tomato.
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
(a) Explain the importance of water in
living organisms
(b) Describe how glycogen is formed from
simpler glucose molecules
26
MultipleChoice
Structured
FreeResponse
1
Textbook
section(s)
4.2
2, 3
3
4.3
(c) Describe how fats are formed from
glycerol and fatty acids
3
3
4.4
(d) Describe how proteins and
polypeptides are formed from amino
acids
3
2, 3
4.5
(e) Carry out experiments to test for the
presence of reducing sugars, starch,
fats and proteins
4, 5
1
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1
4.3, 4.4, 4.5
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Class:
Worksheet 4
(
Name:
)
Date:
Enzymes
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Enzymes
Functions
Build
up
complex
substances
Break down
complex
substances
are
Biological
catalysts
Mode of action
Characteristics
Speed up
reactions
Lower activation
energy
small
Only
amount needed
Lock and key
hypothesis
mainly
made of
for Chapter 5
CONNECT IT!
Proteins
Denaturation occurs
at extremes of
temperature or pH
Class
based on type
of reaction
catalysed e.g.
Hydrolases
Enzymes are specific
Work best at optimum
temperature and
optimum pH
Substrate fits
into enzyme’s
active site
forms
Enzyme-substrate
Catalyse reversible
reactions
complex
forms
Product
once formed,
product leaves
Enzyme molecule
free to take part
in another reaction
Temperature
affected by
pH
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Enzymes are
A
B
C
D
2.
proteins that are used up in chemical reactions
proteins that catalyse chemical reactions at any temperature
proteins that catalyse chemical reactions in living organisms
proteins that speed up the breakdown of complex compounds into simpler substances ( C )
Enzymes are added to biological washing powders to remove stains. Which would be the most
effective enzymes in removing chocolate milk stains?
A
B
C
D
3.
.
Amylase and catalase
Amylase and maltase
Protease and catalase
Protease and lipase
( D )
The diagram shows an experiment that was carried out in water at different temperatures.
water
mixture of amylase and
starch in a Visking tubing
The water was tested for the presence of reducing sugar at 30-second intervals. At which temperature
would reducing sugar be detected most rapidly?
A
B
C
D
28
10°C
20°C
40°C
100°C
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( C )
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4.
Which characteristic of enzymes is the diagram below trying to illustrate?
+
+
enzyme
subtrate A
complex X
enzyme
+
product Y
product Z
+
enzyme
A
B
C
D
5.
subtrate B
Enzymes are specific in nature.
Enzymes speed up chemical reactions.
Enzymes work best at optimum pH.
Enzymes work best at optimum temperature.
In the ‘lock and key’ hypothesis, what is the ‘lock’, and what is the ‘key’?
Lock
Key
A
Enzyme
Substrate
B
Substrate
Enzyme
C
Product
Enzyme
D
Enzyme
Product
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( A )
( A )
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6.
Which graph correctly shows the effect of pH on the rate of reaction of an enzyme-catalysed
reaction?
A
B
Rate of
reaction
Rate of
reaction
pH
pH
C
D
Rate of
reaction
Rate of
reaction
pH
pH
( B )
7.
Curve X represents an enzyme-catalysed reaction under optimum conditions. Curve Y shows the
action of the same enzyme on the same substrate, but with one alteration to the reaction condition.
Substrate
concentration/%
100
curve Y
50
curve X
Time/min
Which of the following factors could give the results shown by curve Y?
A
B
C
D
30
A 10°C decrease in temperature
A decreased substrate concentration
An increased enzyme concentration
An increased substrate concentration
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( A )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
X is an unknown substance extracted from a living organism. A student was required to investigate
the ability of X to bring about the hydrolysis of starch. She set up two water baths, one containing
boiling water (100°C) and the other containing water at 36°C.
The student used the water baths and set up the reaction mixtures as follows:
• Test tube 1: 1 cm3 of X (pre-treated at 100°C for 1 minute) + 9 cm3 of distilled water
• Test tube 2: 1 cm3 of X (pre-treated at 36°C for 1 minute) + 9 cm3 of distilled water
• Test tube 3: 1 cm3 of X (pre-treated at 100°C for 1 minute) + 9 cm3 of starch
• Test tube 4: 1 cm3 of X (pre-treated at 36°C for 1 minute) + 9 cm3 of starch
• Test tube 5: 1 cm3 of distilled water + 9 cm3 of starch
The reaction mixtures were placed in the water bath that contained water at 36°C. After 15 minutes,
the student tested the mixture in each test tube for the presence of reducing sugar using
Benedict’s test. Her observations were as follows:
Test tube
Observation for Benedict's test
1
Mixture remained blue
2
Mixture remained blue
3
Mixture remained blue
4
Mixture turned from blue to orange-red
5
Mixture remained blue
(a) Based on the student's observations, what is the action of substance X on starch?
X breaks down starch (a non-reducing sugar) into a reducing sugar (maltose).
(b) What evidence supports that substance X contains an enzyme?
X is specific in action. That is, it hydrolyses only starch. / When X is pre-treated at 100°C
(test tube 3), it does not change starch to maltose. This shows that X is an enzyme, and is denatured
at high temperatures.
(c) Suggest two experiments that the student could perform to find out if substance X contains
an enzyme.
The student could either change the pH of the reaction mixture to see if X is sensitive to pH, or the
student could use the Biuret test to check if X contains protein, since all enzymes are made
of proteins.
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(d) What is the purpose of including test tubes 1 and 2? Why are they necessary?
Test tubes 1 and 2 act as controls. Both test tubes show that X (an exract from a living organism)
does not originally contain reducing sugar. Hence, when starch is added into test tube 4, and the
content is eventually tested positive for reducing sugar, it shows that the reducing sugar is due to the
hydrolysis of starch by X at 36°C.
2.
An experiment was conducted to investigate the action of the enzyme amylase in solutions of
different pH. Eight test tubes were set up, each filled with 5 cm3 of buffered solutions of pH 3, 4,
5, 6, 7, 8, 9 and 10 respectively. 5 cm3 of amylase and 30 cm3 of starch were then added to each
test tube, in sequence. 1 cm3 of the mixture was taken out every 30 seconds, and tested for starch
using the iodine test, until it gave a negative starch test. The time taken to digest all the starch was
recorded. The results are represented in the graph below.
Time taken to
convert all the
starch/min
1
2 3 4 5 6 7 8 9 10
pH
(a) What variable (factor) was being tested in this experiment?
It was the pH of the reaction.
(b) Name two conditions that had to be kept constant.
The volume of reagents and temperature had to be kept constant.
(c) From the results, what is the optimum pH of amylase? Explain your answer.
It is pH 7. This is because, amylase took the shortest time to convert the starch to maltose
at pH 7.
(d) Sketch on the diagram below, how the amount of substrate varies during the reaction at
optimum conditions.
Amount of substrate
left in reaction/
arbitrary unit
1 2 3 4 5 6 7 8 9 10
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Time taken/min
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3.
A dish is filled with milk agar made by mixing milk with agar powder. Four holes are cut in the milk
agar, and each hole is filled with the substances shown.
A
distilled water
B
D
milk agar
protease solution
C
protease solution + concentrated
sodium hydroxide solution
boiled protease solution
(a) Write a word equation to show the effect of protease on milk proteins.
milk proteins
protease
polypeptide/peptide/amino acids
(b) After one day of incubation at 37°C, the agar plate is put under a light to observe for clear
zones around the holes.
(i)
Why should one look for clear zones around the holes?
If the enzyme digested the milk proteins in the agar, it will turn the cloudy areas into a clear zone.
(ii) State what you would observe in each hole.
Hole A: Clear zone seen
Hole B: No clear zone seen
Hole C: No clear zone seen
Hole D: No clear zone seen
(c) Explain the purpose of the distilled water in hole D.
The distilled water in hole D is used as a control to show that it is the protease that digests milk
proteins to polypetide/peptide/amino acids.
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4.
The enzyme catalase catalyses the breakdown of hydrogen peroxide to water and oxygen. An
experiment was set up to find the initial rate of reaction of catalase. The volume of oxygen is
measured at every 30-second interval. The results are shown below.
Time/s
30
60
90
120
150
180
210
240
270
300
Gas volume collected/cm3
6
12
16
19
22
23
24
25
25.5
26
(a) Explain the meaning of 'catalyse'.
It means to speed up the rate of a chemical reaction.
(b) Plot a graph of the results obtained.
Graph of volume of gas collected against time
×
×
×
(110, 24)
×
×
Gas volume
collected/
25
cm3
×
20
×
×
15
×
10
×
5
(15, 5)
0
50
100
150
200
250
300
Time/s
(c) From the graph, calculate the initial rate of reaction. Show your working clearly.
Initial rate of reaction =
Y1 – Y0
X1 – X0
24 – 5
= 110 – 15
19
1
= 95 = 5 = 0.2 cm3/s
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(d)
Name two conditions or factors that had to be kept constant in this experiment.
Any two of the following: Temperature / pH / Amount of enzyme used
LEARN & APPLY
Go through the worked example below, then try to answer the Free-Response Questions.
Worked Example
Explain the importance of enzymes in plants.
Thought Process
Giving examples will help to answer the questions. It is important to take note that the question is
asking for plants.
Answer
Points to cover
1. Enzymes help to speed up chemical reactions in plants.
2. Without enzymes, many reactions in plants will take a long time to complete.
3. For example, photosynthesis and respiration require enzymes to speed up these reactions.
4. Enzymes are also important in seed germination. Enzymes will digest the stored starch into glucose
for the embryo to germinate and grow.
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Section C: Free-Response Questions
Answer the following questions.
1.
Explain, with reasons and examples, how the biological activity of an enzyme may be affected by:
(a) changes in pH; and
(b) increasing temperatures.
(a) Enzymes are sensitive to the acidity or alkalinity of a solution. Some work best in acidic
conditions, for example, pepsin in the stomach, whereas others work best in alkaline
conditions, for example, pancreatic amylase. Extreme changes in pH denature the enzyme which is
protein in nature. When an enzyme is denatured, it loses its active site shape, and the substrate can
no longer fit into it. So its biological activity decreases.
(b) Enzymes work best under optimum temperature. A high temperature increases the kinetic energy
supplied to the reacting molecules, which then increases the rate of effective collisions between
substrates and enzymes. The rate of the reaction increases up to the optimum temperature. Beyond
the optimum temperature, an enzyme, being protein in nature, will be denatured, and the active site
will lose its shape. The rate of the biological reaction will, therefore, decrease.
2.
(a) Describe the major properties of enzymes.
(b) Discuss the mode of action of an enzyme in terms of active site, enzyme-substrate complex
and enzyme specificity.
(a) Enzymes are highly specific in action. They are mainly made up of proteins. Enzymes speed up
chemical reactions without themselves being changed at the end of the reaction. Small amounts
of enzymes are capable of catalysing a large number of reactions. Enzymes work within a narrow
range of conditions. For instance, enzymes have an optimum working temperature, and beyond a
certain temperature, they are denatured. Enzymes are also affected by the acidity or alkalinity of the
solutions in which they act.
(b) An enzyme acts on a substrate and converts it into a product. The binding of a substrate to the
active site of an enzyme is specific in nature. A substrate fits into an enzyme’s active site, like how a
key fits into a lock, forming an enzyme-substrate complex. The active site on the enzyme is a region
on the protein with a specific shape where the substrate binds.
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
MultipleChoice
Textbook
section(s)
(a) Define an enzyme
1
5.1
(b) State the function of enzymes
1
5.1
(c) Explain how enzymes are classified
2
3
4, 5, 7
1, 3, 5
(d) Describe the characteristics of
enzymes
(e) Describe the mode of enzyme action
based on the ‘lock-and-key’ hypothesis
5
(f) Explain how conditions such as
temperature and pH can affect the rate
of an enzyme-catalysed reaction
3, 6, 7
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Structured
FreeResponse
1, 2, 4
5.1
2
5.2
2
5.2
1
5.2
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Class:
Worksheet 5
(
Name:
)
Date:
Nutrition in Humans
for Chapter 6
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Nutrition
consists
of
Feeding
Digestion
in
movement
along
Alimentary canal
Teeth
Salivary
Buccal cavity
(mouth)
glands
Absorption
Assimilation
Peristalsis
rhythmic, wave-like
muscular contractions
of the gut wall
Salivary
secrete
amylase
Tongue
Pharynx
Amylase
Maltase
Protease
produce
enzymes
contains
intestinal
cells
Oesophagus
Stomach
Lipase
Hydrochloric acid
Duodenum
secretes
Ileum
Gastric
juice
contains
Small intestine
Pepsin
Jejunum
Large
intestine
Organs and glands
associated with the gut
adapted for
absorption
Rectum
Liver
Gall bladder
Anus
secretes
stored in
Capillaries
Villi
Folds
Egestion
join to
form
Hepatic
portal vein
transports
sugars to
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Pancreas
Pancreatic
juice
secretes
Bile
Glucagon
deamination
of amino
acids
Urea
Insulin
Worksheet 5
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Carbohydrate digestion occurs mainly in the
A
B
C
D
2.
( B )
Hepatic artery
Hepatic portal vein
Hepatic vein
Pulmonary artery
( B )
ileum
large intestine
liver
stomach
( C )
What happens to alcohol after it enters the human body?
A
B
C
D
40
To break down fat into fatty acids and glycerol
To emulsify fat into minute fat globules
To transport the digested fat into the bloodstream
To transport the digested fat into the lacteals
Excess amino acids are toxic to the human body, and must be deaminated. Excess amino acids are
.
deaminated in the
A
B
C
D
5.
( A )
Which blood vessel transports absorbed food substances to the liver?
A
B
C
D
4.
mouth and duodenum
mouth and stomach
stomach and duodenum
stomach and ileum
What is the function of bile?
A
B
C
D
3.
.
Alcohol is absorbed by the stomach.
Alcohol is deaminated by the liver.
Alcohol is detoxified by the liver.
Alcohol is passed out as urine.
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( C )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
Complete the table below, which illustrates the process of digestion.
Region of digestion
Active enzyme
Substrate
Product(s)
Mouth
Amylase
Starch
Maltose
Stomach
Pepsin
Proteins
Polypeptides
Maltase
Maltose
Glucose
Peptidase
Polypeptides
Amino acids
Lipase
Fats
Fatty acids and glycerol
Duodenum
2.
The diagram shows part of the human digestive system.
D
A
E
B
C
(a) Identify A.
The stomach
(b) What are the functions of parts B, C and E during digestion?
