Please check the examination details below before entering your candidate information
Candidate surname Other names
Centre Number Candidate Number
Pearson Edexcel International GCSE (9–1)
Monday 09 June 2025
Morning (Time: 1 hour 15 minutes) Paper
reference 4BI1/2B
Biology
UNIT: 4BI1
PAPER: 2B
You must have: Total Marks
Calculator, ruler
Instructions
•• Use black ink or ball-point pen.
If pencil is used for diagrams/sketches/graphs it must be dark (HB or B).
• Fill in the boxes at the top of this page with your name,
centre number and candidate number.
•• Answer all questions.
Answer the questions in the spaces provided
– there may be more space than you need.
• Show all the steps in any calculations and state the units.
Information
•• The total mark for this paper is 70.
The marks for each question are shown in brackets
– use this as a guide as to how much time to spend on each question.
Advice
•• Read each question carefully before you start to answer it.
Write your answers neatly and in good English.
•• Try to answer every question.
Check your answers if you have time at the end.
Turn over
P78875A
©2025 Pearson Education Ltd.
Y:1/1/1/1/1/1/1/
*P78875A0124*
, Answer ALL questions.
Some questions must be answered with a cross in a box . If you change your mind about an
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
answer, put a line through the box and then mark your new answer with a cross .
1 Read the passage below. Use the information in the passage and your own knowledge
to answer the questions that follow.
Rivers – the arteries of the world
Rivers are important supplies of water for drinking, farming, industry, and leisure
activities. Like our circulatory system, rivers are essential for transport, and have
a homeostatic effect on nature. The biodiversity in rivers is high as they are the
habitat for many different species. In many countries rivers are under threat from
5 human impact, particularly the release of untreated sewage.
Flooding can cause untreated sewage to run into rivers from pipelines. Scientists
estimated that in England and Wales during 2022, sewage was released into rivers
for a total time of 300 000 hours. This sewage came from 1200 different pipelines.
Untreated sewage may contain fertilisers, pesticides, pathogenic bacteria, and
10 pharmaceutical drugs.
(Source: © ANDY DAVIES / SCIENCE PHOTO LIBRARY)
The photograph shows sewage being released into a river. The sewage causes
the growth of something called ‘sewage fungus’. Sewage fungus looks like fungus
but is a solid collection of several types of anaerobic bacteria. Sewage fungus is
common in rivers that are polluted with untreated sewage or are near to cattle
15 and intensive crop farms. If sewage fungus is found in a river it often indicates
that the biodiversity of the river will be low.
Pesticides from agriculture are also released into rivers, and these are frequently
transferred through natural food chains. Even pharmaceutical drugs, such as
those containing the hormones oestrogen and progesterone, have been found in
20 polluted rivers. These drugs must have been consumed by humans, excreted and
then released into the sewage flowing into rivers.
Untreated sewage can also contain pathogenic species of bacteria that then enter
rivers. If humans are infected with these bacteria, the large intestine absorbs less
water, causing diarrhoea. Some of the bacteria found in sewage are resistant
25 to antibiotics.
2
*P78875A0224*
, Scientists are looking for ways to prevent river pollution. One way is to reduce
the risk of pollution from fertilisers and from cattle urine and faeces. Woodchip
bioreactors are being trialled in agricultural fields that are near to rivers. These
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
bioreactors are pits filled with woodchips and denitrifying bacteria. Water
30 drains through these bioreactors, which helps to remove nitrates before they
reach the rivers. In some countries, efforts are being made to replant forests
in areas upstream of rivers to reduce river flooding and the risk of untreated
sewage release.
(a) Rivers have a homeostatic effect on nature. This is similar to the role of
homeostasis in humans.
State what is meant by the term homeostasis (lines 2 and 3).
(1)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
(b) Calculate the mean number of hours that each pipeline released sewage into
rivers in 2022 (lines 7 and 8).
(1)
mean number = .................................. ............... . . . . . hours
(c) (i) Sewage fungus is not a fungus but is made from several different species
of bacteria.
Which of these structures are present both in fungi and in bacteria?
(1)
A cell wall and cytoplasm only
B cell wall and nucleus only
C cell wall, cytoplasm and nucleus
D cytoplasm and nucleus only
3
*P78875A0324* Turn over
, (ii) Explain why rivers near to farms may have low biodiversity (lines 13 to 16).
(4)
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
(d) Oestrogen and progesterone in polluted water lower the levels of FSH and LH
in mammals.
(i) State why lower levels of FSH can reduce fertility in mammals.
(1)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
(ii) State why lower levels of LH can reduce fertility in mammals.
(1)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . . . .
(e) (i) Pathogenic bacteria produce poisons that prevent the active transport of salt
into the blood vessels surrounding the intestines.
Explain why preventing the transport of salt into the blood vessels will cause
more water to be present in faeces (lines 22 to 24).
