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IB Biology 3rd Edn PEQs

chemistry 101 (University of Alberta)

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FOR THE
IB DIPLOMA
PROGRAMME

THIRD EDITION

Biology
C. J. Clegg
Andrew Davis
Christopher Talbot

Practice
Exam-style
Questions

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Contents
A Unity and diversity
A1.1 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
A1.2 Nucleic acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
A2.1 Origins of cells (HL only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
A2.2 Cell structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
A2.3 Viruses (HL only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
A3.1 Diversity of organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
A3.2 Classification and cladistics (HL only) . . . . . . . . . . . . . . . . . . . . . . . 13
A4.1 Evolution and speciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
A4.2 Conservation of biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

B Form and function

B1.1 Carbohydrates and lipids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
B1.2 Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
B2.1 Membranes and membrane transport . . . . . . . . . . . . . . . . . . . . . . . . 27
B2.2 Organelles and compartmentalization . . . . . . . . . . . . . . . . . . . . . . . 30
B2.3 Cell specialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
B3.1 Gas exchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
B3.2 Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
B3.3 Muscle and motility (HL only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
B4.1 Adaptation to environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
B4.2 Ecological niches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

C Interaction and interdependence

C1.1 Enzymes and metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
C1.2 Cell respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
C1.3 Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
C2.1 Chemical signalling (HL only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
C2.2 Neural signalling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
C3.1 Integration of body systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
C3.2 Defence against disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
C4.1 Populations and communities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
C4.2 Transfers of energy and matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

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D Continuity and change

D1.1 DNA replication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
D1.2 Protein synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
D1.3 Mutation and gene editing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
D2.1 Cell and nuclear division. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
D2.2 Gene expression (HL only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
D2.3 Water potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
D3.1 Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
D3.2 Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
D3.3 Homeostasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
D4.1 Natural selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
D4.2 Stability and change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
D4.3 Climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

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A1.1 Water
■ Paper 1
1 Which diagram correctly indicates the polarity in a water molecule?
A δ– B δ+ C δ– D δ–
O O O H
H H H H H H O O
δ– δ+ δ– δ– δ+ δ+ δ+ δ+
Higher Level Paper 1, Time Zone 1, May 09, Q8

2 With regards to water molecules, where do hydrogen bonds form?

A Within a water molecule, between the negatively charged hydrogen atom and positively
charged oxygen atom
B Between different water molecules, between the negatively charged hydrogen atom and
positively charged oxygen atom
C Within a water molecule, between the positively charged hydrogen atom and negatively
charged oxygen atom
D Between different water molecules, between the positively charged hydrogen atom and
negatively charged oxygen atom
3 Four properties of water are listed below. Which of the properties explain why water makes
a good solvent?
I The polarity of water molecules
II The high speci昀椀c heat capacity of water
III Hydrogen bonds
IV Water is less dense as a solid than as a liquid
A I and II only
B I and III only
C III and IV only
D I, II and IV
4 Which is the correct explanation of cohesion?
A The property of the surface of a liquid that allows it to resist an external force
B The force by which individual molecules of the same type are attracted
C The force by which individual molecules link to surrounding surfaces
D The force by which individual molecules of different types are attracted
5 To investigate the thermal properties of water, students placed hot water in two thin plastic
cups and measured their rate of cooling. The sides of one cup were covered with tissue paper
soaked in hot water; the other cup was left uncovered. The temperature was recorded with a
thermometer every 4 minutes for 20 minutes. The temperature in the laboratory was 18 °C.

thermometer

hot wet tissue hot water

water paper

Biology for the IB Diploma Programme A1.1 Water 1

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80

70 Key uncovered
covered with wet
60 tissue paper

temperature/°C
50

40

30

20

10

0
0 4 8 12 16 20
time/minutes

a Calculate the change in temperature in each cup after 20 minutes:

i uncovered
ii covered with wet tissue paper. [1]
b State two conditions that must be the same for each cup at the start of the experiment. [2]
c Predict the temperature of the water in the cups after 3 hours. [1]
Standard Level Paper 3, Time Zone 0, November 17, Q1a–c

(Questions 6–8 HL only)

6 The abundance of water over billions of years of Earth’s history has allowed life to evolve.
Which of the following is an explanation for the origin of water on Earth?
A It has always been found on the surface
B Volcanic activity
C It was formed by respiration when life evolved
D It was brought to Earth on asteroids
7 Why was water retained on the early Earth?
A Temperatures were low enough to condense water
B Seas were able to form
C The ozone layer prevented water from evaporating
D The water cycle had been established
8 What is a correct de昀椀nition for ‘Goldilocks zone’?
A Zone in a planetary system where gold is found
B Speci昀椀c distance from a star where the gravitational pull is not too great or too small
C Speci昀椀c distance from a star where the temperature is suitable for liquid water and
therefore life
D Area of a planet where water is found

Biology for the IB Diploma Programme A1.1 Water 2

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■ Paper 2 (Question 7 HL only)

1 With the use of a diagram, outline how hydrogen bonds 7 The Goldilocks zone is the area around a star where
form in water. [3] the temperature allows water to exist in liquid form.
2 a Draw three water molecules and show how bonds The closest and furthest distances from the star where
can form between water molecules. [2] liquid water can be found depend, partly, on the size and
b Annotate your diagram with the name of temperature of the star. Water is believed to be essential
the bond. [1] for the evolution of cellular organisms.
c Indicate the polarity in each water molecule. [1] Kepler-186 is a dwarf star in the constellation of
3 Water has important solvent properties. Explain these Cygnus. It has a mass of 0.37 suns and its luminosity
properties using examples to illustrate your answer. [3] is 0.01 suns. It is known to have 昀椀ve planets (see the
Standard Level Paper 2, Time Zone 0, November 17, Q3b table below). The smallest one, B, is only 8% larger than
Earth, while the largest one, D, is almost 40% larger.
4 Identify the properties of water molecules that permit
Planet Distance/AU Orbit/days
them to move upwards in plants. [2]
B 0.04 3.88
5 Describe the importance of water to living organisms. [5] C 0.06 7.26
Higher Level Paper 2, Time Zone 0, November 15, Q7c D 0.09 13.34
E 0.12 22.40
6 Explain the relationship between the properties of water
F 0.40 129.94
and its uses in living organisms as a coolant, a medium
for metabolic reactions and a transport medium. [8] An astronomical unit (AU) is the mean distance of the
Earth from the Sun; this distance varies as the Earth
orbits the Sun in an ellipse.
Luminosity is a measure of brightness or power of a
star, the amount of energy that a star emits from its
surface in one second. It is usually expressed in watts
and measured in terms of the luminosity of the Sun.
a Calculate the distance in AU of the Goldilocks
zone for Kepler-186 using the formula
√luminosity of the star × 0.7 for the inner edge of
the habitable zone and √luminosity × 1.5 for the
outer edge of the zone. [1]
b Deduce which, if any, of the 昀椀ve planets orbiting
Kepler-186 are in the Goldilocks zone. [1]
c State one other factor which determines whether
a planet is in the Goldilocks zone. [1]
d Outline the physical properties of water
which result from hydrogen bonding between
water molecules. [3]

Biology for the IB Diploma Programme A1.1 Water 3

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A1.2 Nucleic acids

■ Paper 1 5 How is an allele different from a gene?
1 What is common to both RNA and DNA? A An allele is made of RNA
A Thymine B An allele is longer
B Nitrogenous bases C An allele is a variety of a gene
C Double helix D An allele cannot be affected by mutation
D Deoxyribose 6 Which statement is a similarity between DNA and RNA?
2 Which statements are characteristics of alleles? A Both contain ribose sugar
I Alleles differ signi昀椀cantly in number of B Both are polymers of nucleotides
base pairs C Both are only found in the nucleus
II Alleles are speci昀椀c forms of a gene D Both contain adenine, cytosine and thymine
III New alleles are formed by mutation 7 What usually distinguishes DNA from RNA?
A I and II only DNA RNA
B I and III only A strands are symmetrical strands are antiparallel
C II and III only B contains adenine contains cytosine
D I, II and III
C pentoses linked to phosphates pentoses linked to bases
Higher Level Paper 1, Time Zone 0, November 19, Q10
D double stranded single stranded
3 Nucleic acids are polymers of nucleotides. What parts of Higher Level Paper 1, Time Zone 0, May 16, Q5
nucleotides are joined together in both DNA and RNA
to make these polymers? (Questions 8–10 HL only)
A Large nitrogenous bases with small 8 Which of the following conclusions are supported by
nitrogenous bases evidence from the Hershey–Chase experiment?
B Nitrogenous bases with hexose sugars A DNA is the genetic material
C Nitrogenous bases with phosphates B Protein is the genetic material
D Pentose sugars with phosphates C Bacteriophages contain DNA
Standard Level Paper 1, Time Zone 1, May 18, Q11 D Cells contain DNA

4 What is the same in all parts of homologous 9 What did Erwin Chargaff discover?
chromosomes? A The number of adenine bases equalled the
A Base pair sequence number of thymine bases
B Sequence of genes B The number of bases varies between
C Alleles different organisms
D Insertions C Uracil is found in RNA
Standard Level Paper 1, Time Zone 1, May 18, Q14 D DNA is the genetic material in cells
10 What is the role of histones?
A Construction of the cytoskeleton in cells
B Packaging of DNA in chromosomes
C Giving stability to plasma membranes
D Enzymic activity in cells

Biology for the IB Diploma Programme A1.2 Nucleic acids 4

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■ Paper 2 4 The diagram shows a section of a DNA molecule.

1 Draw a labelled diagram of a section of DNA showing State what is indicated by the labels a, b, c and d. [2]
four nucleotides. [5] a
Standard Level Paper 2, Time Zone 0, November 15, Q5a
T
2 Sketch the complementary strand to complete
the section of a DNA diagram with the correct
complementary bases. [3] c
b

G d

5 Hydrogen bonds can exist both within and between

molecules in living organisms and have an impact on
C their structure and function. Explain the importance of
hydrogen bonding for living organisms. [7]
3 List two structural features that are the same between Higher Level Paper 2, Time Zone 1, May 18, Q6c
RNA and DNA. [2]
(Questions 6 and 7 HL only)
6 Deduce the signi昀椀cance of the positively charged
histone protein and the negatively charged DNA. [3]
7 Explain how scienti昀椀c evidence was used to describe
the structure and function of DNA. [8]

Biology for the IB Diploma Programme A1.2 Nucleic acids 5

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A2.1 Origins of cells (HL only)

■ Paper 1 (HL only) 3 Which of the following features suggest that RNA had a
1 The atmosphere on the early Earth included: central role in the origin of life?
A Ammonia I RNA is a carrier of genetic information
B Oxygen II RNA can act as a catalyst
C Ozone III RNA contains the base uracil not thymine
D Carbon monoxide A I only
B I and II
2 Where did the Last Universal Common Ancestor
C I, II and III
(LUCA) probably evolve?
D None of those listed
A Salt marshes
B Deep sea hydrothermal vents
C Peat swamp
D Extinct volcanoes

4 The synthesis of complex organic molecules in sea water is believed to be an important step in
the evolution of life on Earth. Researchers investigated whether the evaporation of sea water
containing amino acids could catalyse the formation of dipeptides such as divaline (valine–
valine) under pre-biotic Earth conditions. They placed different amino acid combinations
in a chamber to simulate the evaporation cycles between high tides in shallow seas. In one
investigation the amino acid valine was used as the substrate and the percentage yield of
divaline was measured after different numbers of evaporation cycles. The experiment was
repeated without a catalyst and with either glycine or histidine as catalysts.
2.25
Key
2.00 no catalyst
percentage yield of divaline/%

1.75 glycine
histidine
1.50

1.25

1.00

0.75

0.50

0.25

0.00
1 4 7
evaporation cycles

a Compare the effectiveness of the two amino acid catalysts used in this experiment. [3]
b This investigation was performed in a chamber at 85 °C leading to total evaporation of
the salt water within one day. The atmosphere inside the chamber consisted of nitrogen,
carbon dioxide and water vapour. Evaluate the experiment on the basis of similarity
with conditions that existed on pre-biotic Earth. [3]
c Outline other possible locations where conditions could have allowed the synthesis of
organic molecules under pre-biotic conditions. [2]
Higher Level Paper 3, Time Zone 1, May 13, Option D Q1

Biology for the IB Diploma Programme A2.1 Origins of cells (HL only) 6
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■ Paper 2 (HL only)

1 a State the name for primitive, phospholipid-enclosed structures that may have preceded
cells. [1]
b State two conditions of pre-biotic Earth. [1]
c Identify two properties of RNA which may have contributed to the origin of life. [2]
2 I

II

III

a i The apparatus above was used in the Miller–Urey experiment. State what condition
of pre-biotic Earth is simulated by I. [1]
ii State two substances used in II to simulate the early atmosphere of the Earth. [1]
iii Identify a compound (not RNA) isolated in III by Miller–Urey in this experiment. [1]
b State two roles of RNA in pre-biotic Earth. [1]
Higher Level Paper 3, Time Zone 0, November 05, Option D Q2

3 Evaluate the Miller–Urey experiment. [4]

Biology for the IB Diploma Programme A2.1 Origins of cells (HL only) 7
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A2.2 Cell structure

■ Paper 1 6 A highly magni昀椀ed electron micrograph of an animal
1 Which is not an idea contained within cell theory? cell was magni昀椀ed ×9600. The following features were
A Cells can only arise from pre-existing cells measured. Complete a copy of the table, expressing the
B All cells contain a nucleus actual size of the features in appropriate units.
C Living organisms are composed of cells which Feature Measurement on scale bar Actual size
are the smallest unit of life diameter of the nucleus 56 mm

D Organisms consisting of only one cell carry out length of a mitochondrion 16 mm

all functions of life width of the cell 14 cm

diameter of a lysosome 4 mm
2 A chloroplast is 6 micrometres long. If a student draws it
pore in the nuclear 3 mm
100 times larger than its actual size, what diameter will envelope
the drawing be in mm? length of the cell 25.5 cm
A 0.06 mm
[3]
B 0.6 mm
C 6 mm (Questions 7–10 HL only)
D 60 mm 7 What evidence do mitochondria and chloroplasts
3 Which of these organelles has a double membrane? provide in support of endosymbiotic theory?
A Nucleus A They exist together in all eukaryote cells
B Lysosome B They have 80S ribosomes similar to eukaryotes
C Endoplasmic reticulum C They have double membranes
D Ribosome D They contain the same DNA as the nucleus of
4 Which feature of both striated muscle and aseptate the cell
fungal hyphae is different from typical cell structure? 8 Mechanisms that are needed for the evolution of
A They have multiple nuclei within a structural unit multicellular organisms include:
B They have a cell wall that is not made of cellulose I Cell adhesion
C They have plasmids II Communication between cells
D They have an absence of cholesterol in the III Differentiation
plasma membrane A I only
Standard Level Paper 1, Time Zone 1, May 18, Q1 B I and II only
C I, II and III
5 The magni昀椀cation of the micrograph is ×1500.
D None of those listed
What is the maximum diameter of the nucleus in the
9 What is evidence for the endosymbiotic theory?
cell labelled X?
A RNA can catalyse metabolic reactions
B Meteorites contain organic molecules
C Amino acids can be synthesized from
inorganic compounds
X D Mitochondria possess their own DNA
Higher Level Paper 1, Time Zone 2, May 17, Q4

10 Which organelle provides evidence that eukaryotic cells

originated when large prokaryotes engulfed small free-
living prokaryotes?
A 10 μm A Chloroplast
B 10 nm B Nucleoid
C 20 μm C 80S ribosome
D 20 nm D Vacuole
Standard Level Paper 1, Time Zone 1, May 18, Q4

Biology for the IB Diploma Programme A2.2 Cell structure 8

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■ Paper 2 a State the name of the structures labelled I and II. [1]
1 Tuberculosis (TB) is an infectious disease caused by b Outline the function of the structure labelled III. [2]
Standard Level Paper 2, Time Zone 2, May 18, Q3ai–ii
the bacterium Mycobacterium tuberculosis. Outline the
structures in M. tuberculosis that are not present in a 7 The electron micrograph shows the structures in an
human cell. [3] exocrine gland cell of the pancreas.
Standard Level Paper 2, Time Zone 2, May 21, Q6a

2 Testis cells are eukaryotic cells. Identify the structures

seen under the electron microscope in testis cells that
are not present in prokaryotic cells. [4]
Higher Level Paper 2, Time Zone 2, May 21, Q5c

3 Unicellular and multicellular organisms share the same

functions of life. Outline four functions of life. [4]
Standard Level Paper 2, Time Zone 1, May 18, Q5b

4 The micrograph shows part of a plant cell with a

II
chloroplast near to a mitochondrion.
chloroplast
I
mitochondrion

a Using the table, identify the organelles labelled

I and II on the electron micrograph and their
principal role. [2]
a State two structural similarities between Organelle Name Principal role
mitochondria and chloroplasts. [2] I
b Compare and contrast the functional roles of II
mitochondria and chloroplasts in cell metabolism. [4] b Compare and contrast the structure and
c Suggest why the mitochondria in the micrograph functions of organelles I and II. [4]
appear to vary in shape. [2] 8 Discuss the cell theory and its limitations. [7]
5 Compare and contrast the structure of the chloroplast Standard Level Paper 2, Time Zone 0, November 18, Q5c
with a typical prokaryotic cell. [4]
(Questions 9–11 HL only)
6 The electron micrograph shows a palisade mesophyll cell.
9 Apart from the ribosomes, explain the evidence for the
I endosymbiotic theory of the origin of eukaryotic cells. [3]
Standard Level Paper 2, Time Zone 0, November 20, Q2d

10 Explain how mitochondria could have been formed

II from free-living prokaryotes. [2]
Higher Level Paper 2, Time Zone 1, May 19, Q3b

11 Explain the reasons for differences between the

proteomes of cells within a multicellular organism. [7]
III

Biology for the IB Diploma Programme A2.2 Cell structure 9

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A2.3 Viruses (HL only)

■ Paper 1 (HL only)
1 Which feature of viruses result in them being considered non-living?
A Viruses are obligate parasites
B Viruses can only be replicated inside a living cell
C Viruses have a protein coat (capsid)
D Viruses contain either RNA or DNA, but never both
2 Which type of enzyme allows a retrovirus to prepare its genome for insertion into a host
cell’s DNA?
A DNA polymerase
B Restriction enzymes
C Reverse transcriptase
D RNA polymerase
3 Which of the following correctly identi昀椀es the reproductive cycles X and Y and structures
A and B?

B
reproductive cycle X reproductive cycle Y

X Y A B
A lytic lysogenic virus DNA provirus

B lysogenic lytic virus DNA prophage

C lytic lysogenic bacterial DNA prophage

D lysogenic lytic bacterial DNA provirus

4 What happens when a bacterial cell that is infected by bacteriophage lambda divides?
A Viral RNA is replicated
B Viral RNA is transcribed from viral DNA
C Viral DNA is replicated
D Viral DNA is made from viral RNA

Biology for the IB Diploma Programme A2.3 Viruses (HL only) 10

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■ Paper 2 (HL only) 2 Describe the structural components of viruses. [6]

1 In December 2013, a boy died of Ebola Virus Disease 3 Compare the lysogenic life cycle to the lytic life cycle. [5]
(EVD) in Guinea, West Africa. However, it was 4 When a bacterial cell is infected with bacteriophage
not until March 2014 that health of昀椀cials reported lambda (λ phage), the virus will enter the lytic cycle.
a mysterious haemorrhagic fever that ‘strikes Describe the lytic cycle of a virus. [5]
like lightning’. 5 Every year, new 昀氀u vaccines are developed to ensure
By the end of 2014, an estimated 20 000 cases had their ef昀椀cacy. Explain the frequent need for new
been reported. vaccines against in昀氀uenza viruses. [2]
The graph shows the number of deaths reported in the 6 Some bacteriophages, such as bacteriophage
months following the outbreak in December 2013. lambda, undergo both lysogenic and lytic cycles.
10 000
Suggest reasons why it may be advantageous for a
bacteriophage to have a lysogenic cycle. [3]
9000

8000

7000
number of deaths

6000

5000

4000

3000

2000

1000

0
0 2 4 6 8 10 12
months since outbreak in December 2013

a Give an estimate of the percentage of reported

cases who had died by the end of 2014. [1]
b Analyse the data for July to August 2014, and
December 2014 to January 2015, to explain
whether the measures taken to control the spread
of Ebola were effective. [2]
c The table shows the number of reported cases
and deaths from Ebola in three different
countries by March 2015. Explain the difference
between the percentage of reported cases who
had died in these three countries. [2]
Countries with Total cases Laboratory Total
widespread (suspected, confirmed deaths
transmission probable, cases
confirmed)
Guinea 3 814 3 358 2 544
Liberia 10 678 3 163 4 810
Sierra Leone 11 829 8 706 3 956

Biology for the IB Diploma Programme A2.3 Viruses (HL only) 11

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A3.1 Diversity of organisms

■ Paper 1
1 What is a feature of the human genome? 2 What determines the genomic size of a species?
A Plasmids A The total amount of DNA
B Messenger RNA B The total number of genes
C Transfer RNA C The total number of alleles
D Mitochondrial DNA D The total number of chromosomes
Higher Level Paper 1, Time Zone 2, May 21, Q10 Standard Level Paper 1, Time Zone 2, May 18, Q13

3 The image shows variation in height of adult humans.

What can explain the variation? (Questions 5 and 6 HL only)

A One pair of alleles and age 5 Dif昀椀culties of applying the biological species
B Polygenic inheritance and nutrition concept include:
C Nutrition and age I Asexually reproducing species
D Autosomal inheritance only II Individuals produced by cloning
Higher Level Paper 1, Time Zone 0, November 18, Q36 III Bacteria that have horizontal gene transfer
A I only
4 What is characteristic of homologous chromosomes?
B I and II
A They have an identical DNA sequence
C I and III
B They are of the same length in karyograms
D I, II and III
C They form pairs in prokaryotes
D They carry the same alleles 6 Cross-breeding between closely related species is
Higher Level Paper 1, Time Zone 0, May 16, Q17 unlikely to produce fertile offspring because:
A Parent chromosome numbers are different
B Diploid zygotes cannot be formed
C Cell division in offspring cannot occur
D Offspring do not have functional reproductive organs

■ Paper 2
1 More than 8 million different species are alive today but (Questions 3 and 4 HL only)
over the course of evolution, more than 4 billion may 3 Explain how species can be identi昀椀ed from
have existed. environmental DNA in a habitat using barcodes. [7]
a Outline the criteria that should be used to assess 4 a Outline how dichotomous keys can be used to
whether a group of organisms is a species. [3] identify specimens. [4]
b Describe the changes that occur in gene pools b Suggest possible limitations of using
during speciation. [5] dichotomous keys to identify specimens. [2]
Higher Level Paper 2, Time Zone 0, November 20, Q8a–b

2 Outline the binomial system of classi昀椀cation. [4]

Standard Level Paper 2, Time Zone 0, November 21, Q6c

Biology for the IB Diploma Programme A3.1 Diversity of organisms 12

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A3.2 Classification and cladistics (HL only)

■ Paper 1 (HL only)
1 The cladogram shows one theory of how species of hominin evolved. What can be deduced
using the information in the cladogram?