B: Produces pancreatic enzymes
C: Site of completion of digestion / absorption of digested products
E: Storage of bile
(c) D produces a substance that is important for fat digestion. State what this substance is,
and its role in fat digestion.
D (the liver) produces bile. Bile emulsifies fats, facilitating the action of lipase.
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(d) (i)
State the blood vessel that carries blood from C to D.
Hepatic portal vein
(ii) State two end-products of digestion carried by this blood vessel.
Amino acids and glucose
Section C: Free-Response Questions
Answer the following questions.
1.
A patient suffering from gall bladder disease has his gall bladder removed. Suggest and explain the
type of diet and lifestyle that he should adopt after his gall bladder is removed.
The patient should eat smaller and more frequent meals because when the gall bladder is removed, bile is no
longer being stored but drains continuously into the intestine. He should also avoid fatty food because there
is less bile to emulsify the fats into smaller fat globules. A high-fat diet will not be digested properly and will
result in diarrhoea or constipation.
2.
Hepatitis B is a viral infection of the liver. Patients suffering from severe Hepatitis B infection may
die eventually due to liver failure. Explain, using your knowledge of the liver, why patients suffering
from Hepatitis B may die from liver failure.
Liver has many functions. Examples include:
– Regulation of blood glucose levels
– Conversion of excess glucose to glycogen, when blood sugar levels are higher than usual, and
conversion of glycogen to glucose, when blood sugar levels are low
– Regulation of the amount of amino acids in the body
– Deamination of excess amino acids
A number of body functions are affected when the patient suffers from liver failure. This eventually leads
to death.
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
(a) Describe the functions of the main
regions of the alimentary canal and
the associated organs, in relation
to ingestion, digestion, absorption,
assimilation and egestion of food
MultipleChoice
Structured
FreeResponse
1
2
1
(b) Describe the functions of enzymes
such as amylase, maltase, protease
and lipase in digestion, listing the
substrates and end-products
(c) State the function of the hepatic
portal vein
(d) State the role that the liver plays in
human nutrition
(e) State the role of the liver in the
breakdown of alcohol
1
5
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6.1, 6.2
6.2
3
2, 4
Textbook
section(s)
6.4
2
6.5
6.5
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Class:
)
Worksheet 6
(
Name:
Date:
Nutrition in Plants
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
for Chapter 7
CONNECT IT!
Photosynthesis
Light intensity
raw materials
limiting
factors
CO2
Carbon dioxide
concentration
affect
affect
Temperature
,
Sunlight ,
Reactions in
chloroplasts
Water
Rate of
photosynthesis
Equation
Carbon dioxide + Water chlorophyll
light energy
Oxygen + Glucose
excess glucose
converted to
Sucrose
for
Transport
converted and
stored as
Starch
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
2.
The equation which best describes photosynthesis in words is
A
carbon dioxide
B
glucose + oxygen
C
glucose + oxygen + water
D
water + carbon dioxide
.
glucose + oxygen + water
water + carbon dioxide
carbon dioxide
glucose + oxygen
( D )
Which of the following cells in a leaf do not contain chloroplasts?
A
B
C
D
Guard cells
Palisade mesophyll cells
Spongy mesophyll cells
Upper epidermal cells
( D )
For questions 3 and 4, refer to the diagram below which shows a section from the leaf of a green plant.
1
2
3
4
vascular
bundle
5
6
3.
46
Which regions contain cells with the highest and lowest number of chloroplasts?
Region with highest number of
chloroplasts
Region with lowest number of
chloroplasts
A
1
2
B
2
6
C
5
2
D
6
1
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( B )
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4.
After a period of bright light, which regions contain the most starch?
A
B
C
D
5.
1 and 6
2 and 4
2 and 5
3 and 5
( C )
The photo below shows part of a leaf. What is X?
X
A
B
C
D
6.
Guard cell
Palisade mesophyll
Spongy mesophyll
Stoma
( D )
How does most of the carbon dioxide enter the photosynthesising cells of a leaf?
A
B
C
D
Diffusion through the
Diffusion through the
Diffusion through the
Diffusion through the
epidermis of the leaf
phloem of the leaf
stomata of the leaf
xylem of the leaf
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( C )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The equation for photosynthesis is usually given as:
Water + Carbon dioxide
light energy
chlorophyll
Glucose + Oxygen
Which organelle does photosynthesis occur in?
Chloroplast
2.
The graph shows the rate of photosynthesis of a plant with increasing light intensity. The temperature
is kept at 20°C.
Rate of
photosynthesis
Light intensity
(a) Describe the relationship between light intensity and the rate of photosynthesis.
The rate of photosynthesis increases as light intensity increases, until a certain value where it
levels off.
(b) Draw a line on the graph to show the rate of photosynthesis against light intensity, when the
temperature is increased to 30°C.
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3.
The diagram shows a cross-section of a dicotyledonous leaf when viewed under a microscope.
A
C
D
B
E
F
(a) Identify the parts labelled A to F.
A:
Palisade mesophyll
D:
Phloem
B:
Spongy mesophyll
E:
Intercellular air space
C:
Xylem
F:
Stoma
(b) State one structural difference between the cells found in A and epidermal cells.
Unlike the cells in A, epidermal cells do not have chloroplasts.
(c) State one function of part C.
To conduct water / To provide mechanical support to the plant
(d) Parts B and F are involved in a similar function. Describe this function, and state its importance
to the plant.
They provide spaces for the exchange of carbon dioxide and oxygen. These gases must be able to
move in and out of the cells so that respiration and photosynthesis may take place.
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4.
The apparatus below can be used to investigate the rate of photosynthesis.
air bubble
plastic tube
graduated
capillary tube
well-lubricated
syringe
cork
dilute sodium
hydrogencarbonate
solution
water at room temperature
water
plant
boiling tube
(a) Suggest what is measured in this experiment to show that photosynthesis has occurred.
The volume of oxygen given off during photosynthesis is being measured.
(b) Describe how this apparatus can be used to measure the effect of light intensity on the rate
of photosynthesis.
Step 1: Shine light on the water plant at varying distances. (Distance between light source and plant
affects the intensity of light falling on the plant.)
Step 2: Use a graduated syringe to measure the volume of oxygen given off and collected at specific
time intervals for each distance at which the light source is placed.
Step 3: Calculate rate of oxygen given off at each distance (light intensity) to study the effect of light
intensity on the rate of photosynthesis.
(c) State three steps that need to be taken during the experiment described in (b) to minimise
sources of error.
Any three of the following: Some time should be allowed for the water plant to adapt to new conditions
before taking readings. / The water plant should be as upright as possible to allow maximum light
exposure. / The cut end of the plant should be positioned upwards. / The light source cannot be
too near the water plant as it will heat the plant and may cause enzymes to be denatured. / The
whole set-up should be air-tight so that the volume of oxygen measured comes from the water
plant only.
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5.
A shoot of Hydrilla was placed in a boiling tube containing pond water. A bench lamp with a 60 W
bulb, shining at the boiling tube, was placed 25 cm away. An oxygen probe was put into the boiling
tube, and the oxygen concentration was recorded using a data logger. The oxygen concentration was
recorded after 5 minutes, and again at 10 minutes. The experiment was then repeated using the
same Hydrilla in the same boiling tube, but with the lamp placed 5 cm away from the boiling tube.
The results are given in the table below.
Distance of lamp/cm
Oxygen concentration after
5 mins/% saturation
Oxygen concentration after
10 mins/% saturation
25
60
65
5
64
84
(a) Draw the experimental set-up as described above.
oxygen sensor
thermometer
interface
computer
boiling tube
light intensity sensor
beaker
pond water
lamp
Hydrilla
retort stand
water bath (to keep
temperature constant)
tripod stand
25 cm
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(b) Based on the results of this experiment, explain the effect of light intensity on oxygen production.
As light intensity increases when the lamp is moved nearer to the plant, more oxygen is produced.
This is due to the increased rate of photosynthesis in the plant under increased light intensity.
(c) (i)
What process are we trying to investigate when we measure the oxygen concentration in
this experiment?
Photosynthesis
(ii) Why is the measurement of oxygen concentration considered an inaccurate measurement
of the rate of the process stated in (c)(i)?
Oxygen is a by-product of photosynthesis. Some of the oxygen produced by photosynthesis,
may be used by the plant for respiration. Hence, the volume of oxygen measured here will be less
than the actual volume produced during photosynthesis.
(d) State one environmental condition that should be kept constant during this experiment.
Describe how this condition can be kept constant.
Any of the following:
Concentration of carbon dioxide. This can be done by adding a known concentration of sodium
hydrogencarbonate into the water. / Temperature. This can be done by using a water bath. The
temperature of the water in the set-up can be measured using a thermometer and adjusted by
adding hot or cold water if needed.
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6.
Photosynthesis takes place mostly in the leaves of plants. The laminae of most leaves are wide
and thin, as shown in the diagram below.
(a) Name the cells in the leaf where most photosynthesis takes place.
Mesophyll cells
(b) Which tissue in the leaf supplies water to the cells for photosynthesis?
Xylem
(c) Explain how having a wide lamina helps a leaf to photosynthesise.
Having a wide lamina means that the leaf has more surface area for light absorption. Light energy is
needed for photosynthesis.
(d) Explain how having a thin lamina helps a leaf to photosynthesise.
Having a thin lamina means that gases such as carbon dioxide, which is one of the raw materials for
photosynthesis, can diffuse easily into the mesophyll cells, since there is a shorter distance to travel.
It is also easier for light to penetrate the leaf to reach all the photosynthetic cells.
(e) Most leaves are covered with a transparent, waterproof cuticle. How does this feature aid in
photosynthesis?
The waterproof cuticle helps prevent excessive water loss by evaporation from the leaf surface.
This ensures that there is enough water for photosynthesis. It also helps to focus the light rays onto
the mesophyll layer.
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Section C: Free-Response Questions
Answer the following questions.
1.
Discuss the major adaptations of the leaf for photosynthesis.
The petiole holds the leaf lamina away from the stem, so that the lamina can absorb sufficient sunlight
and air. The leaf lamina has a large flat surface compared to its volume. This enables the leaf to
absorb the maximum amount of sunlight for photosynthesis. A thin, wide lamina ensures that
carbon dioxide, the raw material for photosynthesis, can rapidly reach the inner cells of the leaf.
A network of veins extends throughout the leaf. Veins are made of the vascular tissues, xylem and
phloem. Xylem transports water and mineral salts to the leaf cells. Phloem transports sugars away from
the leaf cells to other parts of the plant. This maintains a concentration gradient, so that the
photosynthetic reactions proceed in the forward direction. A waxy cuticle on the leaf epidermis protects
the leaf by reducing the evaporation of water. Water is an essential raw material for photosynthesis. Lack
of water would also cause the leaf to wilt, reducing surface area for light absorption. Stomata on the lower
epidermis open in sunlight, allowing carbon dioxide to diffuse in and oxygen to diffuse out. Mesophyll cells
of the leaf contain numerous chloroplasts. Chloroplasts contain chlorophyll, which absorbs light energy
for photosynthesis. Mesophyll cells in the upper regions of the leaf (palisade mesophyll cells), contain
more chloroplasts than the spongy mesophyll cells, since more light energy can be absorbed near the leaf
surface. An interconnecting system of air spaces in the lower regions of the leaf (spongy mesophyll) allow
rapid diffusion of carbon dioxide into mesophyll cells.
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2.
(a) Describe an experiment to show the effect of temperature on the rate of photosynthesis.
Step 1: Submerge a water plant like Hydrilla, with a length of 5 cm, in a boiling tube filled with dilute
sodium hydrogencarbonate solution. Ensure that the cut end of the water plant is positioned upwards.
Place this boiling tube in a water bath. Place a thermometer in the water bath to check that the
temperature is kept constant. Step 2: Place a lamp with a 60 W bulb, 10 cm from the plant. Keep this
distance constant throughout the experiment. Step 3: Add ice-cubes or cold water to the water bath
to adjust the temperature to 5°C. Allow some time for the plant to adapt to the conditions provided,
before taking readings. Step 4: Count the number of bubbles produced by the plant over a period of
5 minutes. Repeat this a few times to obtain an average rate. Step 5: Repeat step 4 at different
temperatures, e.g. 15°C, 25°C, 35°C, 45°C, 55°C, 65°C and 75°C. Step 6: Record the results in a
table. Plot a graph to show the rate of bubbling per minute against the temperature.
(b) Discuss why the following statement is true: “Temperature will only increase the rate of
photosynthesis to a certain extent. At very high temperatures, the rate of photosynthesis
will decrease.”
Photosynthesis is an enzyme-catalysed reaction. There will be increased collisions of enzyme and
substrate molecules, as temperature increases. This results in more enzyme-substrate complexes
being formed, and thus, an increased rate of reaction. However, at very high temperatures, enzymes
being protein in nature, will be denatured. The substrate no longer fits into the active site, and an
enzyme-substrate complex cannot be formed. Thus, the rate of photosynthesis will decrease.
© 2013 Marshall Cavendish International (Singapore) Private Limited
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Worksheet 6
55
8/25/12 4:53 PM
WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
MultipleChoice
(a) State that chlorophyll traps light energy,
and converts it into chemical energy for
the formation of carbohydrates
(b) State the equation, in words,
for photosynthesis
1
(c) Investigate and state the factors
affecting the rate of photosynthesis
7.1
1
7.1
2, 4, 5
5
3
(e) Relate how the structure of the leaf is
adapted to its functions
2, 3, 4
1, 6
Worksheet 6
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6
Textbook
section(s)
1
(d) Identify and label the various
cellular and tissue structures of a
dicotyledonous leaf, as seen under the
microscope
(f) Outline the intake of carbon dioxide
and water by plants
56
Structured
FreeResponse
2
7.1
7.2
1
7.2
7.2
© 2013 Marshall Cavendish International (Singapore) Private Limited
8/25/12 4:53 PM
Class:
Worksheet 7
(
Name:
)
Date:
Transport in Humans
for Chapter 8
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Circulatory system
Blood
consists of
Components
Red blood
cells
White blood
cells
contain
for
Haemoglobin
Blood
clotting
Lymphocytes
Phagocytes
binds to
oxygen
Plasma
Platelets
Phagocytosis
fibrin
threads
entangle
blood cells
to form
a mass
(clot)
in spaces
between
tissue cells
and blood
capillaries
contains
Tissue
fluid
Antibodies
produce
Blood vessels
Arteries
branch
into
Arterioles
branch
into
Capillaries
join to
form
Venules
join to
form
Veins
e.g.
contain
Coronary arteries
Internal valves
bring nutrients
and oxygen to
two upper
chambers
Atria
two lower
chambers
Ventricles
(singular: atrium )
Heart
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
After centrifugation, blood separates into three layers as shown in the diagram below.