(2)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
4
*P78875A0424*
Candidate surname Other names
Centre Number Candidate Number
Pearson Edexcel International GCSE (9–1)
Monday 09 June 2025
Morning (Time: 1 hour 15 minutes) Paper
reference 4BI1/2B
Biology
UNIT: 4BI1
PAPER: 2B
You must have: Total Marks
Calculator, ruler
Instructions
•• Use black ink or ball-point pen.
If pencil is used for diagrams/sketches/graphs it must be dark (HB or B).
• Fill in the boxes at the top of this page with your name,
centre number and candidate number.
•• Answer all questions.
Answer the questions in the spaces provided
– there may be more space than you need.
• Show all the steps in any calculations and state the units.
Information
•• The total mark for this paper is 70.
The marks for each question are shown in brackets
– use this as a guide as to how much time to spend on each question.
Advice
•• Read each question carefully before you start to answer it.
Write your answers neatly and in good English.
•• Try to answer every question.
Check your answers if you have time at the end.
Turn over
P78875A
©2025 Pearson Education Ltd.
Y:1/1/1/1/1/1/1/
*P78875A0124*
, Answer ALL questions.
Some questions must be answered with a cross in a box . If you change your mind about an
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
answer, put a line through the box and then mark your new answer with a cross .
1 Read the passage below. Use the information in the passage and your own knowledge
to answer the questions that follow.
Rivers – the arteries of the world
Rivers are important supplies of water for drinking, farming, industry, and leisure
activities. Like our circulatory system, rivers are essential for transport, and have
a homeostatic effect on nature. The biodiversity in rivers is high as they are the
habitat for many different species. In many countries rivers are under threat from
5 human impact, particularly the release of untreated sewage.
Flooding can cause untreated sewage to run into rivers from pipelines. Scientists
estimated that in England and Wales during 2022, sewage was released into rivers
for a total time of 300 000 hours. This sewage came from 1200 different pipelines.
Untreated sewage may contain fertilisers, pesticides, pathogenic bacteria, and
10 pharmaceutical drugs.
(Source: © ANDY DAVIES / SCIENCE PHOTO LIBRARY)
The photograph shows sewage being released into a river. The sewage causes
the growth of something called ‘sewage fungus’. Sewage fungus looks like fungus
but is a solid collection of several types of anaerobic bacteria. Sewage fungus is
common in rivers that are polluted with untreated sewage or are near to cattle
15 and intensive crop farms. If sewage fungus is found in a river it often indicates
that the biodiversity of the river will be low.
Pesticides from agriculture are also released into rivers, and these are frequently
transferred through natural food chains. Even pharmaceutical drugs, such as
those containing the hormones oestrogen and progesterone, have been found in
20 polluted rivers. These drugs must have been consumed by humans, excreted and
then released into the sewage flowing into rivers.
Untreated sewage can also contain pathogenic species of bacteria that then enter
rivers. If humans are infected with these bacteria, the large intestine absorbs less
water, causing diarrhoea. Some of the bacteria found in sewage are resistant
25 to antibiotics.
2
*P78875A0224*
, Scientists are looking for ways to prevent river pollution. One way is to reduce
the risk of pollution from fertilisers and from cattle urine and faeces. Woodchip
bioreactors are being trialled in agricultural fields that are near to rivers. These
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
bioreactors are pits filled with woodchips and denitrifying bacteria. Water
30 drains through these bioreactors, which helps to remove nitrates before they
reach the rivers. In some countries, efforts are being made to replant forests
in areas upstream of rivers to reduce river flooding and the risk of untreated
sewage release.
(a) Rivers have a homeostatic effect on nature. This is similar to the role of
homeostasis in humans.
State what is meant by the term homeostasis (lines 2 and 3).
(1)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
(b) Calculate the mean number of hours that each pipeline released sewage into
rivers in 2022 (lines 7 and 8).
(1)
mean number = .................................. ............... . . . . . hours
(c) (i) Sewage fungus is not a fungus but is made from several different species
of bacteria.
Which of these structures are present both in fungi and in bacteria?
(1)
A cell wall and cytoplasm only
B cell wall and nucleus only
C cell wall, cytoplasm and nucleus
D cytoplasm and nucleus only
3
*P78875A0324* Turn over
, (ii) Explain why rivers near to farms may have low biodiversity (lines 13 to 16).
(4)
DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
(d) Oestrogen and progesterone in polluted water lower the levels of FSH and LH
in mammals.
(i) State why lower levels of FSH can reduce fertility in mammals.
(1)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
(ii) State why lower levels of LH can reduce fertility in mammals.
(1)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . . . .
(e) (i) Pathogenic bacteria produce poisons that prevent the active transport of salt
into the blood vessels surrounding the intestines.
Explain why preventing the transport of salt into the blood vessels will cause
more water to be present in faeces (lines 22 to 24).
(2)
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................................................................................ ................ . . . . . . . . . . . . . . . . . . . .
4
*P78875A0424*
