How does the combined contraceptive pill prevent pregnancy?

It contains oestrogen and progesterone, which inhibit the release of FSH so no egg matures in the ovary.

Give one advantage and one disadvantage of using the contraceptive pill.

It is more than 99% effective when taken correctly, but it can cause side effects such as headaches and raised blood pressure and gives no protection against sexually transmitted infections.

How does a condom prevent pregnancy?

It acts as a barrier that stops the sperm reaching the egg.

Give two advantages of barrier methods over hormonal methods of contraception.

They also protect against sexually transmitted infections and they have no hormonal side effects.

What is sterilisation, and why does it suit only some people?

The sperm ducts or the oviducts are cut or tied so gametes can never meet; it is meant to be permanent and is very difficult to reverse.

OCR GCSE Biology A J247

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Protein synthesis and the triplet code Enzyme action, and investigating enzymes Cellular respiration as an exothermic process Aerobic and anaerobic respiration compared Synthesis and breakdown of carbohydrates, proteins and lipids Photosynthesis: producers and the process Photosynthesis as endothermic, and investigating it Limiting factors in photosynthesis

Community Level Systems

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Genes, Inheritance and Selection

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Global Challenges

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Organism Level Systems

Topic overview The nervous system and coordinated responses The reflex arc The eye and its common defects The structure and function of the brain Investigating and treating the brain Hormonal coordination, thyroxine and adrenaline Hormones in reproduction and the menstrual cycle Contraception and treating infertility Plant hormones and their commercial uses Homeostasis, and the skin in temperature control Insulin and glucagon in blood sugar control Type 1 and type 2 diabetes Osmotic changes in body fluids, and the kidneys The kidney tubule and the effect of ADH Responding to temperature and osmotic challenges

Scaling Up

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Organism Level Systems

Contraception and treating infertility

3 things to know
Paper 3

Overview

How the combined pill, implants, injections, patches, condoms, sterilisation and natural methods prevent pregnancy, their effectiveness, advantages and drawbacks, how FSH and LH given as fertility drugs help a woman conceive, the stages, drawbacks, multiple births and ethical objections of in vitro fertilisation, and injecting a single sperm into an egg.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why are natural methods that avoid intercourse near the time of ovulation less reliable?

Key term

Name three hormonal methods of contraception other than the pill.

Key term

Which methods of contraception are the most effective, and how do condoms compare?

Questions from this subtopic

Each one with the model answer underneath.

1
How does the combined contraceptive pill prevent pregnancy?
Model answer
It contains oestrogen and progesterone, which inhibit the release of FSH so no egg matures in the ovary.
2
Name three hormonal methods of contraception other than the pill.
Model answer
The contraceptive implant, the contraceptive injection and the skin patch.
3
Give one advantage and one disadvantage of using the contraceptive pill.
Model answer
It is more than 99% effective when taken correctly, but it can cause side effects such as headaches and raised blood pressure and gives no protection against sexually transmitted infections.
4
How does a condom prevent pregnancy?
Model answer
It acts as a barrier that stops the sperm reaching the egg.
5
Give two advantages of barrier methods over hormonal methods of contraception.
Model answer
They also protect against sexually transmitted infections and they have no hormonal side effects.
6
What is sterilisation, and why does it suit only some people?
Model answer
The sperm ducts or the oviducts are cut or tied so gametes can never meet; it is meant to be permanent and is very difficult to reverse.

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Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

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Algae and .

phytoplanktonfungianimals

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AThe blood becomes too dilute.

BLess ADH is released.

CThe collecting ducts become less permeable.

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Egestion means passing out of undigested food as faeces.

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