Layer X is the topmost layer and is yellowish and translucent. Layer Y is the bottom layer and is
dark red in colour.
X
Y
What are the functions of the components of blood in layers X and Y?
2.
Layer X
Layer Y
A
Defend the body against foreign
substances
Transport nutrients and waste
materials
B
Transport nutrients and waste
materials
Transport oxygen
C
Transport oxygen
Defend the body against
foreign substances
D
Transport oxygen
Transport nutrients and waste
materials
In which of the following regions will the highest pressure develop?
A
B
C
D
3.
Left atrium
Left ventricle
Pulmonary artery
Pulmonary vein
( B )
A person living at a high altitude, where there is low oxygen concentration, will adapt physiologically
by
.
A
B
C
D
58
( B )
decreasing the number of red blood cells
feeling dizzy and nauseous
increasing his breathing rate
increasing the number of red blood cells
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( D )
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4.
The diagram below shows cross-sections of two types of blood vessels. (The blood vessels are not
drawn to scale.)
P
Q
What is the identity of P and Q?
5.
P
Q
A
Artery
Capillary
B
Artery
Vein
C
Capillary
Artery
D
Capillary
Vein
What causes the 'lub' and 'dub' sounds of a heartbeat?
A
B
C
D
6.
( C )
The
The
The
The
backflow of blood hitting the heart muscles
closure of the semi-lunar valves, bicuspid valve and tricuspid valve
flow of blood into the pulmonary vein and aorta
return of blood into the heart from the venae cavae and pulmonary artery
( B )
The diagram below shows a section of the human heart.
4
3
1
2
Which of the numbered part(s) of the heart carries/carry oxygenated blood?
A
B
C
D
1
4
1
3
only
only
and 2 only
and 4 only
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( C )
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7.
After a patient underwent heart surgery, there was an increase in the number of white blood cells
in his body. What could be a possible reason for this increase?
A
B
C
D
The patient might have developed an infection after the surgery.
The patient might need more nutrients to be transported around his body.
The patient might need more oxygen to help him recover faster.
The patient might need to accelerate the clotting of his blood to prevent excessive
blood loss from the surgery.
( A )
Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The diagram represents some blood cells.
X
Y
Z
(a) Name the cells labelled X and Y.
X: Red blood cell
Y: White blood cell
(b) Z is involved in blood clotting. Name Z.
Platelet
(c) State one function of X and Y.
X: To transport oxygen from the lungs to all the parts of the body
Y: Phagocytosis
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2.
The graph shows the blood pressure in the aorta and left ventricle during two cardiac cycles.
Pressure/
mm of Hg
pressure in the
aorta
pressure in the
left ventricle
0
0.5
1.0
1.5
Time/s
(a) How long is a cardiac cycle?
1.12 second – 0.32 second = 0.80 second
(b) State the duration in each cardiac cycle when the aortic valve (semi-lunar valve) is closed.
Explain how you arrived at your answer.
1.02 second – 0.22 second = 0.80 second
The aortic valve remains closed throughout the interval where the aortic pressure is above ventricular
pressure.
(c) If a line indicating pressure in the right ventricle is drawn on this graph, state one similarity and
one difference it would have with the existing line indicating pressure in the left ventricle.
The pattern of the two lines, and the shape of the graphs would be the same.
The pressure in the right ventricle would be lower than that in the left ventricle.
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3.
(a) Complete the diagram by drawing in the path of blood into and out of the heart.
(i) Use a black/blue pen to show the path of deoxygenated blood into and out of the heart.
(ii) Use a red pen to show the path of oxygenated blood into and out of the heart.
Key
oxygenated
blood
N
M
deoxygenated
blood
B
A
(b) Name valves M and N.
M: Semilunar valve / Aortic valve
N: Bicuspid valve
(c) Which side, A or B, is the left side of the heart? Explain your answer.
B is the left side, because the muscular wall is thicker than that of side A.
(d) When the left ventricle is full and the muscles contract to force the blood into the aorta, valve N
closes. Why does valve N close?
To prevent the backflow of blood into the atrium
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4.
The diagram shows the external view of a person’s heart.
X
(a) If there is a blockage at X, state what will happen to this person.
The cardiac muscles will be deprived of oxygen and nutrients. A prolonged lack of oxygen
causes the heart muscles to die eventually.
(b) Suggest two causes of such a blockage.
Any two of the following: Diet rich in cholesterol / smoking / stress
(c) State two ways in which a person can prevent a blockage at X.
Any two of the following: More exercise / No smoking / Proper diet such as avoiding a high-fat diet
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Section C: Free-Response Questions
Answer the following questions.
1.
Arteries and veins are two different types of blood vessels found in the human body. Compare and
contrast the structures of arteries and veins with reference to their functions.
Arteries (except the pulmonary artery) carry blood away from the heart, while veins (except the pulmonary
vein) carry blood back to the heart. Arteries have thick, muscular walls to withstand the high pressure of
the blood being pumped out of the heart. The walls are also elastic, so that they can stretch and recoil,
helping to push the blood along the artery in spurts. The blood pressure in the veins is much lower than
in the arteries, and blood flows more slowly and smoothly in the veins. Hence, the walls of veins are not
as thick and muscular as those of arteries of about the same size. Veins also contain less elastic tissue.
Most veins have internal valves along their length to prevent backflow of blood. Arteries do not contain
internal valves.
2.
Describe the route taken by the blood from the intestine to the kidney. List all the major blood vessels
and organs involved.
Blood flows from the intestine via the hepatic portal vein to the liver, then via the hepatic vein and the
posterior vena cava to the heart, then via the pulmonary artery to the lungs, then via the pulmonary vein
back to the heart, and finally, via the aorta and the renal artery to the kidney.
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
(a) State the components of blood and
their roles in transport and defence
(b) Relate the structures of arteries, veins
and capillaries to their functions
MultipleChoice
Structured
1, 3, 7
1
4, 6
(c) Identify the main blood vessels to and
from the heart, lungs, liver and kidneys
Textbook
section(s)
8.2, 8.3
1
8.4
1, 2
8.5
(d) Describe the structure and function
of the heart in terms of muscular
contraction and the working of valves
5
2, 3
8.5
(e) Outline the cardiac cycle in terms
of what happens during systole and
diastole
2
2, 3
8.5
4
8.6
(f) Describe coronary heart disease in
terms of the occlusion of coronary
arteries, and list the possible causes,
such as diet, stress and smoking,
stating the possible preventive
measures
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Class:
Worksheet 8
(
Name:
)
Date:
Transport in Plants
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
for Chapter 9
CONNECT IT!
Transport in plants
things transported
Water and
minerals
Food
Glucose produced
by photosynthesis
is converted into
sucrose and amino
acids
enter
Root hair cells
by
Differences
in water
potential
between
solution in
soil and
cell sap
due
to
Osmosis
Diffusion
transported
to other plant
parts by
Active transport
Translocation
minerals and ions
water
transported to other plant
parts by
Loss of
water
vapour from
causes upward
movement in
via
Xylem
make up
Phloem
Vascular
Transpiration
the aerial
parts of a
plant
in excess will result in
tissues
Temperature
rate of
transpiration
affected by
Wind speed
Wilting
Humidity
Light intensity
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
The diagram shows sections of a leaf and of the stem of a plant.
1
3
2
4
Leaf
Stem
Which regions represent the tissues that transport manufactured food substances?
2.
Leaf
Stem
A
1
3
B
1
4
C
2
3
D
2
4
( C )
The diagram shows a section from the stem of a plant.
P
Q
What substances are present in the parts labelled P and Q?
68
Substance in P
Substance in Q
A
Amino acids
Sucrose
B
Sucrose
Amino acids
C
Sucrose
Water
D
Water
Water
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( C )
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3. The diagram shows a section from the leaf of a plant.
X
The structure labelled X
A
B
C
D
4.
.
absorbs green light
is capable of carrying out photosynthesis
prevents sugar loss
prevents excessive water loss
( D )
Part of the branch in the diagram below has been ‘ringed’. What will happen to apple Y after
some time?
apple X
apple Y
A
B
C
D
Grows bigger
Remains the same
Same size as apple X at the end of the experiment
Shrinks in size
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( D )
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5.
Which conditions would cause a plant to wilt most rapidly?
A
B
C
D
6.
High humidity, high temperature, high wind speed
High humidity, low temperature, high wind speed
Low humidity, high temperature, high wind speed
Low humidity, low temperature, high wind speed
( C )
Which graph shows the effect of air movement (wind speed) on the transpiration rate of a plant?
A
B
Rate of
transpiration
Rate of
transpiration
Wind speed
C
Wind speed
D
Rate of
transpiration
Rate of
transpiration
Wind speed
7.
Translocation in plants is defined as
A
B
C
D
70
( C )
.
the loss of air from the stomata
the loss of water vapour from the stomata
the transport of manufactured food in the phloem tissue
the transport of water in the phloem tissue
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Wind speed
( C )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
A group of students tested leaves from two different plants, thyme and mint, in order to find out which
leaf surface had more stomata. The thyme plant had fewer leaves compared to the mint plant.
Average weight loss/%
Mint
Thyme
Petroleum jelly on both leaf surfaces
14
13
Petroleum jelly on lower leaf surface only
41
20
Petroleum jelly on upper leaf surface only
44
30
(a) From which surface did the mint leaf lose the most water? Explain your answer.
The lower leaf surface, because when the jelly was on the upper leaf surface, the weight loss was
the highest.
(b) Which surface of the thyme leaf has more stomata? Explain your answer.
Lower leaf surface, because the weight loss was the highest only when the jelly was placed on the
upper leaf surface. When there are more stomata, more water is lost.
(c) Explain the difference in the results for the two types of leaves.
Thyme loses less water than mint plant. This could be because thyme has fewer leaves, that is, a
smaller surface area, or because it has fewer stomata.
(d) Based on the experimental results, which plant would be better adapted to hotter, drier
conditions? Give a reason for your answer.
Thyme, because the percentage of water loss is lower compared with mint.
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2.
The following graphs show the average size of the stomata on the leaves of two plants during a
24-hour period. One plant was kept in a moist environment, while the other was kept in a hot and
dry environment.
A
B
Average
stomatal
size
Average
stomatal
size
night
day
night
night
day
Time/h
(a) (i)
night
Time/h
Which graph best represents the plant in a hot and dry environment?
B
(ii) Explain the reason for your answer in (a)(i).
The average stomata size decreases at mid-day, which is the hottest time of the day.
With a decreased stomata size, less water will be lost through the stomata.
(iii) Explain why the average stomatal size at night is smaller than that during the day.
At night, there is no light, hence, photosynthesis does not occur. The sugars accumulated in
the guard cells during the day, are used up. This increases the water potential in the guard
cells, and water leaves via osmosis. The guard cells become flaccid, and the stomata will close.
(b) Predict two structural features that the plant in the hot and dry environment will have that
allows it to survive or adapt well in hot and dry conditions.
Any two of the following:
Reduced surface area of leaves / Sunken stomata / Presence of trichome or hairs in leaf /
Thicker cuticle
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3.
The following diagrams show the transverse sections of the leaves of two different plants.
A
B
(a) Which plant, A or B, is from a dry environment?
Plant A
(b) Name and describe two observable features of the plant in (a) which help it to adapt to the dry
environment.
Any two of the following: Rolled up leaf to make the air around the stomata saturated with water
vapour / reduce the surface area exposed to the dry air / Sunken stomata to make the air around
the stomata saturated with water vapour / Trichomes (hair) to trap water vapour / Thick cuticle
(impermeable/waterproof) to prevent excessive water loss by evaporation
4.
The diagram below shows a potometer.
shoot
rubber
tubing
reservoir of
water
scale
tap
air bubble
capillary tube
(a) Name the process by which water is lost from the shoot.
Transpiration
(b) What does the potometer directly measure?
It measures the amount of water absorbed by the shoot.
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(c) Suggest two reasons why the measurement in (b) is not necessarily the same as the rate of the
process stated in (a).
Any two of the following:
Water taken up by the shoot will be used in photosynthesis. / Water taken up may be used in
reactions such as hydrolysis. / Water taken up may be used to maintain plant turgidity.
(d) State two factors that might affect the shoot’s rate of water loss.
Any two of the following:
Temperature / Wind speed or velocity / Humidity / Light intensity
LEARN & APPLY
Go through the worked example below, then try to answer the Free-Response Questions.
Worked Example
Explain how a plant absorbs water.
Thought Process
This question needs to be answered in several parts. The answer should consist of the following points:
• Which parts of plants are involved in water absorption?
• What processes are involved?
• What environmental conditions affect the absorption of water?
Answer
Points to cover
1. Water absorption occurs mainly at the root hair cells, as they provide a large surface area for
absorption.
2. The cell sap of root hairs has lower water potential than the soil solution.
3. Water potential in soil solution is higher than in the root hair cell sap. Water moves from the soil,
across the permeable cell wall of the root hair cell, across the partially permeable cell membrane
of the root hair cell, into the cell by osmosis.
4. The water potential of the root hair cell is now higher than that of the neighbouring cells.
5. Water thus leaves the root hair cells, and enters the neighbouring cells by osmosis.
6. When the water potential of the soil solution is low, for example, during the dry season, the
root hair cells use active transport to absorb dissolved mineral salts. As the mineral salts are
dissolved in water, their movement into the plant cells will lower the water potential, and bring
water into the cells by osmosis.
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Section C: Free-Response Questions
Answer the following questions.
1.
The diagram below shows a xylem vessel.
(a) Are xylem vessels living or dead structures? Give one reason for your answer.
They are dead structures. They do not contain cytoplasm.
(b) What are the main functions of xylem vessels? State three ways in which xylem vessels are
adapted to their functions.
They transport water and dissolved mineral salts from the roots to the stem and leaves, and
provide mechanical support to the plant. A xylem vessel does not have any cross walls and
cytoplasm. This enables water to move easily through the lumen. Lignin deposited on the walls,
helps strengthen the walls and prevent the vessel from collapsing. When bundled together, the xylem
vessels provide mechanical support to the plant.
2.
(a) Describe how the adaptation of a plant root is similar to the adaptation of the lining of the
small intestine in humans for the absorption of nutrients.
Both are involved in absorption. Since efficient absorption requires high surface area to volume
ratio, the root hair is long and narrow, while the lining of the intestine has numerous folds.
