Biology  by Bradford
IB Biology 2025 · Theme D · Continuity and change

D3.1 Reproduction. Practice questions with markscheme.

53 original IB-style questions on D3.1, written from the 2025 guide: 25 multiple-choice, 16 short-answer, 5 data-based, 3 drawing, 2 extended-response part, 2 labelling. Below is a 21-mark standard-level practice paper built from them, ready to hand out as a class quiz or homework, or to sit yourself and mark against the scheme. Print it, project it, or build a fresh one on the same topic.

What the guide asks for

12 statements at SL and HL, 8 additional higher level.

  1. D3.1.1SL / HL Differences between sexual and asexual reproduction
  2. D3.1.2SL / HL Role of meiosis and fusion of gametes in the sexual life cycle
  3. D3.1.3SL / HL Differences between male and female sexes in sexual reproduction
  4. D3.1.4SL / HL Anatomy of the human male and female reproductive systems
  5. D3.1.5SL / HL Changes during the ovarian and uterine cycles and their hormonal regulation
  6. D3.1.6SL / HL Fertilization in humans
  7. D3.1.7SL / HL Use of hormones in in vitro fertilization (IVF) treatment
  8. D3.1.8SL / HL Sexual reproduction in flowering plants
  9. D3.1.9SL / HL Features of an insect-pollinated flower
  10. D3.1.10SL / HL Methods of promoting cross-pollination
  11. D3.1.11SL / HL Self-incompatibility mechanisms to increase genetic variation within a species
  12. D3.1.12SL / HL Dispersal and germination of seeds
  13. D3.1.13HL Control of the developmental changes of puberty by gonadotropin-releasing hormone and steroid sex hormones
  14. D3.1.14HL Spermatogenesis and oogenesis in humans
  15. D3.1.15HL Mechanisms to prevent polyspermy
  16. D3.1.16HL Development of a blastocyst and implantation in the endometrium
  17. D3.1.17HL Pregnancy testing by detection of human chorionic gonadotropin secretion
  18. D3.1.18HL Role of the placenta in foetal development inside the uterus
  19. D3.1.19HL Hormonal control of pregnancy and childbirth
  20. D3.1.20HL Hormone replacement therapy and the risk of coronary heart disease

In the bank for D3.1

  • 25 multiple-choice
  • 16 short-answer
  • 5 data-based
  • 3 drawing
  • 2 extended-response part
  • 2 labelling
  • 18 higher level only

Every question is original and tagged to a guide statement. See the whole bank →

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The practice paper

Take it on screen → Build a fresh paper Paper code BbB-EAAAAAAABBQAO8xA
Biology · topic quiz
Standard level · topic practice, not an exam format
30 minutes21 marks

Paper code: this paper was generated, so the code is its recipe. Enter it at biologybybradford.com/exam-maker to rebuild this exact paper and its markscheme.

Covers D3.1 Reproduction
Name:
1.

In vitro fertilization (IVF) typically involves which sequence?

[1]
  1. Hormonal stimulation → egg collection → in vitro fertilization → embryo transfer
  2. Egg collection → hormonal stimulation → embryo transfer → fertilization in the uterus
  3. Fertilization inside the body → egg collection → embryo freezing → embryo transfer
  4. Ovulation suppression → fertilization in the oviduct → egg collection → embryo transfer
2.

A pollen tube grows from structure II to an ovule in structure III and delivers a male nucleus. Which process is completed when the nuclei fuse?

[1]
IIIIIIIVpetalsepalfilamentstylereceptacleHalf of an insect-pollinated flower
  1. Pollination
  2. Fertilization
  3. Germination
  4. Seed dispersal
3.

Which statement about fertilization in humans is correct?

[1]
  1. It is internal, occurring normally in the oviduct
  2. It is external: the gametes fuse in fluid outside the body
  3. It occurs in the uterus, immediately after implantation
  4. It involves the fusion of many sperm nuclei with one egg nucleus
4.

Which hormone triggers ovulation around the middle of the menstrual cycle?

[1]
  1. Follicle-stimulating hormone falling to zero
  2. Progesterone from the corpus luteum
  3. A steady low level of oestradiol
  4. A surge of luteinizing hormone (LH)
5.

Many hermaphroditic flowers avoid self-pollination by maturing their anthers and stigmas at different times (protandry or protogyny). What does this mechanism promote?

[1]
  1. Faster development of seeds after fertilization
  2. Wind pollination instead of insect pollination
  3. Production of larger and longer-lasting flowers
  4. Cross-pollination between different individuals
6.