A. afarensis A The closest species to K. platyops is

A. garhi A. africanus
A. africanus
B A. afarensis is extinct
K. platyops
P. aethiopicus
C The DNA of H. sapiens is the same as
P. robustus that of H. ergaster
P. boisei D H. sapiens and P. robustus shared a
H. habilis common ancestor
H. rudolfensis
Standard Level Paper 1, Time Zone 0, November 21, Q23
H. ergaster
H. sapiens

2 Which evolutionary pathway is most likely to result in the evolution of analogous structures in
Species W and Z?

A Species V B Species V C Species V Species Y D Species V

Species W Species X Species Y

Species Y

Species X Species W Species Z Species X

Species W Species Z Species X

Species Y Species W

Species Z Species Z

Standard Level Paper 1, Time Zone 2, May 21, Q21

3 What information can be deduced from the sequence of nodes in a cladogram?

A The geological period in which the species in the clade diverged from their
common ancestor
B The probable sequence of divergence among the species in the clade
C The number of characteristics the species have in common
D The number of mutations that have occurred since the species shared a common ancestor
Standard Level Paper 1, Time Zone 2, May 21, Q23

Biology for the IB Diploma Programme A3.2 Classification and cladistics (HL only) 13
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4 The diagram shows living organisms divided into the three domains. Select the row in the
table that correctly identi昀椀es W, X, Y and Z.

animals
slime
moulds
fungi

plants
ciliates
*
*
flagellates

Z
* Y

* X

W X Y Z
A prokaryote LUCA archaea eukaryote

B LUCA eubacteria archaea eukaryote

C eubacteria archaea LUCA prokaryote

D LUCA prokaryote eubacteria eukaryote

5 The 昀椀gwort family is a large one consisting of many 昀氀owering plants that look similar.
For what reason have some members of the family been reclassi昀椀ed into a new family?
A Cladistic analysis shows the differences in 昀氀ower structure to be fewer than the
shared similarities
B DNA analysis shows the similarities in 昀氀ower shape to be a product of convergent evolution
C DNA analysis shows some of the families to have suffered recent mutations in only one gene
D DNA analysis shows the similarities between the seed dispersal strategies to be a
product of divergent evolution
Standard Level Paper 1, Time Zone 2, May 18, Q23

Biology for the IB Diploma Programme A3.2 Classification and cladistics (HL only) 14
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■ Paper 2 (HL only)

1 Analyse the following cladogram, showing evolutionary relationships between humans and
other primates.

New World Old World gibbons and

lemurs lorises tarsiers monkeys monkeys siamangs orang-utans gorillas chimpanzee bonobo human
present

25

40

50

58

63

time (mya)

a Which species are most distantly related to humans? [1]

b Describe the relationship between lemurs and lorises and the other primate groups. [2]
c Describe and suggest reasons for the relationship between Old World and
New World monkeys. [3]

2 The scienti昀椀c name of the Arizona mud turtle is 4 Describe what is shown in a cladogram. [3]
Kinosternon arizonense and for the yellow mud turtle it Higher Level Paper 2, Time Zone 0, November 19, Q3a
is Kinosternon flavescens.
5 Outline the types of evidence that can be used to place a
a State what is meant by the binomial system of
species in a particular clade. [3]
naming living organisms. [2]
b State if these two turtles belong to the same 6 Living organisms have been placed in three domains:
i) class ii) genus iii) species. [3] archaea, eubacteria and eukaryote. Distinguish the
c Sophora flavescens is the scienti昀椀c name of a eukaryote from the archaea. [3]
different organism. State if this particular species Eukaryote Archaea

has some evolutionary relationship with the

yellow mud turtle based on their scienti昀椀c names. [2]
d Outline with a named example how scientists use
the binomial system to avoid confusion. [2] Standard Level Paper 2, Time Zone 0,
November 16, Q5a (modified)
3 Outline the use of analogous and homologous traits in
natural classi昀椀cation. [4]
Higher Level Paper 2, Time Zone 1, May 21, Q7c

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7 The following cladogram shows three possible evolutionary routes for the turtle (Turtles 1,
Turtles 2 and Turtles 3). The taxa in italics are extinct.
mammals

Milleretta

Eunotosaurus

Odontochelys

Proganochelys

Turtles 3

Turtles 2

lizards

tuatara

Turtles 1
Diapsida

birds

crocodiles

a i State the organism most closely related to the lizards. [1]

ii Based on the taxa shown, deduce a dif昀椀culty in gathering data to study turtle ancestry. [1]
b i Molecular evidence is often used to construct a cladogram. Describe one type of
molecular-based evidence to identify members of a clade. [2]
ii Suggest one type of additional evidence that could provide strong support for
Turtles 3 as the evolutionary route for turtles rather than Turtles 1 or Turtles 2. [1]
c Taxonomists aim to place species into genera, families and higher taxa according to
their evolutionary origins. This is known as natural classi昀椀cation.
Explain the usefulness of natural classi昀椀cation in biodiversity research. [2]
Standard Level Paper 2, Time Zone 1, May 17, Q4a–c

8 Analyse the following cladogram to deduce evolutionary relationships between vertebrate

groups. Then answer the questions below.
a Which group was the 昀椀rst to evolve? [1]
b What characteristic separates 昀椀sh
from other vertebrate groups? [1]
rodents and
sharks bony fish amphibians primates rabbits crocodiles birds c What feature is characteristic to all
groups except sharks? [1]
d What characteristic separates
hair eggs with sharks from bony 昀椀sh? [1]
shells e Which features are the most recently
evolved? [1]
amniotic egg
f Which organism will have DNA
four limbs most similar to the bird? [1]
9 Explain how cladistics can be
bony skeleton
used to investigate whether the
vertebrae classi昀椀cation of groups corresponds to
evolutionary relationships. [7]

Biology for the IB Diploma Programme A3.2 Classification and cladistics (HL only) 16
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A4.1 Evolution and speciation

■ Paper 1 5 Humans have been selectively breeding animals and
1 Lamarck and Darwin had different theories for how plants for thousands of years.
species changed over time. Which statement is part of a Outline how selective breeding provides
Darwin’s evolutionary theory? evidence for evolution. [3]
A Changes an organism experienced during its life b Compare and contrast selective breeding and
can be passed on to offspring natural selection. [4]
B The inheritance of acquired characteristics (Questions 6–9 HL only)
C Change in the heritable characteristics of 6 Which is the correct de昀椀nition for sympatric speciation?
a population A Speciation that occurs with geographical separation
D Complexity arises due to usage or disuse of B Speciation that occurs without
particular traits geographical separation
2 Which of the following is an example of C Speciation that occurs on islands
arti昀椀cial selection? D Speciation that occurs through selective breeding
A Keeping animals in zoos 7 Which of the following is a cause of
B Breeding of wild mustard to create different allopatric speciation?
types of vegetable A Sexual dimorphism
C Evolution of antibiotic resistance in bacteria B Hybridization
D The pentadactyl limb of vertebrates C Cohabitation
3 Why are DNA or RNA base sequences or amino acid D Geographical isolation
sequences in proteins considered evidence for evolution? 8 Which statement correctly de昀椀nes polyploidy?
A Closely related organisms have similarities in A A process resulting from non-disjunction
their base and amino acid sequences B A process that results in more than two sets of
B DNA sequences are converted into mRNA chromosomes in the nuclear genome
C mRNA is used to produce proteins C A process that results in one diploid and one
D All organisms contain DNA and proteins haploid nucleus
4 Birds, bats and humans are all vertebrates with D A process that results in four polar bodies
pentadactyl limbs. Birds and bats use their forelimbs
to 昀氀y whereas humans can use them to lift and
manipulate objects. Outline how the bird, bat and
human forelimb can be used to illustrate the concept
of homologous structures. [2]
Higher Level Paper 2, Time Zone 1, May 18, Q2b

Biology for the IB Diploma Programme A4.1 Evolution and speciation 17

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9 The 昀椀gure below shows 昀椀nches of the subfamily Geospizinae from the Galápagos Islands.
Through a series of studies, these endemic 昀椀nches were found to have evolved by adaptive
radiation from an ancestral species that was originally found on mainland South America.

large tree
finch medium ground
small ground
Camarhynchus finch
finch
psittacula Geospiza
Geospiza
fuliginosa fortis
small tree
finch
Camarhynchus large ground
parvulus finch
Geospiza
tip-biting magnirostris

woodpecker
finch
Camarhynchus
pallidus cactus
mainly edge
finch
probing animal crushing
Geospiza
mainly scandens
plant

sharp-billed mixed
ground finch These finches are exclusive and, hence, endemic
Geospiza probe diet to the Galápagos Islands. There are 14–15
difficilis and crush species in total all derived from a common
ancestor and living in the same, largely
undisturbed environment.

warbler beak action

finch
Certhidea
olivacea

a Explain how these various species of 昀椀nches could have arisen. [3]
A new honeycreeper has been found on Daphne Major, one of the Galápagos Islands. Based on its
structural and behavioural features (such as song), biologists suggested that the new species is a
hybrid of the medium ground 昀椀nch (Geospiza fortis) and the large cactus 昀椀nch (Geospiza conirostris).
Genomic sequencing has con昀椀rmed this new species of Darwin’s 昀椀nch.
b Suggest why it is not advisable to determine the phylogenetic relationship of this newfound
昀椀nch to the rest of the Galápagos Island 昀椀nches purely based on morphological and
behavioural features (form, structure and activity). [1]

■ Paper 2 (Questions 4–8 HL only)

1 Compare and contrast divergent and 4 Outline how the mixing of alleles between species
convergent evolution. [5] can be prevented. [4]
2 Explain, using examples, how evolution may happen 5 Compare and contrast allopatric and
in response to environmental change. [7] sympatric speciation. [5]
3 With examples, discuss the factors that contribute 6 Describe the process of adaptive radiation. [3]
to speciation. [7] 7 Outline how DNA can be studied to determine
phylogeny of organisms. [5]
8 Explain how polyploidy has led to the rapid
evolution of invasive plant species such as knotweed
or smartweed. [7]

Biology for the IB Diploma Programme A4.1 Evolution and speciation 18

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A4.2 Conservation of biodiversity

■ Paper 1 6 The North Island giant moa was hunted to extinction by
1 Which statement de昀椀nes ecosystem diversity? humans. What was a consequence of the extinction of
A The number of species in an area this 昀氀ightless bird?
B The range of different habitats or number of A Less 昀椀re frequency
ecological niches per unit area in an ecosystem B Altering vegetation composition and structure
C The range of biotic and abiotic factors in an area C Increased seed dispersal
D The number of ecosystems in an area D Increased urbanization

2 Look at the four ecosystems listed below. Which 7 In two areas of moorland of the same approximate size,
ecosystem would have the highest species richness? the number of plants was counted. The results are shown
A Desert in the table.
B Rainforest Type of plant Moorland Moorland
area 1 area 2
C Temperate forest
rosebay willow herb (Chamerion 456 35
D Hydrothermal vent angustifolium)
3 Species of beetle were collected in four different sheep’s sorrel (Rumex acetosella) 421 1 420
habitats. The Simpson’s reciprocal index was calculated heath bedstraw (Galium saxatile) 386 150
for each habitat, as shown in the table. bog asphodel (Narthecium 437 95
ossifragum)
Habitat Simpson’s reciprocal index
Total 1 700 1 700
1 2.35
2 4.00 a Compare and contrast the abundance, richness
3 2.50 and evenness of the two areas of moorland. [2]
4 1.50 b Explain which would have the highest Simpson’s
reciprocal index. [3]
Which statement is correct?
c Suggest reasons for the differences in diversity
A Habitat 1 has the largest number of species
between the two areas. [2]
B Habitat 1 has the greatest evenness
C Results for Habitat 1 and Habitat 3 are not 8 Look at the graph below.
signi昀椀cantly different a Explain the relationship between forest area and
D Habitat 4 has the lowest genetic diversity number of forest-interior bird species. [1]
b Suggest why there is variation in the data. [1]
4 What does the evidence of fossils suggest about the
c Suggest what other factors, apart from forest
number of species on Earth today?
area, would affect the number of forest-interior
A The number of species is increasing rapidly
bird species. [3]
B The number of species has stabilized
C There are currently more species alive on Earth 10
today than at any time in the past
D The number of species is 昀氀uctuating
species richness

5
5 Which of the following is an example of an
anthropogenic cause of species extinction?
A An asteroid impact
2
B Volcanic eruptions
C Logging leading to rainforest loss forest-interior birds
D Ice ages 1
1 10 100 500
forest area/ha

Biology for the IB Diploma Programme A4.2 Conservation of biodiversity 19

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■ Paper 2
1 The graph below shows the decline of North Sea cod stocks as a result of over昀椀shing.

Key
level of cod fishing, exploitation rate
300 amount (biomass) of cod spawning (reproducing) 60

exploitation rate/% (amount of fishing)

55
250
spawning stock biomass
50
200
45
150
40

100
35

50 30
1963 1973 1983 1993 1997
year

a Describe the changes in the amount of cod spawning between 1963 and 1997. [2]
b Explain the relationship between the level of cod 昀椀shing and changes in spawning
stock biomass. [3]
c Evaluate the success of 昀椀sh management techniques over this period. [3]

2 European zoos are devoting much effort to conserving 100 100

and breeding Amur leopards in captivity. Evaluate
rabbit mortality
the role of ex situ conservation in the protection of 80
rabbit mortality/%

Amur leopards. [5]

virus virulence/%
3 The European wild rabbit was introduced to Australia 60
90
in 1859. The herbivore spread rapidly. There were no
natural predators in Australia to control their number 40

and rabbits quickly overran large parts of the continent. virus

20 virulence
Grassland, available to herds of herbivores, principally
cows and sheep, was affected. As a biological control 80
0
measure, a myxoma virus that had been discovered in 0 1 2 3 4 5 6
South American rabbits (a different species from the years

European rabbit) was introduced in 1950.

a Describe changes in virus virulence over the
Myxoma virus causes a parasitic disease of rabbits, six-year period. [2]
myxomatosis, but on its original continent, the effects b Explain the relationship between virus virulence
were mild. The changing effects of this virus on rabbit and rabbit mortality. [3]
mortality (1950–56) are shown in the graph, as is the c Evaluate eradication programmes and biological
resulting change in virulence of the virus. Mortality control as measures to reduce the impact of
refers to the death rate seen in the rabbits, and virus alien species. [3]
virulence to the degree of toxicity or the injury-
4 Suggest how a named invasive species may have
producing potential of the virus.
altered the evolutionary pathways of native species. [7]
5 The survival of endangered species is supported
by nature reserves and by breeding programmes at
zoos and seed banks at botanical gardens. Compare
and contrast these approaches, identifying particular
strengths and possible drawbacks. [7]

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B1.1 Carbohydrates and lipids

■ Paper 1 5 Which of the following statements about
1 What feature of carbon makes it most suitable as a basis polysaccharides can be used to describe both
for life? amylopectin and cellulose?
A Its abundance on Earth I Adjacent glucose molecules are rotated by 180°
B Its bonding properties II Contains 1,4 glycosidic bonds
C Its relative atomic mass III Polymer of α-glucose
D Its presence in the early atmosphere of the Earth A II only
B III only
2 Which sugars are both disaccharides?
C I and II only
A Lactose and fructose
D II and III only
B Fructose and galactose
C Maltose and lactose 6 Which are functions of lipids?
D Galactose and maltose A Hydrophilic solvent and energy storage
B Hydrophobic and hydrophilic solvent
3 Monosaccharides are the building blocks
C Thermal insulation and energy storage
of polysaccharides. By which process are
D Thermal insulation and hydrophilic solvent
polysaccharides formed?
A Addition of hydrogen 7 What distinguishes cellulose from glycogen and starch?
B Removal of hydrogen A Only cellulose is found in plants
C Hydrolysis B Only cellulose is made up of glucose monomers
D Condensation C Cellulose is far more branched than starch
Standard Level Paper 1, Time Zone 0, November 00, Q5 and glycogen
D Cellulose has a structural role whereas starch and
4 What is the molecule shown in the diagram below? glycogen function in energy storage
Standard Level Paper 1, Time Zone 1, May 21, Q8
CH2OH

H H
8 The diagram shows two polysaccharides, formed from
C O
condensation of many glucose molecules. What are the
H
C C names of X and Y?
OH H

OH C C OH

H OH

A β-glucose
B Fructose X Y

C α-glucose
X Y
D Deoxyribose
A glycogen amylose

B amylopectin amylase

C amylase glycogen

D amylose amylopectin

Standard Level Paper 1, Time Zone 2, May 19, Q7

Biology for the IB Diploma Programme B1.1 Carbohydrates and lipids 21

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■ Paper 2
1 Migrating birds must refuel along the way in order to continue 昀氀ying. A 昀椀eld study was
conducted among four different species of migrating birds known to stop at high-quality and
low-quality food sites. Birds were captured and weighed at the two sites. Blood samples were
taken from the birds to determine nutrient levels in their blood.
Among birds, high triglyceride concentration in blood plasma indicates fat deposition whereas
high butyrate concentration in blood plasma indicates fat utilization and fasting. The following
data summarizes triglyceride levels and butyrate levels measured for the same groups of birds.
triglyceride levels butyrate levels
1.8 1.4
concentration/arbitrary units

1.6
1.2
1.4
1.0
1.2
1.0 0.8

0.8 0.6
0.6
0.4
0.4
0.2
0.2
0.0 0.0
HT WS AR MW HT WS AR MW
species species

Key Site 1 Site 2

HT: Hermit thrush AR: American robin

WS: White-throated sparrow MW: Magnolia warbler

a Describe, using the triglyceride levels graph, the results at Site 1 and Site 2 for all of
the birds. [2]
b Explain the differences in the triglyceride level and the butyrate level for the hermit
thrush at Site 1 and Site 2. [2]
c Scientists have hypothesized that the food quality is better at Site 1 than at Site 2.
Evaluate this hypothesis using the data provided. [2]
d Suggest one advantage and one disadvantage for blood sampling rather than weighing
birds to assess food quality at stopover sites. [2]
Higher Level Paper 2, Time Zone 2, May 10, Q1e–h

2 a Distinguish between the structure and function of starch and cellulose in plants. [5]
b Explain how the structure of cellulose makes it suitable as a component of cell walls. [3]
3 Explain the advantages of having both lipid and glycogen as energy stores in the
human body. [3]

Biology for the IB Diploma Programme B1.1 Carbohydrates and lipids 22

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B1.2 Proteins
■ Paper 1
1 Which of the following correctly shows a peptide bond between two amino acids?

A H R O O R H D H O
H

H N C C C C N H N C C OH

H
H H R

B O R H H R O
R O
H
HO C C N N C C OH
N C C OH

H H H
H

C H
R O H R O

N C C N C C OH

H
H H

2 How many molecules of water are required to completely hydrolyse a polypeptide made up of
23 amino acids?
A 11 B 22 C 23 D 24
3 What is denaturation?
A A structural change of a protein that results in the loss of its biological properties
B A change in the genetic code of an organism
C A change in the amino acid sequence of a protein causing a disruption of its three-dimensional shape
D The process by which amino acids are broken down and ammonia is released
4 Which of the molecules contain peptide bonds or are sugar molecules?
I O H H H H H H H H H H H H H H H H H

HO C C C C C C C C C C C C C C C C C C H

H H H H H H H H H H H H H H

II CH2OH III H O H O H O IV CH2OH CH2OH

O O O
H H H H H H
H H2N C C N C C N C C OH H H
OH H OH H OH H
HO OH HO O OH
H H H CH2
H C OH
H OH H OH H OH
CH2
H

CH3

Contain peptide bonds Are sugar molecules

A I, III II

B III II, IV

C I, III, IV II

D I III, IV

Higher Level Paper 1, Time Zone 0, November 17, Q5

Biology for the IB Diploma Programme B1.2 Proteins 23

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5 How does the proteome of a species contain a

relative alpha helix content/arbitrary units

larger number of proteins than genes that code for 1.0
these proteins? 0.9
A Some proteins have more than one polypeptide chain 0.8
B There are genes that code for several proteins X
0.7
C Not all proteins are coded for by the genome
0.6
D Some proteins are coded for by other proteins
Standard Level Paper 1, Time Zone 1, May 17, Q15 0.5

0.4
(Questions 6–12 HL only) 0.3
6 The image shows the structure of the protein 20 30 40 50 60 70 80 90
haemoglobin. temperature/°C

A Rapid increase in beta pleated sheets

B Rapid formation of hydrogen bonds
C Rapid increase in denatured protein molecules
D Rapid decrease in peptide bonds
haem Higher Level Paper 1, Time Zone 2, May 17, Q9
group

10 The image represents a model of a protein. Which level

of structure is indicated by X on the image?

