Syllabus Edition

First teaching 2023

First exams 2025

Practice Paper 1A (HL IB Biology)

Practice Paper Questions

1 mark

Water (H₂O) and methane (CH₄) are simple compounds with covalent bonds and a similar molecular mass.

In theory, this should mean that they share similar physical and chemical properties however, this is not the case.

The table below compares some of the features of methane and water:

	Water	Methane
Molecular weight	18	16
Latent heat of vaporisation / kJ kg^-1	2 260	510
Specific heat capacity / kJ kg^-1 °C^-1	4.2	2.2
Melting point / °C	0	-182
Boiling point / °C	100	-162

Which of the statements below correctly describes the reason for these property differences?

Water is able to form hydrogen bonds with adjacent water molecules.
Methane forms a tetrahedral structure due to the fact carbon is able to form four covalent bonds.
Methane has a higher energy content in its bonds than water.
Water has a higher density than methane in a liquid state.

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1 mark

What was a key limitation of the Miller-Urey experiment according to current understanding?

They used too much UV radiation in their experiment
The experiment did not run for long enough
The high levels of methane they used did not accurately reflect early Earth conditions
They only included methane, ammonia, hydrogen and water in the experiment

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1 mark

John Cairns carried out a study in which he kept E. coli bacteria in a solution containing radioactive thymine.

What was he able to conclude from the results of his study?

Prokaryotes have a circular chromosome.
E. coli have a circular chromosome.
Autoradiography does not produce clear enough results to determine whether bacteria have one chromosome or many.
Bacteria replicate their DNA using a structure called a replication fork.

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1 mark

Which of the following statements correctly distinguishes antigenic drift from antigenic shift in viral evolution?

Antigenic drift involves rapid, unpredictable genetic changes, while antigenic shift involves slow, gradual accumulation of mutations.
Antigenic drift occurs when two viruses combine their genetic material in a single host cell, while antigenic shift results from small mutations over time.
Antigenic drift involves the gradual accumulation of small genetic changes, while antigenic shift occurs when two or more viruses combine their genetic material, leading to a major change.
Antigenic drift leads to new virus types unrecognisable to the immune system, while antigenic shift creates only minor changes in viral surface proteins.

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1 mark

Which of the following series of statements about genome sequencing is correct?

A	Scientists now know the location and role of every human gene	The genomes of humans are the only genomes to be sequenced in their entirety	Advancing computer technology means that the rate at which a genome can be sequenced continues to increase
B	Scientists can now look for correlations between changes in a gene and particular human traits	The genomes of humans are the only genomes to be sequenced in their entirety	Genome sequencing technology is now so advanced that further developments are not expected
C	Scientists can now look for correlations between changes in a gene and particular human traits	The genomes of many species have now been sequenced	Advancing computer technology means that the rate at which a genome can be sequenced continues to increase
D	Scientists can now look for correlations between changes in a gene and particular human traits	The genomes of many species have now been sequenced	Genome sequencing technology is now so advanced that further developments are not expected

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1 mark

RNA analysis led to the development of the three domains system of classifying organisms. More recent methods of building evolutionary trees has led to the proposal of the two domains system. The image compares the three domains tree and the two domains tree.

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Which of the following pairs of statements correctly compares the three domains and two domains trees?

	Three domains	Two domains
A.	The eubacteria form a clade	The eubacteria form a clade
B.	The eukaryotes share a common ancestor with the archaea	The common ancestor of all the eukaryotes is within the archaea
C.	The archaea form a clade	The archaea form a clade
D.	The eukaryotes are more closely related to the euryarchaeota than to any other group	The eukaryotes are more closely related to the lokiarchaeota than to any other group

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1 mark

Which of the following would be the best description of the events depicted in the diagram? q6_10-3_gene_pools_speciation_ib_biology_hl_mcq

A geographical barrier separated two populations of the same species and over time they adapted to new conditions in their environment
A temporal barrier meant that the two populations were not able to reproduce during the same season anymore and formed new species
A geographical barrier separated two populations of different species and over time they adapted to seasonal differences in their habitat
A temporal barrier separated two populations which led to behavioural changes that resulted in speciation

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1 mark

Which of the following is a correct explanation for biodiversity change?