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(b) Systemic pesticides are pesticides that are absorbed and transported to all parts of
the plant. Describe how spraying systemic pesticides directly on the leaves, kills insects such as
aphids, which feed on shoots that are grown after the spraying.
Systemic pesticides sprayed directly on the plant, are absorbed by the leaves of the plant. These
pesticides are then transported to all parts of the plant through the phloem, and accumulated in plant
tissues. Insects which feed on shoots that have grown after the spraying period, will take in these
pesticides and be killed.
3.
Products of photosynthesis, such as sucrose, are translocated via the phloem from sites of
production in green leaves to places where they are utilised, such as seeds, fruits, roots and new
leaves. These places are known as ‘sinks’.
(a) Describe a pathway by which a sucrose molecule is transported from the leaf to a sink such
as a fruit.
One such pathway by which sucrose is transported, is the route taken by the sucrose molecule from
the cells in the leaf to the fruit. The sucrose molecule moves from the mesophyll cells in the leaf to
the phloem in a vascular bundle of the leaf. This is followed by movement to the phloem in a vascular
bundle of the fruit, and finally to the cells of the fruit.
(b) Suggest and provide one reason why a sucrose molecule may be transported to a particular
sink and not to other sinks.
Sucrose will first be transported to sinks which have higher rates of metabolic activity, such as
growing points (shoot and root tips). In these locations, sucrose can be converted into
glucose. The glucose produced can then be used for tissue respiration to release energy for
metabolic activity.
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4.
A student set up a potometer to investigate the amount of water taken up by a leafy shoot.
shoot
rubber
tubing
reservoir of
water
scale
tap
air bubble
capillary tube
The distance that the air bubble travelled along the capillary tube, was measured every two minutes.
The results of the experiment are shown in the table below.
Time/minutes
0
2
4
6
8
10
12
14
16
18
20
Distance travelled/mm
0
7
20
33
45
57
72
85
99
108
122
22
24
(a) Draw a graph to show the results.
Distance
travelled/mm
125
Graph of distance travelled against time taken
×
×
100
×
×
75
×
×
50
×
×
25
×
×
0
×
2
4
6
8
10
12
14
16
18
20
Time/min
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(b) Comment on the graph with reference to water uptake and water loss in the plant.
The movement of the air bubble along the capillary tube indicates the uptake of water by the
plant. The distance travelled is proportional to the volume of water taken up by the plant.
From the graph, the rate of water uptake by the plant is proportional to the rate of water loss
through transpiration.
The rate of water uptake by the plant can be determined by calculating the gradient of the line,
102.5 – 5
which is 17.2 – 0.8 mm/min = 5.95 mm/min.
(c) Describe how water from the capillary tube enters the shoot to reach one of the leaves.
Transpiration in the leaves creates a transpiration pull, which draws water up the xylem vessels to the
leaves; water in the container enters the shoot to replace the water lost in transpiration.
WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
(a) Identify the positions, and explain
the functions of xylem vessels and
phloem in sections of a herbaceous
dicotyledonous leaf and stem under
the light microscope
MultipleChoice
Structured
1, 2
4, 7
(d) Relate the structure and function of
root hairs to their surface area, and to
water and ion update
(e) State what is transpiration
(f) Describe the effects of variation of air
movement, temperature, humidity and
light intensity on transpiration rate, and
explain how wilting occurs
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Textbook
section(s)
9.1
(b) Briefly explain the movement of water
through the stem in terms of
transpiration pull
(c) Define translocation
FreeResponse
1
9.2
3
9.2
2
9.3
3
1, 4
4
9.4
5, 6
2, 3, 4
4
9.4
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Class:
Worksheet 9
(
Name:
)
Date:
Respiration in Humans
for Chapter 10
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Oxidation of food
substances e.g. glucose,
with the release of energy
Respiration
types
oxygen
oxygen
not required
produces
small amount
of energy
Anaerobic
Aerobic
equation in
human cells
equation in human
muscle cells
Glucose
Lactic
Glucose + Oxygen
acid
required
in humans, oxygen
obtained and carbon
dioxide removed
(gas exchange) by
produces
large amount
of energy
Carbon +
dioxide
Water
Breathing
chemical
contents of
cigarette smoke
Smoking
Nicotine
Tar
Carbon monoxide
Irritants
Inspiration
damages
Expiration
air rushes in
Bronchioles
Bronchi
Larynx
Trachea
Nasal
passages
air rushes out
lined with cilia
Alveoli
gas dissolves
in moist lining
supplied
with
oxygen
diffuses out
into
Capillaries
+ O2
Red
contain
blood cells
Oxyhaemoglobin
Haemoglobin
– O2
red blood cells carry
oxygen to cells
carbon dioxide
Hydrogencarbonate
ions (in blood plasma)
Carbonic acid
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Carbon dioxide + Water
oxygen
used for
respiration
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Cellular respiration is best described as
A
B
C
D
2.
a process by which carbon dioxide is inhaled, and oxygen is exhaled
a process by which oxygen is inhaled, and carbon dioxide is exhaled
a process by which sugar is produced from carbon dioxide and water in the
presence of light and chloroplasts
a process by which sugars are oxidised to release chemical energy
( D )
.
The site of aerobic respiration is the
A
B
C
D
3.
.
chloroplast
endoplasmic reticulum
mitochondrion
nucleus
( C )
The diagram below shows part of the human respiratory system. Identify the trachea.
I
II
III
A
B
C
D
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I
II
III
IV
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IV
( B )
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For questions 4 and 5, refer to the experimental set-up shown below.
original position of drop of
coloured water
air in
syringe
X
Y
capillary tube
grasshopper
wire gauze
sodium hydroxide pellets
4.
What is the role of the sodium hydroxide pellets?
A
B
C
D
5.
( A )
After a while, what would be the position of the drop of coloured water?
A
B
C
D
6.
To absorb carbon dioxide
To absorb oxygen
To absorb water vapour
To act as food for the grasshopper
Disappears from the capillary tube
Nearer position X
Nearer position Y
No change in position
Which of the following correctly describes the diagram below, which depicts the exchange of gases in
the human circulatory system?
P
100 mm Hg O2
40 mm Hg CO2
40 mm Hg O2
46 mm Hg CO2
A
B
C
D
R is a blood capillary, and blood flow is from P to Q
R is a blood capillary, and blood flow is from Q to P
R is an alveolus, and blood flow is from P to Q
R is an alveolus, and blood flow is from Q to P
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( B )
R
Q
95 mm Hg O2
40 mm Hg CO2
( C )
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7.
A person's breathing rate over a period of time is shown below.
Breathing
rate/
arbitrary
units
0
1
2
3
4
5
6
7
8
9
10
Time/minutes
Which statement best describes the change in the person's breathing rate from the 1-minute point
to the 3-minute point?
A
B
C
D
The person is dying.
The person is exercising.
The person is listening to music.
The person is sleeping.
( B )
Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The following experiment was performed to demonstrate that microorganisms in the soil respire.
B
A
soil
concentrated
potassium
hydroxide
solution
C
D
hydrogencarbonate
indicator
(a) What is the error in the experimental set-up? How should this error be corrected?
The delivery tube A should be submerged in the concentrated potassium hydroxide solution, so
that air will be directed into the concentrated potassium hydroxide solution, before entering test
tube C.
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(b) Assuming that the error has been corrected, how should the pump draw air through the
apparatus? Should it be from A to B or from B to A?
From A to B
(c) In which test tube, C or D, would the hydrogencarbonate indicator solution change in
appearance?
D
(d) What causes the change in appearance of the hydrogencarbonate indicator solution?
Microorganisms in the soil respired and released carbon dioxide, which dissolved in the
hydrogencarbonate indicator solution to form carbonic acid.
(e) Write a word equation to illustrate aerobic respiration in soil microorganisms.
Glucose + Oxygen
2.
Carbon dioxide + Water + Energy
The graph below shows changes in the concentration of lactic acid in the blood of a person
performing vigorous exercise.
Concentration of
lactic acid
X
Y
Z
Time
(a) In which region, X, Y or Z, is the person actually exercising?
Y
(b) Write a word equation to show how lactic acid is formed during vigorous exercise.
Glucose
Lactic acid + Energy
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(c) Describe the effects of an increasing lactic acid concentration on the muscles during Y.
The increasing amount of lactic acid will cause the person to suffer from muscle pains and fatigue.
(d) Explain why there is a gradual decrease in lactic acid concentration in region Z.
The person stops exercising and rests. The lactic acid is removed from the muscles, and transported
to the liver, where it is oxidised to release energy.
3.
The figure below shows the human respiratory system.
A
B
rib
C
D
E
F
Identify structures A to F.
A: Larynx
B: Trachea
C: Bronchus
D: Bronchiole
E: Alveolus/Alveoli
F: Diaphragm
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4.
The diagram below shows a section of the alveolus.
Gas in
Gas out
Direction
of blood
flow
Using the diagram provided, state two adaptations of an alveolus which allow it to exchange gases
effectively in the lungs.
Any two of the following: It is highly folded and spherical in shape, hence, it has a large surface area. /
Wall is one-cell thick, so it is easy for gases to diffuse through. / Its surface is lined with moisture for
oxygen to dissolve in.
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LEARN & APPLY
Go through the worked example below, then try to answer the Free-Response Questions.
Worked Example
Describe the movement of carbon dioxide from the body cells to the air spaces in the lungs.
Thought Process
You need to state how carbon dioxide is produced in body cells, as well as, how carbon dioxide is
transported from the cells to the lungs. Think about the process and reactions involved.
Answer
Points to cover
1. Carbon dioxide, which is produced in cells during cellular respiration, diffuses out into the tissue
fluid before diffusing into the capillary network.
2. This carbon dioxide will diffuse into blood in the capillaries due to a concentration gradient of
carbon dioxide between the cells and the blood.
3. Carbon dioxide diffuses into red blood cells and is converted into hydrogencarbonate ions.
4. Hydrocarbonate ions then diffuse into blood plasma and are carried to the lungs.
5. In the lungs, the hydrogencarbonate ions diffuse into red blood cells and are converted into
carbon dioxide.
6. Carbon dioxide then diffuses across the blood capillaries into the air spaces in the alveoli of the
lungs, due to the concentration gradient of carbon dioxide between the red blood cells and the
air spaces in the lungs.
Section C: Free-Response Questions
Answer the following questions.
1.
Describe three ways in which smoking damages the lungs.
Tar deposited in the lungs contains carcinogens and increases the risk of lung cancer.
Carbon monoxide in smoke increases fat deposition on the inner surface of arteries, which may result in
blockage of the coronary arteries. This might cause a heart attack, as less oxygen is transported to the
heart. Irritants cause coughing. Prolonged violent coughing could lead to emphysema, in which the alveolar
walls break down.
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2.
The diagram below shows a section of an alveolus and a blood capillary near it. Annotate the
diagram to describe the movement of oxygen when it enters the lungs.
high oxygen
concentration in air
from atmosphere
red blood cells leave
the lungs; oxygen
bound to haemoglobin
is carried to the heart
oxygen dissolves
in layer of moisture
lining alveolus
low oxygen
concentration
in red blood cells
entering the
lungs
dissolved oxygen diffuses
through one-cell thick capillary
wall into red blood cells, and
combines with haemoglobin
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
MultipleChoice
Structured
(a) Identify parts of the human respiratory
system in diagrams
3
3
(b) State the characteristics of the
exchange surface of alveoli, and
describe the role it plays in gas
exchange
6
4
(c) Describe the effects of tobacco smoke
on our health
(d) Define and state the equation (in words
only) for aerobic respiration in humans
88
Textbook
section(s)
10.3
2
10.3
1
10.5
1
10.1
(e) Define and state the equation (in
words only) for anaerobic respiration in
humans
2
10.1
(f) Describe the effect of lactic acid in
muscles during exercise
2
10.1
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1, 2, 4, 5, 7
FreeResponse
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Class:
Worksheet 10
(
Name:
)
Date:
Coordination and Response
for Chapters 11, 12 and 13
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
PNS: Peripheral
nervous system
Receptors
Nerves
Coordination and response
Nervous
Control
Hormonal
Control
carried
out by
Hormones
produced by
CNS:
nervous system
Central
Endocrine glands
e.g.
Spinal cord
Brain
Adrenal
glands
Islets of Langerhans
(in pancreas )
produce
produce
consists of
Sensory
Stimulus
neurone
received by
travels along
Sense organ
Relay / Intermediate
to
neurone
to
Motor
Impulse
produces
neurone
e.g.
Eye
Insulin
Adrenaline
Effector
to
Reflex
action
produces
e.g.
pupil reflex
Sensory neurone
in optic nerve
Bright light
Retina
receives
to
via
relay
neurone
Brain
Motor
neurone
produces
Light
Cornea
refracted by
Lens
onto
Retina
focal length
controlled by
sends
impulses
through
Optic nerve
to
Brain
Suspensory ligament
Iris
muscles
Pupil constricts, reducing
amount of light entering eye
Impulse
and
to
to
travels
along
received by
Ciliary muscles
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Glucagon
interprets
image
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Which of the following correctly identifies X and Y?
X
2.
Y
X
Y
A
Motor neurone
Motor neurone
B
Motor neurone
Sensory neurone
C
Motor neurone
Relay neurone
D
Sensory neurone
Motor neurone
( D )
A nerve impulse is transmitted along three neurones as shown below.
W
Y
X
Z
The sensory neurone is represented by
A
B
C
D
90
.
W
X
Y
Z
( B )
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3.
Cataract is a medical condition in which patients experience blurred/cloudy vision due to difficulties
in focusing light rays onto the retina. Which part of the eye is affected in this condition?
P
Q
S
R
A
B
C
D
4.
5.
P
Q
R
S
( C )
Which of the following correctly describes the changes that take place when a person looks at
a distant object?
Ciliary muscle
Suspensory ligament
Shape of lens
A
Contracts
Becomes less taut
Becomes more convex
B
Contracts
Becomes taut
Becomes less convex
C
Relaxes
Becomes less taut
Becomes less convex
D
Relaxes
Becomes taut
Becomes less convex
( D )
The diagram shows the front view of the pupil of a person in a bright room.
radial muscle
circular muscle
What happens when the light in the room is switched off?
Radial muscle
Circular muscle
Pupil size
A
Contracts
Relaxes
Decreases
B
Contracts
Relaxes
Increases
C
Relaxes
Contracts
Decreases
D
Relaxes
Contracts
Increases
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( B )
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6.