What level of protein structure bonds the α and β chains

together?
X
A Primary
B Secondary
C Tertiary
D Quaternary
Higher Level Paper 1, Time Zone 1, November 21, Q6

7 What is found in insulin molecules?

A Phosphates
B Nucleotides
C Peptide bonds A Primary C Tertiary
D Fatty acids B Secondary D Quaternary
8 Which types of interactions are found in a part of a 11 Which statement about the primary structure of a
protein with secondary but not tertiary structure? protein is not correct?
I Hydrogen bonds A It is unique to that protein
II Disul昀椀de bridges B It is the sequence of amino acids in that protein
III Ionic bonds from the N to C terminus
A I only C It is hydrogen bonded
B I and II only D It determines the three-dimensional shape of the
C II and III only folded protein molecule
D I, II and III 12 Which statement refers to the quaternary structure
Higher Level Paper 1, Time Zone 1, May 17, Q28 of collagen?
A Each polypeptide chain takes the form of an
9 Scientists have heated a solution containing the protein
extended helix
albumin and measured its relative alpha helix content,
B Every third amino acid is glycine
shown on the graph. What does the zone labelled
C Many triple helices, with covalent cross-links, lie
X indicate?
parallel with each other, forming 昀椀brils
D Three helical polypeptide chains wind round each
other to form a right-handed rope-like structure

Biology for the IB Diploma Programme B1.2 Proteins 24

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■ Paper 2
1 Cadmium ions are poisonous to most bacteria. However, some bacteria are able to resist
the toxic effect by producing stress proteins. Scientists investigated the production of these
proteins in Vibrio sp. bacteria by giving them cadmium chloride solution for up to 60 minutes.
The graph shows the synthesis of all proteins (measured in arbitrary units) for these bacteria
and control bacteria which were not exposed to the cadmium chloride solution.

synthesis/arbitrary units
0.8
0.7
rate of protein 0.6
0.5 Key
0.4 experimental
0.3 control
0.2
0.1
0
0 10 20 30 40 50
time/min 60
utes

a Identify the rate of protein synthesis in the control group at 40 minutes. [1]
b Identify any pattern in the rate of protein synthesis in the experimental group
throughout the experiment. [2]
c Compare and contrast the rate of protein synthesis in both groups. [3]
2 a De昀椀ne the term proteome. [1]
b Identify the location in the cell where polypeptides are synthesized from amino acids. [1]
c A short polypeptide is comprised of 昀椀ve amino acids. Calculate the possible number of
different amino acid sequences for this polypeptide, assuming that 20 amino acids are
available for protein synthesis. [1]
3 a Draw a molecular diagram of an amino acid to show its general structure [3]
Standard Level Paper 2, Time Zone 2, May 17, Q5a

b Outline the range of functions of proteins in cells. [5]

Standard Level Paper 2, Time Zone 1, May 21, Q6c

4 Explain how proteins are denatured by extreme pH and heat. [4]

5 Explain why the shape of globular proteins that are enzymes is important in enzyme action. [3]
6 The diagram below shows the structure of the amino acids glycine and alanine.
H

H H C H
H O H O

N C C N C C

H OH H OH
H H
glycine alanine

a On a copy of the diagram, draw a box to identify the R-group of alanine. [1]
b Draw a labelled diagram to show the reaction between alanine and glycine to form
a dipeptide. [3]

Biology for the IB Diploma Programme B1.2 Proteins 25

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(Questions 7–11 HL only)

7 The diagram shows alpha amylase.

a Explain the secondary structure of this protein molecule. [3]

Higher Level Paper 2, Time Zone 2, May 18, Q4a

b Describe the impact of primary structure on the form and function of proteins. [3]
8 Explain how chemical diversity in the R-groups of amino acids is the basis for the
immense diversity in protein form and function. [5]
9 Outline the effect of polar and non-polar amino acids on the tertiary structure of proteins. [4]
10 Distinguish between conjugated and non-conjugated proteins. [3]
11 Explain the relationship between form and function in globular and 昀椀brous proteins. [7]

Biology for the IB Diploma Programme B1.2 Proteins 26

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B2.1 Membranes and membrane transport

■ Paper 1 5 What is the role of an aquaporin?
1 The diagram below shows a plasma membrane. A Channel protein for water
What are the correct names for structures X and Y? B Movement of ions against their concentration gradient
C Movement of glucose down a concentration gradient
Y D Moving water out, not into, a cell
6 The diagram below shows a section through a plasma
membrane. Which modes of transport across the
membrane are shown by I and II?
II
X
I
X Y
A phospholipid integral protein

B channel protein glycocalyx

C extrinsic protein fatty acid

D phosphate head fatty acid tail

2 Which features of phospholipids give them their

amphipathic properties? I II
A Acidic phosphate groups and basic lipids A osmosis facilitated diffusion
B Basic phosphate groups and acidic lipids
B facilitated diffusion simple diffusion
C Hydrophobic phosphate groups and hydrophilic
C simple diffusion facilitated diffusion
fatty acids
D active transport facilitated diffusion
D Hydrophilic phosphate groups and hydrophobic
fatty acids 7 The table shows concentrations of potassium ions and
3 Plasma membranes are 昀氀uid due to: sodium ions inside and outside human cells.
A The amphipathic properties of phospholipids What explains these concentrations?
B The water present on the outside of the Concentration of ions / 10 −3 mol dm−3
plasma membrane Ions Intracellular Extracellular
C The integral proteins with polar and non-polar potassium ions 135 4
regions interacting with phospholipids sodium ions 10 145
D Vesicles fusing with the plasma membrane A Potassium ions diffuse in and sodium ions
during exocytosis diffuse out
4 Which is the correct de昀椀nition of osmosis? B Sodium ions diffuse in and potassium ions
A Movement of water from low to high concentration diffuse out
B Movement of water from higher to lower C Active transport pumps sodium ions in and
concentration potassium ions out
C Movement of water from lower water potential D Active transport pumps sodium ions out and
to higher water potential through a partially potassium ions in
permeable membrane Standard Level Paper 1, Time Zone 2, May 19, Q5
D Movement of water from a dilute to more
concentrated solute solution through a partially
permeable membrane

Biology for the IB Diploma Programme B2.1 Membranes and membrane transport 27
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8 Which type of transportation happens in the sodium– 12 Nicotinic acetylcholine receptors are an example of:
potassium pump? A Voltage-gated potassium channels
A Simple diffusion B Voltage-gated sodium channels
B Osmosis C Ligand–receptor interaction
C Facilitated diffusion D Neurotransmitter-gated ion channels
D Active transport 13 Cholesterol is found in the cell membrane.
(Questions 9–14 HL only) An experiment was carried out to investigate the
9 Which statement applies to cholesterol? effects of temperature on the 昀氀uidity of the membrane.
A It is hydrophobic and found on the inside of the The results are shown in the graph below.
phospholipid bilayer fluid-like
B It is hydrophilic and found outside the without
cholesterol
phospholipid bilayer
C It impacts on membrane 昀氀uidity with

membrane
cholesterol

fluidity
D It is transported in association with glucose in
the blood
10 Which of the following is used in indirect
active transport?
A Sodium–potassium pumps solid-like Tm

B Sodium-dependent glucose cotransporters temperature

C Voltage-gated sodium channels
a Describe the effects of temperature on
D Aquaporins
membrane 昀氀uidity. [2]
11 What is the role of cell-adhesion molecules (CAMs)? b Explain the effects of cholesterol on membrane
A Antigen recognition 昀氀uidity at different temperatures. [7]
B Attachment of endothelium to basement c Suggest the advantage of the trends shown by
membrane in capillaries these data for animals with cholesterol in their
C Used in different types of cell–cell junction membranes which live in Arctic areas. [3]
D Used in antigen–antibody interactions

14 An investigation was carried out on the composition of fatty acids in the cell membranes
of a bacterium, Chryseobacterium frigidisoli PB4, sampled from Antarctic glacier soils.
The habitat of the bacteria is characterized by extremely low temperatures.
The effect of changing temperature on fatty acid composition was analysed. Data are
presented in the graph below, which shows the relative proportion of unsaturated and
saturated fatty acids from C. frigidisoli PB4 cultivated at different temperatures

30 a Compare and contrast the relative

percentage of saturated and unsaturated
relative percentage of the

fatty acids at different temperatures. [3]

major fatty acids/%

20
b Explain the trends seen in the data for
saturated and unsaturated fatty acids at
different temperatures. [7]
c Suggest reasons why the composition
10
of both fatty acids changes in the way
Key
saturated fatty acids demonstrated by the data. [3]
unsaturated fatty acids
0

0 5 10 15 20
temperature/°C

Biology for the IB Diploma Programme B2.1 Membranes and membrane transport 28
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■ Paper 2 (Question 4 HL only)

1 Draw and label a 2D section of an animal 4 The 昀椀gure below shows two mechanisms for
cell membrane. [4] transporting material across membranes.
2 a Outline the roles of phospholipids, cholesterol X
and glycolipids in the plasma membrane at the
cell surface. [6]
b Outline the functions of proteins in
cell membranes. [5]
Standard Level Paper 2, Time Zone 1, May 19, Q7b (modified)

3 Describe four types of membrane transport, including

their use of energy. [6] Y
Standard Level Paper 2, Time Zone 2, May 19, Q5 (modified)

a State the names for processes X and Y. [2]

b Explain the role both processes play in the
transport of material into and out from cells. [5]

Biology for the IB Diploma Programme B2.1 Membranes and membrane transport 29
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B2.2 Organelles and compartmentalization

■ Paper 1 6 Adaptations of the chloroplast for photosynthesis include:
1 Which structure found in eukaryotes has a I Contains 70S ribosomes
single membrane? II Large surface area of thylakoid membranes
A Nucleus with photosystems
B Lysosome III Small volumes of 昀氀uid inside thylakoids
C Chloroplast A I only
D Mitochondrion B I and II
Standard Level Paper 1, Time Zone 1, May 17, Q1 C II and III
D I, II and III
2 What do chloroplasts and mitochondria have in common?
A Both are found in the cells of prokaryotes ■ Paper 2
B Both contain 70S ribosomes 1 State the part of the chloroplast where enzymes and
C Both occur in all eukaryotic cells substrates of the Calvin cycle are found. [1]
D Both are found in a Paramecium 2 De昀椀ne the term nuclear pore. [1]
(Questions 3–6 HL only) 3 Diversity is a property of life at all levels of
3 The mitochondrion's form relates to its function because: biological organization.
A It has a folded inner membrane which increases a Outline the diversity of carbon compounds. [7]
ATP production b Eukaryotic cells contain a variety of
B It has a cylindrical shape which is hydrodynamic different organelles. Describe the role of
C It is small and so has a small surface area compartmentalization in cells. [4]
compared to its size for diffusion c Biodiversity is the variety of life in all its forms,
D It is transparent and so light can pass through levels and combinations. Explain the advantages
4 The advantages of having a membrane surrounding the of classi昀椀cation in biology. [4]
genetic material of the cell include: 4 Outline the advantages of separating the contents of the
I Protects DNA from other cellular reactions nucleus from those of the cytoplasm. [5]
that occur in the cytoplasm 5 Describe how different organelles are adapted to
II Allows gene transcription and translation to perform speci昀椀c functions. [6]
be kept separate 6 Explain how the development of ultracentrifugation led
III Stops DNA from being removed by exocytosis to an increased understanding of cell biology. [7]
A I only
7 Outline the role of membranes in the
B I and II
compartmentalization of cells. [7]
C I and III
D II and III
5 What is the function of the Golgi apparatus?
A Processing and packaging of proteins for export
from the cell
B Protein synthesis
C Production of ATP
D Programmed cell death (apoptosis)

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(Questions 8–12 HL only) 9 Compare and contrast how the structures of chloroplasts
8 The 昀椀gure shows organelles in a eukaryotic cell. and mitochondria are adapted for their functions. [7]
10 Distinguish the structure and function of free ribosomes
nucleus
and those of the rough endoplasmic reticulum. [4]
C
11 Describe the role of clathrin in the formation
of vesicles. [4]
12 Explain the functional bene昀椀ts of the double
membrane of the nucleus. [6]
D
A

B
polysome

a On a copy of the 昀椀gure, label structures A–F. [3]

A polysome is identi昀椀ed in the image.
b Describe the role of polysomes in eukaryotic cells. [3]

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B2.3 Cell specialization

■ Paper 1 5 Which of the following is a specialization of
1 Which of the following is the property of a totipotent female gametes?
stem cell? A Motile
A Can create, maintain and repair the cells of one B Small size to increase surface area
particular organ or tissue C Large cytoplasm
B Can create, maintain and repair cells of several D Spherical in shape
organs or tissues 6 An investigation was carried out on the surface
C Able to develop into many different types of area : mass ratio of different mammal species. Tracings
cells or tissues in the body, except for becoming were made of the skins of different mammals, and the
placental cells masses of the animals recorded.
D Capable of giving rise to any cell type in Table 1 gives the skin areas and masses of each animal.
an organism The surface area : mass ratio is calculated for each animal.
2 If cells of a multicellular organism have the same genes, ■ Table 1 Masses and skin area for eight different mammals, arranged
in order of size
how can there be many different cell types in a body?
A Some genes but not others are expressed in each Mammal Mass (g) Area of Surface
cell type skin (cm3) area / mass

B Cells lose some genes as development occurs 48-hour old gerbil 3 13 4.30

C Genes do not determine the structure of a cell adult male pygmy shrew 5 19 3.80
adult male mouse 29 70 2.41
D Cells must practice division of labour in order
4-day old hamster 67 139 2.08
to survive
Standard Level Paper 1, Time Zone 0, November 18, Q1 adult female gerbil 74 107 1.45
adult mole 76 97 1.28
3 Look at the sizes of the cells below. What is the correct adult male rat 410 405 0.99
order of size from smallest to largest? adult female hamster 681 616 0.91
I Cell I 90 µm adult grey squirrel 650 444 0.68
II Cell II 0.1 mm a Suggest why mass not volume was used in
III Cell III 200 nm this investigation. [1]
IV Cell IV 2 × 10−6 m b Describe the relationship between surface
A I → II → III → IV area : mass ratio and the size of animals in the
B II → III → IV → I investigation. [1]
C III → IV → I → II c Suggest the effects of increased size on heat loss
D IV → III → II → I in mammals. [4]
4 Which graph represents the change in cell surface area- Table 2 shows the mass, area of skin, and surface
to-volume ratio with increasing cell diameter? area : mass ratio of juvenile (infant) and adult mammals.
A B ■ Table 2 Masses and skin area for juvenile and adult mammals of
surface area :

surface area :

two species
volume

volume

Mammal Mass (g) Area of Surface

skin (cm3) area / mass
baby gerbil 3 13 4.30
cell diameter cell diameter
adult gerbil 74 107 1.45
C D baby hamster 67 139 2.08
surface area :

surface area :

adult hamster 681 616 0.91

volume

volume

d Describe the change in surface area : mass ratio of

juveniles compared to the adult of the same species. [1]
cell diameter cell diameter e Suggest how human babies can be treated to
Standard Level Paper 1, Time Zone 1, May 19, Q1
overcome the issues identi昀椀ed in part c. [3]

Biology for the IB Diploma Programme B2.3 Cell specialization 32

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(Questions 7–12 HL only) 11 In premature babies born earlier than the 30th week
7 The micrograph shows part of a human sperm cell. of pregnancy, type II pneumocytes are usually not
Which region of the cell is responsible for the greatest fully developed, so they do not carry out their function
production of ATP? normally. What is a possible consequence of this?
A The number of alveoli reduces
B The size of the alveoli increases
C Capillary networks do not develop fully and
oxygen is not absorbed
D D Surface tension between alveoli does not
decrease and the alveoli stick together
Standard Level Paper 1, Time Zone 2, May 19, Q26

12 This light micrograph shows muscle tissue.

C
B
I

A
5 μm
II
Higher Level Paper 1, Time Zone 1,
November 21, Q40 (modified)

III
8 Where in the body are type I pneumocytes found?
A Alveoli
B Small intestine
C Capillaries
D Bronchi
9 How do respiratory gases cross the membrane of
pneumocytes during gas exchange? a This muscle is made from repeating dark bands
A Facilitated diffusion (structure I). State the name of this type of
B Gated-ion channels muscle. [1]
C Active transport b Identify the structures labelled II and III in the
D Simple diffusion micrograph. [2]
10 What feature distinguishes striated muscle 昀椀bres from c Discuss whether the tissue shown in the
cheek cells, sperm cells and epithelial cells of the small micrograph consists of cells or not. [2]
Higher Level Paper 2, Time Zone 0,
intestine? November 19, Q5ai–b (modified)
A Mitochondria
B Nucleoid regions
C Multinucleate structure
D Membrane-bound organelles

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■ Paper 2 (Questions 6–9 HL only)

1 Outline the properties of stem cells. [3] 6 The diagram shows the structure of an alveolus and an
2 Describe the role of stem cell niches in adult humans. [4] adjacent capillary.

3 Distinguish between totipotent, pluripotent and

multipotent stem cells. [3]
4 a Outline how size is an aspect of cell
specialization. [4] alveolus
b Explain why surface area-to-volume ratio is a
type I
constraint on cell size. [5] pneumocytes
5 Describe the processes following fertilization that lead
to the development of specialized cells. [7] type II
pneumocytes

a i Describe the functions of type I and type II

pneumocytes. [2]
ii Explain how the form of type I pneumocytes
is linked to their function. [3]
b Explain how gases are exchanged between the air
in the alveolus and the blood in the capillaries. [3]
7 Explain how the form of cardiac muscle cells
determines their function. [7]
8 Compare and contrast the adaptations of sperm and
egg cells. [7]
9 Using the surface area-to-volume relationship, explain
why models are useful arti昀椀cial representations of
natural phenomena. [7]

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B3.1 Gas exchange

■ Paper 1
1 What occurs during inhalation?
External intercostal muscles Movement of ribs
A relax fall

B contract fall

C relax rise

D contract rise

Standard Level Paper 1, Time Zone 0, November 21, Q27

2 Which is an adaptation to increase rates of gas exchange in the lung?

A Small surface area
B Dry surface
C Large number of capillaries
D Muscular alveoli
3 The graph shows a spirometer trace taken during exercise. What does this spirometer
trace show?
5

4
volume/dm3

0
20 40 60 80 100 120 140
time/s

A The breathing rate is 11 breaths per minute

B The tidal volume is 4 dm3
C The inspiratory reserve is 5 dm3
D The expiratory reserve is 1 dm3

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4 A student designed an experiment to study the transpiration through the leaves of a tomato
plant (Solanum lycopersicum). Measurements were taken in the initial conditions with 昀椀ve
leaves on a tomato shoot and then again after each of the 昀椀ve leaves was removed.
14

transpiration rate/µl min−1

12

10

0
0 1 2 3 4 5
number of leaves removed

a i Describe the trend in the data. [1]

ii Transpiration continued after the 昀椀fth leaf had been removed. Suggest what can
be concluded. [1]
b State the independent variable in this investigation. [1]
c Explain how the results in the graph could have been obtained. [2]
Higher Level Paper 3, Time Zone 0, November 19, Q2a–c

5 In an experiment to explore the effect of exercise on ventilation rate, a subject breathed into a
data logging sensor that measured air 昀氀ow.
The graphs show the result before the subject exercised and immediately after the exercise
had 昀椀nished.
before exercise

0
volume/L

–1

–2

0 5 10 15
time/s

after exercise

0
volume/L

–1

–2

0 5 10 15
time/s

a Determine the ventilation rate after exercise. [2]

b Describe how the mean tidal volume after exercise could be determined using the graph. [2]
c Predict, with a reason, the effect of exercise on the rate of cell respiration. [1]
d Identify a muscle responsible for increasing the volume of the chest cavity. [1]
Standard Level Paper 3, Time Zone 2, May 18, Q3a–d

Biology for the IB Diploma Programme B3.1 Gas exchange 36

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6 A study was conducted on 25 healthy, non-smoking males to look at the effect of exercise
and altitude on ventilation rate. Subjects were 昀椀rst asked to rest in a sitting position for six
minutes. They then pedalled for three periods of six minutes at increasing exercise intensity:
at 20%, 30% and 40% of their maximal aerobic power. The entire study was conducted either
in normal sea level oxygen conditions or in lower oxygen conditions simulating an altitude of
4000 m. The results are shown in the bar chart.
60
Key
50 rest
ventilation rate/dm3 min−1
20% of maximal aerobic power
40
30% of maximal aerobic power

40% of maximal aerobic power

30

20

10

0
sea level 4000 m

a State one other variable that should have been controlled in this study. [1]
b Compare and contrast the effect of increasing exercise intensity at sea level and at an
altitude of 4000 m. [2]
c Outline how ventilation rate could have been monitored in this study. [2]
Standard Level Paper 3, Time Zone 2, May 19, Q3a–c

7 A spirometer was used to measure the ventilation rate of a person at rest and pedalling at
22 km per hour on an exercise bike.
at rest
air volume/dm 3

Key
2 inhalation exhalation

0
0 20 40 60 80 100 120
time/s

22 km per hour

2
air volume/dm 3

0
0 20 40 60 80 100 120
time/s

a Calculate the difference in ventilation rate between resting and exercising. [1]
b Explain the change in the tidal volume during exercise. [3]
Standard Level Paper 3, Time Zone 1, May 17, Q3a–b

Biology for the IB Diploma Programme B3.1 Gas exchange 37

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(Questions 8 and 9 HL only) 2 Describe the process of inhalation. [4]

8 Adaptations of foetal and adult haemoglobin for the 3 Explain the process of gas exchange taking place in
transport of oxygen include: the alveoli. [7]
I Cooperative binding of oxygen to haem groups Standard Level Paper 2, Time Zone 1, May 21, Q7b
II Allosteric binding of carbon dioxide
4 Adult humans may absorb more than 500 litres
III Competitive inhibition of antioxidant enzymes
of oxygen per day. Explain how gas exchange is
A I only
maintained in the human respiratory system. [7]
B I and II Higher Level Paper 2, Time Zone 0, November 18, Q6c
C I, II and III
D I and III (Questions 5–7 HL only)
9 What effect does an increase in carbon dioxide have 5 The graph below shows the oxygen dissociation curve at
on haemoglobin? a low CO2 concentration.
A Decreased dissociation of oxygen
100
B Increased dissociation of oxygen
C Decreased haemoglobin synthesis

oxygen saturation/%
D Increased breakdown of the haem group

■ Paper 2 50
1 The graph shows the ventilation rate and tidal volume
of a well-trained runner during exercise on a treadmill.
The tidal volume is the volume of air being moved in
and out of the lungs in each breath.
0
80 2.8 pO2
Key
ventilation rate 2.6 a An increase in metabolic activity results in
70 tidal volume
2.4 greater release of CO2 into the blood. On a copy
of the graph, draw the oxygen dissociation
ventilation rate/breaths min −1

60 2.2
tidal volume/L breath −1

curve during intense exercise when the CO2

2.0 concentration of the blood is high. [1]
50 b Explain how the increase in CO2 concentration
1.8
affects the release of oxygen to respiring cells. [2]
40 1.6 Higher Level Paper 3, Time Zone 1, May 17, Q21bi–ii

1.4 6 Explain how oxygen dissociation curves can be used

30 to represent the af昀椀nity of haemoglobin for oxygen at
1.2
different oxygen concentrations. [5]
20 1.0 7 Outline how an increase in carbon dioxide causes
increased dissociation of oxygen and how this bene昀椀ts
9 12 15 18
treadmill speed/km h–1
actively respiring tissues. [7]

a State the apparatus used to measure the

tidal volume. [1]
b Calculate the total volume of air inhaled during
one minute during the highest velocity of the
treadmill in this test, giving the units. [2]
c Compare and contrast the effect of increasing
treadmill speed on the ventilation rate and tidal
volume in this runner. [2]
Higher Level Paper 3, Time Zone 1, May 18, Q2a–c

Biology for the IB Diploma Programme B3.1 Gas exchange 38

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B3.2 Transport
■ Paper 1 6 In an investigation to compare the elasticity of arteries
1 What is a property of arteries? and veins, rings of the same diameter (20 mm) of artery
A Arteries have elastic walls and vein tissue were cut from blood vessels obtained
B Arteries have valves from a mammal.
C All arteries carry oxygenated blood Each ring was attached to a clamp. Multiple masses of
D Arteries receive blood from the atria 10 g were added and removed. The vertical diameter
Standard Level Paper 1, Time Zone 1, May 21, Q27 of the artery and the vein was measured, both with the
mass and once the mass had been removed. The results
2 The image shows part of a section through the stem of a
are shown in the table.
non-woody plant. Where does transport of sucrose occur?

