Reproduction and fertility | AQA GCSE Biology Notes

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The key idea

Hormones coordinate the menstrual cycle.Fertility treatments can alter hormone levels to stimulate egg maturation and release.

Hormones in the menstrual cycleFour hormones coordinate egg maturation, ovulation and the uterus lining.

Revision notes

The bit that matters

Learn the process in clean chunks. If a sentence explains a cause, make sure you can say the effect too.

The menstrual cycle

The menstrual cycle is controlled by four hormones.FSH from the $pit$ uitary gland causes an egg to mature in the ovary and stimulates oestrogen production.Oestrogen builds up the uterus lining and triggers a surge in LH.LH from the $pit$ uitary causes ovulation, the release of the egg, and progesterone from the ovary maintains the uterus lining in the second half of the cycle.

Hormonal contraception

Hormonal methods of contraception prevent pregnancy.Oral contraceptives contain hormones such as oestrogen and progesterone that inhibit FSH production so no eggs mature.Other methods include injections, implants and patches that slowly release progesterone, which thickens cervical mucus and inhibits egg maturation and release.

Treating infertility

If a woman does not produce enough FSH and LH her eggs may not mature, so these hormones can be given as a fertility drug to stimulate ovulation.In vitro fertilisation, or IVF, involves giving FSH and LH to mature several eggs, collecting them, fertilising them with sperm in the laboratory and inserting one or two embryos into the uterus.IVF is emotionally and physically stressful and success rates are not high.

Adrenaline and thyroxine

Adrenaline is produced by the adrenal glands in times of fear or stress and increases heart rate, boosting oxygen and glucose delivery to muscles for fight or flight.Thyroxine from the thyroid gland regulates the basal metabolic rate and is important for growth and development.Thyroxine is controlled by negative feedback so that its level stays roughly constant.

Key terms

Definitions to learn

FSH

Follicle stimulating hormone from the $pit$ uitary that matures an egg and stimulates oestrogen.

LH

Luteinising hormone from the $pit$ uitary that triggers ovulation.

Oestrogen

An ovary hormone that builds the uterus lining and triggers an LH surge.

Progesterone

An ovary hormone that maintains the uterus lining.

Ovulation

The release of an egg from the ovary, around day 14 of the cycle.

IVF

In vitro fertilisation, where eggs are fertilised outside the body and an embryo is implanted.

Worked example

Explain the roles of FSH and LH in the menstrual cycle.

FSH causes an egg to mature in an ovary.

LH triggers ovulation.

The hormones act at different stages of the cycle.

Final answer

FSH matures an egg; LH triggers its release.

Exam habit

Name the specific hormone, its source gland and its target organ.For the menstrual cycle, state at which stage each hormone peaks.'Hormones control reproduction' alone scores nothing — be precise.

Watch out

Do not confuse ovulation with menstruation.

Examiner tips

How to score full marks

1Learn the role of each of the four hormones and the order in which they act across the cycle.
2For contraception, link the hormone to its effect, for example progesterone thickens cervical mucus and inhibits egg release.
3When evaluating IVF or contraception, give balanced points covering both benefits and drawbacks.

Practice questions

Try these yourself

Open each answer only after you have explained the full biological process.

1State one role of oestrogen.

Mark scheme

1.Think uterine lining or FSH control.

It rebuilds the uterus lining and inhibits FSH while stimulating LH.

2How can IVF help a couple conceive?

Mark scheme

1.Outline fertilisation and implantation.

Eggs are fertilised outside the body and embryos are transferred into the uterus.

3Give one ethical issue linked to IVF.

Mark scheme

1.Consider unused embryos or access.

Possible issues include unused embryo disposal, genetic screening or unequal access.

4Name the hormone that causes an egg to mature in the ovary.[1 mark]

Mark scheme

1.Recall the $pit$ uitary hormone that starts the cycle.

FSH or follicle stimulating hormone (1)

5What is ovulation?[1 mark]

Mark scheme

1.State what is released and from where.

The release of an egg from the ovary (1)

6Describe the role of oestrogen in the menstrual cycle.[2 marks]

Mark scheme

1.State its effect on the uterus and on LH.

Oestrogen causes the lining of the uterus to build up or thicken (1); and it stimulates the release of LH (1)

7Explain how the oral contraceptive

pil

l prevents pregnancy.[3 marks]

Mark scheme

1.Link the hormones to FSH and egg maturation.

The

pil

l contains oestrogen and or progesterone (1); these inhibit the production of FSH (1); so no eggs mature or are released (1)

8A couple are unable to conceive because the woman produces too little FSH and LH. Describe how IVF could be used to help them have a baby, and give one drawback of the treatment.[5 marks]

Mark scheme

1.Describe the IVF steps.
2.Give a balanced drawback.

FSH and LH are given to stimulate the maturation of several eggs (1); the eggs are collected and fertilised by sperm in the laboratory (1); the fertilised eggs develop into embryos (1); one or two embryos are inserted into the uterus (1); a drawback is that it is physically and emotionally stressful, or success rates are low (1)

9Explain why progesterone levels are high during the second half of the menstrual cycle and what happens when they fall.[4 marks]

Mark scheme

1.Link progesterone to maintenance of the uterus lining.
2.State the consequence of falling levels.

After ovulation the follicle produces progesterone (1); progesterone maintains the thickened uterus lining ready for implantation of an embryo (1); if fertilisation does not occur, progesterone levels fall (1); the uterus lining breaks down and menstruation occurs (1).

10State two advantages and two disadvantages of using the contraceptive

pil

l compared to a barrier method such as a condom.[4 marks]

Mark scheme

1.Consider effectiveness, convenience and health effects.
2.Consider protection against STIs.

Advantages: highly effective at preventing pregnancy if taken correctly (1); does not interrupt intercourse (1). Disadvantages: does not protect against sexually transmitted infections (1); may cause side effects such as mood changes or blood clots in some users (1).

11Explain the role of negative feedback in regulating thyroxine levels in the blood.[4 marks]

Mark scheme

1.Describe what happens when thyroxine rises.
2.Explain how this is an example of negative feedback.

When thyroxine concentration rises, this is detected by the

pit

uitary gland (1); the

pit

uitary reduces its release of TSH (thyroid stimulating hormone) (1); less TSH means the thyroid gland produces less thyroxine (1); the level falls back towards normal, completing the negative feedback loop (1).

12Evaluate the use of IVF as a fertility treatment, considering scientific, ethical and social factors.[6 marks]

Mark scheme

1.Give benefits.
2.Give ethical concerns.
3.Give a balanced conclusion.

IVF gives couples who cannot conceive naturally the chance to have a child (1); it can be used in cases of blocked fallopian tubes, low sperm count or hormone deficiencies (1); however success rates are relatively low (approximately 20-30% per cycle) and multiple attempts may be needed (1); unused embryos are typically destroyed, raising ethical concerns about the status of the embryo (1); it is expensive and emotionally draining (1); overall IVF is a valuable treatment for infertility but should be offered with full information about success rates and ethical implications (1).

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