Species extinctions occur due to anthropogenic extinction.
Scientists have changed the way species are classified.
Classification can be subjective.
There are more species alive today than have been alive in the past.

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1 mark

A study was conducted to investigate the effect of different fatty acids on the levels of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) in the human bloodstream. An increase in LDL levels in the blood has been linked to an increase in the risk of developing coronary heart disease (CHD). The results are shown in the graphs below.
h-2

Which of the following conclusions would be the most valid concerning the data?

trans monounsaturated fatty acids led to the most significant change in the HDL levels, leading to a decreased risk of developing CHD
All the fatty acids led to an increase in the HDL levels in the bloodstream, which would lead to a decrease in the risk of developing CHD
cis monounsaturated fatty acids caused the greatest decrease in LDL levels and would result in a lowered risk of developing CHD
cis monounsaturated fatty acids led to a smaller decrease in LDL levels than cis polyunsaturated fatty acids which would lead to a greater decrease in the risk of developing CHD

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1 mark

Which of the following diagrams correctly shows the structure of a dipeptide?

q8-2-3-proteins-medium-ib-hl-biology

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1 mark

Membranes in cells include the following components:

Cholesterol
Glycoproteins
Phospholipids
Proteins

Which row of the table shows the correct function of each component?

	Stabilising the hydrophobic layer	Recognising self / non-self	Limiting movement of water	Transporting ions through membranes
A.	1	2	3	4
B.	3	1	2	4
C.	1	3	1	2
D.	4	3	4	2

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1 mark

Vesicles are membrane-bound sacs used for transport and storage. Clathrins are proteins that help with the formation of vesicles.

What is the correct order of events for vesicle formation?

	Step 1	Step 2	Step 3	Step 4
A	A clathrin coated pit is formed on the surface of the cell membrane	Cytoskeleton proteins help the clathrin pit to deepen and eventually seal off, trapping the target molecules inside	Receptor proteins on the cell surface bind to the target molecules	A vesicle is now formed
B	A clathrin coated pit is formed on the surface of the cell membrane	Receptor proteins on the cell surface bind to the target molecules	Cytoskeleton proteins help the clathrin pit to deepen and eventually seal off, trapping the target molecules inside	A vesicle is now formed
C	Receptor proteins on the cell surface bind to the target molecules	A clathrin coated pit is formed on the surface of the cell membrane	Cytoskeleton proteins help the clathrin pit to deepen and eventually seal off, trapping the target molecules inside	A vesicle is now formed
D	Receptor proteins on the cell surface bind to the target molecules	Cytoskeleton proteins help the clathrin pit to deepen and eventually seal off, trapping the target molecules inside	A clathrin coated pit is formed on the surface of the cell membrane	A vesicle is now formed

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1 mark

Current research is making great advances in the therapeutic use of stem cells. Embryonic stem cells are delivering promising results in treating diseases such as Stargardt’s disease due to their unique characteristics.

Which of the following are not characteristics of embryonic stem cells?

They have the potential to develop into any type of tissue if taken within the first few days after fertilisation
They can be stimulated in a laboratory setting to develop into any specialised cell type
A small number remain in many tissues of the body, such as bone marrow, skin and the liver to replace damaged or dead cells
They can divide an unlimited number of times to produce a large number of cells that can become specialised

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1 mark

What does a potometer measure?

The rate of photosynthesis of a plant
The rate of water uptake of a plant
The rate of respiration of a plant
The rate of transpiration of a plant

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1 mark

The diagram below shows the heart and associated blood vessels.

screenshot-2023-07-12-at-9-14-40-pm

Which of the following would be correct for the flow of blood through the heart?

4 → 3 → 2 → 1
3 → 4 → 2 → 1
2 → 1 → 4 → 3
1 → 2 → 3 → 4

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1 mark

A student drew a diagrammatic representation of a transverse section of a plant stem based on what they saw using a light microscope. q5_9-1_transport_in_the_xylem_of_plants_ib_biology_hl_mcq

Identify the correct labels required for the drawing above.

	I	II	III	IV	V
A	Vascular bundle	Pith	Phloem	Cambium	Xylem
B	Phloem	Xylem	Vascular bundle	Cambium	Pith
C	Vascular bundle	Xylem	Pith	Cambium	Phloem
D	Vascular bundle	Cambium	Pith	Xylem	Phloem

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1 mark

Rigor mortis describes the stiffening of body muscles due to chemical change in myofibrils after death. Knowledge of the stages of rigor mortis allows pathologists to estimate the time of death accurately.

