Syllabus Edition

First teaching 2023

First exams 2025

|

Reproduction (HL IB Biology)

Exam Questions

4 hours68 questions
1a
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3 marks

The graph below shows changing testosterone levels in male and female humans from before birth until old-age. Note that the scale on the x-axis is not evenly distributed.

_d4gN0-r_e-3a

Compare and contrast the changes in testosterone levels for males and females.

1b
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1 mark

Label the graph in part a) with an X at roughly the point at which puberty begins in males.

1c
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2 marks

State two physiological changes that would occur in males at the point you have marked X on the graph in part a).

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2a
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1 mark

The process of reproduction is controlled by a series of hormones. The graph below shows changes in the levels of reproductive hormones A-D in females during a single menstrual cycle.

1-3

Identify, with a reason, the hormone represented by line A.

2b
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2 marks

Line C represents the hormone progesterone.

(i)

Identify the source of the hormone progesterone during the regular menstrual cycle.

[1]

(ii)

State one role of progesterone.

[1]

2c
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2 marks

A common treatment for fertility problems is in vitro fertilisation, or IVF. During IVF a woman will be given medication containing the hormone FSH.

Explain why medication containing FSH is administered during IVF.

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3
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4 marks

Draw a labelled diagram of the female reproductive system.

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4a
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2 marks

The diagram shows a human egg and three sperm cells at the moment of fertilisation. 9WOrJSD6_e-2a

Suggest why the egg is so much larger than one sperm, even though they carry the same amount of genetic information as each other. 

4b
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1 mark

State the number of chromosomes in a human egg. 

4c
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1 mark

Name the cell that forms when a sperm fertilises an egg. 

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5a
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1 mark

The following diagram shows the process of oogenesis in a human ovary.

oogenesis-in-the-ovary-sq

Identify the structure present at stage 2 in the diagram.

5b
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2 marks

Describe what is happening to the structure identified in a) between steps 3 and in the diagram in part a).

5c
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3 marks

Identify three similarities between the processes of oogenesis and spermatogenesis.

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6a
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2 marks

Humans are placental mammals.

Outline what is meant by the term placental mammal.

6b
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4 marks

The table below lists some of the substances that are transported across the placenta, as well as the names of some transport mechanisms.

Substance Transport mechanism
Carbon dioxide and oxygen  
Glucose  
Antibodies  
Water  

endocytosis             facilitated diffusion               diffusion              osmosis

Identify the transport mechanism for each of the substances by correctly matching them in the table.

6c
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1 mark

The placenta primarily consists of finger-like projections called placental, or chorionic, villi.

Suggest why the number of these villi increases throughout the course of a pregnancy.

6d
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2 marks

The placenta is also responsible for producing key pregnancy hormones.

(i)
Identify one hormone produced by the placenta.

[1]

(ii)

State the function of the hormone identified in part i).

[1]

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7a
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2 marks

The diagram below shows some of the events that can occur in the female reproductive system after ovulation.

Ovulation to implantation SQ

Identify the events occurring at X and Y in the diagram.

7b
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1 mark

Event X involves a series of mechanisms that prevent polyspermy.

Define the term polyspermy.

7c
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2 marks

One of the mechanisms that prevents polyspermy is known as the cortical reaction.

Describe the steps of the cortical reaction.

7d
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2 marks

Process Y is essential for pregnancy to occur.

Explain the importance of process Y

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8a
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4 marks

Describe the secretion and role of human chorionic gonadotropin (hCG) in early pregnancy.

8b
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7 marks

The process of childbirth occurs in several stages.

Outline the events that occur during childbirth.

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9a
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3 marks

The image below shows a bee feeding on nectar from a flower. 

(I)
Identify the small specks indicated X

bee-pollinating---sq

[1]

(II)
Explain how the flower benefits from feeding nectar to insects such as bees.

[2]

9b
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1 mark

State the name of the type of relationship that exists between the bee and the flower in part c) of this question.  

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10a
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2 marks

Gregor Mendel's landmark experiments on the basis of genetic inheritance, involved the flowering plant the sweet pea (Lathyrus odoratus). In these experiments, Mendel transferred the male sexual organs of certain plants to the female sexual organs of separate plants as a way of performing crosses.

Before completing the transfer, he cut away the male sexual organs of the recipient plants before the transfer.

Explain why. 

10b
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6 marks

The image below shows a flower. 

flower-to-label---sq

Label the parts A - F indicated. 

10c
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1 mark

State the name of the part of the flower shown in part b) that receives pollen during sexual reproduction. 

10d
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2 marks

State the principal purpose of the:

(i) Petals

(ii) Sepal 

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11a
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3 marks

The diagram below shows two types of seed; sycamore and dandelion.

Seeds dispersed by wind - SQ

State the method by which these seeds are dispersed and in each case, one adaptation of the seed that allows effective dispersal.  

11b
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2 marks

Seeds such as those shown in part a) are more effective if they can be dispersed far away from the parent plant.

Explain why. 

