Describe the roles of the placenta and amniotic fluid in supporting the development of an embryo during pregnancy.

Pearson Edexcel International GCSE Biology (4BI1) — 3.1 Reproduction · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

The placenta supplies the embryo with nutrients and oxygen from the mother’s blood, allowing the exchange of substances without the two blood supplies mixing. It also removes waste products from the embryo.
The amniotic fluid surrounds the embryo, providing a cushion that protects it from physical damage and shock, and helps maintain a stable temperature.

Examiner tips

Use the exact terms ‘placenta’, ‘amniotic fluid’, ‘nutrients’, ‘oxygen’, ‘exchange’, ‘waste’, ‘cushion’, ‘protect’
Show the two separate functions of each organ – one for the placenta, one for the fluid
Keep the answer short and to the point to fit the 4‑mark limit

Common mistakes

Mixing up the roles of the placenta and amniotic fluid, e.g. saying the fluid supplies nutrients
Using vague words like ‘help’ instead of specific functions such as ‘exchange’ or ‘protect’
Omitting the fact that the placenta’s blood vessels do not mix with the mother’s

Mark scheme (4 marks)

The placenta provides nutrients to the developing embryo
The placenta allows exchange of substances / oxygen between mother and embryo (without blood mixing)
Amniotic fluid surrounds the embryo
Amniotic fluid protects the embryo (from physical damage / shock)

Key terms in this question

placenta · amniotic fluid · embryo