D3.1 Reproduction
Practice exam-style IB Biology questions for Reproduction, aligned with the syllabus and grouped by topic.
Question 1
In anisogamous species, what is the prime difference between male and female gametes?
A.
The female gamete contains no cytoplasm.
B.
The male gamete is diploid before fertilization.
C.
The male gamete travels to the female gamete.
D.
The female gamete is produced in larger numbers than sperm.
Question 2
What is the function of the epididymis in the human male reproductive system?
A.
Addition of fructose-containing fluid to semen
B.
Transfer of semen into the vagina
C.
Storage and maturation of sperm before ejaculation
D.
Production of testosterone and sperm
Question 3
A population of unicellular eukaryotes is well adapted to a stable pond environment. What reproductive process would most rapidly preserve its successful genotype in offspring?
A.
Fertilization after meiosis
B.
Sexual reproduction by fusion of gametes
C.
Cross-pollination between unrelated individuals
D.
Asexual reproduction by mitotic division
Question 4
What is the role of meiosis in a sexual life cycle?
A.
It produces haploid nuclei and breaks up parental allele combinations.
B.
It restores the diploid chromosome number in the zygote.
C.
It prevents mutation by copying chromosomes without recombination.
D.
It produces two diploid nuclei during the first division of the zygote.
Question 5
What distinguishes pollination from fertilization in flowering plants?
A.
Pollination produces gametes by meiosis; fertilization produces pollen grains.
B.
Pollination occurs inside ovules; fertilization occurs on anthers.
C.
Pollination is transfer of pollen to a stigma; fertilization is fusion of gametes in an ovule.
D.
Pollination is embryo formation; fertilization is seed dispersal.
Question 6
What occurs during seed germination?
A.
Pollen is transferred from anther to stigma.
B.
The embryo resumes growth using mobilized food reserves.
C.
The seed is moved away from the parent plant.
D.
A male gamete fuses with an egg cell.
Question 7
What hormonal change initiates the onset of puberty?
A.
Complete inhibition of steroid sex hormone secretion
B.
Increased pulsatile release of GnRH by the hypothalamus
C.
Secretion of hCG by the developing placenta
D.
Decreased secretion of LH and FSH by the pituitary
Question 8
What is a blastocyst?
A.
A hollow early embryo with an outer cell layer and an inner cell mass
B.
A mature follicle immediately before ovulation
C.
A sperm cell after the acrosome reaction
D.
A thickened region of the endometrium after menstruation
Question 9
What directly triggers ovulation in the human menstrual cycle?
A.
Maximum progesterone secretion by the corpus luteum
B.
A fall in follicle-stimulating hormone at menstruation
C.
Breakdown of the endometrium
D.
A surge in luteinizing hormone
Question 10
During human fertilization, what sperm component normally enters the egg and contributes to the embryo’s nuclear inheritance?
A.
The sperm tail
B.
The whole sperm cell as a permanent organelle
C.
The sperm mitochondria
D.
The sperm nucleus
Question 11
What is the usual outcome of meiosis from one primary spermatocyte in humans?
A.
Two diploid spermatogonia
B.
One haploid sperm and one large polar body
C.
Four haploid spermatids that differentiate into sperm
D.
One large egg and three polar bodies
Question 12
What is the effect of the cortical reaction after the first sperm fuses with a human egg?
A.
It hardens the zona pellucida and prevents additional sperm entry.
B.
It causes the sperm tail to enter the egg cytoplasm.
C.
It releases acrosomal enzymes from the sperm head.
D.
It stimulates meiosis in the sperm nucleus.
Question 13
What is detected by most urine pregnancy tests?
A.
LH using the acrosome reaction
B.
hCG using monoclonal antibodies
C.
Progesterone using enzyme substrates
D.
Oestradiol using placental villi
Question 14
What exchange process is mainly responsible for glucose movement from maternal blood to foetal blood across the placenta?
A.
Active contraction of the myometrium
B.
Osmosis through placental villi
C.
Facilitated diffusion across the placental barrier
D.
Exocytosis from foetal capillaries
Question 15
What creates positive feedback during childbirth?
A.
FSH stimulates follicles to secrete oestradiol.
B.
hCG maintains the corpus luteum until birth.
C.
Progesterone inhibits myometrium contraction throughout labour.
D.
Cervix stretching causes oxytocin release, which strengthens contractions and further stretching.
Question 16
The diagram shows a simplified male reproductive system.
State the function of the scrotum.
[1]
Outline the functions of the testis and seminal vesicle.
[1]
Question 17
In IVF treatment, hormone secretion is medically controlled.
State the purpose of suppressing the normal secretion of FSH and LH.
[1]
Outline how artificial hormone doses increase the chance of collecting eggs.
[1]
Question 18
Flowering plants reproduce sexually even when a flower is hermaphroditic.
