OCR GCSE Biology A: Hormones in contraception and fertility treatment, and plant hormones (J247) – Revision Notes

These notes condense statements B3.2e to B3.2i of module B3.2 in the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), for first assessment in 2018. Use the study guide for full explanations and worked examples. Bold statements in the specification are tested in the Higher Tier only: here that means B3.2f, B3.2i, and gibberellins and ethene in B3.2h. They are labelled “Higher Tier only”. Course pages: OCR GCSE Biology hub | checklist | practice questions | free 10-minute diagnostics.

Key terms

Term	Meaning
Contraception	Methods that reduce the chance of pregnancy
Perfect use	Method used correctly every time
Typical use	Real-life use, including mistakes and missed doses
Infertility	Inability to conceive naturally
IVF	Eggs fertilised in a laboratory dish, then embryos placed in the uterus (Higher Tier only)
Auxin	Plant hormone made in shoot and root tips; controls cell elongation
Tropism	Growth response to a stimulus, towards or away from it
Phototropism / gravitropism	Growth response to light / to gravity

B3.2e: Contraception (both tiers)

Hormonal methods

Method	Hormone(s)	Main action
Combined pill	Oestrogen and progesterone	Inhibit FSH, so no egg matures or is released
Progesterone-only pill	Progesterone	Thickens cervical mucus; may also stop ovulation
Implant, injection	Progesterone	Slow release over weeks or years
Patch	Both	Absorbed through skin
Hormonal coil (IUS)	Progesterone	Released locally in the uterus

Non-hormonal methods: condoms, diaphragm or cap, copper coil (IUD), natural family planning, vasectomy, female sterilisation, abstinence.

Method for evaluating (use every time)

1. Effectiveness: perfect against typical use.
2. Side effects and health risks.
3. Protection from infection (only condoms give some).
4. Convenience, reversibility and who must remember.
5. Personal, cultural and ethical views.
6. End with a judgement: which method suits which situation.

Calculation reminder. Expected pregnancies = users × (rate per 100) ÷ 100. For 300 pill users at 9 per 100: 300 × 9 ÷ 100 = 27. For 300 condom users at 18 per 100: 54. The difference is 54 − 27 = 27 pregnancies.

B3.2f: Treating infertility (Higher Tier only)

• Cause often linked to low FSH or LH, so eggs do not mature or ovulation does not occur.
• Fertility drugs: FSH and LH, or drugs that make the pituitary release more.
• FSH: eggs mature. LH: ovulation.

IVF in steps

1. FSH and LH given: several eggs mature.
2. Eggs collected.
3. Eggs and sperm mixed in a dish.
4. Embryos grown for a few days.
5. One or two placed in the uterus.
6. Progesterone often given to support the uterus lining.

Evaluation points. For: helps couples who cannot conceive otherwise. Against: cost, emotional and physical strain, success not guaranteed, multiple births if several embryos are placed, ovarian overstimulation, ethical views about unused embryos.

Success rate. Rate = live births ÷ cycles × 100. Example: 45 births from 150 cycles is 45 ÷ 150 × 100 = 30%.

B3.2g: Auxin and tropisms (both tiers)

Response	Where auxin collects	Effect on growth	Result
Shoot, light from one side	Shaded side	More elongation on shaded side	Bends towards light (positive phototropism)
Shoot on its side	Lower side	More elongation below	Grows up (negative gravitropism)
Root on its side	Lower side	High auxin inhibits elongation in roots	Grows down (positive gravitropism)

Key points

• Auxin is made in the tip and moves back to the elongating zone.
• Unequal distribution of auxin gives unequal growth, and unequal growth gives bending.
• Tip removed: no response. Tip covered: no response. Tip uncovered but lower part covered: response still happens.

B3.2h: Variety of effects

Hormone	Effects	Tier
Auxins	Cell elongation, so shoot growth	Both
Gibberellins	Stem growth; germination (enzymes break down stored food); can promote flowering	Higher Tier only
Ethene	Fruit ripening; shedding of leaves	Higher Tier only

Ripe fruit gives off ethene, a gas, which ripens fruit nearby: the reason one bad banana can spoil the bowl.

B3.2i: Uses of plant hormones (Higher Tier only)

Use	Hormone	How it works
Rooting powder	Auxin	Cuttings form roots, so many identical plants are made
Selective herbicide	Synthetic auxin	Broad-leaved weeds grow out of control and die; grasses and cereals survive
Seedless fruit	Auxin or gibberellin	Unpollinated flower develops a fruit without seeds
Ripening on demand	Ethene	Fruit picked green, ripened at destination
Altering dormancy	Gibberellins	End dormancy so seeds germinate together

Worked reminders

Data on bending. A shoot lit from one side bends 30°. With the tip removed, it does not bend. With a foil cap over the tip, it does not bend. With foil round the stem below the tip, it bends 28°. Say: the tip detects light and makes auxin, and the response happens below the tip. A cap on the tip blocks the light, so no signal is made unequally.