Hormones are destroyed in the
A
B
C
D
7.
.
kidney
liver
pancreas
stomach
( B )
.
The function of the hormone insulin is to
A
B
C
D
allow glucose to enter the bloodstream
break down glucose
prevent glucose from being excreted by the kidney
trigger the conversion of glucose into glycogen
( D )
For questions 8 and 9, refer to the diagram shown below.
Hormone X
secreted
Blood glucose
concentration
increases
Blood glucose
concentration
decreases
Hormone Y
secreted
8.
9.
Which gland will secrete hormone X, and when will it be secreted?
Gland secreting hormone X
When
A
Islets of Langerhans
After a meal
B
Islets of Langerhans
During exercise
C
Liver
After a meal
D
Liver
Before a meal
( A )
What is the identity of hormones X and Y?
Hormone X
Hormone Y
A
Adrenaline
Insulin
B
Glucagon
Glycogen
C
Glycogen
Adrenaline
D
Insulin
Glucagon
( D )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The diagram below shows a specialised cell.
Y
X
(a) Name the type of neurone shown.
It is a sensory neurone.
(b) Part X is connected to a receptor. Give one example of such a receptor.
The nerve endings in the skin/eye (or any sense organ)
(c) What does part Y connect to?
The central nervous system / dendrites of a relay neurone
(d) What is the role of this specialised cell?
To conduct nerve impulses from the sensory receptor to the central nervous system
2.
A person moved from a brightly-lit room to a dark room. He was unable to see for the first few
minutes. Gradually, he was able to see fairly well in the dark room.
(a) Explain how the pupils of eyes in a brightly-lit room differ from those in a dark room.
The pupils of eyes in a brightly-lit room have a smaller diameter (constrict) due to the contraction
of the circular muscle and relaxation of the radial muscle in the iris. In a dark room, the pupils of
eyes will have a larger diameter (dilate) to allow more light to pass into the eyes. The radial muscles
contract and the circular muscles relax.
(b) Explain why the person was not able to see when he first stepped into the dark room.
Visual purple is bleached in bright light. In the dark, it takes some time for visual purple to be
re-formed in the rods; only then will the rods be sensitive to dim light.
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3.
(a) What are endocrine glands?
Endocrine glands are ductless glands that secrete hormones directly into the bloodstream.
(b) Give an example of an endocrine gland.
Adrenal gland / Islets of Langerhans / Gonads / Pituitary gland / Thyroid gland
(c) Describe a hormone with reference to the endocrine gland that produces it, and state its effect(s)
on its target organ(s).
Insulin is produced by the islets of Langerhans (pancreas), and is secreted into the bloodstream.
Insulin is then transported to the liver and muscles (target organs), where it decreases the blood
glucose concentration by stimulating cells to increase their uptake of glucose, and to convert glucose
into glycogen for storage.
(d) Besides hormones, how else can information be relayed in the body?
Information can be relayed via nerve impulses.
4.
When the blood glucose level in the body decreases, the hormone glucagon is released to restore
the blood glucose level.
(a) Suggest a scenario where the blood glucose level decreases below the normal level.
An example would be during exercise / starvation.
(b) Explain how glucagon helps to restore the blood glucose level.
Glucagon stimulates liver and muscle cells to convert glycogen into glucose, which is then released
into the bloodstream.
(c) Where is glucagon secreted from?
It is secreted from the islets of Langerhans in the pancreas.
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LEARN & APPLY
Go through the worked example below, then try to answer the Free-Response Questions.
Worked Example
Compare and contrast nervous control and hormonal control.
Thought Process
In the answer, both similarities and differences between nervous control and hormonal control are
required. Think about the functions of these controls, their effects and their speed of action.
Answer
Points to cover
1. Both nervous and hormonal controls are used to control processes in the body to maintain a
constant internal environment (homeostasis).
2. Both require a stimulus to cause the transmission of a message to target organ.
3. Nervous control involves nervous impulses (electric signals), while hormonal control involves
hormones (chemical substances).
4. The response in nervous control is quick, while that in hormonal control is relatively slower.
5. The response in nervous control is short-lived, while the response in hormonal control may either be
short-lived or long-lived.
6. Nervous control may be voluntary or involuntary, while hormonal control is always involuntary.
7. The effect of nervous control is usually localised, while in hormonal control, more than one target
organ may be affected.
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Section C: Free-Response Questions
Answer the following questions.
1.
Describe the general structure of the nervous system using the following terms: central nervous
system, effector, motor neurone, peripheral nervous system, and sensory neurone.
The nervous system is made up of the central nervous system (CNS) consisting of the brain and the
spinal cord, the peripheral nervous system (PNS) consisting of the cranial nerves from the brain,
the spinal nerves from the spinal cord, and the sense organs. Since the sense organs receive stimuli,
they are known as receptors. In response to stimuli, sensory neurones (receptor neurones) will transmit
impulses from the receptor to the CNS. A motor neurone (effector neurone) then transmits impulses from
the CNS to the effector such as muscle fibres, which will carry out the required action.
2.
Explain the nervous pathway involved in the following scenarios.
(a) The pupils of a person’s eyes change when the person moves from a dark room to a
bright room.
The size of the pupil determines the amount of light entering the eye. The size of each pupil is
controlled by two sets of involuntary muscles in the iris, namely, the circular muscles and the radial
muscles. When a person tries to see in a bright room after moving from a dark room, impulses are
produced that send signals to the central nervous system (CNS). The CNS, in turn, generates signals
via motor neurones, which cause the circular muscles of the iris to contract, and the radial muscles
to relax. This allows each pupil to constrict, therefore decreasing the amount of light entering
the eyes.
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(b) The lenses of a person's eyes change shape when the person focuses on a distant object.
When focusing on a distant object, the ciliary muscles relax, pulling the suspensory ligaments.
The suspensory ligaments then become taut, and in turn pull the edge of the lens. This causes
the lens to become thinner and less convex, which increases its focal length. Light rays from
the distant object will then be sharply focused on the retina, causing photoreceptors to be
stimulated. Nerve impulses produced are then transmitted by optic nerves to the central
nervous system (CNS). The brain then interprets the impulses, causing the person to see the
distant object.
WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
MultipleChoice
Structured
FreeResponse
(a) Understand how components of the
nervous system, such as the brain,
spinal cord and nerves, co-ordinate
and regulate bodily functions
2
1
1, 2
(b) Identify sensory neurones, relay
neurones and motor neurones; and
outline their functions
1
1
3, 4, 5
2
(c) State how the main components of
the eye work to produce a focused
image of near and distant objects, and
how they respond when exposed to
different light intensities
(d) State what is meant by an
endocrine gland
11.2, 11.3
11.2
2
12.1, 12.2
3
13.1, 13.2
(e) Define hormones (with reference to
certain examples), identify their mode
of action; and state the organ which
they are destroyed in
6, 7
3
13.1
(f) Outline how insulin and glucagon
regulate blood glucose levels
8, 9
4
13.3
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Textbook
section(s)
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Class:
Worksheet 11
(
Name:
)
Date:
Reproduction in Plants
for Chapter 14
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Reproduction in
plants
Offspring
genetically
identical to
parents
parts
Sexual
Asexual
Flowering plants
in
male and female
gametes brought
together
by
Offspring
genetically
different
from
parents
Self - pollination
Pollination
Sepal
may be
Cross - pollination
Petal
land on stigma
of female
flower of same
species
Receptacle
pollen grains are
transferred by
Pedicel
Anther
Stamen
parts
Filament
Carpel
Stigma
parts
Pollen
grains
Insect
Wind
after pollination,
germinates to
form
e.g.
e.g.
Clitoria
Ischaemum
produces
Style
Pollen
tube
Ovary
contains
male
two
nuclei travel
down
Ovule
contains
fuse with
Ovum
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
One of the advantages of asexual reproduction is that
A
B
C
D
.
all the beneficial characteristics of the parent are passed on to the offspring
less offspring are produced
more offspring are produced
there is more genetic variation in the offspring
( A )
For questions 2 and 3, refer to the diagram below, which shows the general section of a flower.
A
D
C
B
2.
3.
Where can male and female gametes be found?
Male gamete
Female gamete
A
A
B
B
A
C
C
B
A
D
B
D
What is structure C?
A
B
C
D
4.
Ovary
Petal
Sepal
Stigma
The carpel consists of
A
B
C
D
100
( D )
anthers and filaments
anthers, stigma and style
petals, sepals and stamens
stigma, style and ovary
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( B )
.
( D )
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5.
Pollination is
A
B
C
D
6.
the fusion of male gametes with the female gametes in the ovary
the fusion of pollen grains with the female gametes in the ovary
the transfer of female gametes to the stigma
the transfer of pollen grains to the stigma of a flower
Self-pollination refers to the
A
B
C
D
7.
.
( D )
.
fusion of pollen grains from a flower with the ovum of a different flower on another plant
fusion of pollen grains from a flower with the ovum of the same flower on the same plant
transfer of pollen grains from the anthers of a flower to the stigma of a different flower on
another plant
transfer of pollen grains from the anthers of a flower to the stigma of the same flower
on the same plant
( D )
The diagram below shows the structure of a generalised flower.
X
Y
Z
Where do pollination and fertilisation take place?
Pollination
Fertilisation
A
X
Y
B
X
Z
C
Y
X
D
Y
Z
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( B )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The diagrams below show a complete flower and a section of a flower of the Kalanchoe plant.
A
B
C
(a) Identify structures A to C.
A: Anther
B: Stigma
C: Ovule
(b) From what you can see in the diagrams, what feature of the flower suggests that the fruit of this
flower is likely to contain more than one seed?
There are many ovules in the ovary.
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2.
The diagram below shows a section of a flower.
G
A
F
B
E
Pollen
Stigma
C
D
(a) Identify structures A to G.
A: Ovary
E: Anther
B: Ovule
F: Filament
C: Style
G: Sepal
D: Petal
(b) Which of the structures A to G is directly involved in pollination?
E
(c) After fertilisation, state which structure will develop into
(i)
a fruit; and
A
(ii) a seed.
B
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Section C: Free-Response Questions
Answer the following questions.
1.
(a) Distinguish between asexual reproduction and sexual reproduction.
Asexual reproduction produces offspring that are identical to the parent, but sexual reproduction
produces offspring that are non-identical to the parents.
Asexual reproduction involves one parent, but sexual reproduction involves two parents.
Sexual reproduction involves fusion of gametes, but asexual reproduction does not involve fusion
of gametes.
Asexual reproduction involves mitosis, but sexual reproduction involves both meiosis and mitosis.
(b) Discuss the advantages and disadvantages of asexual reproduction.
Advantages:
-– The offspring produced are identical to the parent, so there is a higher chance of the good
characteristics of the parent being passed on to the offspring.
-– Only one parent is involved. It does not depend on external agents like wind.
Disadvantage:
-– There will be no genetic variation among the offspring. Therefore, the offspring will be less adapted
to changes in the environment.
(c) What are some special features of plants that enable them to carry out sexual reproduction?
Plants may have flowers. These are reproductive organs that enable plants to carry out sexual
reproduction. The parts of the flower that are involved in the reproduction process are the
stamen and pistil. The stamen consists of the anther and filament, with the anther producing male
gametes. The pistil consists of the stigma, style and ovary. The ovary contains at least one ovule
with a female gamete.
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2.
(a) Distinguish between pollination and fertilisation in flowering plants.
Pollination is the transfer of pollen grains from the anther to the stigma.
Fertilisation is the fusion of the male gamete with the female gamete to produce a zygote.
(b) Outline the growth of the pollen tube and its entry into the ovule.
Step 1: After pollination, the pollen grains germinate in response to the sugary fluid secreted by
the mature stigma.
Step 2: A pollen tube grows out from each pollen grain.
Step 3: The cytoplasm of each pollen grain enters the pollen tube.
Step 4: As the pollen tube grows, it secretes enzymes to digest the surrounding tissue of the stigma
and style. Thus, the pollen tube penetrates the style as it grows.
Step 5: The pollen tube enters the ovule usually through an opening in the ovule wall called
the micropyle.
Step 6: Within the ovule, the tip of the pollen tube absorbs sap and bursts, releasing two
male gametes.
(c) Describe fertilisation in flowering plants.
Fertilisation in flowering plants occurs in the following steps:
Step 1: Pollen settles on a mature stigma. The stigma secretes a sugary fluid.
Step 2: Pollen grain produces a pollen tube.
Step 3: Pollen tube grows downwards towards the ovule, enters the ovule, and releases two
male gametes.
Step 4: One male gamete fuses with the ovum to form a zygote.
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
(a) Define sexual and asexual reproduction, and
differentiate between the two processes
(b) Identify the main parts of a flower in
diagrams/photos
MultipleChoice
1
2, 3, 4
(c) State the functions of the sepals, petals,
anthers and carpels
(d) Outline the process of pollination, and
distinguish between self-pollination and
cross-pollination
Structured
5, 6, 7
FreeResponse
1
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14.1
1(a), 2(a)
14.2
2(b)
14.2
2(b)
2
(e) State the characteristics of insect-pollinated
and wind-pollinated flowers, and distinguish
between the two types of flowers
(f) Describe the growth of the pollen tube and
the process of fertilisation in flowering plants
Textbook
section(s)
14.3
14.3
1(b), 2(c)
2
14.4
© 2013 Marshall Cavendish International (Singapore) Private Limited
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Class:
)
Worksheet 12
(
Name:
Date:
Reproduction in Humans
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
for Chapter 15
CONNECT IT!
Seminal vesicles
Reproduction
in humans
Cowper’s gland
secrete fluid
that mixes
with sperms
to form
Prostate gland
Cervix
Semen
Scrotum
Organ systems
Uterus
ejaculated
into vagina
during sexual
intercourse
Penis
Male
Female
Urethra
Oviducts
Vagina
Sperm
Ovaries
Epididymis
and
progesterone
produce
fuse
Ova
(singular: ovum)
Sperm
Testosterone
Gestation
Fertilisation
control
may spread
some
STI-causing
agents
Testes
produce
Oestrogen
duct
Zygote
Embryo
Fetus
Birth
day 1–5
Menstruation
Menstrual
cycle
(for a 28-day
cycle)
Ovulation
day 14
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Sperms are produced in the
A
B
C
D
2.
.
epididymis
penis
sperm duct
testes
( D )
The diagram below shows a side view of the male reproductive system.
X
Y
Z
What is the function of X, Y and Z?
X
3.