B 20 mm
A
C
ring of tissue blood vessel
D
clamp

Higher Level Paper 1, Time Zone 2, May 21, Q33 ruler

3 Which process is most responsible for movement of

ring of tissue
water from roots to leaves of a plant on a hot sunny day?
A Active translocation of mineral ions in roots
B Active transport of organic compounds into
10
sieve tubes gm mass

C Raised hydrostatic pressure gradients

D Evaporation of water from mesophyll cell walls
Higher Level Paper 1, Time Zone 0, November 19, Q32
Diameter of vein / mm Diameter of artery / mm
4 What is an advantage of capillary walls being one cell Mass / g With mass Mass removed With mass Mass removed
thick in the systemic circulation? 0 20 20 20 20
A To allow carbon dioxide to diffuse into tissues 10 26 26 26 22
B To allow glucose to diffuse out of tissues 20 34 33 30 23
C To allow oxygen to diffuse into tissues 30 38 36 35 23
D To allow urea to diffuse into tissues 40 40 37 38 24
5 Which process and cause are responsible for water a State the independent and dependent variables in
uptake by the roots? this experiment. [2]
Processes Cause b State one feature of the rings that has to be kept
A simple diffusion solute concentration in the root lower than constant apart from their initial diameter. [1]
in the soil c Explain the differences between the results
B osmosis solute concentration in the root greater shown for vein and artery. [3]
than in the soil
Standard Level Paper 3, Time Zone 0, November 20, Q2a–c
C osmosis solute concentration in the root lower than
in the soil
D cohesion solute concentration in the root greater
than in the soil
Higher Level Paper 1, Time Zone 1, May 17, Q32

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(Questions 7–12 HL only) 10 The diagram shows the human heart. After a red blood
7 The mammalian heart has four chambers: right cell picks up oxygen in the lungs, which sequence shows
atrium, left atrium, right ventricle and left ventricle. the path it could take when passing through the heart
The sinoatrial node is located in the wall of one of these during its circuit of the body?
chambers. Which chamber is it?
A Right atrium C Left atrium I
B Right ventricle D Left ventricle
8 What blood 昀氀ow does the right semilunar valve prevent?
A Back昀氀ow of blood to the right atrium during
ventricular contraction IV
B Blood 昀氀owing from the aorta back into the heart
when the ventricle is 昀椀lling
C Blood 昀氀owing from the pulmonary artery to the III II
right ventricle when the heart is relaxing
D Blood 昀氀owing from the right atrium to the vena
cava when the right atrium contracts
Standard Level Paper 1, Time Zone 1, May 21, Q29 A I → II → III → IV
B II → I → IV → III
9 The diagram shows changes in pressure in the C IV → III → I → II
left atrium, left ventricle and aorta during a single D IV → III → II → I
cardiac cycle. At what point during the cycle does the Standard Level Paper 1, Time Zone 0, November 19, Q26
atrioventricular valve close?
11 In which blood vessel connected to the heart does blood
120
have the lowest carbon dioxide concentration?
100
A Pulmonary vein
B B Vena cava
blood pressure/mm Hg

C
80 C Pulmonary artery
Key D Hepatic portal vein
60 aorta
left ventricle 12 The diagram shows red blood cells and undifferentiated
left atrium tissue cells.
40

D Diffusion of oxygen from blood cells to tissue cells is

20 A
represented by arrow 3 in the diagram. What molecules
are shown diffusing by arrow 1 and arrow 2?
0
0 0.2 0.4 0.6
1
time/s

Standard Level Paper 1, Time Zone 2, May 21, Q25 2

3

Arrow 1 Arrow 2
A carbon dioxide urea

B water glucose

C glucose carbon dioxide

D fatty acids amino acids

Standard Level Paper 1, Time Zone 0, November 17, Q25

Biology for the IB Diploma Programme B3.2 Transport 40

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■ Paper 2
1 This micrograph shows a transverse section of an artery.

×100

a Outline how the specialized structures of arteries help them to achieve their functions. [3]
Standard Level Paper 2, Time Zone 0, November 21, Q4a (modified)

b Distinguish between the structures of arteries, veins and capillaries. [6]

2 Plants have developed ef昀椀cient methods for transport of water and organic materials.
Distinguish between the xylem and phloem of plants. [5]
3 Explain the processes that cause water to move from the roots of plants to their leaves. [7]
(Questions 4–8 HL only)
4 a State the name of the valves that prevent blood 昀氀owing from the arteries back into
the heart. [1]
The drawing shows the typical action potential waveforms with the different phases of the
cardiac cycle recorded in different regions of a human heart.

phases
sinoatrial node
1
2
left atrium 0 3

4
atrioventricular
node

conducting fibre

ventricular
muscle

left 0.0 0.2 0.4 0.6 0.8 1.0

right
ventricle
ventricle seconds

b Distinguish between the different phases of the cardiac cycle in the atria and in the
ventricular muscle. [2]
Standard Level Paper 3, Time Zone 2, May 19, Q18b–c

5 Compare and contrast the single circulation of bony 昀椀sh and the double circulation
of mammals. [4]
6 Outline the control mechanism of the heart rate. [5]
7 Outline how root pressure is generated in xylem. [5]
8 Explain the formation and reuptake of tissue 昀氀uid. [7]

Biology for the IB Diploma Programme B3.2 Transport 41

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B3.3 Muscle and motility (HL only)

■ Paper 1 (HL only) 3 What is a similarity between human and insect muscles?
1 The diagram shows structures involved in contraction of A They are attached to an exoskeleton
a sarcomere. What is X? B They work as antagonistic pairs
C The 昀氀exor muscles straighten the joint
× D They move bones
Higher Level Paper 1, Time Zone 0, November 19, Q38

4 What is the role of the joint capsule in a hip joint?

A It seals the joint to retain the synovial 昀氀uid
B It provides a point of attachment for muscles
C It produces cartilage to reduce friction during
A Myosin 昀椀lament movement
B Sarcomere D It directs the formation of bone tissue during
C Actin 昀椀lament growth and development
Higher Level Paper 1, Time Zone 1, May 19, Q38 (modified)
D Myo昀椀bril
Higher Level Paper 1, Time Zone 2, May 21, Q38
5 Which process is part of the mechanism that controls
2 What is the role of calcium ions in muscle contraction? muscle contraction?
A To enable actin to expose binding sites on myosin A Troponin enables actin heads to attach to ATP
B To bind to troponin, exposing binding sites on actin and slide along myosin
C To prevent an action potential in the muscle B Myosin heads attach to troponin and
membrane tropomyosin pulls on actin 昀椀laments
D To bind to tropomyosin, blocking binding sites C Tropomyosin attaches to calcium and breaks the
on actin bond between actin and myosin
Higher Level Paper 1, Time Zone 0, November 20, Q38 D Calcium frees actin 昀椀laments for myosin heads
to attach
Higher Level Paper 1, Time Zone 0, May 16, Q38

6 The diagram shows two states of skeletal muscle, relaxed and contracted.
Which process is part of muscle contraction?
Z line

relaxed muscle

contracted muscle

Z line

A Myosin 昀椀laments cause the actin 昀椀laments to shorten

B Ca2+ from the sarcoplasmic reticulum binds to the myosin heads
C ATP provides energy for the movement of the myosin heads
D Ca2+ binds to tropomyosin and uncovers troponin
Higher Level Paper 1, Time Zone 2, May 18, Q38

Biology for the IB Diploma Programme B3.3 Muscle and motility (HL only) 42
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■ Paper 2 (HL only) 2 The 昀椀gure shows part of a myo昀椀bril from

1 Figure 1 is a diagram that shows part of a skeletal muscle.
muscle myo昀椀bril.
Z line thick filament Z line thin filament Z line
Z Y Z

A band A band
sarcomere sarcomere

a Describe two features, visible in the diagram,

which show that the myo昀椀bril is contracted. [2]
b Explain the role of ATP in bringing about
W X
contraction of a muscle 昀椀bre. [2]
Figure 1
3 Explain the relationship to a muscle of:
a Name the protein present in the 昀椀laments a a muscle 昀椀bre [1]
labelled W and X. [1] b a myo昀椀bril [1]
b Figure 2 shows the cut ends of the protein c a myosin 昀椀lament. [1]
昀椀laments when the myo昀椀bril was cut at position
4 Explain how a muscle 昀椀bre contracts. [7]
Y. Figure 3 shows the protein 昀椀laments when the
myo昀椀bril was cut at the same distance from a Z 5 Outline the role of the protein titin and antagonistic
line at a different stage of contraction. Explain muscles in muscle relaxation. [5]
why the pattern of protein 昀椀laments differs in
Figure 2 and Figure 3. [2]

Figure 2

Figure 3

c Describe the role of calcium ions in the

contraction of a sarcomere. [4]

Biology for the IB Diploma Programme B3.3 Muscle and motility (HL only) 43
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B4.1 Adaptation to environment

high
■ Paper 1

number of wolves
wolves wolves
1 Over time, the hull of a sunken ship may become eliminated reintroduced
colonized by a wide range of marine organisms. (1926) (1995)

What term is used to describe all of the organisms living

in and on a sunken ship? low
A A community 1900 1920 1940 1960 1980 2000
high
B An ecological niche end of elk

number of elk
culling
C A population (1968)
D An ecosystem
Standard Level Paper 1, Time Zone 1, May 21, Q20

2 What is the ecological term for a group of the same type low
1900 1920 1940 1960 1980 2000
of organism living together in one area? year
A Community
a Outline the changes in elk population between
B Domain
the years 1930 and 2004. [3]
C Ecosystem
b List two biotic factors, other than wolf predation
D Population
or culling, that could affect the elk population. [2]
3 In 1789 Gilbert White, a naturalist, observed eight
Higher Level Paper 3, Time Zone 0, November 20, Q18a–b
breeding pairs of swifts (Apus apus) in the English village
of Selborne. On average, each pair of swifts produces two 2 The climograph shows data collected at Mangalore,
offspring per year. This would allow the population to India. The natural vegetation of the surrounding area is
rise to 1030 swifts over 200 years. A bird survey carried forest and the climate is tropical.
out in 1983 revealed only 12 breeding pairs in this village. 1200 35
Key
What could have prevented the numbers rising to 1030? 30
1000 temperature
precipitation/mm

I The number of nesting sites remained the same

temperature/°C
25 precipitation
800
II The food supply of the swifts remained constant 20
III Predatory birds in the area were exterminated 600
15
A I only 400
10
B I and II only 200 5
C II and III only
0 0
D I, II and III J F M A M J J A S O N D
Standard Level Paper 1, Time Zone 0, November 18, Q19 months

a i Using the climograph, calculate the range

■ Paper 2 of temperature. [1]
1 The elimination of wolves (Canis lupus) from ii Using the climograph, identify the
Yellowstone National Park in 1926 and their relationship between maximum temperature
reintroduction in 1995 provided the opportunity to and rainfall. [1]
examine ecological interactions with elk (Cervus iii Using the climograph, outline the pattern
elaphus). The National Park Service made efforts of rainfall. [1]
between the 1920s and 1968 to reduce the size of elk b Natural forests in the area around Mangalore
herds by culling (selective killing) because of concerns contain hardwood trees such as teak (Tectona
about overgrazing. grandis), which are deciduous, shedding their
The graphs provide the trends for the numbers of wolves leaves once a year. Suggest, with a reason, when
and elk in Yellowstone National Park from 1900 to 2004. this might happen. [2]
Higher Level Paper 3, Time Zone 2, May 19, Q15ai–b

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3 Outline the conditions required for coral a Calculate the total number of M. lucifugus 昀氀ights
reef formation. [4] that were recorded in the summer of 2007. [1]
4 The climograph shows the distribution of biomes b Suggest one limitation of this recording method
according to the temperature and rainfall of land areas in determining the accurate mean number of
on Earth. individual bats 昀氀ying. [1]
c i Calculate the percentage decline in the mean
number of M. lucifugus 昀氀ights for 2009 when
mean annual temperature/°C

I
–10
taiga compared to 2008. [1]
ii Evaluate the conclusion that the decline in the
0 population of M. lucifugus is due to infection
by the fungus. [2]
10
The graph shows data from a small group of infected
bats that died during hibernation. The average time
20 II
III IV interval between hibernation emergence periods and the
date of death were recorded using temperature sensors
30
0 1 2 3 4 for these bats.
mean annual rainfall/m
14

mean interval between hibernation

emergence periods/days
a Identify the ecosystem with the appropriate 12
numeral from the climograph. [2]
10
Ecosystem Numeral
8
tropical rainforest
6
desert
tundra 4

b Referring to the climograph, explain reasons that 2

the nutrient store in the litter layer of the taiga is 0

greater than in the tropical rainforest. [3] 28 Nov 18 Dec 7 Jan 27 Jan 16 Feb 8 Mar
date of death
Standard Level Paper 3, Time Zone 0, November 16, Q12a–b
d Outline the relationship between date of death
5 White-nose syndrome (WNS) is a disease caused by and the mean interval between hibernation
the fungus Geomyces destructans. This kills bats from emergence periods. [1]
many species during their winter hibernation. Scientists e Discuss whether the data in the graph show
used echolocation to record the number of bat 昀氀ights that there is a causal link between the date of
over a station in 10-minute sample periods during the death and the interval between hibernation
summers of 2007 to 2009. The graph shows the mean emergence periods. [2]
number of 昀氀ights and number of recording samples for f Suggest one reason, other than the interval
little brown bats (Myotis lucifugus), a species affected between hibernation emergence periods, for
by the fungus, along with those of hoary bats (Lasiurus some infected bats surviving longer than others. [1]
cinereus), which are not affected. g Using all of the data, predict the effect of WNS
40 on bat populations. [3]
Key
35 Higher Level Paper 2, Time Zone 1, May 18, Q1a–c, f–i
mean number of bats flying
in 10-minute sample periods

Myotis lucifugus
(affected)
30 6 Outline adaptations to life in hot deserts and
Lasiurus cinereus
25 (unaffected) tropical rainforest. [5]
20 7 Explain how abiotic factors can affect the distribution of
15 species in an ecosystem. [6]
Standard Level Paper 3, Time Zone 1, May 18, Q15 (modified)
10

5 8 The orchid mantis, a predatory insect that lives in the

0 tropical rainforests of South East Asia, has an adult
year: 2007 2008 2009
samples: 79 151 144
form that resembles an orchid 昀氀ower. Suggest how
this insect may have evolved. [7]

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9 The 昀椀gure below represents a transect through a freshwater ecosystem. Notice that a range
of habitats within the ecosystem are identi昀椀ed, and that the feeding relationships of the
community of different organisms are highlighted.

energy from sunlight

submerged
rooted plants
plants stems provide a
floating
are microhabitat for
plants
producers algae growing
plankton
on them
examples
herbivores reed swamp
of habitats
eat plants of margin
carnivores open surface
consumers eat animals water
detritivores
eat dead mud deposited
organic on pond bottom
matter
decomposers on
detritus
surface of mud sediment
feeding
containing
fish on
nutrient
pond mud
reserve

Determine which of the terms shown below describe each of the listed features of a freshwater
lake (one or more terms may 昀椀t each feature).
population ecosystem habitat abiotic factor community biomass
a The whole lake [1]
b All the frogs of the lake [1]
c The 昀氀ow of water through the lake [1]
d All the plants and animals present [1]
e The total mass of vegetation growing in the lake [1]
f The mud of the lake [1]
g The temperature variations in the lake [1]

Biology for the IB Diploma Programme B4.1 Adaptation to environment 46

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B4.2 Ecological niches

■ Paper 1 4 Galium (bedstraw) is a matt-forming herb, found
1 Which organism would be classi昀椀ed as a saprotroph? on grassland, moors, heaths and woods. Ecologists
A A single-celled eukaryote that obtains organic have noticed that two species, Galium saxatile and
molecules by photosynthesis and ingestion of G. sylvestre, do not grow together. G. saxatile is found
other single-celled organisms on acidic peat soils and G. sylvestre on limestone soils.
B An anemone that uses the stinging cells in its An experiment is carried out to investigate the
tentacles to paralyse its prey, which is passed to fundamental and realized niches of these species. Seeds
an internal gastric cavity through a single opening are taken of both species and planted separately in boxes
C A fungus that feeds by secretion of digestive containing both types of soil. The 昀椀gure below shows
enzymes onto its food and absorption of the results of the experiment.
digested material
25
D A dung beetle that feeds on the faeces of Key
other animals G. saxatile
20
2 Hummingbirds eat 昀氀ower nectar and small insects. G. sylvestre

To which nutritional group do they belong?

germination/%
15
A Autotrophs
B Heterotrophs
C Mixotrophs 10

D Saprotrophs
3 Which organism can be described as an autotroph? 5
I A fungus that digests its food externally and
absorbs the products of digestion 0
basic acidic
II A single-celled eukaryote that is able
soils
to photosynthesize
III A koala bear that feeds by ingesting leaves a Describe the results of this experiment. [2]
from an acacia tree b Suggest a reason for the results, and what they
A I only indicate about the fundamental and realized
B II only niches of both species. [3]
C I and II
D I and III

Biology for the IB Diploma Programme B4.2 Ecological niches 47

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5 The model describes the fundamental and realized niches of a species of microscopic marine
arthropod in the Northern hemisphere with respect to two different factors (X and Y).
The abundance of the species is shown over 12 months. The fundamental niche is separated into
昀椀ve zones ranging from critical to optimal conditions. The population of the species in its realized
niche each month is represented by an oval. The size of each oval shows the population abundance.
Factor Y

Jul
May
Apr Aug
Sep
Oct
Nov
Jan Jun
Dec
Feb Mar

Factor X
lethal critical low medium high optimal

Fundamental niche condition

a Distinguish between fundamental niche and realized niche. [1]

b State the month where the population reaches its maximum. [1]
c i Outline how factor Y affects the species from January to April. [2]
ii Suggest, with a reason, what factor Y could be. [2]
Higher Level Paper 3, Time Zone 2, May 18, Q16a–c

6 Ecologists studied the distribution of 昀椀ve species of insectivorous wood warblers of the genus
Dendorica living on different parts of coniferous trees in mature forests.

Cape May
Blackburnian (D. tigrina)
(D. fusca)

Black throated
Bay-breasted green (D. virens)
(D. castanea)

Myrtle
(D. coronata)

a Outline the principle of competitive exclusion. [2]

b Other than position in the tree, suggest two ways in which the niches of the warblers in
the ecosystem may differ. [2]
c The diagram shows the realized niches of the 昀椀ve species of warbler. Suggest how the
fundamental niche of D. castanea might differ from its realized niche. [2]
Standard Level Paper 3, Time Zone 0, November 20, Q12a–d

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■ Paper 2 2 Distinguish between obligate anaerobes, facultative

anaerobes and obligate aerobes. [5]
1 a Compare and contrast the mode of nutrition of
detritivores and decomposers. [2] 3 Outline the diversity of nutrition in Archaea. [3]
Detritivores Decomposers 4 Adaptations enable organisms to survive in their
Similarity environment. Outline the range of adaptations for
Difference the following:
a plants for harvesting light [2]
b Euglena (see diagram) is a well-known
b herbivores for feeding on plants and of plants for
freshwater example of a protist that uses
resisting herbivory [3]
mixotrophic nutrition. Explain the mode of
c predators for 昀椀nding, catching and killing prey
nutrition in Euglena. [3]
and of prey animals for resisting predation. [4]
5 Explain the relationship between dentition and the diet
of omnivorous and herbivorous representative members
of the family Hominidae. [7]
6 Using examples, explain why knowledge of the
ecological niche of a species is important for
its conservation. [7]

Biology for the IB Diploma Programme B4.2 Ecological niches 49

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C1.1 Enzymes and metabolism

■ Paper 1 4 The rate of hydrolysis of 昀椀sh proteins using the enzymes
1 Which of the following statements does anabolic papain and pancreatin was monitored using the
reactions include? apparatus shown (Figure 1). The pH decreased with the
A Hydrolysis of macromolecules into monomers progress of hydrolysis, so alkali in the burette was added
in digestion as necessary in order for the hydrolysis to proceed
B The formation of lactic acid in anaerobic respiration at constant pH. The rate of protein hydrolysis was
C Oxidation of substrates in respiration measured as the amount of alkali added. Measurements
D Formation of macromolecules from monomers were taken at constant conditions of temperature and pH
by condensation for two enzyme concentrations, 1% and 0.1% (Figure 2).

2 What is meant by the term induced-fit binding?

burette
A Substrate and active site are complementary in shape
B Both substrate and enzymes change shape when
binding occurs
C Enzymes bind to a speci昀椀c substrate
D Enzymes can be immobilized pH meter
3 What is the effect of enzymes on activation energy? pH probe
stirrer
A Lower the amount of energy required to activate
reaction
the reacting molecules vessel
B Increase the amount of energy required to
water
activate the reacting molecules bath
C Change the shape of the active site Figure 1
D Provide a stable reaction pathway

25

20
total volume of
alkali added/ml

15
Key
10 papain 1%
pancreatin 1%
5 papain 0.1%
pancreatin 0.1%
0
0 50 100 150 200 250
duration of hydrolysis/min
Figure 2

a State the effect of enzyme concentration on the

hydrolysis of proteins. [1]
b Sketch on a copy of the graph the curve
expected if the hydrolysis were performed using
papain 0.5 %. [1]
c Explain what would happen to 昀椀sh protein
hydrolysis if no alkali were added to the
reaction vessel. [3]
Higher Level Paper 3, Time Zone 0, November 16, Q1a–c

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(Questions 5–7 HL only) ■ Paper 2

5 Which of the following are examples of extracellular 1 Some enzymes function optimally in acidic conditions,
enzyme-catalysed reactions? while other enzymes function optimally in alkaline or
I Glycolysis neutral conditions. Explain why different enzymes have
II The Krebs cycle different optimal pH values, relating your answer to the
III Chemical digestion in the gut structure of the active site. [4]
A I only
(Questions 2–5 HL only)
B I and II
2 The sketch shows the relationship between the reaction
C I, II and III
rate and substrate concentration in the presence and the
D III only
absence of a competitive inhibitor. Explain the effect of
6 Which of the following is an example of
the competitive inhibitor on the reaction rate. [2]
feedback inhibition?
A Change to transpeptidases that confers resistance
to penicillin no inhibitor

B The metabolic pathway that produces isoleucine

with inhibitor
C The use of statins to control HDLs

reaction rate
D Metabolic processes of the Calvin cycle
7 Why is heat generation in metabolic
reactions inevitable?
A Energy transfers are not 100% ef昀椀cient
B Energy can neither be created nor destroyed
C Energy transfers are exothermic
substrate concentration
D Most animals are warm blooded
Higher Level Paper 2, Time Zone 2, May 17, Q2a

3 Outline the importance of enzymes to

metabolic processes. [4]
Higher Level Paper 2, Time Zone 0, November 16, Q3b

4 Outline the control of metabolism by end-product

inhibition. [5]
Higher Level Paper 2, Time Zone 1, May 19, Q5b

5 Explain how the structure of proteins determines their

function and optimal operating conditions. [9]

Biology for the IB Diploma Programme C1.1 Enzymes and metabolism 51

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C1.2 Cell respiration

■ Paper 1 3 Which of the following processes require ATP?
1 Which of the following occurs when ATP is converted I Active transport across membranes
into ADP? II Anabolism
I Energy is stored III Catabolism
II Energy is released IV Movement of chromosomes
III Condensation reactions A I and II
IV Hydrolysis reactions B I, II and III
A I only C I, II and IV
B I and II D I and IV
C II and IV 4 What is the difference between anaerobic and aerobic
D I and IV cell respiration in humans?
2 Which is an ethical concern to consider when A Anaerobic respiration releases more energy
doing experiments using a respirometer to measure B Aerobic respiration requires oxygen but
respiration rate? anaerobic does not
A Avoid contact with soda lime C Aerobic respiration occurs in the cytoplasm and
B Ensure suf昀椀cient carbon dioxide concentration anaerobic respiration in mitochondria
C Do not use glassware D Aerobic respiration uses glucose as a substrate
D Do not seal the manometer and anaerobic respiration uses fatty acids

5 The oxygen consumption rate of the 昀椀sh Oplegnathus insignis was examined in a respirometer
at three different water temperatures and at four different body masses.

