Syllabus Edition

First teaching 2014

Last exams 2024

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Sexual Reproduction (DP IB Biology: HL)

Exam Questions

3 hours35 questions
1a
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3 marks

The diagram below shows the structure of a mature human sperm cell.

structure-of-a-sperm-cell-sq

Identify structures A-C.

1b
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2 marks

Describe the role of structure A within the sperm cell shown in part a).

1c
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2 marks

A sperm cell is an example of a haploid cell.

(i)

Define the term haploid.

[1]

(ii)

Explain the importance of a sperm cell being haploid.

[1]

1d
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1 mark

Structure B in part a) assists with the process of fertilisation.

Identify the substances contained within structure B that assist with fertilisation.

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2a
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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.

2b
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2 marks

Describe what is happening to the structure identified in a) between steps 3 and 4 in the diagram in part a).

2c
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3 marks

Identify three similarities between the processes of oogenesis and spermatogenesis.

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3a
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2 marks

Humans are placental mammals.

Outline what is meant by the term placental mammal.

3b
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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.

3c
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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.

3d
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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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4a
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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.

4b
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1 mark

Event X involves a series of mechanisms that prevent polyspermy.

Define the term polyspermy.

4c
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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.

4d
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2 marks

Process Y is essential for pregnancy to occur.

Explain the importance of process Y

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5a
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4 marks

One mark is available for clarity of communication throughout this question.

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

5b
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7 marks

The process of childbirth occurs in several stages.

Outline the events that occur during childbirth.

5c
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4 marks

Draw an annotated diagram of a mature human ovum.

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1a3 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. 

1b3 marks

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

1c3 marks

Contrast the processes of spermatogenesis and oogenesis.

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2a3 marks

Compare and contrast internal and external fertilisation.

2b2 marks

Fertilisation in humans is followed by implantation of the blastocyst.

Outline the events that allow implantation to occur.

2c2 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.

2d2 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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3a3 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.

3b2 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.            

3c3 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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4a2 marks

The graph below shows levels of a synthetic oestrogen called ethinylestradiol at different sampling locations along a river. Note that a treatment plant treats sewage wastewater before releasing treated water back into a river.

q4a_11-4_sexual_reproduction_medium_ib_hl_biology_sq-png

Calculate the percentage increase in ethinylestradiol concentration between 1 km upstream of the treatment plant and the point of discharge from the treatment plant.

4b2 marks

One study investigated the effect of ethinylestradiol on reproduction in one species of fish. The researchers exposed fish in separate mesocosms to different concentrations of ethinylestradiol.

Explain why the scientists chose to carry out their investigation in mesocosms.

4c4 marks

The scientists measured the effect of changing ethinylestradiol levels on egg production and embryo formation in fish populations. Their results are shown in the graph below.  Note that the symbol * denotes a result that is significantly different from the control (0 ng L-1).q4c_11-4_sexual_reproduction_medium_ib_hl_biology_sq-png

A student read these results and concluded that ethinylestradiol was harmful to reproduction in fish.

Use all the information provided throughout Q4 to evaluate the student’s conclusion.

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5a4 marks

One mark is available for clarity of communication throughout this question.

Draw an annotated diagram of a mature human sperm cell.

5b5 marks

Describe the process of fertilisation in humans.

5c7 marks

Outline the process of oogenesis.

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1a
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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.

1b
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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.

1c
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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.

1d
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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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2a
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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.

2b
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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.

2c
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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.

2d
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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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3a
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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.

3b
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1 mark

Scientists measured the effect of changing ethinylestradiol levels on egg production and embryo formation in a species of fish. 

Use your knowledge of the effects of oestrogen pollution to suggest a hypothesis for this investigation.

3c
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2 marks

The results of the investigation described at part c) are shown in the graph below. Note that the symbol ∗ indicates a result that differs significantly from the control (0 ng L-1).

q4c_11-4_sexual_reproduction_medium_ib_hl_biology_sq-png

Suggest a possible explanation for the result obtained at an ethinylestradiol concentration of 11 ng L-1.

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4a
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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.

4b
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2 marks

Black bear mating season typically occurs from June to August but implantation of the blastocyst will only happen during November or December. Their cubs are born in January or February weighing between 250 and 400 grams and with very little fur covering their bodies. They are blind at this stage and rely on smell to locate their mother. 

Based on the information provided, suggest:

(i)

Why black bears are considered to be altricial.

[1]

(ii)

The benefit to the mother of the reproductive strategy described above.

[1]

4c
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2 marks

Large mammals are typically precocial with long gestation periods.

Explain the advantage of this strategy.

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5a
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3 marks

One mark is available for clarity of communication throughout this question.

Outline the role of the zona pellucida in an oocyte.

5b
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7 marks

Compare and contrast the processes of oogenesis and spermatogenesis

5c
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5 marks

Explain the advantages of internal fertilisation to terrestrial animals.

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