11c
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2 marks
The coco de mer is a seed that comes from a type of palm tree native to the Seychelles. Lodoicea maldivica is the species that produces the largest seeds known in nature. One such seed was found that had a mass of 25kg. To show the scale, a coco de mer seed is pictured below in the hands of a human. 

coco-de-mer-seed---sq

Suggest why some plants like the dandelion and sycamore have small, lightweight seeds whereas others produce huge seeds like the coco de mer. 

11d
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2 marks

Describe how seeds found in fruit such as apple pips are dispersed. 

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1a
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2 marks

The diagram shows the female reproductive system in front view2ot7_qMw_1

Identify structures 1 and 2.

1b
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1 mark

State the function of structure 3 from part (a).

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2a
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2 marks

In vitro fertilisation, known as IVF, involves fertilisation of a female egg outside of the human body. The hormones FSH and LH are used in IVF.

State the functions of FSH and LH in IVF.

2b
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2 marks

A fertility clinic investigated the effect of body mass index (BMI) on the outcome of the percentage of women who had successful implantation, became and remained pregnant, and were able to take home a healthy baby following IVF treatment.

Their results are shown in the graph below.

t9PtZI23_3

The clinic advised women with a BMI greater than 30kg/m² to lose weight before embarking on IVF treatment.

Use the data to explain why.

2c
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1 mark

State what is meant by the term superovulation.

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3a
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5 marks

Outline the events that occur, including the hormones involved, during days 14-28 of the menstrual cycle in the absence of fertilisation.

3b
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3 marks

The hormone oestrogen is involved in both positive and negative feedback loops within the menstrual cycle.

Explain how oestrogen functions in both positive and negative feedback within the menstrual cycle.

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4a3 marks

The image below shows a cross-section through a seminiferous tubule during spermatogenesis.

q1a_11-4_sexual_reproduction_medium_ib_hl_biology_sq

Identify the cells labelled A-C in the image. 

4b3 marks

Outline the events that take place between the formation of cells C and B labelled in part a).

4c3 marks

Contrast the processes of spermatogenesis and oogenesis.

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5a2 marks

Fertilisation in humans is followed by implantation of the blastocyst.

Outline the events that allow implantation to occur.

5b2 marks

Once implantation has occurred, part of the blastocyst develops into the placenta. The transfer of antibodies from mother to foetus at the placenta in several different species can be seen in the graph below.q2c_11-4_sexual_reproduction_medium_ib_hl_biology_sq-png

Contrast the changes in antibody concentration in the foetuses of humans and rats.

5c2 marks

Suggest, with a reason, which of the species in the graph shown in part c) will need the least maternal care from birth.

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6a3 marks

The graph below shows the relative levels of three hormones during pregnancy.q3a_11-4_sexual_reproduction_medium_ib_hl_biology_sq-png

Identify, with a reason, the hormone labelled X in the graph above.

6b2 marks

As the woman’s body prepares to give birth, a fourth hormone, oxytocin, has an important role.

Sketch what you might expect to happen to levels of oxytocin on the graph in part a).

Note that hormone Y in the graph in part a) is progesterone.            

6c3 marks

Oxytocin is part of a positive feedback loop during birth.

Outline the role of this positive feedback loop during birth.

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7a5 marks

Describe the process of fertilisation in humans.

7b7 marks

Outline the process of oogenesis.

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8
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2 marks

The life cycle of a flower involves a vegetative phase, during which the plant may be able to reproduce asexually, and a reproductive phase, during which sexual reproduction is possible.

Contrast asexual and sexual reproduction.

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9a
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2 marks

Explain why the relationship between flowering plants and pollinators can be considered mutualistic.

9b
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3 marks

The following diagram shows the reproductive parts of two flowers of the same species.

q2c_9-4_reproduction_in_plants_medium_ib_hl_biology_sq

   

Identify structures A to C and state how each contributes to the process of sexual reproduction in the plant.

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10a
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3 marks

Pollination is the first step in sexual reproduction in plants.

Describe the events that occur after a pollen grain lands on the stigma of a flower until fertilisation happens.

10b
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2 marks

The following table shows the number of honey bee colonies documented by a beekeeper on a farm from 2008 to 2018.

Year

Number of living colonies

2008

36

2010

34

2012

22

2014

23

2016

27

2018

21

 

Calculate the percentage decrease in bee colonies from 2008 to 2018.

10c
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3 marks

Suggest the impacts that a decline in pollinators would have on the wider ecosystem.

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11a
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2 marks

The following investigation was set up to determine the conditions needed for germination.

q4c_9-4_reproduction_in_plants_medium_ib_hl_biology_sq
           

Identify the control in this experiment and explain the importance of including this test tube in the investigation.

11b
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1 mark

Explain why no seeds would germinate if test tube D from the investigation at c) was placed in an environment with a temperature of 45°C.

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12
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3 marks

Outline the adaptations of seeds with different methods of seed dispersal in flowering plants.

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1a
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7 marks

Draw a labelled diagram of the male reproductive system.

1b
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8 marks

Describe the role of hormones in the regulation of the menstrual cycle.

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25 marks

Outline the process which occurs in a pregnancy test to give a positive test result.