water computer used

supply to record oxygen
oxygen
meter

respirometer

water out

400
oxygen consumption

300
rate/mg O2 kg−1 h−1

200

Key
100
23 °C
18 °C
13 °C
0
0 200 400 600
body mass/g

a Suggest how the oxygen consumption rate is determined using this apparatus. [2]
b State the relationship between body mass and the oxygen consumption of 昀椀sh. [1]
c Predict the effects of global warming on aerobic respiration in 昀椀sh. [2]
Standard Level Paper 3, Time Zone 2, May 17, Q1a–c

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6 In an experiment measuring oxygen consumption, a laboratory mouse was placed in a

respirometer for a short time. Soda lime solution absorbed any carbon dioxide produced
during the experiment.

capillary tube bell jar

wire mesh

coloured water soda lime solution

a Suggest the purpose of the wire mesh. [1]

b Describe how the apparatus measures the oxygen consumption of the mouse. [3]
c Discuss whether the apparatus would be suitable for measuring the oxygen
consumption of a small green plant during respiration. [3]
Standard Level Paper 3, Time Zone 0, November 16, Q1a–c

(Questions 7–10 HL only)

7 In which part of the cell does glycolysis take place?
A Cytoplasm
B RER
C Mitochondria
D Nucleus
8 Which of the following is a role of the electron transport chain?
A Generate an electron gradient
B Generate a proton gradient
C Transport oxygen to a terminal acceptor
D Transport NAD+
9 What is the conversion of pyruvate to lactate a means of?
A Continuing aerobic respiration
B Regenerating NAD in anaerobic cell respiration
C Providing substrates for the link reaction
D Transferring energy by reduced NAD to the electron transport chain

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10 The TEM shows part of a human pancreas cell including ■ Paper 2

a mitochondrion. 1 Outline the role of ATP in cells. [3]
2 Distinguish between anaerobic and aerobic cell
respiration in humans. [5]
3 Describe an experiment to investigate the effect of
a named variable on the rate of cell respiration in
an organism. [7]
4 Explain how cell respiration affects each level of
biological organization. [9]
(Questions 5–8 HL only)
5 With reference to cellular respiration, distinguish
between the cytoplasm and mitochondria in terms of
ATP production, use of oxygen and release of CO2. [3]
0.4 μm 6 All living organisms depend on a continuous supply
of energy.
a Draw an annotated diagram of the mitochondrion. [3]
Explain the stages of aerobic respiration that occur in
b Calculate the magni昀椀cation of the image. [1]
the mitochondria of eukaryotes. [8]
c i List the molecules that are taken into the
Higher Level Paper 2, Time Zone 2, May 18, Q6a
mitochondria for the metabolic pathway of
aerobic respiration. [2] 7 Oxygen is needed to complete aerobic cell respiration.
ii Suggest how these molecules move into Explain how chemical energy for use in the cell is
the mitochondria. [1] generated by electron transport and chemiosmosis. [8]
d Outline how ATP is generated in mitochondria Higher Level Paper 2, Time Zone 1, May 17, Q5a
by chemiosmosis. [5]
8 Explain the relationship between the structure of a
mitochondrion and its function. [9]

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C1.3 Photosynthesis
■ Paper 1 a Identify a pigment found in all three organisms. [1]
1 Which of the following describes how the hydrogen b Compare and contrast absorption spectra and
used in photosynthesis to convert carbon dioxide to action spectra. [2]
glucose is obtained? c Porphyra also contains phycoerythrin, which is a
A Condensation reactions red pigment.
B Splitting water molecules i Suggest a reason for phycoerythrin being
C Catabolic metabolic pathways absent from the Porphyra chromatogram. [1]
D Metabolism of triglycerides ii Predict one colour of light that will be
absorbed ef昀椀ciently by phycoerythrin. [1]
2 Which of the following is a limiting factor that affects
Standard Level Paper 3, Time Zone 2, May 18, Q1a–c
the rate of photosynthesis?
I Temperature (Questions 5–7 HL only)
II Oxygen concentration 5 Which are the products of the light-dependent reaction?
III Carbon dioxide concentration A Reduced NAD and ATP
A I and II B Reduced NADP and ATP
B I, II and III C Glucose and oxygen
C I and III D Glucose and ATP
D II and III
6 Where does the light-independent reaction take place in
3 Which technique can be used to separate and identify the chloroplast?
photosynthetic pigments? A The stroma
A Centrifugation B The intermembrane space of thylakoids
B Gel electrophoresis C Between the outer and inner membranes
C Spectrophotometry D The grana
D Chromatography
4 Chromatography is a technique used to separate the
components of a mixture. The photosynthetic pigments
from three organisms were separated by thin layer
chromatography: spinach (Spinacia oleracea), a red alga
(Porphyra) and a brown alga (Fucus).
Spinacia oleracea Porphyra Fucus

β-carotene β-carotene β-carotene

(orange) (orange) (orange)

chlorophyll a chlorophyll a
(blue-green) (blue-green)
chlorophyll a
chlorophyll b (blue-green)
(yellow-green)

xanthophylls
xanthophylls (yellow) fucoxanthin
(yellow) (bright orange-brown)

chlorophyll c
(pale green)

origin origin origin

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7 Sodium alginate beads were prepared containing a suspension of Chlorella algae.

These beads were placed in nine small jars containing hydrogen carbonate indicator solution.
Hydrogen carbonate indicator is commonly used to detect changes in pH.
The jars were placed at different distances from a lamp, which was the only light source.
The distances ranged from 40 to 130 centimetres. Jars were placed one at a time to avoid the
jars from shading each other. Colour changes were observed.

increasing CO2 in indicator atmospheric decreasing CO2 in indicator

CO2 level
yellow orange red magenta purple
pH 7.6 pH 7.8 pH 8.0 pH 8.2 pH 8.4 pH 8.6 pH 8.8 pH 9.0 pH 9.2

lamp

1 2 3 4 5 6 7 8 9

a State the name of the process which occurs in the chloroplasts of Chlorella that uses CO2. [1]
b The colours of the indicator in the jars ranged from yellow to purple after 昀椀ve hours.
Predict the distribution of indicator colours in jars 1 to 9. [1]
c Explain the scienti昀椀c reasoning for your hypothesis. [3]
d Suggest one other factor that has to be kept constant in all the jars during the experiment. [1]
Higher Level Paper 3, Time Zone 0, November 20, Q3a–bii

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■ Paper 2 2 Distinguish between action and absorption spectra. [4]

1 Isoprene is a chemical synthesized and emitted in 3 Describe how photosynthetic pigments can be
large amounts by some plant species, especially oak separated using chromatography and how this is used
(Quercus sp.) and poplar (Populus sp.) trees. It has been to calculate Rf values. [5]
suggested that isoprene increases the tolerance of plants 4 Outline how carbon dioxide-enrichment experiments
to high temperatures, which can cause a decrease in can be used to predict future rates of photosynthesis
photosynthesis rates. and plant growth. [6]
Black poplar (Populus nigra) plants were subjected to 5 Explain how controlled experiments can be used to
two raised temperatures and to drought. Measurements investigate the effect of limiting factors on the rate
of photosynthesis and isoprene emission were made of photosynthesis. [7]
during a 35-day-long drought stress (drought period) (Questions 6–11 HL only)
and 3 and 15 days after re-watering stressed plants
6 In cyclic photophosphorylation, predict which of the
(recovery period). The rate of photosynthesis was
following occur:
recorded as the carbon dioxide taken up per unit of leaf
■ photoactivation of photosystem I
per second.
■ reduction of NADP+
35 Key ■ production of ATP. [1]
isoprene emission/

30 25 °C 35 °C
7 Draw a diagram of a chloroplast to show its structure
mol m−2 s−1

25
20 as revealed by electron microscopy. Annotate your
15 diagram to indicate the adaptations of the chloroplast to
10 its functions. [3]
5
drought recovery 8 Explain the role of hydrogen ions used in
0
25
photosynthesis. [7]
rate of photosynthesis/

Higher Level Paper 2, Time Zone 2, May 21, Q6a

20
mol m−2 s−1

15 9 Compare and contrast cell respiration

10
and photosynthesis. [7]

5
10 Compare and contrast chemiosmosis in
drought recovery mitochondria and chloroplasts. [7]
0
0 14 30 35 38 50 11 Explain the role of proteins in photosynthesis. [9]
time/days

a Suggest one method other than measuring CO2

uptake by which the rate of photosynthesis could
have been measured in these experiments. [1]
b Suggest why heat treatment may reduce
photosynthesis rates. [2]
c Outline the effect of drought and re-watering on
the rate of photosynthesis. [1]
d Describe the isoprene emissions during the
drought and recovery periods at 25 °C. [2]
e Compare the effect of the two temperatures on
the emission of isoprene. [2]
Higher Level Paper 4, Time Zone 1, May 13, Q1a–e

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C2.1 Chemical signalling (HL only)

■ Paper 1 (HL only) 6 Hormones such as oestradiol affect female metabolism.
1 Which of the following statements about receptors How does this hormone act on its target cells?
is true? A It activates an enzyme cascade that ampli昀椀es the
A Receptors are found only on the surface of cells hormone signal
in the plasma membrane B It alters speci昀椀c receptor sites on the cell
B Receptors are speci昀椀c to the signal ligand surface membrane
C Most receptors can bind many different C It enters the cell and binds to nuclear receptors
signal ligands D It inhibits the synthesis of cholesterol molecules
D All receptors can act as channels to 7 Why do many signal transduction pathways use
regulate movement of substances across the second messengers?
plasma membrane A To amplify the message by directly
2 What is the name given to the molecule that binds to the phosphorylating proteins
particular three-dimensional structure of a receptor site? B To induce a signal from the outside to the inside
A Ligand of the cell
B Scaffold protein C To relay the message from the inside of the
C Ion channel membrane throughout the cytoplasm
D G protein D To transport a signal through the lipid bilayer
portion of the plasma membrane
3 Which one of the following is the best description of cell
signalling in multicellular organisms? 8 Which of the following is a similarity between
A Intracellular G protein-linked receptors and tyrosine kinase receptors?
B Intercellular A Activation that results from binding of GTP
C Both intercellular and intracellular B Formation of a dimer following binding of a
D Neither intercellular or intracellular signal molecule
C Regions of the receptor that span the
4 Which one of the following is determined by bacteria
plasma membrane
using quorum sensing?
D Signal-binding sites speci昀椀c for steroid hormones
A Density of the bacterial population
B The concentration of nutrients in the 9 Which type of cellular response represents a long-term
surrounding medium response to an external signal?
C The speed of the surrounding liquid medium A Change in enzyme conformation (shape)
D The size of the bacterial population B Secretion of a hormone into the bloodstream
C Phosphorylation of an intracellular protein
5 Which substance can act as a second messenger?
D Activation of a gene expressing an enzyme
A A kinase
B ADP 10 What are two bene昀椀ts of having a cascade of cellular
C Cyclic AMP events during signal transduction?
D A peptide hormone A Increased ampli昀椀cation of the signal and
increased distribution of the signal
B Increased ampli昀椀cation of the signal and
increased energy consumption
C Decreased speed of response and increased
energy consumption
D Increased speci昀椀city and increased targeting of
the signal

Biology for the IB Diploma Programme C2.1 Chemical signalling (HL only) 58
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■ Paper 2 (HL only)

1 The diagram below shows the effect of insulin on glucose uptake.

a Suggest, in humans, one type of cell where insulin receptors are mainly found. [1]
b Describe the processes 1–4 in the diagram. [4]
c Outline the role that insulin plays in cell metabolism. [3]
2 Describe the importance of ATP in cell signalling. [3]
3 Suggest one advantage and one disadvantage of a signalling cascade. [2]
4 Explain the role of kinases in cell signalling. [2]
5 Describe how insulin and glucagon control blood glucose levels. State where these
hormones come from, the type of receptors they bind to and how they affect the levels
of blood glucose. [6]
6 Compare and contrast the role of hormones and neurotransmitters in chemical signalling. [7]
7 Explain why cell signalling is important for the functioning of organisms. [9]

Biology for the IB Diploma Programme C2.1 Chemical signalling (HL only) 59
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C2.2 Neural signalling

■ Paper 1
1 Which statement applies to an axon at rest?
A There is no electric potential difference between the external and internal surfaces of
the plasma membrane
B The external surface of the plasma membrane is positive relative to the internal surface
C The external surface of the plasma membrane is negative relative to the internal surface
D The internal surface of the plasma membrane has a much higher concentration of
sodium ions
Higher Level Paper 1, Time Zone 1, May 21, Q22

2 The image shows a neuron. Which letter shows the cell body?

C
A

B D

Standard Level Paper 1, Time Zone 0, November 18, Q28 (modified)

3 Neurotransmitters are released into the synaptic cleft 5 The graph shows changes in the membrane potential in
from the presynaptic neuron and travel to a receptor on an action potential. What is the approximate value of the
the postsynaptic neuron membrane. Which processes threshold potential?
are required for this to happen? +50
membrane potential/mV

Release into synaptic cleft Travel to postsynaptic

neuron membrane
A exocytosis diffusion 0

B active transport diffusion

C exocytosis active transport −50

D active transport active transport −70
Standard Level Paper 1, Time Zone 1, May 17, Q25 −90

0 1 2 3 4 5
(Questions 4–7 HL only) time/ms
4 Which of the following de昀椀nitions refers A −89 mV
to repolarization? B −70 mV
A The return of polarity towards the resting C −50 mV
potential following depolarization D +47 mV
B A temporary and local reversal of the Standard Level Paper 1, Time Zone 0,
resting potential November 21, Q28 (modified)
C A period during which a nerve is unresponsive to
6 What can oscilloscopes be used to measure?
further stimulation
I Resting potentials
D The potential difference produced across the
II Action potentials
plasma membrane of the nerve cell when stimulated
III Number of impulses per second
A I only
B I and II
C I, II and III
D III only

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7 How do exogenous chemicals affect synaptic transmission?

A Causing vesicles to fuse to the presynaptic membrane
B Increasing the concentration of cholinesterase
C Causing a reduction in the diameter of the synaptic cleft
D Blocking reuptake of the neurotransmitter

■ Paper 2
1 Analyse the data shown in the 昀椀gure below, which shows the effect of nerve 昀椀bre diameter on
conduction velocity for a variety of different animals.

Pendeus
Teleost Earthworm
myelinated medial giant
Macrobrachium
100
MYELINATED

Squid
conduction velocity/m s−1

Mammalian Crayfish giants

myelinated
Prawn

Frog myel. Lobster

10

Lamprey Crab and crayfish

unmyel. miscellaneous
Polychaete
giants
UNMYELINATED

Hydrozoan [Na+]
Cat unmyel.
1
1 10 100 1000
fibre diameter/µm

Hydrozoan [Ca2+]

Lines indicate general relations over a range of diameters, many taken from Bullock and Horridge
(1965) but adjusted to a standard temperature of 20 °C (Chapman and Pankhurst 1967). Specific
labelled points or lines from the following sources: Squid: Hartline & Young 1936 cited in Pumphrey
and Young (1938); Earthworm: Eccles, Granit & Young (1932); Penaeus and Macrobrachium:
Kusano (1966). Crayfish: Govind and Lang (1976); Hydromedusa: Mackie and Meech (1985).

a Compare and contrast the speed in myelinated and non-myelinated 昀椀bres. [4]
b Explain the effect of size of axon diameter and myelination on conduction velocity. [7]
2 The diagram shows part of two neurons.

Ca2+
X

Na+

a State the name of the structure shown. [1]

b X indicates the movement of a structure in the neuron. Explain what events trigger this
movement and what happens next. [3]
Standard Level Paper 2, Time Zone 0, November 20, Q3bi–ii

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3 Outline the way the resting potential allows a nerve cell Mouse alarm
Fox scent Stoat scent Control
compound
to be ready for the transmission of a nerve impulse. [4]
4 Using a labelled diagram, explain how impulses are 1
transmitted across a synapse. [8]
5 Neural signalling requires an understanding of many 2
different topics in biology. Explain how the nervous

G1 neurons
system transmits signals throughout the body. [9] 3

(Questions 6–10 HL only)

4
6 Mice (Mus musculus) have various defence systems
against predators such as foxes (Vulpus vulpus) or stoats
5
(Mustela erminea). The mice release speci昀椀c alarm
compounds when under threat that serve as danger
6
signals for other mice. Predators also release scents that
the mice can detect. Figure 3
In one study, mice were exposed to paper soaked in a State the percentage of G2 neurons in the mice
compounds taken from other mice, foxes or stoats in a that respond to the fox scent. [1]
test chamber. The scientists then measured the reaction b Using evidence from the chart, identify, giving a
of three different groups of neurons used in smelling: reason, which group of neurons responded most
G1, G2 and G3, as shown in the diagram (Figure 1). to the chemicals. [1]
The percentage of G1, G2 and G3 neurons responding to c State the name of the instrument used to make
the mouse, fox and stoat compounds, as well as a control these neural traces. [1]
compound, are shown in the chart (Figure 2). d Distinguish between the effects of the mouse
The scientists recorded the neural traces (action and alarm compound and the effects of the control
resting potentials) of six G1 neurons exposed to the compound on the G1 neurons. [1]
compounds from the different animals. The horizontal e Compare and contrast the effects of the
bar beneath each trace corresponds to the time of mouse alarm compound and stoat scent on the
exposure to the test compound (Figure 3). G1 neurons. [2]
f Deduce whether there is a correlation between
G2 the neural traces and the percentage of
responding G1 neurons. [2]
G1 Standard Level Paper 2, Time Zone 2, May 19, Q1 (part)

7 a The brain requires a large energy input.

Suggest one reason for this. [1]
b Outline the functional magnetic resonance
G3 imaging (fMRI) technique for brain research. [2]
Higher Level Paper 3, Time Zone 1, May 18, Q5b–c
Figure 1
8 Explain the effect of neonicotinoid pesticides on the
Mouse alarm cholinergic synapses of insects. [5]
Fox scent Stoat scent Control
compound
9 Outline how cocaine affects the nervous system and
G1 why it can lead to addiction. [5]
10 Explain the propagation of electrical impulses along a
G2
neuron including the role of myelin. [7]
Standard Level Paper 2, Time Zone 0, May 16, Q5
G3

Key

> 75% 25–75% 10–25% < 10% 0%

Figure 2

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C3.1 Integration of body systems

■ Paper 1 (Questions 7–10 HL only)
1 What is meant by emergent properties? 7 The diagram shows a plant shoot and the direction of the
A A property which a complex system has but light which the shoot received.
which the individual parts do not have
B Knowledge of the individual parts of a system
is suf昀椀cient to understand or predict overall
system behaviour
C The separate activities of the parts of a larger system light
D The growth of an organ or tissue from an organism
2 How can the integration of organs in animal bodies
be achieved?
I Hormonal signalling
II Nervous signalling
III Transport of materials and energy
A I only What are the direction of movement and the effect of
B I and II auxin in the tip of a plant shoot when receiving light
C I, II and III from one side?
D I and III Direction of movement Effect of auxin on cell
3 Which of the following does the cerebellum have a of auxin elongation
role in? A towards light promotes
A Visual processing B towards light inhibits
B Auditory processing C away from light promotes
C Coordinating skeletal muscle contraction and D away from light inhibits
balance
Higher Level Paper 1, Time Zone 1, November 21, Q33
D Breathing and maintaining heart rate
4 What role does epinephrine facilitate? 8 How does auxin contribute to phototropism?
A Intense muscle contraction A It increases production of light-sensitive proteins
B Storage of glucose as glycogen B It increases growth of cells on the shaded side of
C Reabsorption of water in the kidney the stem
D Decreased heart rate C It inhibits growth of axillary buds
5 Which hormone regulates the hours of sleep D It inhibits stem elongation
Higher Level Paper 1, Time Zone 2, May 21, Q34
and wakefulness?
A Oestradiol 9 The image shows seedlings that have been exposed to
B Insulin unidirectional light.
C Auxin
D Melatonin
Standard Level Paper 1, Time Zone 0,
November 21, Q29 (modified)

6 Which of the following controls peristalsis in

the intestine?
A The cerebellum
B The central nervous system
C The enteric nervous system
D The peripheral nervous system

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Which statement explains the growth towards the (Questions 7–9 HL only)
light source? 7 Outline how both qualitative and quantitative data can
A Light causes auxin to inhibit cell division in the be used to assess trophic responses in seedlings. [5]
shoot meristem
8 Auxin can be used to promote the development of roots
B Light causes auxin to promote cell division in the
from stem and leafy cuttings in some plants. In a study
shoot meristem
into the distribution of auxin in the development of
C Auxin is concentrated in the side of the shoot
these roots, scientists measured the amount of auxin in
with light and inhibits cell elongation
different leaves of a shoot tip of Petunia hybrida.
D Auxin is concentrated in the side of the shoot
The 昀椀gure indicates the numbering of leaves on the shoot,
without light and promotes cell elongation
Higher Level Paper 1, Time Zone 2, May 18, Q30
from L1 as the youngest and smallest to L6 as the largest
and oldest leaf. The developmental stage of L5 and L6
10 Ethylene stimulates the changes in fruits that occur was very similar, so L5 was not analysed. The stem base
during ripening by the process of: is the lowest part of the cutting where roots may form.
A Negative feedback The graph shows the auxin concentration in the different
B Positive feedback leaves.
C Respiration
D Photosynthesis 1cm
L5
■ Paper 2
L3
1 Compare and contrast hormonal and L2
nervous communication. [7] L1
Higher Level Paper 2, Time Zone 1, May 21, Q6c
L6
2 Distinguish between conscious and
unconscious processes. [3] L4

3 The central nervous system (CNS) gathers sensory

information and coordinates activity. Outline how stem base

coordination is achieved by:

a Input to the spinal cord and cerebral hemispheres 80
of the brain. [3] 70
auxin concentration/pmol g−1

b Output from the cerebral hemispheres of the

60
brain to muscles. [3]
50
4 Compare and contrast the structure and function of
sensory and motor neurons. [6] 40

5 Explain the role of baroreceptors and chemoreceptors in 30

the control of heart rate. [5]
20
6 Using a named species, explain how each level of
10
biological organization (molecules, cells, organism and
ecosystem) contributes to the emergent properties of the 0
L1 L2 L3 L4 L6
whole organism. [7]
leaf

a Calculate the difference in the concentration of

auxin found in L1 and L6. [1]
b Identify the relationship between the
concentration of auxin and the age of the
different leaves. [2]

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N-1-naphthylphthalamic acid (NPA) is an inhibitor used to block auxin transport. NPA was
sprayed onto the leaves of a set of cuttings for 14 days. Development of the roots in control
(non-treated) and NPA-treated cuttings was measured 14 days after taking the cuttings.
The table shows the in昀氀uence of NPA on rooting.
Mean number of roots Mean root length / cm Mean total root length per
per cutting cutting / cm
control 53.2 1.4 47.4
NPA-treated 8.0 0.6 1.0

c Analyse the effect of NPA on the formation of roots. [2]

The scientists also measured the changes in auxin concentration in L6 and the stem base
during the early period of root formation. They recorded the concentration in the control and
NPA-treated cuttings for 24 hours after taking the cuttings.

