A LEVEL BIOLOGY A: Actual June 2025 PAST PAPER 2: Biological Diversity. All Assessment
Questions & Mark Scheme [OCR H420/02]
Exam Resource Summary
The A Level Biology A June 2025 Biological Diversity Paper (OCR H420/02) integrates the full official
examination paper with its detailed mark scheme to provide a clear, structured, and exam-focused revision
resource. This paper assesses students’ understanding of biodiversity, classification, evolution, ecology,
and the biological principles that explain variation within and between species. Candidates must apply
knowledge to new contexts, interpret and analyse data, and demonstrate strong conceptual reasoning across
a wide range of ecological and evolutionary themes. By presenting each question alongside its marking
criteria, the resource offers precise guidance on scientific accuracy, analytical depth, and the structured
explanations required for higher-band responses. This combined format supports effective revision,
strengthens problem-solving and evaluative skills, and prepares students for success in the May/June 2026
OCR A Level Biology A Biological Diversity examination.
OCR is an exempt Charity
Turn over
, 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
, 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
, 4
6 Some students are conducting an osmosis investigation using cylinders of potato.
They cut cylinders of potato 50 mm long using the ruler shown in the diagram.
0 10 20 30 40 50 60 70 80 90 100
mm
What is the percentage uncertainty in the length of the potato cylinders?
A 0.25%
B 0.5%
C 1%
D 2%
Your answer [1]
© OCR 2025
Questions & Mark Scheme [OCR H420/02]
Exam Resource Summary
The A Level Biology A June 2025 Biological Diversity Paper (OCR H420/02) integrates the full official
examination paper with its detailed mark scheme to provide a clear, structured, and exam-focused revision
resource. This paper assesses students’ understanding of biodiversity, classification, evolution, ecology,
and the biological principles that explain variation within and between species. Candidates must apply
knowledge to new contexts, interpret and analyse data, and demonstrate strong conceptual reasoning across
a wide range of ecological and evolutionary themes. By presenting each question alongside its marking
criteria, the resource offers precise guidance on scientific accuracy, analytical depth, and the structured
explanations required for higher-band responses. This combined format supports effective revision,
strengthens problem-solving and evaluative skills, and prepares students for success in the May/June 2026
OCR A Level Biology A Biological Diversity examination.
OCR is an exempt Charity
Turn over
, 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
, 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
, 4
6 Some students are conducting an osmosis investigation using cylinders of potato.
They cut cylinders of potato 50 mm long using the ruler shown in the diagram.
0 10 20 30 40 50 60 70 80 90 100
mm
What is the percentage uncertainty in the length of the potato cylinders?
A 0.25%
B 0.5%
C 1%
D 2%
Your answer [1]
© OCR 2025