Algor mortis refers to the gradual decrease in the body's temperature after death.

The graph shows the onset of Rigor mortis and Algor mortis after death. 11-2_q5h

Which of the following options shows a valid explanation for the trends shown in the graph?

	Trend	Explanation
A	Body temperature decreases from 0 to 36 hours after death	Calcium is not replenished due to lack of ATP
B	Rigor mortis peaks at 12 hours after death	ATP is no longer available to break actin-myosin cross bridges
C	Body temperature increases slightly 36 hours after death	Energy is released from hydrolysis of the remaining ATP
D	Rigor mortis increases gradually after death	ATP becomes depleted so muscles cannot remain relaxed.

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1 mark

Which of the following statements about adaptations to abiotic factors is correct?

Some grasses are able to release chemicals that attract the predators of insect herbivore species.
Some grasses are adapted to increase the water vapour concentration gradient between their leaves and the surrounding air.
Mangroves are adapted to survive in an environment with limited fresh water availability.
Mangroves deal with low oxygen availability by absorbing oxygen from the atmosphere via their stomata.

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1 mark

The table below contains information about the dentition of three extinct hominid species. Note that 'pits' are deeper, larger regions of tooth wear than scratches.

Species	Dentition features
Australopithecus africanus	Small canine and incisor teeth and large molar and premolar teeth Fewer pits on the surface of fossilised teeth than on those of P. robustus
Paranthropus robustus	Large chewing muscles attached to the jaw Large molar and premolar teeth Both pits and scratches present on the surface of fossilised teeth Thick protective tooth enamel
Homo floresiensis	Molar teeth are reduced in size compared to other early hominids Smaller biting force than that calculated for Australopithecus

Which of the following conclusions can be drawn from the information in the table?

Australopithecus africanus consumed meat as an important part of its diet.
Paranthropus robustus had more seeds and nuts in its diet than Australopithecus africanus.
Homo floresiensis consumed more tough plant material than Australopithecus africanus.
Homo floresiensis had a similar diet to that of modern humans.

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1 mark

The following diagram shows the three stages involved in enzyme catalysis.

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Which of the following provides the most accurate description of the events occurring at each stage?

	1	2	3
A.	The substrate collides with the enzyme	New bonds are forming within the substrate molecule	Chemical substances are released from the enzyme
B.	The substrate collides with the active site of the enzyme	The substrate is bound to the active site of the enzyme	The products are released from the active site
C.	The substrate binds to the enzyme	New chemical substances are formed while attached to the enzyme	These substances are released from the enzyme
D.	The substate collides with the active site of the enzyme	The substrate changes into different chemical substances	The products are released from the active site

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1 mark

The rate of oxygen consumption was compared in yeast cells incubated with and without glucose at three different temperatures under aerobic conditions. The yeast cells were incubated for a period of 3 minutes during which the rate of O₂ consumption was measured with an O₂sensor.

biology-2-7-ib-hl-q6

What can be concluded from the results of this experiment?

Glucose affects the rate of oxygen consumption at higher temperatures less than it does at lower temperatures.
Rate of cell respiration increases with temperature.
Glucose is broken down faster at 55°C.
Yeast does not break down glucose at lower temperatures.

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1 mark

The following steps describe processes involved in oxidative phosphorylation.

Redox reactions drive the movement of protons across the cristae to the intermembrane space
Oxygen molecules combine with protons and electrons to form water
NADH and FADH donate electrons to the first transport protein in the chain
Hydrogen ions (protons) are also released as the coenzymes are oxidised
A high concentration of protons in the intermembrane space creates an electrochemical gradient
Electrons move down the proteins in a series of redox reactions
Protons move down the electrochemical gradient through enzyme ATP synthase

Which of the following shows the correct sequence for these steps?

1 → 4 → 6 → 2 → 5 → 7→ 3
3 → 4 → 6 → 1 → 5 → 7→ 2
3 → 6 → 1→ 5 → 7→ 2 → 4
6 → 3 → 5 → 7→ 2→ 4 → 1

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1 mark

In photosynthesis, the following reaction occurs:

2H₂O → 4e^- + 4H⁺ + O₂

What happens to the oxygen generated through this reaction?