50
auxin concentration in L6/pmol g−1

Key
400
control NPA-treated
40

in stem base/pmol g−1

auxin concentration
300
30

200
20

10 100

0 0
0 2 4 6 12 24 0 2 4 6 12 24
time after cutting/hours time after cutting/hours

d i Compare and contrast the changes in auxin concentration in the stem base over
time for the control and NPA-treated cuttings. [2]
ii Deduce the effect of NPA on auxin transport between L6 and the stem base. [2]
e Based on all the data presented and your knowledge of auxin, discuss the pattern of
auxin production and distribution in the leaves, and the possible relationship to root
formation in leafy cuttings of Petunia hybrida. [3]
Higher Level Paper 2, Time Zone 2, May 17, Q1a–e

9 Outline how the hormone auxin controls phototropism in plant shoots. [5]
Higher Level Paper 2, Time Zone 1, May 21, Q6b

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C3.2 Defence against disease

■ Paper 1
1 What occurs as a result of a cut in the skin of a 昀椀nger?
A Prothrombin is transformed into thrombin
B Fibrin is converted to insoluble 昀椀brinogen
C Platelets produce antibodies to prevent infection
D Clotting factors are released from red blood cells
Standard Level Paper 1, Time Zone 0, November 21, Q25

2 A person was infected with a pathogen and then later in life they were reinfected with the
same pathogen. The graph shows the concentration of antibodies found in the blood that were
produced in response to these two infections.
concentration of antibodies

0 10 20 30 40 0 10 20 30 40

first delay second

infection infection
time/days

What is the reason for the faster rise in antibody concentration after the second infection?
A The patient had previously been vaccinated with the antibody
B Antibodies had been stored after the 昀椀rst exposure
C Lymphocytes rapidly reproduced to form plasma cells
D The second exposure was more infectious
Standard Level Paper 1, Time Zone 0, November 21, Q26

3 Which cells does HIV attack?

I Lymphocytes
II Macrophages
III Platelets
IV Erythrocytes (red blood cells)
A I only
B I and II
C I, II and III
D IV only

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4 What is non-speci昀椀c immunity to disease? ■ Paper 2

A Blocking prokaryotic metabolism with antibiotics 1 Some blood proteins are involved in defence against
B Production of antibodies by lymphocytes infectious disease. Explain the roles of named types of
C Endocytosis of pathogens by white blood cells blood proteins in different defence mechanisms. [8]
D Production of cloned plasma cells Standard Level Paper 2, Time Zone 2, May 17, Q5c
Standard Level Paper 1, Time Zone 0, November 19, Q27
2 Tuberculosis (TB) is an infectious disease caused by the
5 Why do antibiotics not damage human cells? bacterium Mycobacterium tuberculosis.
A The antibiotic is only taken for a short time a Outline the structures in M. tuberculosis that are
B The antibiotic dose is too small to be harmful to not present in a human cell. [3]
human cells b Explain the production of antibodies when a
C The antibiotic is broken down by cell metabolism patient is infected with the TB bacterium. [7]
D Human metabolism is different from c Describe the risk to the human population of
bacterial metabolism indiscriminate use of antibiotics. [5]
6 Which components of the blood provide speci昀椀c Standard Level Paper 2, Time Zone 2, May 21, Q6a–c
immunity against infectious diseases?
A Plasma 3 Describe what is meant by innate immune response. [2]
B Memory cells 4 Outline the immune response that leads to the
C Platelets production of antibodies after a traditional vaccination
D Phagocytes against a speci昀椀c viral infection. [3]
7 What is a characteristic of antigens? 5 Vaccination has been used successfully to control
A They recognize foreign substances the spread of many infectious diseases in the
B They are produced in bone marrow population. Explain how vaccination works in terms of
C They cause disease in humans immunological memory and herd immunity. [4]
D They stimulate the production of antibodies 6 Explain why antibiotic resistance is an example of
Standard Level Paper 1, Time Zone 0, November 17, Q26 evolution by natural selection. [7]
7 Describe how careful observations have led to progress
in the control of infectious diseases. [6]

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C4.1 Populations and communities

■ Paper 1 5 Limpets are molluscs with conical shells that cling
1 Which level(s) of ecological complexity involve(s) biotic tightly to rocks on seashores. In a study of two species
factors but not abiotic factors? of limpets found on rocks along the Oregon coast,
I Community 30 randomly placed quadrats were used to determine
II Ecosystem how often the two species occurred together. The table
III Population shows the data that were collected.
A I only Lottia pelta Lottia pelta Total
present absent
B II only
Lottia scutum present 15 5 20
C I and II only
Lottia scutum absent 5 5 10
D I and III only
Total 20 10 30
Standard Level Paper 1, Time Zone 0, November 20, Q16
Which statistical method will determine whether these
2 Which is the correct de昀椀nition for carrying capacity?
two species occur together by chance or by some kind
A The number of different species that can be
of interaction?
supported by a given environment
A Chi-squared test
B The minimum number of a species that can be
B t-test
supported by a given environment
C Standard deviation
C The maximum number of a species that can be
D Means and ranges
supported by a given environment
Standard Level Paper 1, Time Zone 0, November 18, Q24
D The total number of individuals of all species in
an area 6 What is an alien species?
3 Which of the following is an example of negative A A species that is introduced into an area by
feedback of population size? human activity
A Predation returning a prey population to its B A species with a large geographical distribution
carrying capacity C A species unrecognized by science
B An increase in prey leading to a decrease D A pathogenic species
in predators 7 In an area of forest measuring 100 m by 100 m, samples
C Density-independent factors were taken to estimate the number of silver maple (Acer
D Exponential growth of a population saccharinum) trees in the forest. The number of trees
4 Which of the following interspecies interactions is an counted in each of 昀椀ve areas of 400 m2 was recorded.
example of parasitism? Approximately how many silver maple trees are in the
A African lion killing a kudo (a savannah herbivore) 10 000 m2 area of forest?
B A fungus causing the death of the evergreen
3
robber frog
C Rhizobium bacteria living in the root nodules of
5
a legume plant
4 5
D A sheep tick attached to the skin of a cat where it
8
has fed on its blood
A 5
B 25
C 125
D 625

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8 Damsel昀氀ies are 昀氀ying insects that feed on other insects. a Identify which of the types of interaction shown
They live on or near ponds and rivers. in the key occur between crabs and seagrass. [2]
An ecologist wants to estimate the size of the damsel昀氀y b Describe how the sea otter indirectly affects
population in a site of special scienti昀椀c interest. seagrass. [2]
c Explain how nutrients can have a positive or
negative bottom-up effect on seagrass. [3]
Higher Level Paper 3, Time Zone 2, May 18, Q15a–c

3 Reef-building corals are formed through a relationship

between coral polyps and an algae called Zooxanthellae.
a Describe the exchange of materials between the
coral’s polyps and Zooxanthellae. [2]
b Outline the relationship between Zooxanthellae
and coral reef species. [2]
c Suggest how sea depth may act as a limiting
a i State the most appropriate method that they factor for coral growth. [2]
should use to estimate the population size. [1]
4 a Explain the factors that can contribute to
ii Outline the method they would use to make
the exponential growth phase in a sigmoid
this estimate. [4]
population curve. [3]
iii Explain the limitations of the method and
b Outline the effect of carrying capacity on the
how they may affect the estimate. [3]
growth of a population. [2]
b Distinguish between ecological methods used to
Higher Level Paper 3, Time Zone 2, May 19, Q16a–b
sample sessile species compared to mobile species. [3]
5 Explain how the introduction of an invasive species
■ Paper 2 will affect the population size of an endemic species,
1 Distinguish between the interspeci昀椀c relationships of and the impact this will have on the biodiversity of the
mutualism, pathogenicity and parasitism, providing an ecosystem in which it is found. [9]
example of each. [3] 6 Explain, using a range of examples, how models are
2 The interaction web shows top-down and bottom-up used in the study of biology. [9]
effects in a seagrass study system.

sea otter
4°

−
F
crabs
3°

F
trophic level

+ −

isopods
2°

F + −
−
+ + − algae growing
− on seagrass
C

1° F+

seagrass
+/−
F

nutrients
Key
top-down effect + positive effect
bottom-up effect − negative effect
direct effect C competition
indirect effect F feeding relationship

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C4.2 Transfers of energy and matter

■ Paper 1 5 The diagram shows the carbon cycle.
1 Which of the following systems is an example of an
J
ecosystem? fuel

A Open systems
B Isolated systems K

C Closed systems
D Deterministic systems
2 In a woodland ecosystem, each tree provides food for CO2 in atmosphere and L
green plants
dissolved in water
numerous aphids which feed on the sap of the tree. The
aphids are eaten by carnivorous beetles, as shown in the
food chain. Which two processes correspond to the labelled arrows?
A K is combustion and L is catabolism
oak tree → aphids → beetles
B J is anabolism and K is respiration
Which pyramid of energy represents this relationship? C J is combustion and K is respiration
D J is anabolism and L is catabolism
A B
Standard Level Paper 1, Time Zone 0, November 17, Q18

6 What restricts the length of a food chain?

A Energy losses between the trophic levels
B A greater biomass at the higher trophic levels
C The number of species in the food web
D The consumption of waste by detritivores
C D
Standard Level Paper 1, Time Zone 0, November 16, Q18

7 The diagram shows the food web for an aquatic

ecosystem in which letters R–Z represent
individual species.
Standard Level Paper 1, Time Zone 0, November 21, Q18
Z
3 Which processes occur in an ecosystem?
I Biomass increases in each successive trophic X Y
level
II Inorganic nutrients are recycled
III Chemical energy is stored in carbon compounds
U V W
A I and II only
B I and III only
C II and III only
D I, II and III R S T

Higher Level Paper 1, Time Zone 2, May 18, Q22 Which organism is a tertiary consumer?
4 Which of the following does chemoautotrophic nutrition A Organism T
involve? B Organism U
A Use of light as the external energy source C Organism W
B Parasitic relationships D Organism Y
Standard Level Paper 1, Time Zone 1, May 19, Q18
C Consuming other organisms
D Oxidation reactions as the energy source

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8 The diagram shows the energy 昀氀ow between 昀椀ve ‘sinks’ 9 Which statement is true for secondary production?
in a terrestrial ecosystem. A It is higher than primary production
B It is the accumulation of carbon compounds in
biomass by autotrophs
secondary consumer detritus feeder
C It is the accumulation of carbon compounds in
biomass by heterotrophs
D It is measured in g m2
primary consumer detritus 10 Plankton are major producers in marine ecosystems.
Only a small proportion of the energy harvested
by plankton is passed to the primary consumers.
Which process in phytoplankton results in the largest
autotrophs loss of energy that could otherwise be utilized
by consumers?
A Reproduction
B Homeostasis
C Excretion
In a typical terrestrial ecosystem, which trophic level
D Respiration
would have the highest biomass?
Higher Level Paper 1, Time Zone 0, November 20, Q16
A Autotrophs
B Primary consumers
C Secondary consumers
D Detritus feeders
Standard Level Paper 1, Time Zone 1, May 21, Q21

11 The diagram shows interactions between food chains in an ecosystem in the African savannah.
Which arrows indicate the 昀氀ow of chemical energy?

sunlight

I hare III
II
cheetah
star grass gazelle
shrike
grasshopper

A I and II only
B I and III only
C II and III only
D I, II and III
Standard Level Paper 1, Time Zone 0, November 18, Q17

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■ Paper 2
1 The blackberry (Rubus fruticosus) is a plant that grows in deciduous woodlands in many parts
of the world. A 30 m transect was laid out in a woodland to investigate the relationship between
light intensity and blackberry growth. The percentage cover of blackberries and the light intensity
were measured at 26 positions along this transect.
100

90

blackberry growth/% cover 80

70

60

50

40

30

20

10

0
0 200 400 600 800 1000 1200 1400 1600
light intensity/lx

a Outline how these results indicate that blackberry distribution is limited by

light intensity. [2]
b Distinguish between the transfer of matter and energy in closed ecosystems. [1]
c A pyramid of energy represents the amount of energy taken in by each trophic level
per unit time and per unit area. Discuss the advantages and disadvantages of the use of
pyramids of energy as models of energy 昀氀ow in an ecosystem. [4]
Standard Level Paper 3, Time Zone 0, November 19, Q12a–c

2 The 昀椀gure below shows the food web of a rocky shore community.

seabirds
blenny
sea-slugs crab

anemones dog whelk barnacle

mussel
flat winkle
rough and edible sponge
isopods, shrimps, winkles limpet topshell
Gammarus, etc.

attached micro attached macro

algae algae
dead matter e.g. Calothrix e.g. Fucus diatoms

a The food web is a model of a real ecosystem. Using the food web as an example,
explain what is meant by the term model. [3]
b Draw a food chain from this food web, showing at least three organisms. [1]
c Analyse the number of trophic levels occupied by seabirds in this food web. [1]

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3 The mass of an individual organism can affect its physiology and feeding ecology.
a State one process that results in the loss of carbon dioxide from a marine organism such
as a crustacean or a jelly昀椀sh. [1]
b The crustacean and the jelly昀椀sh obtain carbon compounds by feeding. State one source
of carbon for marine organisms, other than feeding. [1]
c Explain how energy enters, 昀氀ows through and is lost from marine food chains. [3]
d Suggest with a reason whether having a large body mass is an advantage or
disadvantage for jelly昀椀sh. [1]
Standard Level Paper 2, Time Zone 2, May 21, Q4a–c, dii

4 Life on Earth is based on carbon compounds, such as proteins, carbohydrates and lipids.
Outline the recycling of carbon compounds in the carbon cycle. [7]
5 Explain the reasons for food chains rarely containing more than four or 昀椀ve trophic levels. [3]
Standard Level Paper 2, Time Zone 0, November 21, Q3bii

6 Describe how detritivores obtain nutrition and the effects they have in ecosystems. [4]
Standard Level Paper 2, Time Zone 1, May 19, Q8a

7 Explain the effect of combustion on the carbon cycle. [7]

8 Explain how climate determines the global distribution of biomes and the levels of
biodiversity they contain. [9]
9 How do models help scientists explain the 昀氀ows of energy through ecosystems? [9]

Biology for the IB Diploma Programme C4.2 Transfers of energy and matter 73
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D1.1 DNA replication

■ Paper 1 5 Over 50 years ago, Meselson and Stahl investigated
1 How is the polymerase chain reaction (PCR) similar to the mechanism of DNA replication. They transferred
the replication of DNA? a rapidly growing population of Escherichia coli from
I DNA is heated to break hydrogen bonds a growth medium containing only 15N to a growth
II DNA strands are separated medium with only 14N. DNA samples were centrifuged
III Free nucleotides are used at high speed in a salt density gradient. In the original
IV DNA polymerase is required published research, DNA molecules of the same density
A I only appear as a band in the UV absorption photographs
B II and IV only as shown.
C I, II and III only
D II, III and IV only
2 What occurs as a result of base pairing during
DNA replication?
A Both strands of the DNA have the same sequence
of purines and pyrimidines
B In each strand, the number of purine bases equals
the number of pyrimidine bases
C Purine bases in one strand become hydrogen-
bonded to purine bases in the other strand
D The number of purine bases in one strand equals
the number of pyrimidine bases in the other strand
3 Why can Taq polymerase be used in the polymerase
chain reaction (PCR)?
A It ensures that primers match the end sequence of
the DNA fragment
B It works with helicase in PCR
C It ensures desired sequences are ampli昀椀ed rather
than non-target DNA
D It does not denature at high temperatures
4 Which are necessary to make DNA replication
semi-conservative?
I Separation of the strands by RNA polymerase
II Complementary base pairing a The density of the DNA band at generation 0 is
III Use of a pre-existing strand as a template 1.724 and the density of the dark band of DNA
A I and II only at generation 4.1 is 1.710. Estimate the density of
B I and III only the DNA band at generation 1.0. [1]
C II and III only b Describe the nitrogen composition of the DNA
D I, II and III band in the E. coli at generation 1.0. [1]
Standard Level Paper 1, Time Zone 2, May 17, Q9 c Explain the pattern shown in generation 3.0. [3]
d This experiment was designed to
demonstrate whether replication was semi-
conservative or conservative. Distinguish
between semi-conservative replication and
conservative replication. [2]
Standard Level Paper 3, Time Zone 0, May 16, Q2a–d

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(Questions 6–8 HL only) ■ Paper 2

6 A drug blocks the activity of DNA primase. Which of 1 A student researcher attempted to clone the human
the following would be affected by this drug? growth hormone (HGH) gene. Two separate samples
A Synthesis of a complete lagging strand of HGH DNA were obtained from DNA libraries and
B Synthesis of a complete leading strand subjected to agarose gel electrophoresis. Results are
C Synthesis of both a complete lagging strand and shown below. Describe how the DNA fragments were
a complete leading strand separated into visible bands. [2]
D No effect, both strands would be
sample 1 sample 2
synthesized normally
7 What is a function of DNA polymerase I?
A Adds nucleotides in a 5ʹ to 3ʹ direction to
−
well
elongate the chain
B Uncoils the DNA double helix and splits it into
two template strands
C Removes RNA primer and replaces it with DNA
D Produces sugar–phosphate bonds to link
Okazaki fragments
Higher Level Paper 1, Time Zone 0, November 19, Q26

8 What are the functions of DNA primase and DNA

polymerase I in DNA replication? +
DNA primase DNA polymerase I
2 Describe the polymerase chain reaction (PCR)
A adds a short DNA primer to replaces RNA with DNA in
the template strand the Okazaki fragments of the and explain one advantage and one limitation of
leading strand this procedure. [7]
B adds a short DNA primer to replaces DNA primers
3 Outline the process of DNA pro昀椀ling. [4]
the template strand with RNA
Higher Level Paper 2, Time Zone 1, May 21, Q8a
C adds a short RNA primer to replaces RNA with DNA in
the template strand the Okazaki fragments of the
leading strand (Questions 4–8 HL only)
D adds a short RNA primer to replaces RNA primers 4 State three structural differences in the formation of the
the template strand with DNA
leading and lagging strands. [4]
Higher Level Paper 1, Time Zone 2, May 19, Q12
5 Describe the role of DNA polymerase III in
DNA replication. [4]
6 A drug blocks the activity of DNA ligase.
a Describe what effect this drug would have on
replication of the leading strand. [2]
b Describe what effect this drug would have on
replication of the lagging strand. [2]
7 Explain the role of proofreading in DNA replication. [4]
8 Explain the roles of speci昀椀c enzymes in prokaryote
DNA replication. [7]
Higher Level Paper 2, Time Zone 0, May 16, Q5b

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D1.2 Protein synthesis

■ Paper 1 A Synthesizing lipids
1 What is the primary function of the organelles labelled B Processing and packaging enzymes
X in the electron micrograph? C Synthesizing proteins to be used within the cell
D Synthesizing proteins to be secreted
2 The data shows part of the genetic code for mRNA.
UUU phenylalanine
UUC phenylalanine
AAA lysine
AAG lysine

Which anticodon could be found on a tRNA molecule

bonded to lysine?
X A AAG
B UUC
C TTT
D GAA
Standard Level Paper 1, Time Zone 0, November 21, Q11

3 The diagram represents transcription and translation. What structures do the letters
X and Y represent?
T
A

A
C
T
G

T
A

A
C

G
A
T

A
A A
A
T

U T
U
G U
A C
A U
C U
A G
U X
U Y
A

X Y
A DNA anticodon

B mRNA anticodon

C DNA codon

D mRNA codon

Standard Level Paper 1, Time Zone 0, November 20, Q9

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4 The diagram shows mRNA codons. 7 Which regions of DNA code for the production of
speci昀椀c proteins?
A Telomeres
B Genes for ribosomal RNA
C Exons
D Regulators of gene expression
Higher Level Paper 1, Time Zone 1, May 21, Q26

8 Which statement applies to tRNA?

A There is at least one type of tRNA that combines
with each known amino acid
B One type of tRNA can combine with all of the
known amino acids
C tRNA carries out its main role within the nucleus
D tRNA is produced by the process of translation
Higher Level Paper 1, Time Zone 1, May 21, Q27

9 What is a feature of transcription in the single-celled

organism shown in the electron micrograph?

The mRNA sequence UGGAACGUA codes for what

amino acid sequence?
A Glycine-Glutamine-Methionine
B Methionine-Glutamine-Glycine
C Threonine-Valine-Histidine
D Tryptophan-Asparagine-Valine
Higher Level Paper 1, Time Zone 0, November 19, Q7

5 What do DNA replication, transcription and translation

have in common?
A Take place in cell nucleus
B Require free nucleotides
C Catalysed by polymerase
D Complementary base pairing
Standard Level Paper 1, Time Zone 1, May 18, Q12 A mRNA splicing
B Removal of introns
(Questions 6–13 HL only)
C Codon–anticodon binding
6 Which of the following statements correctly describes
D Synthesis of RNA in a 5′ to 3′ direction
introns and/or exons in a eukaryotic cell? Higher Level Paper 1, Time Zone 2, May 21, Q27
A Mutations to introns have no effect on the
primary structure of protein 10 The number of protein-coding genes in the human
B Different combinations of exons and introns genome is estimated to be about 20 000, which is much
allow more than one type of protein to be coded less than the size of the proteome. What is one reason
for by a gene for this?
C Exons are always translated into proteins A Exons are removed from RNA before translation
D A single base-pair deletion on the 昀椀rst exon of a B There are more types of amino acids than
gene is likely to be more harmful than one that nucleotides
occurs on the last exon of a gene C mRNA can be spliced after transcription
D Base substitutions occur during transcription
Higher Level Paper 1, Time Zone 0, November 20, Q26

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11 The diagram shows the three-dimensional structure A mRNA

of tRNA. B An amino acid
What can attach to the region marked X? C An anticodon
D The P site of the ribosome
Higher Level Paper 1, Time Zone 0, November 20, Q28

12 The diagram shows the arrangement of introns and exons in a segment of pre-mRNA.
Pre-mRNA is immature mRNA containing introns and exons.
Exon A Intron A Exon B Intron B Exon C Intron C Exon D
5’ 3’

Which is a mature mRNA molecule derived from the pre-mRNA by splicing?

