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

This guide covers statements B3.2e to B3.2i of module B3.2 (Coordination and control: the endocrine system) in the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), for first assessment in 2018. In the specification, B3.2f and B3.2i are in bold, and so is the part of B3.2h on gibberellins and ethene. Those parts are tested in the Higher Tier papers only and are labelled “Higher Tier only” below. B3.2e, B3.2g and the auxin part of B3.2h are for both tiers. The hormones of the menstrual cycle (B3.2a to B3.2d) are in a separate guide.

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What this unit covers

Statement	What you must be able to do	Tier
B3.2e	Explain how hormones are used in contraception; evaluate hormonal and non-hormonal methods, including their relative effectiveness	Both
B3.2f	Explain how hormones are used in modern reproductive technologies to treat infertility	Higher Tier only
B3.2g	Explain how plant hormones control growth, including unequal distribution of auxin in phototropism and gravitropism	Both
B3.2h	Describe effects of plant hormones: auxins (growth) for both tiers; gibberellins and ethene, with germination, ripening, flower opening and leaf shedding, Higher Tier only	Both / Higher
B3.2i	Describe how people use plant hormones: selective herbicides, root cuttings, seedless fruit, altering dormancy	Higher Tier only

B3.2e: Hormones in contraception (both tiers)

Contraception lowers the chance of pregnancy. Some methods use hormones. Others do not.

How hormonal methods work. The combined pill contains oestrogen and progesterone. Taken every day, it keeps the levels of both hormones in the blood fairly high. High oestrogen and progesterone inhibit the release of FSH from the pituitary gland. Without FSH, follicles do not mature and no egg is released, so there is nothing for sperm to fertilise. Progesterone also thickens the mucus at the cervix, which makes it harder for sperm to pass. The progesterone-only pill relies mainly on this mucus effect, and for some women it also stops ovulation.

Other hormonal methods deliver progesterone (or both hormones) in a different way. The injection and the implant release progesterone slowly for weeks or years. The patch is worn on the skin and releases both hormones. The hormonal coil (IUS) sits in the uterus and releases progesterone locally.

Non-hormonal methods.

• Barrier methods: male and female condoms and the diaphragm or cap stop sperm meeting the egg. Only condoms also reduce the risk of sexually transmitted infections.
• Copper coil (IUD): placed in the uterus, it makes the uterus unwelcoming to sperm and to a fertilised egg.
• Natural family planning: not having sex around the time an egg may be present.
• Surgical methods: vasectomy blocks the sperm ducts; female sterilisation blocks the oviducts. They are intended to be permanent.
• Abstinence: not having sex at all is the only method that is completely effective.

Comparing effectiveness

Effectiveness depends on how the method is used. “Perfect use” means every time, exactly as instructed. “Typical use” includes missed pills and condoms that slip or tear. Methods that need no daily action (implant, coil) have a small gap between the two. Approximate typical-use figures, in the style of public health information, are below. Exact values differ between sources.

Method	Approx. pregnancies per 100 women in one year (typical use)
Combined pill	9
Contraceptive injection	6
Male condom	18
Implant or coil	fewer than 1

Worked example 1. A clinic expects 250 couples to rely on male condoms for a year (typical use, 18 per 100) and a similar group of 250 to use the combined pill (9 per 100).

• Condoms: 250 × 18 ÷ 100 = 45 pregnancies.
• Pill: 250 × 9 ÷ 100 = 22.5, so about 23 pregnancies.
• Difference: 45 − 22.5 = 22.5, so about 23 more with condoms.
• If condoms were used perfectly (2 per 100), the figure would be 250 × 2 ÷ 100 = 5. The gap between 45 and 5 shows how much human error matters.

Evaluating methods

A good evaluation weighs several factors and reaches a judgement. Use these:

1. Effectiveness, under both perfect and typical use.
2. Side effects. Hormonal methods can cause headaches, mood changes, breast tenderness or changes in bleeding. The combined pill carries a small increased risk of blood clots for some women. Early pills had a higher oestrogen dose and more side effects, so doses were lowered.
3. Protection from infection. Hormones give none. Condoms give some.
4. Convenience and reversibility. A daily pill is easy to forget. Sterilisation is hard to reverse. Most other methods are reversible, though fertility may take a little time to return.
5. Personal, cultural, religious or ethical views, and access to advice.

Example judgement. For someone unlikely to remember a daily tablet, the implant suits better than the pill: fewer than 1 pregnancy per 100 compared with 9, and no daily action. It gives no protection from infection, so condoms may still be needed.

B3.2f: Hormones to treat infertility (Higher Tier only)

Infertility means a couple cannot conceive naturally. A common cause is that a woman does not ovulate regularly, because her FSH and LH levels are too low.

Fertility drugs. Giving FSH and LH (or drugs such as clomifene that make the pituitary release more of them) stimulates follicles to mature and eggs to be released. FSH stimulates eggs to mature. LH triggers ovulation.

IVF (in vitro fertilisation). In IVF, eggs are fertilised outside the body (“in vitro” means in glass).

1. The woman is given FSH and LH so that several eggs mature at once, instead of the usual one.
2. The eggs are collected and mixed with sperm in a dish in the laboratory.
3. The fertilised eggs develop into tiny embryos for a few days.
4. One or two healthy embryos are placed in the uterus.
5. Progesterone is often given afterwards, to keep the lining of the uterus ready for implantation.

