worked solutions
model answers
, Oxford Cambridge and RSA
Friday 13 June 2025 – Morning
A Level Biology A
H420/02 Biological diversity
Time allowed: 2 hours 15 minutes
You can use:
* 1 8 4 7 4 5 7 2 7 8 *
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 4 2 0 0 2 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 100.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 32 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/4260/1] OCR is an exempt Charity
DC (WW/CT) 345421/6 Turn over
for more: tyrionpapers.com
, 2
Section A
You should spend a maximum of 20 minutes on this section.
Write your answer to each question in the box provided.
1 Hydrogen bonds are important for the physical and chemical properties of water.
How do hydrogen bonds form in water?
A Electronegative (δ–) oxygen atoms are attracted to the electropositive (δ+) hydrogen atoms
of adjacent water molecules.
B Electronegative (δ–) oxygen atoms are attracted to the electropositive (δ+) hydrogen atoms
within the same water molecule.
C Electropositive (δ+) oxygen atoms are attracted to the electronegative (δ–) hydrogen atoms
of adjacent water molecules.
D Electropositive (δ+) oxygen atoms are attracted to the electronegative (δ–) hydrogen atoms
within the same water molecule.
Your answer [1]
2 Water has many properties that are important for living organisms.
Which property of water molecules explains why small animals, such as pond skaters, are able to
move over the surface of water without sinking?
A Adhesion
B Buoyancy
C Cohesion
D Density
Your answer [1]
© OCR 2025
for more: tyrionpapers.com
, 3
3 What is a disadvantage of using microorganisms to make food for human consumption?
A Competition from contaminating microorganisms can reduce yield.
B Food produced by microorganisms is low in fat.
C Microorganisms can be grown on waste materials.
D Use of microorganisms for food production raises fewer ethical concerns than use of
animals.
Your answer [1]
4 Culturing microorganisms on nutrient agar requires aseptic techniques.
What is not part of a standard aseptic procedure when culturing microorganisms?
A Disinfect the work area before starting.
B Ensure equipment does not touch any unsterilised surfaces before use.
C Pass the agar plate through a Bunsen flame before use.
D Work near a Bunsen flame.
Your answer [1]
5 Batch fermentation with microorganisms is used to produce a range of useful substances.
Which of the following are important for achieving maximum yield during a batch fermentation
process?
1. Temperature should be maintained close to the optimum.
2. Temperature should be low to reduce costs.
3. Substrate should be constantly added to maintain a high concentration.
A 1, 2 and 3
B Only 1 and 2
C Only 2 and 3
D Only 1
Your answer [1]
© OCR 2025 Turn over
for more: tyrionpapers.com
model answers
, Oxford Cambridge and RSA
Friday 13 June 2025 – Morning
A Level Biology A
H420/02 Biological diversity
Time allowed: 2 hours 15 minutes
You can use:
* 1 8 4 7 4 5 7 2 7 8 *
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 4 2 0 0 2 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 100.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 32 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/4260/1] OCR is an exempt Charity
DC (WW/CT) 345421/6 Turn over
for more: tyrionpapers.com
, 2
Section A
You should spend a maximum of 20 minutes on this section.
Write your answer to each question in the box provided.
1 Hydrogen bonds are important for the physical and chemical properties of water.
How do hydrogen bonds form in water?
A Electronegative (δ–) oxygen atoms are attracted to the electropositive (δ+) hydrogen atoms
of adjacent water molecules.
B Electronegative (δ–) oxygen atoms are attracted to the electropositive (δ+) hydrogen atoms
within the same water molecule.
C Electropositive (δ+) oxygen atoms are attracted to the electronegative (δ–) hydrogen atoms
of adjacent water molecules.
D Electropositive (δ+) oxygen atoms are attracted to the electronegative (δ–) hydrogen atoms
within the same water molecule.
Your answer [1]
2 Water has many properties that are important for living organisms.
Which property of water molecules explains why small animals, such as pond skaters, are able to
move over the surface of water without sinking?
A Adhesion
B Buoyancy
C Cohesion
D Density
Your answer [1]
© OCR 2025
for more: tyrionpapers.com
, 3
3 What is a disadvantage of using microorganisms to make food for human consumption?
A Competition from contaminating microorganisms can reduce yield.
B Food produced by microorganisms is low in fat.
C Microorganisms can be grown on waste materials.
D Use of microorganisms for food production raises fewer ethical concerns than use of
animals.
Your answer [1]
4 Culturing microorganisms on nutrient agar requires aseptic techniques.
What is not part of a standard aseptic procedure when culturing microorganisms?
A Disinfect the work area before starting.
B Ensure equipment does not touch any unsterilised surfaces before use.
C Pass the agar plate through a Bunsen flame before use.
D Work near a Bunsen flame.
Your answer [1]
5 Batch fermentation with microorganisms is used to produce a range of useful substances.
Which of the following are important for achieving maximum yield during a batch fermentation
process?
1. Temperature should be maintained close to the optimum.
2. Temperature should be low to reduce costs.
3. Substrate should be constantly added to maintain a high concentration.
A 1, 2 and 3
B Only 1 and 2
C Only 2 and 3
D Only 1
Your answer [1]
© OCR 2025 Turn over
for more: tyrionpapers.com