Z
A
Passage for both
urine and sperms
Passage for sperms
Production of sperms
B
Passage for both
urine and sperms
Production of sperms
Passage for sperms
C
Passage for sperms
Passage for both urine
and sperms
Production of sperms
D
Production of sperms
Passage for sperms
Passage for both urine
and sperms
( C )
Where does fertilisation occur?
A
B
C
D
108
Y
Cervix
Ovary
Oviduct
Uterus
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( C )
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4.
The following diagram shows the concentration of female sex hormones in the blood over time.
Hormone
level
Key
oestrogen
progesterone
X
Time
Y
What happens at point X and point Y?
5.
X
Y
A
Menstruation
Ovulation
B
Menstruation
Repair of uterus wall lining
C
Repair of uterus wall lining
Menstruation
D
Repair of uterus wall lining
Ovulation
Risk of Human Immunodeficiency Virus (HIV) infection is best reduced by
.
A
B
C
D
( C )
not having blood transfusions
regular exercise and a healthy diet
keeping to one sexual partner
taking anti-viral medications
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( D )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The diagram below shows how the thickness of the uterine lining changes over time during a
menstrual cycle lasting 28 days.
Thickness
of uterine
lining
0 1 2 3 4
5 6 7
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Days
(a) On which day(s) is the woman most fertile?
Day 13 to 15
(b) What causes the decrease in the thickness of the uterine lining from day 0 to day 5?
Menstruation occurs. The uterine lining breaks down and is discharged from the body due to the drop
in progesterone production that occurs after the egg is not fertilised.
(c) If the woman is pregnant, what will happen to the thickness of the uterine lining after day 28?
The uterine lining will remain thick and spongy with blood vessels.
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(d) On the diagram below, draw a graph to show how the level of progesterone changes over the
course of the menstrual cycle, assuming that the woman is not pregnant.
Progesterone
level
1
2.
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Days
The diagram below shows the front view of the female reproductive system.
A
X
C
B
D
E
(a) Identify structures A to E.
A: Oviduct
B: Ovary
C: Uterine wall / Uterus / Uterine lining
D: Cervix
E: Vagina
(b) State the functions of structures A to C.
A is the oviduct, which is the passage for the egg as well as the site of fertilisation.
B is the ovary, which is the place where the eggs/ova develop.
C is the uterine wall, which is the site for embryo implantation.
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(c) How does the shape of structure A at point X help its function?
Structure A is a narrow muscular tube leading from B to C. It has a funnel-like opening at X, which
makes it easier for the egg to enter.
Section C: Free-Response Questions
Answer the following questions.
1.
Distinguish between the following terms:
(a) semen and sperm; and
Sperm is the male gamete produced in the testes. Semen is a fluid containing sperms.
This fluid is first secreted from the prostate gland and Cowper’s gland, before it is mixed with
sperms to activate them.
(b) ovary and oviduct.
The ovary produces eggs and female sex hormones. When eggs mature, they are released from the
ovary. The oviduct is a narrow muscular tube, which connects the ovary to the uterus. The mature
eggs released from the ovary, travel along the oviduct into the uterus. Fertilisation occurs in the
oviduct.
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2.
The table below shows the number of reported HIV/AIDS (Acquired Immune Deficiency Syndrome)
cases in Singapore from year 2000 to 2010.
Year
Total number of HIV/AIDS cases
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
226
237
234
242
311
317
359
423
456
463
441
(Source: Ministry of Health, Singapore 2011)
(a) Describe the general trend observed for the number of HIV/AIDS cases in Singapore over the
last 10-year period.
The number of HIV/AIDS cases in Singapore increased over the last 10 years.
(b) Explain how HIV/AIDS can be transmitted.
AIDS is caused by the human immunodeficiency virus (HIV).
HIV is transmitted through the exchange of body fluids such as semen/blood.
As such, HIV/AIDS can be transmitted by having unprotected sex with an infected person. It can also
be transmitted by sharing needles and syringes used by an infected person for injecting drugs.
(c) Describe ways in which the number of HIV/AIDS cases can be reduced.
Not be promiscuous / Have one sexual partner only
Use of condoms
No sharing of needles/syringes
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
Structured
FreeResponse
1, 2
2
1(a), 1(b)
15.2, 15.3
(b) Describe stages in the menstrual
cycle with reference to the effect of
hormones
4
1
1(c)
15.4
(c) Describe fertilisation and the process
of early development of the zygote
3
(d) Understand how the human
immunodeficiency virus (HIV) can be
transmitted between individuals, and
suggest methods to control the spread
of the disease
5
(a) Identify on diagrams, structures in the
male and female reproductive systems,
and state their respective functions
114
Textbook
section(s)
MultipleChoice
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15.5
2
15.6
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Class:
)
Worksheet 13
(
Name:
Date:
Heredity and Molecular Genetics
for Chapters 16 and 17
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
Deoxyribose
sugars
Phosphate
groups
consist
of
Nucleotides
made up
of
Nitrogenous
bases
(A, T, C, G)
and environment
Represented by letters
e.g. T or t, IO or IA
Allele
part of
Genes sequences
DNA
of
found
in
that code for
characteristics
expressed in
homozygous(TT)
and
heterozygous(Tt)
conditions
Recessive
expressed
in only
homozygous(tt)
condition
Homozygous
Heterozygous
tt or TT
Tt
leads to
Variation
variation
Discontinuous variation
Complete
dominance
e.g.
additive
effect
of many
genes
Tall or dwarf
pea plants
can cause
Mutation
types
Continuous
in humans may be
Autosome
e.g. in pea plants
Dominant
Chromosomes
Phenotype
affects
Genotype
may be
lead
to
different
forms of the
same gene
Sex
chromosome
Mutagen
Gene mutation
e.g
Hb gene mutation
causes
Sickle-cell
anaemia
Chromosomal mutation
e.g.
Trisomy ( three copies) of chromosome 21
caused by a few genes
causes
Down's syndrome
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
Phenotype is determined by
A
B
C
D
.
environmental factors only
genotype and environmental factors
genotype only
mutation only
( B )
For questions 2 and 3, refer to the following diagram showing the family tree of a family with
phenylketonuria (PKU). PKU is a disease that is expressed in homozygous recessive individuals. PKU
patients cannot break down the amino acid called phenylalanine.
Key
normal female
normal male
P
PKU female
Generation I
PKU male
R
Q
S
Generation II
Generation III
T
2.
Which of the following best describes the genotype of individuals in the family tree?
A
B
C
D
3.
( B )
What is the chance that T will be normal?
A
B
C
D
116
P and Q are homozygous dominant.
P and Q are heterozygous.
R and S are homozygous dominant.
R is homozygous dominant, and S is heterozygous.
25%
50%
75%
100%
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( C )
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4.
The Rhesus blood group system is a human blood group system. It is the most clinically important
blood group system after ABO. In humans, the allele for the Rhesus-positive trait (H) is dominant
to the allele for the Rhesus-negative trait (h). If a homozygous Rhesus-positive woman and a
homozygous Rhesus-negative man have children, what is the probability of their first child being
Rhesus-positive?
A
B
C
D
5.
22
22
23
23
chromosomes
chromosomes
chromosomes
chromosomes
and
and
and
and
one
one
one
one
X
X
X
X
.
chromosome
or Y chromosome
chromosome
or Y chromosome
( A )
.
Sickle-cell anaemia is an example of a
A
B
C
D
7.
( D )
The nucleus of the human female gamete contains
A
B
C
D
6.
0%
25%
75%
100%
bacterial infection
chromosomal mutation
dietary deficiency disease
gene mutation
( D )
The graphs below show the distributions, within a human population, for height and for earlobe type.
Percentage of
population
Percentage of
population
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Height/m
Free
earlobe
Attached
earlobe
Which type of variation does each characteristic exhibit?
Height
Type of earlobe
A
Continuous
Continuous
B
Continuous
Discontinuous
C
Discontinuous
Continuous
D
Discontinuous
Discontinuous
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( B )
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8.
Which of the following characteristics is an example of continuous variation?
A
B
C
D
9.
Ability to roll tongue
Blood type
Gender
Length of feet
( D )
The following diagram shows part of a DNA molecule.
X
Y
Z
Identify X, Y and Z.
X
Y
Z
A
Deoxyribose sugar
Nitrogenous base
Phosphate group
B
Nitrogenous base
Deoxyribose sugar
Phosphate group
C
Phosphate group
Deoxyribose sugar
Nitrogenous base
D
Phosphate group
Nitrogenous base
Deoxyribose sugar
( C )
10. Which of the following correctly lists all the nitrogenous bases in DNA?
A
B
C
D
118
Adenine, cytosine, guanine, thymine
Adenine, cytosine, guanine, uracil
Alanine, cytosine, guanine, thymine
Alanine, cytosine, guanine, uracil
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( A )
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The sex of a person is determined by the combination of X and Y chromosomes present.
Female cells have two X chromosomes, while male cells have one X and one Y chromosome.
(a) State whether the male or the female gamete determines the sex of a child.
Male gamete
(b) In the space below, draw a genetic diagram to show that there is an equal chance that a baby
can be a boy or a girl.
Parental phenotypes
Parental genotypes
Male
XY
X
Y
X
X
XX
Female
XX
Female
XY
Male
XY
Male
Gametes
Offspring genotypes
Offspring phenotypes
Female
XX
ⴛ
Offspring phenotypic
ratio
Female : Male = 1 : 1
(c) The following diagram shows all the chromosomes (the karyotype) of a person.
1
13
2
14
15
3
16
4
17
18
5
19
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6
20
7
8
21
9
10
22
11
12
23
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(i)
Identify the sex of the person from which the chromosomes were taken. Explain your
answer.
The person would be a male, because the 23rd pair of chromosomes consists of an
X chromosome and a Y chromosome.
(ii) Suggest, with a reason, what condition will be present in this person.
The condition will be Down’s syndrome, because an extra chromosome 21 is present.
2.
Sickle-cell anaemia is a condition in which red blood cells contain abnormal haemoglobin. People
who inherit two sickle-cell alleles, are seriously anaemic and usually die young. Those who are
heterozygous are only mildly affected.
(a) State the process that brought about the sickle-cell gene.
Gene mutation
(b) Suggest, with a reason, whether the allele, that gives rise to sickle-cell anaemia is
dominant or recessive.
The allele is recessive, because only those with two sickle-cell alleles (homozygous recessive)
exhibit the trait, whereas those with only one sickle-cell allele (heterozygous) are less affected
by the disease.
(c) The diagram below shows a family tree with some members of a family being affected by
sickle-cell anaemia.
Key
normal female
normal male
affected female
I
affected male
1
2
II
7
III
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3
?
4
5
6
?
8
© 2013 Marshall Cavendish International (Singapore) Private Limited
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Using ‘N’ to represent the normal allele and ‘n’ to represent the sickle-cell allele,
(i) State the genotype(s) of persons 1 and 2. Explain your answer.
The genotype of persons 1 and 2 is Nn, because one of their offspring, person 3, has
sickle-cell anaemia. This means that person 3 must have inherited the sickle-cell allele from
both 1 and 2.
(ii) Person 4 often complains of becoming tired easily. He had his blood tested. What is the
probability that he has sickle-cell anaemia? Use a genetic diagram to show this.
Parental phenotypes
Parental genotypes
Gametes
Offspring genotypes
Offspring phenotypes
Offspring phenotypic
ratio
Normal
Nn
Normal
Nn
ⴛ
N
n
N
n
NN
Normal
Nn
Normal
Nn
Normal
nn
Affected
Normal : Affected = 3 : 1
Person 4 has a 25% chance of having sickle-cell anaemia.
(d) Explain why a person with two sickle-cell alleles will usually die young.
A person with two sickle-cell alleles, has abnormal haemoglobin in his or her red blood cells. The
red blood cells have a shorter lifespan due to frequent changes in shape and clumping. Thus,
there are insufficient red blood cells to carry the oxygen required for respiration around the body.
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3.
A scientist analysed a double stranded DNA sample and found that 15% of its nitrogenous bases
were adenine. Calculate the percentage of the other nitrogenous bases in the DNA sample. Explain
your answer.
According to the base pairing rule, adenine pairs with thymine, while guanine pairs with cytosine,
hence, given that adenine is 15%,
percentage of thymine = percentage of adenine = 15%
100% – (15% + 15%)
2
70%
=
2
percentage of guanine = percentage of cytosine =
= 35%
Section C: Free-Response Questions
Answer the following questions.
1.
(a) Distinguish between
(i) a gene and an allele; and
A gene is a segment of DNA that stores hereditary information. Genes can have different
forms, for example, a gene for height can code for ‘short’ or ‘tall’. Different forms of the
same gene are called alleles, which occupy the same locus in homologous chromosomes.
(ii) genotype and phenotype.
Genotype is the genetic make-up of an organism, that is, the combination of genes in the
organism, whereas phenotype is a result of genes and the effects of the environment on the
organism. The genotype of an organism cannot be observed directly, whereas its phenotype,
which is an expressed trait, is usually visible in its outward appearance.
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(b) Draw a genetic diagram to show the inheritance of height in pea plants when two heterozygous
tall pea plants cross. The tall allele is the dominant allele.
Let T be the dominant allele (allele for tallness).
Let t be the recessive allele (allele for dwarfness).
Parental phenotype
Parental genotype
Gametes
Offspring genotypes
Offspring phenotypes
Offspring phenotypic ratio
2.
Tall
Tt
Tall
Tt
ⴛ
T
t
T
t
TT
Tall
Tt
Tall
Tt
Tall
tt
Short
Tall : Short = 3 : 1
(a) Distinguish between continuous variation and discontinuous variation.
Continuous variation deals with phenotypes that range from one extreme to the other. It
is brought about by the additive effect of many genes. Continuous variation is affected by
environmental conditions. Discontinuous variation is brought about by one or a few genes.
This results in clear-cut phenotypes with no intermediate forms between traits. Unlike
continuous variation, discontinuous variation is not affected by environmental conditions.
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(b) Discuss the possible causes of mutation, and give an example where a mutation is
advantageous to an organism.
Mutation occurs when there is an error during the replication of the gene or the chromosome.
It can also be caused by mutagens such as radiation and chemicals. The gene mutation
that causes sickle-cell anaemia, may be advantageous in places where malaria is common.
Individuals who are heterozygous for the sickle-cell allele, are more resistant to malaria,
because a small percentage of their red blood cells are sickle-shaped (mutated). As these
individuals do not fully contract either disease, they have better chances of surviving and
reproducing, compared to homozygous or normal individuals. This selection ensures that the
recessive allele persists in the population.
WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
MultipleChoice
Structured
(a) Distinguish between "gene" and "allele"
Textbook
section(s)
1
16.2
1
16.2
1
16.2, 16.3
(b) Understand and explain commonly used
terms in the study of heredity, such as
"dominant", "recessive", "homozygous",
"heterozygous", "phenotype" and
"genotype"
1, 2
(c) Solve problems, and predict results of
monohybrid inheritance using genetic
diagrams
3, 4
1, 2
(d) Describe the determination of sex in
humans with reference to the XX and XY
chromosomes
5
1
(e) Differentiate between discontinuous and
continuous variation
7, 8
(f) Describe different types of mutation and
their causes
6
2
9, 10
3
17.1
3
17.1, 17.2
(g) State the composition of DNA and its
structure
(h) Understand and apply the rules of base
pairing
124
FreeResponse
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16.3
2
16.4
2
16.5
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Class:
Worksheet 14
(
Name:
)
Date:
CONNECT IT!
Complete the concept map below using keywords learnt in the chapter. Discuss with your
classmates how the concept map can be extended.
affected
by
Ecosystem
affect
important
processes
Abiotic
factors
Biotic
factors
Human
activity
Non-cyclic
energy flow
e.g.
Carbon
cycle
results in
such
as
physical
factors
causes
e.g.
Pollution
to maintain
Biodiversity
e.g. water
pollution by
Energy
transfer
Light
between
Temperature
Sewage
Water
Inorganic wastes
intensity
availability
Oxygen content
can be
compared
using
e.g.
Conservation
Industry
Trophic
levels
Pyramid of
numbers
results
in need
for
such as
living things that
interact with an
organism
Nutrient
cycling
for Chapters 18 and 19
Ecology and Our Impact on the
Ecosystem
Insecticide
Salinity of soil/water
pH of soil/water
Ecological
pyramids
stored in
fatty tissues
of organisms
Pyramid of
biomass
Bioaccumulation
Producers
Consumers
Decomposers
feeding
relationship
represented as
Food chains
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interlinked
to form
Food
web
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125
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TEST IT!
Section A: Multiple-Choice Questions
Choose the correct answer, and write its letter in the brackets provided.
1.
The diagram below shows a food web.
aphid
plant
ladybird
caterpillar
snake
small bird
owl
shrew
badger
Which one of the following organisms is a secondary consumer?
A
B
C
D
2.
Aphid
Caterpillar
Small bird
Snake
( C )
Which of the following pyramids represents the biomass of the organisms in the food chain below?
tree
aphid
A
B
C
D
bird
( B )
3.
Producers are organisms that
A
B
C
D
126
break down dead organic matter
can convert light energy into chemical energy
live on or in the body of another organism
obtain energy from other organisms on which they feed
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.
( B )
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4.
Sewage pollutes water and causes a
A
B
C
D
5.
in
in
in
in
the
the
the
the
carbon dioxide concentration
dissolved nitrate concentration
number of decomposers
oxygen concentration
( D )
.
Bioaccumulation refers to the build-up of
A
B
C
D
6.
decrease
decrease
decrease
decrease
.
biodegradable chemicals along a food chain
energy along a food chain
living organisms along a food chain
non-biodegradable chemicals in an organism
( D )
A factory discharges sewage into a river at point P. Which of the following graphs illustrates the
changes in the level of dissolved oxygen in an organism?
A
B
Level of
dissolved
oxygen
P
C
Distance from the
source of the river
P
D
Level of
dissolved
oxygen
P
Level of
dissolved
oxygen
Distance from the
source of the river
Level of
dissolved
oxygen
Distance from the
source of the river
P
Distance from the
source of the river
( C )
7.
Which types of microbes are used in the treatment of sewage?
A
B
C
D
Aerobic bacteria, anaerobic bacteria and fungi
Aerobic bacteria and anaerobic bacteria
Aerobic bacteria and fungi
Anaerobic bacteria and fungi
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Section B: Structured Questions
Answer the following questions in the spaces provided.
1.
The pyramid of biomass for a forest is shown below. The width of each band represents the biomass
of each trophic level.
eagles
sparrows
caterpillars
trees
(a) What is the correct unit used to record biomass?
It is kilogramme per unit area.
(b) Why are pyramids of biomass more useful when studying a particular ecosystem than pyramids
of numbers?
Pyramids of numbers may be inverted if organisms of one trophic level are parasitic on organisms of
another trophic level. Hence, it is not an accurate representation of the transfer of energy.
(c) From the pyramid of biomass, identify
(i) the producer; and
Trees
(ii) the secondary consumer.
Sparrows
(d) Insecticide was sprayed onto the trees to control the number of caterpillars. After a few
years, scientists noticed that there was a decline in the number of eagles in the forest.
Suggest two reasons for the decline.
The first reason is that bioaccumulation had occurred. The insecticide had accumulated in
the caterpillars’ bodies. When the sparrows ate the caterpillars, the insecticide further accumulated in
the sparrows, as each sparrow fed on many caterpillars. When the eagles fed on the sparrows, more
insecticide accumulated in the eagles. Hence, the eagles were poisoned. The second reason is that
the decrease in caterpillars led to the decrease in sparrow population, as there was less food for the
sparrows. This in turn resulted in less food for the eagles, causing the eagle population to decrease.
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2.
The diagram shows the energy and nutrient pathways in a food chain.
The
Sun
energy pathways:
CO2
nutrient pathway:
Herbivores
Energy lost
Dead organic matter
Producer
Carnivores
(a) What nutrient is illustrated in the nutrient pathway?
Carbon
(b) How does the producer take in energy from the Sun?
It obtains energy from photosynthesis in which, chlorophyll absorbs light energy and converts it to
chemical energy stored in the form of carbohydrate molecules.
(c) Why do the arrows representing the energy pathway decrease in size from the Sun to the
carnivores?
This is because, energy is lost as heat, and some energy accumulates as biomass (mass of the
organisms). Thus, only a small percentage of the energy is transferred to the next trophic level.
(d) A carbon sink is an area that stores carbon compounds for an indefinite period. Name
two natural places on Earth that can be considered as carbon sinks.
Any two of the following: Soil/Forest/Ocean/Savanna
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3.
The diagram below shows the effects of human activities in a town.
residential
area
forest
river
factory
(a) Organic matter is discharged from the residential area.
(i)
State the effects of the discharge of this organic matter on the organisms in the river.
The organic matter provides a rich source of food for bacteria in the river. This will increase the
bacterial population, which uses up more oxygen from the river water. This in turn decreases the
oxygen concentration in the water for other organisms. The other organisms in the river will die due to
a lack of oxygen.
(ii) How would the concentration of dissolved oxygen change as water flows downstream from
the residential area?
Further downstream, there is no more waste material being discharged into the river, which causes
the bacterial population to decrease. Therefore, the dissolved oxygen concentration will increase.
(b) The factory discharges high-temperature waste into the river. How would this discharge affect the
organisms in the river?
High-temperature waste will increase the temperature of the river. Since enzymes denature at high
temperatures, important enzyme reactions that are essential for the survival of organisms, may not occur.
Therefore, the populations of the river organisms will decrease.
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(c) Suggest two ways to improve the quality of water in the river.
Firstly, treat the sewage before discharging it, to remove toxic materials and bacteria. Secondly,
use microorganisms that can break down organic matter / toxic matter to pre-treat the waste water
(bioremediation) before discharging it.
LEARN & APPLY
Go through the worked example below, then try to answer the Free-Response Questions.
Worked Example
Describe how humans cause water pollution.
Thought Process
Your answer should focus on the effects of human activities, and not on natural disasters. You should
include a definition of pollution, the source of pollutants, and the effects of these pollutants on water.
Answer
Points to cover
1. Pollution is the addition of substances to the environment that damage it, making it
undesirable or unfit for life.
2. Most of the time, pollution is brought about by human activities as the human population
increases, and industrialisation and urbanisation become more prevalent. Waste materials from
factories, and untreated sewage dumped into rivers and streams, pollute the water (sources
of pollutants).
3. Waste materials from factories may include poisonous chemicals or metals such as mercury,
lead, zinc and arsenic. They make the water unsafe to drink. It is also unsafe to consume fish
living in such polluted water.
4. Untreated sewage, especially with high nitrate content, is a good source of food for bacteria.
Bacteria grow and multiply rapidly, using up the oxygen in water.
5. Other organisms in the water such as fishes and plants die due to a lack of oxygen in the water
(the bacteria also cause diseases such as cholera and typhoid — making the water unsafe to
drink).
6. Nitrates, present in fertilisers that are leached into the river, may promote growth of algae (algal
bloom). The algae will block sunlight for photosynthesis of underwater plants. As plants die and
decompose, the level of oxygen decreases, and organisms such as fishes die.
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Section C: Free-Response Questions
Answer the following questions.
Discuss the importance of
1.
conserving species to maintain biodiversity;
Biodiversity is a valuable natural resource. Conserving species prevents the extinction of species,
and maintains a stable and balanced ecosystem. In addition, conservation is of scientific value, as
the study of biodiversity provides useful information to humans. Many animals and plants are a
major source of human food. Many organisms are sources of raw materials for industries, medicinal
drugs and natural insecticides. Conserving species is also necessary to maintain a large gene pool, so
that agricultural produce can be improved through cross-breeding different varieties of wild plants and
animals with favourable genes.
2.
proper treatment of sewage before discharge; and
Untreated sewage may contain disease-causing bacteria that can potentially affect large human
populations when it enters sources of drinking water. The organic waste in sewage are a good
source of food for bacteria, leading to rapid increases in the bacterial population. As bacteria use up
the oxygen in the water, other organisms die due to a lack of dissolved oxygen. Anaerobic bacteria
continue breaking down organic waste and releasing bad-smelling gases in the process. Untreated
sewage, if discharged into rivers or lakes, can also lead to eutrophication, causing the death of
organisms due to a lack of oxygen.
3.
controlling the use of pesticides.
Uncontrolled use of pesticides can pollute water bodies and contaminate food sources when
non-biodegradable pesticides are washed by rainwater into streams, rivers and lakes. These
pesticides may accumulate in the bodies of consumers that feed on contaminated organisms,
resulting in the pesticides being passed along the food chains. Eventually, humans and top
consumers suffer the toxic effects due to bioaccumulation. In addition, the use of a pesticide in
excess could promote the growth of populations of pests that develop resistance to the pesticide.
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WORK ON IT!
Circle the question(s) you have answered incorrectly. Then, revisit the relevant section(s) in the
textbook to strengthen your understanding of the key concept(s).
Questions
Learning objectives
MultipleChoice
(a) Describe the non-cyclical nature of
energy flow
(b) Understand and explain terms such as
"producers", "consumers" and "trophic
level" in the context of food chains and
food webs
2
2
(e) Describe the carbon cycle and the role
of carbon sinks
(f) Describe and evaluate the effects of
water pollution by sewage, inorganic
waste and insecticides
4, 5, 6
(g) Outline the role of microorganisms in
sewage treatment
7
(h) Discuss reasons for conservation of
species
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Textbook
section(s)
18.4, 18.5
1, 3
(c) Explain how energy losses occur along
food chains, and the efficiency of
energy transfer between trophic levels
(d) Interpret pyramids of numbers and
biomass
Structured
FreeResponse
18.4
2
18.5
1
18.5
2
18.6, 18.7
1, 3
2, 3
19.1
19.1
1
19.2
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Class:
Model Examination Paper
(
Name:
)
Date:
Section A: Multiple-Choice Questions
Answer ALL the questions in this section. For each question, there are four possible answers,
A, B, C and D. Choose the correct answer, and write its letter in the brackets provided.
1.
When comparing a plant cell to an animal cell, one would expect to find
A
B
C
D
2.
B
C
D
Carbon
Carbon
Carbon
Carbon
monoxide and irritants
monoxide and nicotine
monoxide and tar
monoxide, nicotine and tar
( B )
To produce male sex hormones that are responsible for the development of male sexual
characteristics
To secrete a fluid that activates the eggs in females
To secrete a fluid that contains enzymes, which break down the egg membrane
To secrete a slippery fluid that contains nutrients and enzymes, which nourish and
activate sperms
( D )
Which of the following correctly matches the substance with its process of entry into an epithelial cell
of the small intestine after a heavy meal?
Substance
Process
A
Amino acids
Osmosis
B
Fats
Active transport
C
Glucose
Diffusion
D
Water
Diffusion
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( C )
What is the role of the prostate gland, the Cowper’s gland and the seminal vesicles in the male
reproductive system?
A
4.
a cellulose cell wall in both the plant and animal cells
a nucleus containing a nucleolus in the animal cell, but not in the plant cell
endoplasmic reticulum in both the plant and animal cells
ribosomes in the animal cell, but not in the plant cell
Which of the following substances in cigarette smoke cause an increased chance of fat deposits
in the coronary arteries?
A
B
C
D
3.
.
( C )
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For questions 5 and 6, refer to the graph of an enzyme-catalysed reaction shown below.
Rate of
reaction
X
Y
Substrate
concentration
5.
Which of the following best describes what happens during interval X?
A
B
C
D
6.
Which of the following best describes what happens during interval Y?
A
B
C
D
7.
Product formation has stopped.
Some of the active sites are unoccupied.
The amount of product being formed is equal to the amount of product being broken down.
The product is being formed at a constant rate.
( B )
Product formation has stopped.
Some of the active sites are unoccupied.
The amount of product being formed equals the amount of product being broken down.
The product is being formed at a constant rate.
( D )
An experiment was conducted to trace the path taken by carbohydrate molecules from a plant, after
a herbivore had consumed the plant. The carbohydrate molecules were labelled with radioactive
carbon. Special equipment were then used to detect these radioactively labelled molecules. Which
of the following paths is correct?
In the plant
8.
A
Glucose
starch
Glucose
maltose
starch
B
Glucose
starch
Maltose
glucose
glycogen
C
Starch
maltose
Glucose
maltose
starch
D
Starch
maltose
Starch
glucose
glycogen
( B )
A patient had his gall bladder removed, and needs to be put on a special diet. Which menu would be
most suitable for this patient?
A
B
C
D
136
In the herbivore
Boiled chicken meat (without skin) and a fresh orange
Chicken sausages and cream cake
Fried fish fillet and boiled potato
Pan-fried fish fillet in cheese sauce and green salad
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( A )
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9.
The diagram below shows part of the digestive system.
X
Y
Z
Which structures produce substances involved in fat digestion?