Worked example 2 (interpreting data). A clinic reports: 240 IVF cycles for women under 35 produced 78 live births; 160 cycles for women aged 40 and over produced 18.

• Under 35: 78 ÷ 240 × 100 = 32.5%.
• 40 and over: 18 ÷ 160 × 100 = 11.25%, about 11.3%.
• Difference: 32.5 − 11.25 = 21.25 percentage points. Say “percentage points”, not “percent”, for a difference between two percentages.
• Conclusion: success per cycle is much lower in the older group. This is one clinic’s data, so it shows a pattern but not the cause.

Evaluating IVF. Advantages: it can help couples who could not otherwise have a child. Disadvantages: it can be expensive, stressful and physically demanding; success is not guaranteed; transferring more than one embryo raises the chance of twins or triplets, which carry higher risks; strong doses of fertility hormones can overstimulate the ovaries; some people have ethical concerns about embryos that are not used.

B3.2g: Plant hormones, auxin and tropisms (both tiers)

Plant hormones are chemicals that regulate growth and development. Auxins are made in the tips of shoots and roots. They spread through the plant to the region behind the tip, where they cause cells to elongate (grow longer). Plants respond to a stimulus by growing towards or away from it. These growth responses are tropisms.

Phototropism

Phototropism is growth in response to light. A shoot tip grows towards light, which is positive phototropism.

1. Light shines on a shoot from one side.
2. Auxin moves to the shaded side, so the auxin is unequally distributed.
3. In shoots, more auxin means more cell elongation, so cells on the shaded side lengthen more than those on the lit side.
4. The shoot bends towards the light.

Gravitropism (geotropism)

Gravitropism is growth in response to gravity.

• A shoot placed on its side: auxin collects on the lower side, those cells elongate more, and the shoot curves upwards. This is negative gravitropism.
• A root placed on its side: auxin also collects on the lower side, but in roots a high auxin concentration inhibits elongation. The upper cells elongate more, and the root curves downwards. This is positive gravitropism, and it anchors the plant and takes roots towards water.

Worked example 3 (experiment). Five seedlings are lit from the right. Their final angles of bending are 34°, 41°, 38°, 36° and 41°. Mean angle = (34 + 41 + 38 + 36 + 41) ÷ 5 = 190 ÷ 5 = 38°. When the tips are cut off, there is no bending. When the tips are covered with foil, there is no bending. When foil covers only the section below the tip, bending still happens (mean 36°).

• Conclusion: the tip detects the light and produces the signal, and the signal passes to the lower region where bending happens.
• Measurements show the shaded side grew 6.0 mm in a day and the lit side 3.5 mm. The shaded side grew 2.5 mm more, which is (6.0 − 3.5) ÷ 3.5 × 100 = 71% more. This supports the explanation of unequal growth.

Worked example 4 (root). A root lies horizontally. Over 8 hours the upper side lengthens by 2.0 mm and the lower side by 1.2 mm. The lower side lengthened by (2.0 − 1.2) ÷ 2.0 × 100 = 40% less. The upper side grows faster, so the root bends downwards.

B3.2h: Effects of plant hormones

• Auxins (both tiers): controlling growth. They promote elongation of cells in the stem, as above.
• Gibberellins (Higher Tier only). They promote stem growth. They also help seeds to germinate: the seed takes in water, gibberellins are released, and they stimulate the production of enzymes that break down the seed’s stored food to supply the growing embryo. In some plants they also promote flowering and flower opening.
• Ethene (Higher Tier only). This gas ripens fruit: it triggers the breakdown of starch to sugar, softening and colour change. Ethene also promotes the shedding of leaves, which is why autumn leaf fall involves it. A ripe fruit gives off ethene, which can ripen fruit nearby. This is why one bad banana can spoil the bowl.

Worked example 5. Green bananas ripen in 7 days alone. Placed with an over-ripe banana, they ripen in 3 days. Reduction = (7 − 3) ÷ 7 × 100 = 57%. Explanation: the ripe banana releases ethene, a gas, which reaches the others and speeds up ripening.

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

• Rooting powder. The cut end of a stem cutting is dipped in powder containing auxin, which stimulates roots to grow, so many identical plants can be produced quickly.
• Selective herbicides. Synthetic auxins are sprayed on lawns and cereal fields. They make broad-leaved weeds grow too fast in an uncontrolled way, and the weeds die. Narrow-leaved plants such as grasses and cereals are largely unaffected. The weedkiller therefore kills one group and spares the other.
• Seedless fruit. Spraying unpollinated flowers with auxin or gibberellin makes the ovary develop into a fruit without fertilisation. The fruit has no seeds (parthenocarpic fruit).
• Ripening. Growers pick fruit green, which is hard and travels without bruising, then expose it to ethene at their destination so that it ripens on time.
• Altering dormancy. Gibberellins can end the dormancy of seeds, so they germinate together when wanted.

Worked example 6. A lawn plot of 2.5 m² contains 48 broad-leaved weeds per m². After spraying, 6 per m² remain. Fall = (48 − 6) ÷ 48 × 100 = 87.5%. Weeds in the plot fell from 120 to 15. Grass survives, so the herbicide is selective.

Common errors

• Forgetting that roots respond to the same auxin in the opposite way to shoots.
• Saying hormonal contraception protects against infection.
• Confusing the role of FSH (eggs mature) with LH (ovulation) in fertility treatment.
• Giving a difference between percentages as “percent” rather than “percentage points”.

Continue with the practice questions or condense with the revision notes.

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.