It is converted into water.
It is incorporated into glucose molecules.
It is used in cellular respiration.
It diffuses out of the plant cell.

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1 mark

A group of scientists wanted to investigate insulin production in mice. They fed one group of mice with a normal diet and another group with a ‘high fat’ diet (containing a high level of both fat and sugar) for three weeks beforehand. They then measured their blood insulin levels after a meal. Their results are shown in Figure 2 below.

Figure 2. Graph to show insulin production over time in two different groups of mice.

Which of the following conclusions cannot be drawn from the data given?

Consuming a 'high-fat' diet leads to a significantly higher peak in blood insulin levels in mice.
Insulin production is faster for the normal diet group in the first 10 minutes after consuming a meal.
Insulin production drops more rapidly for the normal diet group between 30 and 90 minutes after a meal.
Between 30 and 90 minutes after a meal, there was approximately a 90% decrease in insulin levels in the blood for mice on a 'high-fat' diet.

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1 mark

The diagram below shows a sensory neurone connected to its associated receptor cells.

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Which best describes the function of the structure labelled A?

Contains most cellular structures
Acts as an electrical insulator
Transmit impulses to the spinal cord
Transmit and recieve impulses to other neurones

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1 mark

Which of A - D gives the most accurate description of how efflux pumps contribute to plant tropisms?

Efflux pumps pump low-density particles to the top of a horizontal root in order to initiate a positive gravitropism.
Light denatures PIN3 proteins which leads to fewer efflux pumps, and hence less cell elongation, on the sunny side of a plant shoot.
Efflux pumps are coded for by PIN3 genes and carry auxins from one cell to another in order to maintain an uneven distribution of auxins.
Efflux pumps carry auxins away from growing tissues on the removal of a stimulus, in order to maintain an even distribution of auxins.

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1 mark

Research was carried out into the emergence of antibiotic resistance in the antibiotics used to treat infection X between the years 2000-2016.

Different antibiotics were recommended during different time periods due to concerns about developing resistance. Note that ciprofloxacin is used to treat a range of infections and not just infection X, while tetracycline is not used to treat infection X but is used to treat many other mild infections.

Some of the results of the research are shown below.

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What conclusion can be drawn from these results?

Resistance evolves when the use of an antibiotic increases.
Ceftriaxone should be used to treat all infections.
Infection X should not be treated with antibiotics.
Tetracycline should no longer be used.

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1 mark

A water quality investigation was carried out after some cases of heavy metal poisoning were detected in a countryside village with a river running through it. The investigators were trying to establish if poisoning was worse on the north or the south of the river.

	North of the river	South of the river
Number of cases of heavy metal poisoning	26	12

The results from a chi-squared test were:

Chi-squared value:	5.2
Degrees of freedom:	1

Critical values table:

Degrees of Freedom	P = 0.05	P = 0.01	P = 0.001
1	3.83	6.64	10.83
2	5.99	9.21	13.82
3	7.82	11.35	16.27

What conclusions can be drawn from the information above?

The χ² value is greater than the critical value so there is an association between heavy metal poisoning and location
The χ² value is lower than the critical value so there is no association between heavy metal poisoning and location
Poisoning from heavy metals is worse in villages
Heavy metals are found in both locations, north and south of the river

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1 mark

The diagram below shows the stages of the carbon cycle.

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Which processes are shown in the diagram?

	I	II	III	IV
A	Fossilisation	Photosynthesis	Respiration	Decomposition
B	Decomposition	Absorption	Photosynthesis	Combustion
C	Decomposition	Absorption	Photosynthesis	Decomposition
D	Decomposition	Photosynthesis	Respiration	Combustion

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1 mark

Which statement can not be concluded from the DNA profile shown?

biology-q5-3-4-med-ib-hl

Parent 1 and parent 2 are profiles of unrelated individuals.
Children 3 and 5 are non-identical twins.
Child 4 is related to parent 1 but not parent 2.
Child 6 is unrelated to any of the other individuals.

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1 mark

During the elongation stage of translation the ribosome ‘translocates’ along the mRNA moving in a 5’ → 3’ direction.