Distinguish between pollination and fertilization.
[1]
State where the female gamete is found in a flower.
[1]
Question 19
A seed begins to germinate after water uptake.
State the first visible sign of germination in many seeds.
[1]
Outline the role of food reserves during germination.
[1]
Question 20
Puberty begins with changes in hypothalamic and pituitary hormone secretion.
State the hypothalamic hormone that increases at the onset of puberty.
[1]
Outline the sequence linking this hormone to secondary sexual characteristics.
[1]
Question 21
After fertilization, the early human embryo forms a blastocyst before implantation.
State two structural features of a blastocyst.
[1]
State where implantation occurs.
[1]
Question 22
The table shows responses of patients undergoing IVF after different daily doses of artificial FSH.
| FSH dose / IU day^-1 | Mature follicles / mean no. | Eggs collected / mean no. | Excessive response / % cycles |
|---|---|---|---|
| 75 | 6.1 | 4.8 | 1 |
| 150 | 9.8 | 8.2 | 4 |
| 225 | 12.4 | 10.6 | 11 |
| 300 | 13.1 | 11.0 | 22 |
State the dependent variable that indicates the strongest ovarian response.
[1]
Describe the effect of increasing FSH dose on ovarian response.
[1]
Suggest why using the highest possible FSH dose may not always be appropriate.
[1]
Question 23
The table summarizes cell products from gametogenesis in typical human ovaries and testes.
| Process | Functional gametes / cell | Polar bodies / cell | Cytoplasm distribution |
|---|---|---|---|
| Spermatogenesis | 4 | 0 | Shared almost equally among 4 sperm |
| Oogenesis | 1 | 2–3 | Most retained in the ovum; little in polar bodies |
Calculate the ratio of functional gametes produced from one primary spermatocyte to one primary oocyte.
[1]
Compare cytoplasm distribution in the two processes.
[1]
Suggest one reason why oogenesis produces one large functional gamete.
[1]
Question 24
Early epidemiological studies found lower CHD incidence among women using HRT, but later randomized controlled trials found a small increase in CHD risk. What best explains why the early correlation was misleading?
A.
Socioeconomic status was a confounding variable associated with CHD risk.
B.
All epidemiological correlations are false.
C.
Randomized trials cannot test cause-and-effect relationships.
D.
HRT cannot affect steroid hormone concentrations.
Question 25
The graph shows relative concentrations of four hormones during a 28-day menstrual cycle.
Identify the hormone that surges at about day 14.
[1]
Explain how changes in oestradiol concentration can cause negative and positive feedback on pituitary secretion.
[1]
Question 26
A hermaphroditic plant species rarely self-fertilizes because its pollen is released before its stigma becomes receptive.
Name this method of promoting cross-pollination.
[1]
Suggest why cross-pollination can increase vigour in offspring.
[1]
Question 27
In a self-incompatible plant, pollen tubes from genetically similar plants stop growing in the style.
State what is meant by self-incompatibility.
[1]
Explain how self-incompatibility can increase genetic variation within a species.
[1]
Question 28
After a sperm fuses with a human egg, a diploid embryo is produced.
State which sperm structures are normally not inherited as functional parts of the embryo.
[1]
Explain how the first mitotic division produces two diploid nuclei.
[1]
Question 29
Compare spermatogenesis and oogenesis in humans.
State one process common to both forms of gametogenesis.
[1]
Compare the numbers of functional gametes and the distribution of cytoplasm produced from one meiotic cell.
[1]
Question 30
The zona pellucida acts as a barrier during fertilization.
Outline the acrosome reaction.
[1]
Explain how the cortical reaction prevents polyspermy.
[1]
Question 31
A urine pregnancy test strip contains mobile dye-labelled antibodies and immobilized antibodies.
State the hormone detected by the test.
[1]
Explain why a coloured test band forms only when this hormone is present.
[1]
State the purpose of the control band.
[1]
Question 32
The placenta allows exchange between maternal and foetal blood without normal mixing of the two blood supplies.
State the function of placental villi.
[1]
Explain two exchange processes that occur across the placental barrier.
[1]
State one substance that moves from foetus to mother.
[1]
Question 33
Hormone concentrations change from early pregnancy to childbirth.
Explain how progesterone maintains pregnancy.
[1]
Explain how oxytocin secretion increases during childbirth.
[1]
Question 34
The graph shows mean concentrations of four hormones during one menstrual cycle.
Identify the day on which ovulation is most likely to occur.
[1]
Describe the change in progesterone concentration after ovulation.
[1]
Explain how the high pre-ovulatory oestradiol concentration leads to ovulation.
[1]
Question 35
Students investigated the effect of release height on the dispersal distance of winged seeds.
Identify the independent and dependent variables.