Many flowering plants produce both pollen and ovules in the same flower, yet are unable to fertilize themselves. Explain how self-incompatibility increases genetic variation within a plant species.

[3]
7.

Outline the advantages of sexual and of asexual reproduction.

[3]
8.

Outline the roles of meiosis and of the fusion of gametes in the sexual life cycle of humans.

[3]
9.

Outline what happens between fertilization of an ovule and the germination of a new plant.

[3]
10.

Outline the differences between male and female gametes in humans, relating each difference to its role.

[4]

Original practice questions © Biology by Bradford · CC BY-NC-SA 4.0 · Not affiliated with or endorsed by the International Baccalaureate Organization.
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Markscheme BbB-EAAAAAAABBQAO8xA

One mark per point; / separates alternative wording within a point, OR separates alternative answers, words in brackets are not required, underlined words are essential. OWTTE = or words to that effect.

1. D3.1.7 [1]
  • A: superovulation (FSH), harvesting, mixing with sperm (or ICSI) in vitro, then embryo transfer;
2. D3.1.8 [1]
  • B: pollination is only the transfer of pollen to the stigma; fertilization is the fusion of male and female gametes inside the ovule, producing the embryo;
3. D3.1.6 [1]
  • A: human fertilization is internal, normally in the oviduct, beginning with fusion of the sperm's cell membrane with the egg cell membrane; implantation happens days later, and only a single sperm participates — its nucleus enters the egg but the nuclei do not fuse (their membranes dissolve and the chromosomes join in a joint mitosis producing two diploid nuclei);
4. D3.1.5 [1]
  • D: high oestradiol triggers (positive feedback) a peak of LH, which causes ovulation (~day 14);
5. D3.1.10 [1]
  • D: temporal separation within the flower means its own pollen misses its own receptive stigma, so genetic variation from outbreeding is favoured;
6. D3.1.11 [3 max]
  • self-pollination / self-fertilization leads to inbreeding;
  • inbreeding decreases genetic diversity (more homozygosity) and (hybrid) vigour, OWTTE;
  • (genetic) self-incompatibility mechanisms prevent pollen from the same plant germinating / growing a pollen tube / fertilizing (e.g. pollen sharing an S-allele with the stigma is rejected);
  • so the male and female gametes that fuse (must) come from different plants / cross-fertilization is ensured;
  • combining alleles from two different parents produces new combinations of alleles / maintains variation in the population, OWTTE;

Accept 'outbreeding' for cross-fertilization. Do not accept 'prevents pollination' alone: pollen may land on the stigma but is prevented from achieving fertilization.

7. D3.1.1 [3 max]
  • sexual: generates genetic variation (meiosis + fertilization);
  • (variation) allows adaptation to changing conditions / disease resistance in populations;
  • asexual: rapid reproduction / no mate needed / all individuals can reproduce;
  • asexual preserves successful (well-adapted) genotypes in stable environments, OWTTE;
8. D3.1.2 [3 max]
  • meiosis (in the gonads/testes and ovaries) produces haploid gametes (n = 23);
  • fusion of gametes (fertilization) produces a diploid zygote (2n = 46), which develops (by mitosis) into the new individual;
  • (so) halving and doubling of the chromosome number alternate, keeping the number constant across generations;
  • meiosis (crossing over, random orientation) and the random fusion of gametes both generate genetic variation among the offspring, OWTTE;
9. D3.1.8, D3.1.12 [3 max]
  • the fertilized ovule develops into a seed (embryo + food store + seed coat);
  • the ovary (wall) develops into a fruit (around the seed);
  • the fruit/seed is dispersed away from the parent (wind/animals/water/explosive), reducing competition;
  • given suitable conditions (water, oxygen, warmth), the seed germinates and the embryo grows into a seedling, OWTTE;
10. D3.1.3 [4 max]
  • sperm are (very) small, whereas eggs are (much) larger, the egg stores food reserves/cytoplasm for the early embryo;
  • sperm are motile (flagellum), whereas the egg is non-motile (moved by the oviduct), sperm must travel to the egg;
  • sperm are produced in vast numbers (continuously), whereas (usually) one egg is released per cycle, many sperm compensate for losses on the journey;
  • sperm have many mitochondria (for swimming) and an acrosome (enzymes to penetrate the egg coat), whereas the egg has a zona pellucida and cortical granules (to control sperm entry);

Comparative phrasing expected; award converse statements.

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