A
B
C
D
X only
Y only
X and Y only
X, Y and Z
( C )
10. A particular characteristic is controlled by a dominant allele, R, and a recessive allele, r. Which of the
crosses will give a 1:1 ratio of two phenotypes among the offspring?
A
B
C
D
RR × rr
Rr × RR
Rr × Rr
Rr × rr
( D )
11. A plant was placed in a bell-jar in a warm and brightly-lit environment. The air in the jar contains carbon
dioxide, where carbon exists as a radioactive isotope.
1
3
2
After six hours, which of the following regions are likely to have high levels of radioactivity?
A
B
C
D
1 and 2
1 and 3
2 and 3
1, 2 and 3
( C )
12. DNA molecules, isolated from a rat cell and a human cell, are found to differ in the sequence of
.
their
A
B
C
D
bases
sugars
phosphates
bases, sugars and phosphates
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For questions 13 and 14, refer to the diagram below, which shows a vertical section of the human heart.
2
4
3
5
1
Y
W
X
Z
13. Which of the following blood vessels contains blood with the highest oxygen concentration?
A
B
C
D
1
2
3
5
( D )
14. Heart sounds are produced by
A
B
C
D
.
closing of valves W and X
closing of valves W, X, Y and Z
opening of valves Y and Z
opening of valves W, Y and Z
( B )
15. The graph below shows the concentration of lactic acid in the blood of an athlete. During which time
period is oxygen debt incurred and repaid?
Concentration of
lactic acid
P
Q
R
Time
138
Oxygen debt incurred
Oxygen debt repaid
A
P
Q and R
B
Q
R
C
P and Q
R
D
Q and R
P
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( B )
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16. The diagram below shows the structure of a flower.
X
Y
W
Z
At which part of the flower can the male and female gametes be found, assuming that there is no
pollination or fertilisation?
Male gamete
Female gamete
A
W
X
B
X
Y
C
Y
Z
D
Z
Y
( C )
17. The diagram below shows the male reproductive and urinary system. What is the tube labelled X?
X
A
B
C
D
Epididymis
Seminal vesicle
Sperm duct (vas deferens)
Ureter
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18. The following family tree shows the inheritance pattern of an inheritable disease.
Key
normal male
affected male
normal female
affected female
P
What is/are the possible genotype(s) of P, who is normal (B represents the normal allele and b
represents the allele for the disease)?
A
B
C
D
BB
bb
Bb
BB, Bb
( C )
19. The rule of complementary base pairing in DNA states that
A
B
C
D
adenine
adenine
adenine
adenine
pairs
pairs
pairs
pairs
with
with
with
with
.
cytosine, while guanine pairs with thymine
guanine, while cytosine pairs with thymine
thymine, while guanine pairs with cytosine
thymine, while guanine pairs with thymine
( C )
20. The graph shows the populations of animal X and animal Y in the same habitat, from 1920
to 1940.
Number of
individuals/
hundreds
80
0
X
60
0
Y
Y
40
0
20
0
1925
1930
1935
1940
Year
What biological relationship between animal X and animal Y is shown in the graph?
A
B
C
D
140
X
X
X
X
and
and
and
and
Y
Y
Y
Y
compete for the same, limited resource.
interact such that one of them benefits, while the other is harmed.
interact such that one is the predator, and the other is the prey.
interact such that both benefit.
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( C )
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Section B: Structured Questions
Answer ALL questions in the spaces provided.
1.
The diagram below shows a simplified representation of the transfer of energy in a generalised
ecosystem. Each box represents a category of organisms, grouped together based on their trophic
position in the ecosystem.
The
Sun
Sun
I
Decomposers
II
III
(a) State the trophic levels of the organisms in boxes I, II and III.
[3]
Box I is the producer.
Box II is the primary consumer.
Box III is the secondary consumer.
(b) State the form of energy that enters organisms in box III.
[1]
It is chemical energy.
(c) Identify which arrow represents the greatest transfer of energy per unit time (add a large ‘ ’ next
to the arrow).
[1]
(d) Explain what the wavy arrows leaving each box represents.
[3]
The wavy arrows represent the energy [1] that is lost as heat [1] due to metabolic activities [1] such
as respiration.
(e) Explain why there are usually not many trophic levels in a food chain.
[2]
This is because energy is lost as it is passed from one trophic level to the next. Usually about 10%
of the energy [1] is passed down from one level to the next. If there are too many trophic levels, the
higher trophic levels will receive very little energy [1] for survival.
[Total: 10 marks]
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2.
The diagram below shows the transverse section of a leaf.
upper epidermis
palisade
mesophyll cell
spongy
mesophyll
cells
lower epidermis
guard cells
(a) Label on the diagram, the different types of cells that can be found in the transverse section of
a leaf
[5]
(b) Draw a small circle in each of the cells in (a) that contains chloroplasts.
[3]
Circle should be drawn in the palisade mesophyll cells [1], spongy mesophyll cells [1] and guard
cells [1].
(c) State two internal features of a leaf, and explain how these features allow the leaf
to photosynthesise more efficiently.
[4]
Any two of the following: Presence of chloroplasts [1] in mesophyll cells and guard cells for
photosynthesis to occur / Guard cells forming stomata [1] for gas exchange [1] / Presence of
vascular bundles [1] to transport water to mesophyll cells for photosynthesis
[Total: 12 marks]
3.
Four cylinders of potato (with a length of 20 mm as shown below) were each placed in
sugar solutions of different concentrations.
20 mm
After one hour, the cylinders were removed and gently blotted dry, before their lengths were measured
again. The results were recorded and shown in the table below.
142
Solution
Original length/mm
Final length/mm
A
20
25
B
20
20
C
20
15
D
20
18
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(a) Which movement mechanism is being investigated in this experiment?
[1]
Osmosis
(b) Which property of the potato cells allows the movement mechanism in (a) to happen?
[1]
Partially permeable membrane
(c) Explain why the length of the cylinders will
(i)
remain unchanged;
[2]
Water potential of the cell sap is the same as the environment [1]; hence, there is no net
movement of water. [1]
(ii) increase; and
[2]
Water potential of the environment is higher than the water potential of the cell sap [1];
hence, water moves from the environment into the cell sap by osmosis. [1]
(iii) decrease.
[2]
Water potential of the environment is lower than the water potential of the cell sap [1];
hence, water moves from the cell sap into the environment by osmosis. [1]
(d) Suggest and explain, which solution is likely to have the same water potential as the
potato cells.
[2]
Solution B. [1] There was no change in the length of the cylinder. [1]
(e) State whether solution A is a dilute or concentrated sugar solution.
[1]
Dilute sugar solution
[Total: 11 marks]
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4.
The diagram below shows the structure of a developing human fetus and part of the uterine wall.
B
A
X
Content in A (arbitrary units)
Content in B (arbitrary units)
• 20 units of oxygen
• 40 units of carbon
dioxide in the form of
hydrogencarbonate ions
• 36 units of glucose
• 32 units of urea
• 50 units of oxygen
• 25 units of carbon dioxide
in the form of
hydrogencarbonate ions
• 78 units of glucose
• 12 units of urea
(a) Identify vessels A and B.
[2]
A is the umbilical artery, B is the umbilical vein.
(b) State the reasons for your answer in (a).
[2]
The umbilical artery carries deoxygenated blood (lower oxygen concentration) and waste products
(higher concentrations of carbon dioxide and urea) away from the fetus. [1] On the other hand, the
umbilical vein carries oxygenated blood (higher oxygen concentration) and food substances (higher
concentration of glucose) to the fetus. [1]
(c) The function of X is to support and protect the fetus. X contains fluids known as the
amniotic fluid. Suggest how X performs its functions.
[2]
It provides buoyancy / acts as a shock absorber. [1] It protects the fetus against mechanical injury. [1]
[Total: 6 marks]
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5.
The action of lipase on fats in three different milk solutions, A, B and C, was investigated. The volumes
of enzyme and milk solutions were kept constant. Lipase breaks down fats into fatty acids and glycerol.
The amount of fatty acids formed can be deduced by measuring the pH of the mixture. The graph below
illustrates the results obtained.
pH of
reaction
mixture
A
B
C
A, 40°C
Sample A, 30˚C
C, 40°C
X
B, 40°C
0
2
4
6
8
10
12
14
16
18
20
(a) State the time taken for the reaction to be completed in milk sample C.
Time/min
[1]
6 minutes
(b) Comparing B and C, suggest a factor that could have affected the rate of reaction between
0 minute and 2 minutes.
[1]
It is the concentration of substrate (fat).
(c) Suggest why the graphs labelled A and C became level at the same height, X.
[2]
The amounts of fats (substrate) in A and C are the same. [1] The graphs become level when all the
fats in the milk solutions are broken down by lipase into fatty acids and glycerol. [1]
(d) On the graph given, draw and label the graph that would be obtained if the same volume of
lipase was added to the same volume of sample A, with the reaction carried out at a
temperature of 30°C.
[2]
[Total: 6 marks]
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Section C: Free-Response Questions
Answer 2 out of 3 questions. Write your answers on the writing paper provided. Label your answers
prominently and neatly. Use a fresh sheet of paper for each question. Hand in Section C separately
from Section B.
1.
Compare and contrast the transport of nutrients and water in plants and humans.
[10]
[Total: 10 marks]
2.
(a) (i)
Define aerobic respiration and photosynthesis.
(ii) Explain the relationship between these two processes, and their importance to living
organisms.
[5]
(b) Gas exchange occurs at the surface of both mesophyll cells in the leaf and at the alveoli in the lungs.
In what ways are the structures and functions of these surfaces similar for gas exchange?
[3]
(c) Phytoplankton are microscopic food producers. Only a small percentage of sunlight reaching a
pond is used by phytoplankton for photosynthesis. Suggest two reasons for this.
[2]
[Total: 10 marks]
3.
Draw a labelled diagram of a cross-section of a dicotyledonous leaf, and use your diagram to describe
the movement of water inside a leaf.
[10]
[Total: 10 marks]
1. Similarities: Both transport systems consist of vessels for transporting substances, [1] and the
transport medium is liquid/fluid. [1]
Differences: Plants have a closed circulatory system driven mainly by transpirational pull in xylem,
whereas humans have a closed circulatory system driven by the pumping of the heart. [2]
Transport vessels in plants include xylem vessels, which are dead cells, and phloem tissue. No organ is
involved. Transport vessels in humans include arteries, veins and capillaries, which are all tissues. An
organ, the heart, acts as a pump. [2]
In plants, water and dissolved ions are transported in the xylem. Manufactured food is transported
by the sieve tubes of the phloem. The different nutrients needed by plants are, thus, transported in
separate vessels. In humans, digested food substances, ions and water are all transported in the
blood. Thus, nutrients are not carried in separate vessels. [2]
The phloem conducts food materials in the form of sucrose and amino acids, from the green parts of
the plant, especially the leaves, to other parts of the plant. The xylem conducts water and dissolved
mineral salts from the roots to the stems and leaves. In humans, blood transports the following:
digested food substances from blood capillaries in the intestines to all parts of the body; excretory
products from tissues to excretory organs; heat from respiring tissues to all parts of the body; and
oxygen from the lungs to all parts of the body. [2]
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Notes
2. (a) (i)
Aerobic respiration is the breakdown of food substances in the presence of oxygen with
the release of a large amount of energy, and carbon dioxide and water as waste products. [1]
Photosynthesis is the process in which light energy absorbed by chlorophyll is transformed into
chemical energy used to synthesise carbohydrates from water and carbon dioxide. Oxygen is
released in the process. [1]
(ii)
In photosynthesis, light energy is transformed into chemical energy stored in carbohydrates,
while in aerobic respiration, chemical energy stored in food such as carbohydrates is released
in the form of heat energy and chemical energy. [1] Photosynthesis provides substrates for
organisms to use in tissue respiration. It provides energy in a usable form for all organisms. [1]
Aerobic respiration releases useful energy from food for organisms to carry out vital activities. [1]
(b) Both mesophyll cells and alveoli are covered with a thin film of moisture to allow gases to dissolve.
[1] Carbon dioxide diffuses rapidly into mesophyll cells in plants, while oxygen diffuses into alveoli
through one-cell thick alveolar walls. [1] Both mesophyll cells and alveoli have large surface areas
to increase the rate of diffusion. [1]
(c) Energy from the sun is lost to the surroundings by reflection from the pond surface, conduction by
water in the pond and convection from the pond surface. [1] Light energy may be absorbed by the
water and converted into heat energy. [1]
3. Water continuously moves out of the mesophyll cells to form a thin layer of moisture around the cells. [1]
As water evaporates from the thin film of moisture, it enters the intercellular air spaces. [1]
From there, water vapour diffuses through the stomata to the drier air outside the leaf. [1]
As water evaporates from the mesophyll cells, the water potential in their cell sap decreases. [1]
They begin to absorb water by osmosis from the cells deeper inside the leaf. [1]
These cells have a lower water potential than the adjacent xylem vessels. Therefore, water passes from
xylem vessels into the surrounding mesophyll cells by osmosis. [1]
This creates the transpiration pull, which helps to draw mineral salts and water from the roots up the
plant. [1]
Drawing [1]
Labels [2]
palisade
mesophyll cell
xylem
spongy mesophyll cell
intercellular air
space
stoma
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2nd Edition
2nd Edition
The Discover Biology for GCE 'O' Level Science Workbook
(2nd Edition) is specially developed to complement the Discover Biology
for GCE ‘O’ Level Science (2nd Edition) textbook. Designed to support learning
with understanding, this workbook is written in line with the 2013 GCE Ordinary
Level Science (Biology) syllabus from the Ministry of Education, Singapore.
Its wide-ranging exercises build foundational knowledge and develop critical
higher-order thinking skills.
Workbook (Teacher’s Edition)
Reinforces concept development
• Concept mapping helps students review and integrate key concepts taught in
a chapter.
2nd Edition
Shapes independent learners and critical thinkers
• Self-evaluation tool at the end of every worksheet helps students monitor their
learning progress.
• A variety of context-based and data-based questions challenge students to train
up their higher-order thinking skills.
Builds skills and exam confidence
• Thought Process in worked examples guides students through essential points
to consider when answering free-response questions.
• A Model Examination Paper gives further practice and boosts exam confidence
by helping students familiarise with the exam format.
Lam Peng Kwan • Eric Y K Lam
Christine Y P Lee
Other components
• Practical Book
• Textbook
Lam Peng Kwan
Eric Y K Lam
Christine Y P Lee
ISBN 978-981-01-1730-6
Workbook
Teacher's Edition
(S)SciB_WB&TE Cover.indd 1
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