[1]
Describe the relationship shown by the graph.
[1]
Suggest two variables that should be controlled to make the investigation valid.
[1]
Question 36
Researchers compared two flower forms of the same plant species: one with nectaries close to the anthers and stigma, and one with nectaries farther from them.
| Nectary position | Mean pollen deposited / grains per stigma | Mean seed set / seeds per flower |
|---|---|---|
| Near anther and stigma | 56 | 38 |
| Distant from anther and stigma | 24 | 21 |
State which flower form is expected to have higher pollen transfer by insects.
[1]
Use the data to describe the effect of nectary position on seed set.
[1]
Suggest how insect visits form a mutualistic relationship with the plant.
[1]
Question 37
The graph shows mean hormone concentrations during childhood and puberty.
Identify the first hormone in the pathway that increases at the onset of puberty.
[1]
Describe the relationship between gonadotropins and steroid sex hormones in the graph.
[1]
Explain how the hormonal pathway produces developmental changes of puberty.
[1]
Question 38
The figure shows results from urine pregnancy test strips for four samples.
| Sample | Control band | Test band |
|---|---|---|
| A | Present | Present |
| B | Present | Absent |
| C | Present | Present |
| D | Absent | Present |
Deduce which sample or samples contain detectable hCG.
[1]
Identify any invalid test result and give a reason.
[1]
Explain why monoclonal antibodies are suitable for detecting hCG.
[1]
Question 39
An early observational study found that women using HRT had lower incidence of coronary heart disease (CHD) than non-users.
State why this observation alone does not prove causation.
[1]
Explain how randomized controlled trials changed the interpretation of the relationship between HRT and CHD.
[1]
Question 40
The table shows pollen tube growth after pollen from three donor plants was placed on stigmas of three recipient plants of a self-incompatible species.
| Recipient | Donor A | Donor B | Donor C |
|---|---|---|---|
| Plant A | No growth | Full growth | Short growth |
| Plant B | Full growth | No growth | Full growth |
| Plant C | Short growth | Full growth | No growth |
Identify one donor-recipient combination that is compatible.
[1]
Identify the evidence that self-pollen is rejected.
[1]
Explain how the pattern in the table can increase genetic variation.
[1]
Question 41
The graph shows rates of exchange across placental villi as villus surface area changes.
Describe the effect of villus surface area on oxygen transfer rate.
[1]
Explain why placental villi increase exchange while maternal and foetal blood do not normally mix.
[1]
Suggest the exchange processes for oxygen and antibodies across the placental barrier.
[1]
Question 42
Distinguish between asexual and sexual reproduction.
[1]
Discuss how meiosis and fertilization contribute to continuity and change in sexually reproducing populations.
[1]
Question 43
Outline the roles of anther, stigma, style, ovary and ovule in flowering plant reproduction.
[1]
Explain how insect-pollinated flowers and cross-pollination mechanisms promote sexual reproduction with genetic variation.
[1]
Question 44
The table compares evidence from an early epidemiological study and a later randomized controlled trial on HRT and coronary heart disease (CHD).
| Study | Design | HRT allocation | Mean SES HRT / 100 | Mean SES no HRT / 100 | CHD risk ratio HRT:no HRT |
|---|---|---|---|---|---|
| Early study | Observational cohort | Chosen with doctor | 72 | 54 | 0.55 |
| Later study | Randomized trial | Random assignment | 61 | 60 | 1.08 |
State the apparent relationship between HRT use and CHD in the epidemiological study.
[1]
Compare the conclusion from the randomized controlled trial with the epidemiological study.
[1]
Evaluate why the randomized controlled trial provides stronger evidence for causation.
[1]
Question 45
Outline the main ovarian and uterine events in a menstrual cycle when pregnancy does not occur.
[1]
Explain the hormonal regulation of these events by FSH, LH, oestradiol and progesterone.
[1]
Question 46
Outline the key events of human fertilization from sperm-egg contact to the entry of the sperm nucleus.
[1]
Explain how IVF uses hormonal control and fertilization procedures to increase the chance of pregnancy.
[1]
Question 47
Outline the hormonal sequence that initiates puberty.
[1]
Compare and contrast spermatogenesis and oogenesis in humans, including how each process supports reproductive function.
[1]
Question 48
Outline why polyspermy must be prevented in humans.
[1]
Explain the mechanisms that allow one sperm to fertilize an egg and then prevent further sperm entry, and describe the development to implantation.
[1]
Question 49
Outline how the placenta enables exchange while separating maternal and foetal blood.
[1]
Discuss hormonal control of pregnancy maintenance and childbirth.
[1]
Question 50
Explain how a pregnancy test detects hCG in urine.
[1]
Evaluate the use of epidemiological correlations and randomized controlled trials in assessing whether HRT affects coronary heart disease risk.
[1]
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