A Exon A Exon B Exon C Exon D

5’ 3’

B Intron A Intron B Intron C Exon A Exon B Exon C Exon D

5’ 3’

C Exon A Exon B Intron A Intron B Intron C Exon C Exon D

5’ 3’

D Intron A Intron B Intron C

5’ 3’

Higher Level Paper 1, Time Zone 1, May 19, Q27

13 Human DNA has been analysed and details of certain genes are shown in the table below.
Gene Gene size / kb mRNA size / kb Number of introns
insulin 1.7 0.4 2
albumin 25.0 2.1 14
phenyalanine hydroxylase 90.0 2.4 12
dystrophin 2 000.0 17.0 12

a Calculate the average size of the introns for the albumin gene (show your workings). [2]
b With reference to the table shown, describe the relationship(s) between the gene size
and the number of introns. [2]

Biology for the IB Diploma Programme D1.2 Protein synthesis 78

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■ Paper 2
1 A short base sequence of mRNA and a table of the genetic code are shown below.
Sequence of mRNA:
AUGAGCCGAAGGUAGCUG
Table of the genetic code:

2nd letter

U C A G

Phe Ser Tyr Cys U

Phe Ser Tyr Cys C
U
Leu Ser STOP STOP A
Leu Ser STOP Trp G
Leu Pro His Arg U
Leu Pro His Arg C
C
Leu Pro Gln Arg A

3rd letter
1st letter

Leu Pro Gln Arg G

Ile Thr Asn Ser U
Ile Thr Asn Ser C
A
Ile Thr Lys Arg A
Met/START Thr Lys Arg G
Val Ala Asp Gly U
Val Ala Asp Gly C
G
Val Ala Glu Gly A
Val Ala Glu Gly G

a Outline the function of codons. [1]

b Determine the sequence of amino acids that could be translated from the sequence
of mRNA. [1]
c Determine the DNA base sequence transcribed to form this sequence of mRNA. [1]
Standard Level Paper 2, Time Zone 0, November 19, Q2a–c

2 Describe the stages in the production of mRNA 7 Describe how the information carried on mRNA allows
by transcription. [5] the synthesis of a complete polypeptide chain. [3]
3 Distinguish between transcription and translation. [4] 8 a State one function for a region of DNA that does
Higher Level Paper 2, Time Zone 0, November 17, Q7b not code for proteins. [1]
b Outline the role of the A-site of ribosomes in
4 Outline how translation depends on complementary
translation. [1]
base pairing. [3]
c Outline the role of tRNA-activating enzymes
Standard Level Paper 2, Time Zone 1, May 17, Q5a
in translation. [2]
(Questions 5–12 HL only) Higher Level Paper 2, Time Zone 2, May 18, Q2biii–cii

5 Telomeres are parts of chromosomes in eukaryotic cells. 9 Describe the roles of the different binding sites for
a Describe the function of telomeres. [4] tRNA on ribosomes during translation. [5]
b Suggest why bacteria do not have telomeres. [1] Higher Level Paper 2, Time Zone 2, May 17, Q6b (modified)
6 5ʹ-capping and 3ʹ-polyadenylation are two kinds of
10 Describe the eukaryotic processing of pre-mRNA in
post-transcriptional modi昀椀cations that are present in
terms of intron splicing, polyadenylation and 5ʹ capping.
eukaryotes but absent in prokaryotes.
[7]
Describe another post-transcriptional modi昀椀cation
11 Describe how protein synthesis in bacteria differs from
necessary to produce mature mRNA in eukaryotes. [2]
that in plant cells. [7]
12 Explain how a polypeptide chain is synthesized in a
eukaryotic cell. [7]

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D1.3 Mutation and gene editing

■ Paper 1 6 CRISPR refers to repeated sequences in which of the
1 Base substitution mutations can have the following following locations?
molecular consequence except which one? A Bacterial DNA
A Changes one codon for an amino acid into B Viral DNA
another codon for that same amino acid C Fungal DNA
B Codon for one amino acid is changed into a D Viral RNA
codon of another amino acid 7 Which of the following is the gene knockout technique
C Reading frame changes downstream of the used for investigating?
mutant site A Trauma on brain cells
D Codon for one amino acid is changed into a B The process of DNA replication
translation termination codon C The function of a gene
2 What are single nucleotide polymorphisms (SNPs) D Mutation rate
caused by?
A Insertion mutations
■ Paper 2
1 State the meaning of the term gene mutation and outline
B Deletion mutations
the various types of gene mutations. [5]
C Base substitution mutations
D Degeneracy of the genetic code 2 DRD4 is a dopamine receptor in humans. The gene
coding for the DRD4 receptor has many alleles, of
3 What are gene mutations caused by?
which an individual can have only two.
I Errors in DNA replication or repair
II Tobacco smoke Three alleles of the DRD4 receptor gene have the
III UV radiation following mutations:
A I only ■ a single base substitution
B I and II ■ a 21 base-pair deletion
C II and III ■ a 13 base-pair deletion.
D I, II and III The 13 base-pair deletion has the most serious
4 What does the inheritance of mutated genes occur via? consequences for the structure of the DRD4 receptor
A Somatic cells protein. Suggest why this is the case. [3]
B Germ cells 3 Explain why substitution mutations may or may not
C Skin cells change a single amino acid in a polypeptide. [5]
D Epithelial cells
4 Explain, using an example, the consequences of a
(Questions 5–7 HL only) deletion mutation. [7]
5 Which of the following is the CRISPR-Cas9 system in (Questions 5–8 HL only)
bacteria similar to in the human body?
5 Outline the way scientists knock out a gene. Use a
A Digestive system
model organism to illustrate your answer. [5]
B Immune system
6 Outline how CRISPR sequences and the enzyme Cas9
C Circulatory system
are used in gene editing. [7]
D Respiratory system
7 Discuss how potential uses of CRISPR raise ethical
issues that must be addressed before implementation. [7]
8 Suggest why highly conserved sequences in genes are
identical or similar over long periods of evolution. [7]

Biology for the IB Diploma Programme D1.3 Mutation and gene editing 80
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D2.1 Cell and nuclear division

■ Paper 1 5 The 昀椀gure shows cells of an onion root tip
1 Which of the following best describes cytokinesis? undergo mitosis.
A The movement of cytoplasmic elements in mitosis
B A process that divides the cytoplasm and is the A
same in animal and plant cells
C The splitting of cytoplasm in a parent cell
between daughter cells
D The process which precedes nuclear division
2 Which of the following include(s) the role of both
mitosis and meiosis in eukaryotes? B

I Avoiding the production of anucleate cells

II Maintaining the chromosome number in
daughter cells
III Cell replacement, proliferation and growth
A I only a i State the names of the stages of mitosis in the
B I and II cells labelled A and B. [2]
C I, II and III ii Outline differences between cells in stages
D III only A and B. [3]
b i Suggest why the onion root tip was used to
3 Cancer is a multi-step process. Some of the stages
study mitosis. [1]
in cancer are listed. What is the correct sequence
ii Outline how the slide shown in the diagram
of events?
may have been prepared. [3]
1 Mutated cell undergoes uncontrolled cell
division by mitosis (Questions 6–9 HL only)
2 Formation of a tumour 6 What process occurs in both mitosis and meiosis?
3 Mutations in tumour suppressor genes and A Formation of chiasmata
proto-oncogenes B Reduction division
4 Cells from the primary tumour metastasize to C Separation of chromatids
other sites via the bloodstream D Exchange of alleles between non-sister chromatids
A 1→4→3→2 Higher Level Paper 1, Time Zone 2, May 21, Q35
B 1→2→3→4
7 In the cell cycle, when does DNA replication occur?
C 3→1→2→4
A Early metaphase
D 3→2→1→4
B C phase of interphase
4 Nocodazole is a chemical used in the study of C S phase of interphase
mitosis. It causes all mitotic cells to stop dividing at D G2 phase of interphase
metaphase. Which statement(s) correctly identify how
8 What forms when two different chromatids of the same
this chemical might work?
homologous pair cross over?
I Nocodazole inhibits chromatin condensing in
A Sister chromatid
the nucleus
B A promoter region
II Nocodazole prevents replication of the centrioles
C Chiasma
III Nocodazole stops sister chromatids migrating
D Spindle 昀椀bre
to opposite poles
Higher Level Paper 1, Time Zone 1, May 18, Q35 (modified)
A III only
B I, II and III
C I and II only
D I and III only

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9 A sample from human epidermal tissue was examined 2 Distinguish between the terms haploid and diploid. [3]
under the microscope to determine a mitotic index. 3 During an immune response, cells divide by mitosis.
The number of cells in each stage of the cell cycle was Suggest how mitosis is involved in an
determined. Data from the investigation is shown in the immune response. [3]
following table:
4 Outline the process of mitosis and its role in
Stage of Interphase Prophase Metaphase Anaphase Telophase
maintaining genetic stability. [7]
cell cycle
Number 100 18 12 5 2 5 Explain the role of meiosis in natural selection
of cells and evolution. [7]
a Calculate the mitotic index for the tissue sample. [1] (Questions 6–10 HL only)
b Outline how the mitotic index can be used in the
6 Outline the role of mitosis in growth and repair of tissue.
identi昀椀cation and treatment of cancer. [3]
[3]
■ Paper 2 7 a Describe the phases of the cell cycle. [3]
1 Prokaryotic organisms such as E. coli divide by binary b Explain how the cell cycle is controlled. [5]
昀椀ssion, not mitosis. Apart from ribosomes, prokaryotes 8 Suggest why embryonic stem cells do not give rise
have no organelles comparable to those found in to tumours. [3]
eukaryotes and have a circular ‘chromosome’ with 9 Describe the development of cancer as a
no centromere. multi-step process. [3]
With reference to the information above and your 10 Outline how mutations can affect the structure and
knowledge of mitosis, suggest why mitosis does not function of an organism. [7]
occur in prokaryotes. [2]

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D2.2 Gene expression (HL only)

■ Paper 1 (HL only) 5 The images in the 昀椀gure below show chromosomal
1 Which of the following are used to regulate transcription? regions with different amounts of methylation in two
I Promoters pairs of identical twins. The photomicrographs were
II Enhancers taken during metaphase. The chromosome number is
III Transcription factors given for each chromosome (chromosomes 1, 3, 12 and
A I only C I, II and III 17 are shown).
B I and II D III only For each chromosome, the diagrams show changes in
2 Which of the following best de昀椀nes epigenesis? levels of methylation between 3-year-old twins and
A The development of patterns of differentiation in 50-year-old twins.
the cells of a multicellular organism Green areas indicate high levels of methylation
B Heritable changes in gene activity that are not (hypermethylation) in one twin compared to the
caused by changes in the DNA base sequences other. Red areas indicate low levels of methylation
C Generation of epidermal cells by mitosis (hypomethylation) in one twin compared to the other.
D Process that occurs when an egg is fertilized by Yellow areas indicate similar levels of methylation in
a sperm both twins.
3 When glucose is absent and lactose is present, lactose
binds to the operon’s repressor.
Which statement best describes what happens next?
A Repressor binds to promoter, transcription
is initiated
B Repressor binds to operator, transcription is
not initiated
C Repressor fails to bind to structural genes,
transcription is not initiated
D Repressor fails to bind to the operator,
transcription is initiated
4 Which row of the table below gives the correct
de昀椀nitions of genome, proteome and transcriptome?
Genome Proteome Transcriptome
A the genetic code the range of the transcription
of an organism amino acids factors used in
that determines found in a cell at a protein synthesis
which proteins particular time
are synthesized
3-year-old twins 50-year-old twins
B the genetic all the proteins the full range of
information expressed in mRNA molecules
contained within an organism expressed from a Compare and contrast levels of methylation in
the nucleus of the genes of chromosomes with increasing age of twins. [3]
an organism an organism
b Suggest what the methylation patterns seen in the
C the whole of all the proteins the range of
two sets of twins indicate. [4]
the genetic expressed within mRNA transcripts
information of a cell, tissue or produced in a
an organism organisms at a specific cell or
certain time tissue type at a
particular time
D varies with the the same in depends on
function, location all the cells of the differential
or environmental an organism expression of
conditions of genes within a cell
the cell

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■ Paper 2 (HL only) 3 Outline how monozygotic twin studies can be used
1 Describe the role of lactose in the regulation of to investigate the effects of the environment on
lac operon. [3] gene expression. [7]

2 Describe and explain the effect of DNA methylation on 4 Explain the role of gene expression as the mechanism
the eukaryotic genome. [3] by which information in genes has effects on
the phenotype. [7]
5 Describe the role of inhibition in controlling
biological systems. [9]

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D2.3 Water potential

■ Paper 1
1 Red blood cells were placed in solutions with different osmotic concentrations. The 昀椀gure shows
the effect of each solution on the cells. Which of the following correctly describes the solutions
the red blood cells were placed in?

X Y Z

ratio of final mean volume of cells to original mean volume of cells

X Y Z 2.0

A hypertonic hypotonic isotonic

1.8
B hypotonic isotonic hypertonic

C isotonic hypotonic hypertonic

1.6
D hypertonic isotonic hypotonic

2 Which of the following occur(s) by osmosis? 1.4

I Absorption of water by soil
II Gain of water from a plant cell in a 1.2
hypotonic environment
III Evaporation of water from the leaves of plants 1.0
IV Absorption of water by cells in the walls of
the digestive tract 0.8
A I and IV
B II and III only 0.6
C II and IV only
D I, II III and IV 0.4
3 The glucose concentration inside an animal cell is 50 100 150 200 250 300
concentration of sodium
6.5 mM dm−3 (where mM = millimole, or the amount chloride solution/mmol dm−3
of a substance equal to a thousandth of a mole).
a Use the terms isotonic, hypotonic or hypertonic
The glucose concentration in the solution surrounding
to explain the results for red cells placed in
the cell increases to 12.5 mM dm−3. What will be the
a sodium chloride solution of the following
likely response?
concentrations:
A The cell will gain water from the solution
i 100 mmol dm−3 [2]
B The cell will lose glucose to the surrounding solution
ii 150 mmol dm−3 [2]
C The cell will lose water and shrink
iii 240 mmol dm−3 [2]
D The cell will remain the same
b No intact cells could be seen in the 50 mmol dm−3
4 Red blood cells were left for the same length of time in
sodium chloride solution at the end of the
sodium chloride solutions of different concentrations.
experiment. Only fragments of membranes could
The 昀椀nal mean volume of the red cells was then
be found. Explain why. [2]
compared with the original mean volume. The results
are shown in the graph.

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(Questions 5–8 HL only) 8 The following diagram shows cells taken from the
5 In which of the following solutions will a cell with a leaf of a plant. Cells A, B and C are next to each other.
water potential of −10 kPa become turgid? The water potential (Ψw) of each cell is shown.
A −5 kPa
B −20 kPa
C −11 kPa
D −10 kPa A=
−355 kPa
6 Water moves through the root tissue of a plant.
Which row of the table describes this movement?
B=
Direction of water Direction of water
−370 kPa
movement in terms of movement in terms of
concentration of solutions water potential
C=
A concentrated to dilute lower to higher −410 kPa
B dilute to concentrated lower to higher

C concentrated to dilute higher to lower

D dilute to concentrated higher to lower

7 The 昀椀gure shows two chambers divided by a partially

permeable membrane, containing solutions with
different water potentials. The solute potential (Ψs) and
pressure potential (Ψp) are given for both solutions.
a i Draw arrows on a copy of the diagram to show
the movement of water between these cells. [1]
A B ii Explain your answer to part i in terms of
ψs = −400 kPa ψs = −500 kPa water potential. [2]
ψp = 300 kPa ψp = 300 kPa b The diagram below shows two plant cells, X
and Y, seen through a microscope. The 昀椀gures
show the solute potential (Ψs ) and the pressure
a Calculate the water potential for side A. [1]
potential (Ψp ) for both cells and the water
b Calculate the water potential for side B. [1]
potential (Ψw) for cell Y.
c Draw an arrow on a copy of the diagram to
indicate the direction of net water 昀氀ow. [1]

Cell X Cell Y
ψp = 1000 kPa ψp = 0 kPa
ψs = −1800 kPa ψs = −1000 kPa
ψw = −1000 kPa

i Calculate the water potential, Ψw, of cell X.

Show your working. [2]
ii State the name of the different conditions
shown by cell X and cell Y, and explain how
these conditions have arisen. [5]

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■ Paper 2 2 State two ways in which osmosis differs from

1 The 昀椀gure below shows a tube containing two different facilitated diffusion. [2]
solutions: a dilute solution on the left and a concentrated 3 Jam contains a high concentration of sugar. Suggest why
solution on the right. The two solutions are separated by bacteria that cause decay do not grow in jam. [3]
a partially permeable membrane. 4 Outline the effects of bathing plant tissues in a
hypotonic solution. [5]
LOW HIGH
concentration concentration 5 Describe how the osmotic concentration of tissue cells
sucrose sucrose
can be determined. [7]
6 Outline the role of the cell membrane in maintaining the
osmotic concentration of cells. [9]
(Questions 7–8 HL only)
7 Suggest why marine plants are rare. [5]
8 Outline the contributions of solute potential and
water solute pressure potential to the water potential of cells
partially with walls. [7]
permeable
membrane

a Predict if the level of the solution will change on

the left-hand or right-hand side of the capillary
tube and, if so, in which direction. [1]
b Explain your answer to part a. [3]

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D3.1 Reproduction
■ Paper 1 ■ Paper 2
1 Which of the following statement(s) include 1 a i Draw and annotate a fully labelled half-
differences between male and female gametes in 昀氀ower diagram of an insect-pollinated 昀氀ower
sexual reproduction? you have studied. [4]
I Male gamete is smaller ii State what insects may visit this 昀氀ower. [1]
II Male gamete has fewer food reserves iii Identify the features of this 昀氀ower that may
III Female gametes are motile attract insects. [2]
A I only C I, II and III b Explain how pollination is brought about in an
B I and II D III only animal-pollinated 昀氀ower. [4]
2 Which of the following is an example of negative 2 State the name of the hormones that:
feedback in the menstrual cycle? a trigger ovulation [1]
A Increasing FSH receptors in the follicles leading b stimulate the growth of the endometrium [1]
to increased oestradiol production c maintain the endometrium and promote its
B Oestradiol inhibiting secretion of FSH from the vascularisation. [1]
pituitary gland 3 Distinguish between asexual and sexual
C Oestradiol stimulating the secretion of LH by the reproduction. [3]
pituitary gland 4 Explain how meiosis breaks up parental combinations
D Progesterone continuing to stimulate the build-up of alleles, and how fusion of gametes produces
of the endometrium new combinations. [4]
3 Which of the following statements is the de昀椀nition 5 Describe the use of hormones in IVF treatment. [5]
of fertilization? 6 Outline how meiosis and two other mechanisms
A Transfer of a male gamete to a female promote genetic variability among individuals of the
B Generation of gametes by meiosis same species. [7]
C Fusion of a male and female gamete
D Production of a haploid cell from a diploid cell (Questions 7–11 HL only)
7 a Explain how the placenta is adapted to
(Questions 4–6 HL only)
its function. [3]
4 What does the release of gonadotropin-releasing
b List the substances exchanged between the foetus
hormone directly stimulate?
and the mother. [2]
I Puberty
c State which processes are used to transfer
II Release of an ovum from an ovary
substances to the foetal blood at the placenta. [2]
III Increased LH and FSH
d Suggest why is it essential that maternal
A I only C I and III and foetal blood circulations do not mix in
B I and II D I, II and III the placenta. [2]
5 Which of the following is a mechanism to prevent 8 Outline the role of mitosis and meiosis
polyspermy? in gametogenesis. [6]
A Reduced meiotic division
9 Distinguish between spermatogenesis and oogenesis. [3]
B The cortical reaction
C Many sperm are produced but only one egg 10 Describe the hormonal control of pregnancy
D Increased spermatogenesis and childbirth. [7]

6 Which hormone is detected by a pregnancy test? 11 Outline the role of chemical signalling in the control of
A Insulin pregnancy and childbirth. [7]
B Epinephrine
C Thyroxin
D Human chorionic gonadotropin

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D3.2 Inheritance
■ Paper 1 6 A dihybrid cross was carried out between two plants to
1 Which of the following is an example of a sex-linked determine whether the genes for seed shape and colour
genetic disorder? are linked. If the genes are unlinked, the expected ratio
A Phenylketonuria of 9:3:3:1 should occur. A chi-squared test was carried
B Haemophilia out on the observed results of the cross. The critical
C Sickle-cell anaemia value for chi-squared at the 5 % level of signi昀椀cance in
D Huntington’s disease this test was 7.82. The calculated value for chi-squared
was 6.25. What can be concluded from this data?
2 Which of the following is a de昀椀nition of phenotype?
A The results prove that the genes are linked
A Capacity to develop traits suited to the environment
B The results prove that the genes are unlinked
B The observable traits of an organism
C There is signi昀椀cant evidence that the genes
C The combination of alleles inherited by an organism
are linked
D Mutation in an autosomal gene that codes for
D There is signi昀椀cant evidence that the genes
an enzyme
are unlinked
3 Which of the following is a description of incomplete Higher Level Paper 1, Time Zone 1, November 21, Q35
dominance?
A Heterozygotes have an intermediate phenotype 7 This is the cross that led to the discovery of non-
B Heterozygotes have a dual phenotype Mendelian ratios in Morgan’s experiments with
C A heterozygous genotype will produce the same Drosophila.
phenotype as one that is homozygous dominant Grey body − Normal wings Black body − Vestigial wings
D More genes are carried by the X chromosome +
b vg+ b vg
than the Y chromosome
×
(Questions 4–8 HL only) b vg b vg
4 Which of the following describes unlinked genes?
Which is the recombinant genotype?
I Segregate in meiosis I
II Undergo independent assortment A b+ vg+ B b vg
III Are mainly found on the X chromosome
A I only b vg b vg+
B I and II
C I, II and III C b+ vg+ D b vg
D III only
5 A dihybrid cross with individuals that are heterozygous b+ vg+ b vg
for both genes will result in which of the following
Higher Level Paper 1, Time Zone 0, May 16, Q22
phenotype ratios?
A 3:1
B 1:1:1:1
C 9:3:3:1
D 1:2:1

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8 An investigation was carried out on the inheritance of 2 Distinguish between the following pairs:
昀氀ower colour in an ornamental plant. The results are a discontinuous variable and continuous variable [2]
shown in Table 1. b autosomes and sex chromosomes [2]
■ Table 1 Outcome of a genetic cross investigating the inheritance of c X chromosomes and Y chromosomes. [2]
flower colour of an ornamental plant
3 Explain what is described as continuous variation by
P generation Red flowered × white flowered using one named example. [4]
F1 All red-flowered plants 4 Mendel carried out a breeding experiment with garden
F1 generation allowed to pea plants in which pure-breeding pea plants grown
self-fertilize
from seeds with a smooth coat were crossed with plants
F2 156 red-flowered plants 44 white-flowered plants
grown from seeds with a wrinkled coat. All the seeds
a Using a copy of Table 2, calculate χ2. [2] produced (the F1 generation) were found to have a
2
(O – E) smooth coat. When plants were grown from these seeds
χ2 = ∑
E and allowed to self-pollinate, the second generation of
■ Table 2 Chi-squared calculation for flower colour observed and seeds (the F2 generation) included both smooth and
expected results
wrinkled seeds in the ratio of 3:1.
Category Predicted O E O−E (O − E)2 (O − E)2/E a In Mendel’s explanation of his results he used the
red- 3 156 term hereditary factor.
flowered
i Identify the modern term for ‘factor’. [1]
plants
white- 1 44
ii State where in the cell they occur. [1]
flowered b The parent plants have diploid cells, while the
plants gametes (sex cells) are haploid. De昀椀ne what is
total meant by haploid and diploid. [2]
b Using the table of critical values (Table 3), c By reference to the above experiment, de昀椀ne the
determine whether there is a signi昀椀cant difference following terms and give an example of each:
between the observed and expected results. [2] i homozygous and heterozygous [2]
■ Table 3 Table of critical values for chi-squared test ii dominant and recessive [2]
iii genotype and phenotype. [2]
Degrees of Probability greater than
freedom d Using appropriate symbols for the alleles for
0.99 0.95 0.90 0.50 0.10 0.05 0.01 0.001
smooth and wrinkled coat, construct a genetic
df = 1 0.00016 0.004 0.016 0.455 2.71 3.84 6.63 10.83
diagram, using a Punnett grid, to show the
df = 2 0.0201 0.103 0.21 1.386 4.60 5.99 9.21 13.82
behaviour of the alleles in this experiment. [4]
c Explain what the results show about the
pattern of inheritance of 昀氀ower colour in the (Questions 5–9 HL only)
ornamental plant. [3] 5 Distinguish between the following pairs:
a monohybrid cross and dihybrid cross [2]
■ Paper 2 b linkage and crossing over [4]
1 The inheritance of ABO blood groups is controlled by c multiple alleles and polygenes. [4]
three alleles of a gene (IA, IB and i). The alleles IA and IB 6 Mendel conducted many experiments with garden
are codominant. pea plants, but some later geneticists used the fruit 昀氀y
a Explain what is meant by the terms: Drosophila in experimental investigations.
i allele [1] a Suggest three reasons why this insect was found
ii codominant. [1] to be useful. [3]
b State all possible genotypes for the following b When dihybrid crosses are carried out,
blood types: the progeny are rarely present in the exact
i A [1] proportions predicted. Explain why small
ii B [1] deviations of this sort arise in dihybrid crosses with:
iii O [1] i garden pea plants [3]
iv AB. [1] ii Drosophila. [3]
Offspring of blood group A and O were born to parents
of blood groups A and B.
c Construct a genetic diagram to show the possible
ABO blood group phenotypes of these children. [4]

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7 In Drosophila, mutants with scarlet eyes and vestigial wings are recessive to 昀氀ies with red eyes
and normal wings. (These contrasting characters are controlled by single genes on different
chromosomes, i.e. they are not linked on a single chromosome.)
Explain the phenotypic ratio to be expected in the F2 generation when normal 昀氀ies are crossed
with scarlet eyes/vestigial wing mutants and sibling crosses of the F1 offspring are then
conducted. Show your reasoning by means of a genetic cross diagram. [7]
8 Haemophilia is a sex-linked disease that affected some members of royal families in Europe
during the nineteenth and twentieth centuries.