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3a
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2 marks

A group of insects called flower thrips includes the species Frankliniella intonsa, as shown in the image below.

frankliniella-intonsa---sq

Adult F. intonsa flower thrips pollinate flowers of the genus Stellera in central and southern Asia. In return for the pollination it receives, Stellera provides sites for F. intonsa to lay their larvae (young).

State how this differs from a more conventional insect-flower mutualistic relationship. 

3b
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2 marks

Changes to abiotic conditions such as those caused by climate change can disrupt mutualism between pollinators and flowering plants. 

Suggest the consequences of extinction of a pollinator on other species. 

3c
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2 marks

A symbiotic relationship between two species is defined as any type of a close and long-term biological interaction between two different biological organisms.

The relationship between a bumblebee and the flowers it feeds from (and pollinates) is referred to as mutualistic.

Using this information, distinguish between symbiosis and mutualism.

3d
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1 mark

The best-documented examples of animal pollinators include bees and other insects. However, some larger animals are very active pollinators. 

One such animal is the honey possum (Tarsipes rostratus), a small marsupial native to southwestern Australia. Some of the pollen that a honey possum comes into contact with is used as a food, with all the available nutrients being used by the honey possum for its own dietary requirements.

honey-possum---sq

Suggest one adaptation, from the image above, of the honey possum that hints at its role as a pollinator. 

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4a
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3 marks

During pregnancy, the placenta releases several hormones into the bloodstream. The graph below shows the relative concentrations of three such hormones, namely corticotropin-releasing hormone (CRH), human placental lactogen (hPL) and relaxin.

1GGXeXXM_pregnancy-hormone-graph-sq

Contrast the changes in relative concentrations of hPL and relaxin.

4b
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2 marks

Recent studies suggest that CRH is involved with regulating the contractile properties of the myometrium.

With reference to the graph in part a) suggest, with a reason, the role of CRH in pregnancy.

4c
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2 marks

The hormone hPL affects several metabolic processes during the course of pregnancy. One such effect is that it decreases the response of the maternal cells to insulin.

Explain how high levels of hPL will benefit the growing foetus.

4d
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2 marks

The hormone relaxin will lead to an increase in renal blood flow during pregnancy.

Suggest why this increased blood flow is important during pregnancy.

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5a
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2 marks

Polycystic ovary syndrome (PCOS) is a common hormonal disorder in women aged 15 to 44. The diagram below shows the progression of oogenesis in the ovary of a person suffering from PCOS.

oogenesis-in-pcos-sq

Contrast the process of oogenesis in a person suffering from PCOS with someone who does not have the condition.

5b
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2 marks

Women suffering from PCOS will often have low levels of progesterone in their bloodstream.

Use the information in part a) to suggest why this is the case.

5c
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2 marks

Scientists investigated the link between PCOS in pregnant women and the risk of premature birth. The study was conducted in the maternity ward of a hospital and only women that had previously been diagnosed with PCOS were included in the PCOS group of the investigation. The results of the investigation are shown in the graph below.

preterm-birth-pcos-graph-sqpreterm-birth-pcos-graph-sq

Calculate the percentage difference between the PCOS and non-PCOS groups that delivered their babies between 32 and 35 weeks of pregnancy. Show your working.

5d
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3 marks

The scientists concluded that pregnant women suffering from PCOS will have an increased risk of premature birth.

Evaluate this conclusion.

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6
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2 marks

The graph below shows the relationship between body mass and gestation period for different species of mammals. 

body-size-vs-gestation-period-sq

The American black bear Ursus americanus is a large carnivore with an average body mass of 70 kg and a gestation period of 220 days.

Draw the data point for the black bear on the graph. Show your working.

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7a
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3 marks

Outline the role of the zona pellucida in an oocyte.

7b
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7 marks

Compare and contrast the processes of oogenesis and spermatogenesis

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8a
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4 marks

Outline the events that take place during the germination of a seed.  

8b
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2 marks

In exploring the effects of subjecting germinating seeds to different growth conditions, the following experiment was set up.  

Method summary:

  • Set up 4 test tubes, each containing cress seeds on cotton wool
  • For test tube A, cotton wool left dry
  • For test tube B, add enough water to the cotton wool so that it becomes moist
  • For test tube C, add enough water to cover the cotton wool and seeds, then carefully add a layer of oil on top of the water
  • For test tube D, add enough water to the cotton wool so that it becomes moist
  • Leave tubes A, B and C at room temperature or incubated at a specific temperature e.g. 20 °C
  • Place tube D in a fridge at approximately 4 °C
  • Compare the results and see which tube has the greatest number of germinated seeds

Factors affecting germination - SQ

Outline the control variables that the scientists would need to adhere to in order to produce valid data. 

8c
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1 mark

Rather than counting the number of seeds that had germinated at the end of the experiment, suggest a more accurate measure of the dependent variable. 

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9
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5 marks

Compare and contrast the methods employed by plants for pollen distribution and seed dispersal.  

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10
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3 marks

Research suggests that exposure to elevated levels of ethinylestradiol (synthetic oestrogen) in males leads to a significant decrease in the diameter of the seminiferous tubules, as well as fewer germinal epithelial cells.

Suggest the effect of these changes on spermatogenesis.

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