Choosing a method. A person wants contraception that works for three years without daily effort and has no wish to become pregnant in that time. Strong answer: name the implant; give its effectiveness (fewer than 1 pregnancy per 100 women per year); say it needs no daily action; give one drawback (changes in bleeding, no infection protection); conclude that it suits this person better than a pill that must be remembered each day.

Percentage change. (new − old) ÷ old × 100. Ripening time cut from 8 days to 5 days: (8 − 5) ÷ 8 × 100 = 37.5%.

Phrases worth learning

• “Hormones in the pill inhibit the release of FSH, so no egg matures.”
• “Progesterone thickens cervical mucus, so sperm cannot reach the egg.”
• “Auxin is unequally distributed, so cells on one side elongate more.”
• “In roots, a high concentration of auxin inhibits elongation.”
• “Synthetic auxins are selective: they affect broad-leaved weeds but not grasses.” (Higher Tier only)
• “Ethene is a gas, so it spreads to nearby fruit.” (Higher Tier only)

Command words in this topic

• Describe: say what happens, in order, without reasons.
• Explain: give the reason, linking cause and effect (for example, auxin moves, so cells elongate, so the shoot bends).
• Evaluate: weigh advantages against disadvantages, then give a judgement supported by evidence.
• Calculate: show the working and give the unit or “per 100” where it applies.
• Suggest: use your knowledge in a new context.

Must-know distinctions

• Shoot and root respond to the same auxin in opposite ways: high auxin promotes elongation in shoots and inhibits it in roots.
• Tropism is the response. Auxin is the hormone causing it.
• Perfect use is not typical use.
• Hormonal methods prevent pregnancy. Only condoms also reduce infection risk.
• FSH matures eggs. LH triggers ovulation.
• “Percentage points” for the difference between two percentages. “Percent” for a relative change.

Quick self-test

1. Name the two hormones in the combined pill.
2. Explain how the combined pill stops ovulation.
3. A clinic gives the contraceptive injection to 600 women. At 6 pregnancies per 100 women per year, how many pregnancies are expected in a year?
4. Give two reasons a person might choose condoms rather than the combined pill.
5. (Higher Tier only) State the job of FSH in IVF treatment.
6. (Higher Tier only) A clinic completes 150 IVF cycles and 45 lead to live births. Calculate the percentage success rate.
7. Where is auxin made in a shoot?
8. A seedling is lit from the left. On which side does auxin collect, and what does it do?
9. Explain why a root placed on its side curves downwards.
10. (Higher Tier only) Which gas ripens fruit, and which plant structure gets shed under its influence?
11. (Higher Tier only) A gardener dips 60 cuttings in rooting powder and 51 root. Calculate the percentage that rooted.
12. (Higher Tier only) Why does a lawn weedkiller kill dandelions but not grass?

Answers

1. Oestrogen and progesterone.
2. They hold back FSH, so follicles do not mature and no egg is released.
3. 600 × 6 ÷ 100 = 36 pregnancies.
4. Any two: protection from infection; no hormonal side effects; used only when needed; easy to obtain.
5. It stimulates several eggs to mature.
6. 45 ÷ 150 × 100 = 30%.
7. In the shoot tip.
8. The shaded (right) side. Cells on that side lengthen faster, so the stem curves toward the light.
9. Auxin collects on the lower side. High auxin inhibits elongation in roots, so the upper side grows faster and the root bends down.
10. Ethene; leaves.
11. 51 ÷ 60 × 100 = 85%.
12. The weedkiller is a synthetic auxin. Broad-leaved weeds respond with uncontrolled growth and die; narrow-leaved grasses largely do not.

Where marks are usually lost

• Describing the effect of a method but not saying how it works (for example, no mention of FSH).
• Evaluating with one-sided points. Give both an advantage and a limitation, then a judgement.
• Mixing perfect-use and typical-use figures in one comparison.
• Saying hormones in the pill “kill sperm”.
• Writing that auxin “makes the shoot grow towards light” without the unequal elongation.
• Using the same explanation for shoots and roots in gravitropism.
• Forgetting units or “per 100” in calculations of expected pregnancies.
• Calling ethene a liquid or a solid. It is a gas.
• Describing IVF as “putting sperm into the woman” rather than fertilisation in a dish.

Official syllabus

OCR, GCSE (9-1) Gateway Science Biology A (J247), specification Version 4.0 (August 2026), for first assessment in 2018. Published by OCR.