Key
Queen Victoria Prince Albert female without haemophilia

female carrier
?
male without haemophilia
Alice Louis IV Leopold Beatrice
male with haemophilia

Henry Irene Alexandra Nicholas Alfonso Victoria

of II XIII
Prussia

a i Draw a Punnett grid to show all the possible genotypes of Queen Victoria’s children. [2]
ii Deduce the genotype of Queen Victoria’s daughter Alice. [1]
The diagram shows the structure of two chromosomes after the 昀椀rst division of meiosis,
assuming that there was no crossing over or chiasmata formation.

A A A A

B B b b

b i Draw the same chromosomes to show their structure at the same stage of meiosis
if there had been one chiasma between two gene loci. [1]
ii State the stage of meiosis where chiasmata formation may occur. [1]
c Explain gene linkage and its effects on inheritance. [2]
d Explain the mechanism that prevents polyspermy during fertilization. [2]
Higher Level Paper 2, Time Zone 0, November 21, Q2ai–c

9 Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance
of autosomal genes is affected by whether the genes are linked or unlinked. Explain the
two types of inheritance, using the example of parents that are heterozygous for two genes
A and B. [7]
Higher Level Paper 2, Time Zone 2, May 21, Q5a

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D3.3 Homeostasis
■ Paper 1 5 What is the function of the loop of Henle?
1 After eating a meal, which hormone is secreted and A To reabsorb glucose
which cell secretes it? B To maintain a hypotonic solution in the medulla
C To maintain a hypertonic solution in the medulla
Hormone Cell in pancreas
D To excrete urea
A glucagon α cells
Higher Level Paper 1, Time Zone 2, May 19, Q33 (modified)
B glucagon β cells

C insulin α cells 6 What is the effect of ADH on the kidney?

A It stimulates reabsorption of glucose in the
D insulin β cells
proximal convoluted tubule
2 Which of the following describes homeostasis? B It inhibits reabsorption of water in the
I Maintenance of the internal environment of Bowman’s capsule
an organism C It stimulates reabsorption of water in the
II Involves negative feedback loops collecting duct
III Involves positive feedback loops D It stimulates reabsorption of ions in the loop
A I only of Henle
B I and II Higher Level Paper 1, Time Zone 2, May 18, Q39 (modified)
C I and III
D III only ■ Paper 2
3 Which of the following are involved in 1 Explain the role of negative feedback loops in
thermoregulation? homeostasis, using a speci昀椀c example. [5]
A Hypothalamus, pituitary gland and thyroxin
2 Describe the mechanisms for thermoregulation
B Pancreas, insulin and glucagon
in humans. [7]
C Adrenal gland and adrenalin
3 Discuss the control of blood glucose levels and the
D Hypothalamus, pituitary gland and FSH
consequences if they are not maintained. [8]
(Questions 4–6 HL only) Standard Level Paper 2, Time Zone 2, May 19, Q6c
4 Where in the nephron is most glucose reabsorbed?
4 Outline how homeostatic mechanisms allow organisms
to adapt to their environment. [7]
(Questions 5–7 HL only)
A D 5 a State the differences in composition of blood
proteins, glucose and urea found in:
i blood before entering the glomerulus [1]
ii glomerular 昀椀ltrate in the Bowman’s capsule [1]
B
iii 昀椀ltrate inside the descending limb of the loop
of Henle. [1]
b Explain how water reabsorption is controlled in
the collecting duct. [4]
C 6 Outline the kidney’s role in osmoregulation. [8]
Higher Level Paper 2, Time Zone 0,
November 20, Q7c (modified)

Higher Level Paper 1, Time Zone 1, November 21, Q39

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D4.1 Natural selection

■ Paper 1 6 Which of the following is a de昀椀nition of
1 Which observation best describes the process of disruptive selection?
natural selection? A Mechanism that maintains a favourable
A A change from simple to more complex characteristic and the alleles responsible for it
organisms over time B Occurs when particular environmental
B A change in size of the population over time conditions favour the extremes of a phenotypic range
C Different rates of reproductive success of C In changing environmental conditions, the
different genotypes majority form of an organism may become
D Spontaneous occurrence of advantageous mutations unsuited to the environment
D Mechanism where one species excludes another
2 Which one of the following is not included in Lamarck’s
from an environment
ideas about the process of evolution?
A Acquired characteristics are inherited 7 The graph shows the relationship between mass at
B Organisms arise by spontaneous generation birth and the percentage that die shortly after birth for
C Evolutionary relationships among organisms can Scottish Blackface lambs.
be depicted by groupings based on similarity 50
D Organisms develop adaptations to the
45
environment through the use and disuse of organs
40
3 Which of the following is an example of a density-
independent factor that may affect the survival of 35
lamb mortality/%

individuals in a population? 30
A Predation
25
B Transfer of pathogens
C High or low temperatures 20
D Competition for limited resources 15
4 Which of the following is a description of
10
sexual selection?
A Process where organisms better adapted to their 5

environment survive and produce more offspring 0

than competitors 2 3 4 5 6 7
mass at birth/kg
B Selection arising through preference by one sex
for certain characteristics in individuals of the What type of selection for the lambs is shown in
other sex the graph?
C Selection in breeding, carried out deliberately by A Disruptive selection, as there is a drop in
humans to alter populations mortality at intermediate birth masses
D Process by which distantly related organisms B Stabilizing selection, as lambs with low or high
independently evolve analogous traits under birth mass are less likely to survive
similar selection pressures C Directional selection, as lambs with a high birth
(Questions 5–7 HL only) mass have high mortality
5 A population’s gene pool was found to have been D There is no evidence in the graph of selection, as
unchanged for many generations. Which of the following survival frequency is not shown
Higher Level Paper 1, Time Zone 1, November 21, Q36
conditions must have existed in the population?
A Mating had always been random
B Genetic drift had often occurred
C Inbreeding has occurred
D Certain alleles are at selective advantage

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■ Paper 2
1 The land snail Cepaea nemoralis is very common in North America and in Europe.
The base colour of its shell varies between brown, pink and yellow, and also in its intensity.
Some shells are unbanded, but most show one to 昀椀ve bands of different width on top of the
shell base colour.
In the early 1950s, scientists studied the proportion of colours and banding of C. nemoralis
in woods and 昀椀elds near Oxford, UK, which differed in the type of plants and background
colour. Each data point on the graph represents the percentage of yellow base colour shells and
unbanded shells in a sample from either one type of wood or 昀椀eld, although other snail colours
were present.
100
Key
woods
90 fields
percentage of yellow base colour shells per sample

80

70

60

50

40

30

20

10

0
0 10 20 30 40 50 60 70 80 90 100
percentage of unbanded shells per sample

a Determine the maximum percentage of yellow base colour shells found in woods. [1]
b Suggest either one possible advantage or one disadvantage of having a banded shell,
stating whether it is an advantage or disadvantage. [1]
c Using the data in the graph, distinguish between the distribution of C. nemoralis shells
in woods and 昀椀elds. [2]
The population of C. nemoralis has been studied for many years in open 昀椀elds in a similar
area. In the following graph, each data point represents the percentage of adults of a given base
colour plotted against the percentage of juveniles of the same base colour collected each year.

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60

40

percentage of adults

20

Key
Shell base colour
yellow
pink
brown
0
0 20 40 60
percentage of juveniles

d Deduce from the data in the graph which shell base colours are on average most and
least frequent among adult snails. [2]
e Discuss whether there is evidence in the data that colour plays a role in the survival
of the snails. [3]
f Using the theory of natural selection, explain the differences shown in the graph
between the three colours of snail. [3]
Standard Level Paper 2, Time Zone 1, May 18, Q1a–f

2 Some lice live in human hair and feed on blood. Shampoos that kill lice have been available for
many years but some lice are now resistant to those shampoos. Two possible hypotheses are
shown in the table.
Discuss which hypothesis is a better explanation of the theory of evolution by natural selection.
Hypothesis A Hypothesis B
Resistant strains of lice were present in the population. Exposure to anti-lice shampoo caused mutations for
Non-resistant lice died with increased use of anti-lice resistance to the shampoo and this resistance is passed
shampoo and resistant lice survived to reproduce. on to offspring.
[3]
Standard Level Paper 2, Time Zone 2, May 17, Q4bii

3 Suggest how natural selection could have brought about the evolution of the skeleton of
a bat’s wing. [5]
4 Compare and contrast natural selection and sexual selection. [5]
5 Referring to each level of biological organization, outline how natural selection leads
to evolution. [7]
(Questions 6–8 HL only)
6 Explain what is meant by directional, stabilizing and disruptive selection. Give examples
of each type of selection. [6]
7 Outline how allele frequencies in gene pools can be used to assess whether natural selection
is taking place. [7]
8 Discuss whether or not the evolution of antibiotic resistance in bacteria is an example of
arti昀椀cial selection. [6]

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D4.2 Stability and change

■ Paper 1 (Questions 4–6 HL only)
1 Which of the following are required for stability 4 Which of the following is a de昀椀nition of succession?
in ecosystems? A Separation of communities into speci昀椀c zones
I Supply of energy according to variables such as altitude
II Recycling of nutrients B The process of change over time in a community
III Genetic diversity C The process of change over distance in a community
A I only C I, II and III D The movement of energy and biomass through a
B I and II D II and III food chain
2 Which of the following is most likely to be an example 5 Which of the following describes changes from pioneer
of a possible tipping point in ecosystem stability? to climax community in a succession?
A Deforestation of the Amazon rainforest Size of Species Complexity Amount of
plants diversity of food webs nutrient cycling
B Bleaching of coral reefs
C Unsustainable harvesting of aquatic ecosystems A decreases increases decreases increases

D Eutrophication of aquatic and marine ecosystems B increases decreases increases decreases

due to leaching C increases increases increases increases

3 Which of the following is an established method D decreases decreases decreases decreases

of rewilding? 6 Which of the following ecosystems is an example of
A Introduction of herbivores cyclical succession?
B Habitat fragmentation A Tropical rainforest C Coral reef
C Reintroduction of apex predators B Wood pasture D Taiga
D Removal of keystone species

■ Paper 2
1 Blue昀椀n tuna (Thunnus orientalis) are top carnivores in the marine ecosystem. Some
radioisotopes of elements are produced by nuclear reactors. Following a nuclear accident at
Fukushima in Japan in March 2011, the levels of certain radioisotopes were measured in the
bodies of blue昀椀n tuna caught off California in August 2011, the other side of the Paci昀椀c Ocean
from Japan. The becquerel (Bq) is a measure of radioactivity.
1000
radioisotope concentration/Bq kg−1

100

Key
2008
2011

10

1
134 137 40
Cs Cs K
radioisotope

Explain how the levels of the caesium (Cs) radioisotopes could have accumulated in the
tissues of these 昀椀sh. [3]
Standard Level Paper 3, Time Zone 0, November 19, Q14a

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2 The sketched map shows the density of microplastics and macroplastics found in a lake within
a national park.
N

W E
S Key
camping site
city

microplastics macroplastics density / g km−2

<200
200–3000
>3000

Prevailing wind direction

a Predict one example of macroplastic pollution that is likely to be found in this lake. [1]
b State two possible effects on organisms of microplastic pollution. [2]
c Outline the effect of wind on the distribution of plastic pollution in this lake. [2]
d Suggest changes in the management of the national park that could reduce the amount
of macroplastic pollution. [3]
Higher Level Paper 3, Time Zone 0, November 16, Q15a–d

3 Extensive areas of the rainforest in Cambodia are being cleared for large-scale rubber
plantations. Distinguish between the sustainability of natural ecosystems such as rainforests
and the sustainability of areas used for agriculture. [3]
Higher Level Paper 2, Time Zone 0, November 18, Q8a

4 Outline the role of keystone species in the sustainability of ecosystems. [4]

5 Describe how leaching of nitrogen and phosphate fertilizers causes eutrophication. [5]
6 Explain how the sustainability of resource harvesting from natural ecosystems can
be assessed. [5]
7 Explain how stability is a function of each level of biological organization. [6]
(Questions 8–12 HL only)
8 A retreating glacier leaves an environment of lifeless glacial deposits, including sands and
gravels. Retreating glaciers often offer suitable sites for primary succession.

glacier

meltwater streams

a State one abiotic factor that will determine the type of ecosystem in a succession. [1]
b Predict the process of succession that takes place on exposed bare ground as the
glacier retreats. [3]
Higher Level Paper 3, Time Zone 1, May 18, Q15a–b

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9 Primary plant succession has been observed in sand dunes adjacent to the northern end of
Lake Michigan, one of the Great Lakes in North America. The youngest sand dunes have
beach grass (Ammophila breviligulata) and prairie bunch grass (Schizachyrium scoparium).
The oldest dunes have coniferous trees (Pinus strobus and Pinus resinosa).
a Predict the differences in the soil characteristics between the youngest and oldest
sand dunes. [3]
b Outline how the type of stable ecosystem that will develop in an area can be predicted
based on climate. [3]
Standard Level Paper 3, Time Zone 0, May 16, Q14a–b

10 The graph is a model showing biomass and respiration levels in a 昀椀eld where farming stops at
time zero and the abandoned land develops into forest.

biomass

respiration

forest succession

0 20 40 60 80 100
years

a Describe the change in biomass over the 100-year period. [2]

b Outline the evidence from the graph that the area had plentiful rainfall. [2]
c Explain the changes in biomass. [2]
d Suggest why biomass continues to increase after the respiration levels plateau. [2]
Higher Level Paper 3, Time Zone 0, May 16, Q16a–d (modified)

11 Explain how changes occur during primary succession. [6]

12 Outline how human in昀氀uences can prevent climax communities from developing. [5]

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D4.3 Climate change

■ Paper 1 3 Which data provides evidence of climate change?
1 Which of the following describes a positive feedback I Carbon dioxide concentration measured
concerning climate change? from air bubbles trapped in an ice core from
A Increased atmospheric temperature results in the the Antarctic
melting of sea ice, which decreases the amount of II Changes in glacier formation and melting
solar radiation re昀氀ected back into space observed through photographs and maps
B Increased burning of fossil fuels increases III Maximum temperatures recorded during
atmospheric CO2 concentration, enhancing the summer each year
greenhouse effect IV Analysis of pollen from plants preserved in
C Melting of glaciers causes an increase in sea levels different layers of lakebed sediments
D Increase in atmospheric temperature causes A I only
many species to move towards increased B I and II
altitudes to stay within their optimum C I, II and III
temperature range D I, II and IV

2 The emission of greenhouse gases such as CO2 and CH4 (Questions 4–6 HL only)
have different impacts on global warming depending on 4 Which of the following are examples of phenological
their concentration in the atmosphere, their atmospheric research?
lifetime and their global-warming potential (GWP). I The timing of 昀氀owering events
GWP was developed to allow comparisons of the global II Bud set in deciduous trees
warming impacts of different gases, and is a measure III Bird migration and nesting
of how much energy the emissions of 1 ton of a gas A I only
will absorb over a given period of time, relative to the B I and II
emissions of 1 ton of carbon dioxide (CO2). C I, II and III
Which row best describes the characteristics of these D III only
greenhouse gases? 5 Which of the following can lead to disruption in the
CO2 CH4 synchrony of phenological events?
A higher GWP lower GWP A Increased rainfall
B Negative feedback mechanisms
B from anthropogenic activities from anthropogenic activities
such as decomposition of such as management of C Higher temperatures earlier in the year
organic waste at landfills manure from livestock
D Lower temperatures later in the year
C from natural processes such from natural processes, such
as soil respiration as cow digestion 6 Which of the following is an example of evolution as a
D shorter atmospheric lifetime longer atmospheric lifetime consequence of climate change?
A Increases to the number of insect life cycles
within a year
B Adaptive radiation in Galápagos 昀椀nches
C Increase in dark brown tawny owls in
populations usually dominated by pale grey owls
D Increase in melanic form of the peppered moth

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■ Paper 2
1 Coral reefs are among the most spectacular ecosystems on Earth. They support a rich diversity
of life and provide economic bene昀椀ts to the people who use them. In Papua New Guinea in
the Paci昀椀c Ocean north of Australia the following data were collected. Coral cover is the
percentage of the reef surface covered by live hard coral.
80 24.70
a Calculate the difference

mean annual ocean temperature/°C

70 24.65 in coral cover in 1996 and
60 24.60 2002. No working required. [1]
coral cover/%
50 24.55 b Describe the evidence that
40 24.50
the ocean temperature has
an effect on coral cover. [2]
30 24.45
c Suggest causes for
20 24.40 the changes in ocean
10 24.35 temperature. [2]
0 24.30
1994 1996 1998 2000 2002 2004
year

Key
percentage coral cover
ocean temperature

In order to test the effect of temperature, live samples of a species of coral, Pocillopora
damicornis, were placed in an experimental chamber at a constant pH, water depth and low
light. All the coral samples were started at 26 °C and half of them were rapidly increased
to 30 °C.

light source

pH meter

coral sample

heat pad kept at 26 °C

containers holding the coral samples
heat pad rapidly increased from 26 °C to 30 °C

The pie charts show the percentage of live and dead tissues at the end of the experiment.

Key
live
dead

constant temperature rapidly increasing temperature

26°C 26°C to 30°C

d Identify one advantage of conducting this experiment in the laboratory rather than in
the ocean. [1]
e Comment on whether the experimental data supports the observed data from the ocean. [1]
Higher Level Paper 2, Time Zone 0, November 16, Q1a–e

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2 The 昀椀gure shows Arctic sea ice extent for the months of September and March of each year
from 1979 through to 2016. September and March are when the minimum and maximum
extents typically occur each year.

sea ice extent/million square miles

March
5

4
September
3

0
1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
year

a State which year has the lowest September sea ice extent recorded. [1]
b State the overall trend in sea ice extent for both September and March. [1]
c Suggest reasons for the reduction in the Arctic ice sheets from 1979 to 2009. [2]
3 Explain how carbon sequestration can be used to mitigate climate change. [7]
4 Describe how climate change can lead to habitat loss and the implications of this
for biodiversity. [7]
5 Outline the role of positive feedback cycles in global warming. [6]
6 a Explain the effects of climate change as atmospheric carbon dioxide
concentration increases. [3]
b Explain two ways in which climate change damages coral reefs. [2]
7 The levels of atmospheric carbon dioxide have been increasing during the past years.
Outline reasons for this increase. [4]
8 The loss of species from ecosystems as a result of anthropogenic (man-made) climate
change is likely to affect food webs.
a Outline how climate change can lead to the loss of species. [3]
b Suggest two reasons why it might be dif昀椀cult to establish how the removal of one
species from a food web might affect others. [4]
9 Describe the impacts of climate change at each level of biological organization. [7]
(Questions 10–12 HL only)
10 Discuss how phenological events can be used to indicate climate change. [5]
11 Outline, using an example, how evolution can occur as a consequence of climate change. [5]
12 Describe how climate change can affect the life cycle of insects and the impact of this
on ecosystems. [5]

Biology for the IB Diploma Programme D4.3 Climate change 101

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Acknowledgements
The Publishers would like to thank the following for permission to reproduce copyright material.
Every effort has been made to trace and acknowledge ownership of copyright. The Publishers will
be glad to make suitable arrangements with any copyright holders whom it has not been possible
to contact.

Photo credits
p.8 © Kevin Mackenzie; p.9 tl Photo © E. Newcomb; bl © Biophoto Associates/Science
Photo Library; r © Don W. Fawcett/Science Source/Science Photo Library; p.24 © OpenStax
Microbiology, https://commons.wikimedia.org/wiki/File:OSC_Microbio_07_04_hemoglobin.jpg/
https://creativecommons.org/licenses/by/4.0/deed.en; p.27 © Kallayanee/stock.adobe.com; p.29
© Aldona/stock.adobe.com; p.33 l © Eye of Science/Science Photo Library; r © Eric Grave/Science
Photo Library; p.39 © Kelly J Cude, PhD College of the Canyons; p.41 © OpenStax Collegehttps://
en.wikipedia.org/wiki/File:2102_Comparison_of_Artery_and_Vein.jpg/https://creativecommons.
org/licenses/by/3.0/deed.en; p.49 © Aldona/stock.adobe.com; p.54 © K.R. Porter/Science Photo
Library; p.59 © Alila Medical Media/stock.adobe.com; p.63 © Anne Gibson, The Micro Gardener,
TheMicroGardener.com; p.69 © Andu/stock.adobe.com; p.74 © Matthew Meselson; p.76 © J.
L. Carson, Ph.D./Science Photo Library; p.77 l © Natros/stock.adobe.com; r © George E. Palade
Electron Microscopy Slide Collection Image from the Medical Historical Library, Harvey Cushing/
John Hay Whitney Medical Library, Yale University; p.78 © Bhaskar/stock.adobe.com; p.81
© Ivan/stock.adobe.com; p.83 © Image from Epigenetic differences arise during the lifetime of
monozygotic twins. © Copyright (2005) National Academy of Sciences, U.S.A. (http://www.pnas.
org/content/102/30/10604); p.97 © Zombiu26/Shutterstock.com
b = bottom, c = centre, l = left, r = right, t = top

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Microorganisms”, 2006. © Pearson Prentice Hall; p.21 Q8 artwork © International Baccalaureate
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Tosato, M., Hurni, N., Sporkert, F., Giroud, C., & Broillet, M.-C. (2013). Mouse alarm pheromone
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