What is the immediate effect of this directional movement?

The tRNA occupying the P site moves to the A site
The E site becomes free
The tRNA occupying the A site moves to the P site
The polypeptide chain is released from the ribosome

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1 mark

The risk of developing a cancerous tumour is increased by exposure to which of the following?

	Ultraviolet light	Benzo[a]pyrene	Carbon monoxide	X-rays
A.	✓	✓	✗	✓
B.	✓	✗	✗	✓
C.	✗	✓	✓	✗
D.	✓	✗	✓	✗

Key: ✓ = increases risk, ✗ = does not increase risk

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1 mark

The following choices each show a bivalent.

Along the length of the bivalent are some values of probability.

Which choice reflects the most likely probabilities of a chiasma forming at each of the positions shown?

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1 mark

Female embryos contain two copies of the X chromosome, even though they initially do not need both copies to be active. In order to avoid producing double the amount of polypeptides required, the paternal X chromosome is inactivated during the first few divisions after fertilisation. This is done by the methylation of lysine on different histones.

Which of the following provides the most accurate explanation of how this would inactivate the paternal X chromosome?

Adding a methyl group to lysine will maintain the negative charge to allow chromatin to become more condensed and inhibit transcription of the genes.
Adding a methyl group to lysine will maintain the positive charge to allow chromatin to become less condensed and inhibit transcription of the genes.
Adding a methyl group to lysine will maintain the positive charge to allow chromatin to become more condensed and promote transcription of the genes.
Adding a methyl group to lysine will maintain the positive charge to allow chromatin to become more condensed and inhibit the transcription of the genes.

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1 mark

The diagram below shows red blood cells that have been bathed in solutions of different solute concentration.

q2-1-3-cell-membrane-medium-ib-hl-biology

Which row of the table correctly describes the three solutions that these red blood cells have been bathed in?

	I	II	III
A.	Isotonic	Hypotonic	Isotonic
B.	Isotonic	Hypertonic	Hypotonic
C.	Isotonic	Hypotonic	Hypertonic
D.	Hypertonic	Hypotonic	Isotonic

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1 mark

The following graph shows the hormones involved in the menstrual cycle.

LZCpjq1u_1

Which line represents the hormone responsible for ovulation?

Line A
Line B
Line C
Line D

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1 mark

In a variety of roses, P is the allele for pink petal colour and D is the allele for double flower.

Which cross will give a 1:1:1:1 ratio of phenotypes in the offspring?

PpDd x ppDd
PpDd x PpDd
PPdd x ppDD
Ppdd x ppDd

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1 mark

The image below shows the appearance of the cells that line the collecting duct when a healthy human has high blood water content (A) and low blood water content (B). Note that aquaporins are transport proteins that allow the passage of water molecules. q8_11-3_the_kidney_osmoregulation_ib_biology_hl_mcq

Which of the following correctly explains the difference between the collecting duct cells of individual A and individual B?

There is more ADH in the blood of individual B.
There is less ADH in the blood of individual B.
Individual B has a longer loop of Henlé.
The collecting duct of individual B descends further into the medulla where the concentration gradient is steepest.

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1 mark

A game farm in South Africa has a population of about 5 000 large antelope called Kudu. Kudu bulls have large, spiralled horns which draw the attention of trophy hunters that frequently visit the game farm.

The antelope are all kept in a large, fenced-off area consisting of open grassland habitat.

Could this be considered an example of a stable gene pool?

No, since there will be a selective pressure to increase the allele frequency for antelope with large horns
No, since there will be a selective pressure for antelope with smaller horns
Yes, it is a large population of antelope with an equal chance to mate with each other
Yes, it is a large population located in a habitat that enables random matings between antelope of different phenotypes

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1 mark

Which of the statements relating to deforestation in the Amazon rainforest is correct?

Only a small area of rainforest is needed to sustain the cycle of transpiration and rainfall that maintains the ecosystem.
A region of rainforest with an area of 4 100 000 km² was reduced to an area of 3 855 000 km² over a ten year period, resulting in a percentage decrease of 6 %.
Scientists know the area of rainforest that needs to be maintained in order to avoid passing a tipping point in rainforest stability.
The Amazon rainforest will be able to recover even if deforestation continues until the stability tipping point is reached.

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