Smoke and the unborn baby
316 words over 29 numbered lines, then 6 parts worth 12 marks (Modular Unit 2 (4WBI2) style, 12–13 marks). Read the article, answer each part, then open its mark scheme and set your mark.
Illustrative article written for Scholar Lab, not a Pearson text. The biology is real; the studies, people and figures are invented or rounded for practice unless a source is named.
Smoke and the unborn baby
During pregnancy, a growing fetus depends completely on its mother for
food and oxygen. These reach it through the placenta, an organ that
grows in the wall of the uterus. The fetus is joined to the placenta
by the umbilical cord, which contains blood vessels. The lungs of the
fetus are not yet working, and its gut has no food to digest.
In the placenta, the blood of the mother and the blood of the fetus
come very close together, but they do not mix. The placenta has many
small, finger-like projections called villi, which give it a large
surface area. Oxygen, glucose and amino acids diffuse from the
mother’s blood into the blood of the fetus. Carbon dioxide and urea
diffuse the other way.
The fetus floats in a bag of amniotic fluid, which cushions it against
bumps and allows it to move as its muscles develop. The fluid is
enclosed by a membrane called the amnion.
Some harmful substances can also cross the placenta. Cigarette smoke
contains carbon monoxide, a gas that combines with haemoglobin in red
blood cells. Haemoglobin that has combined with carbon monoxide cannot
carry oxygen. Nicotine from the smoke also makes blood vessels
narrower, so less blood flows through the placenta.
A hospital recorded the birth mass of babies born at full term over
three years. The mothers were placed in three groups according to how
many cigarettes they said they smoked each day during pregnancy. The
results are shown in Figure 1. Babies with a low birth mass are more
likely to suffer from infections and breathing problems in the first
weeks of life.
Midwives offer every pregnant woman who smokes help to stop. Women who
stop early in pregnancy usually have babies of a similar birth mass to
those of non-smokers. Smoking near a pregnant woman can also harm the
fetus, because she breathes in the smoke too.
Figure 1 Mean birth mass of babies born at full term
Read the article and study the figure. Use the information in the article and your own knowledge to answer the questions. The lines in brackets show where to look; select them to highlight the text.
Use the information in the article and your own knowledge to answer the questions. The lines in brackets show you where to look; select them to highlight the text.
State what is meant by the term fetus.
(1)Explain how the placenta is adapted for the exchange of substances between the mother and the fetus.
(3)Give one function of the amniotic fluid.
(1)Use Figure 1 to calculate the difference in mean birth mass between babies of mothers who did not smoke and babies of mothers who smoked more than 10 cigarettes a day. Give your answer in grams.
(2)Explain why smoking during pregnancy can reduce the birth mass of a baby.
(3)Suggest two reasons why the hospital’s results may not show the full effect of smoking on birth mass.
(2)Total for this question: 12 marks
0 / 12 marks · 0 of 6 parts rated
Open each mark scheme, compare it with your answer and set your mark. Only your marks are kept, in this browser on this device; your written answers are never saved. Green is full marks, amber is half or more, red is under half.