Oxford Cambridge and
RSA Examinations
GCEBiology AH420/03:
Unified biology A Level
with marking scheme.
, Oxford Cambridge and RSA
Wednesday 21 June 2023 – Morning
A Level Biology A
H420/03 Unified biology
Time allowed: 1 hour 30 minutes
You can use:
* 9 8 9 7 2 8 8 4 6 6 *
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 4 2 0 0 3 *
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 70.
• 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 24 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2023 [601/4260/1] OCR is an exempt Charity
DC (EF/SG) 316164/5 Turn over
, 2
1 Cats are mammals.
(a) A light micrograph of a section through the trachea of a cat is shown in Fig. 1.1.
Fig. 1.1
A
B
C
(i) Name the tissues labelled A and B in Fig. 1.1.
A ........................................................................................................................................
B ........................................................................................................................................
[2]
(ii) Name the two types of cell in the box labelled C in Fig. 1.1 and outline their functions.
1 Name ..........................................................................................................................
Function .....................................................................................................................
2 Name .........................................................................................................................
Function .....................................................................................................................
[2]
© OCR 2023
, 3
(b) Alveoli increase the surface area to volume ratio (SA:V) in the lungs of cats and other
mammals.
(i) An alveolus in the lung of a cat has:
• a spherical shape
• a diameter of 0.13 mm
• a surface area of 0.053 mm2.
Calculate the SA:V of this alveolus.
Use the formula: volume of sphere = 4 πr 3
3
SA:V = ........................................................... [3]
(ii) Explain why the large SA:V of alveoli is an advantage to mammals.
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [1]
© OCR 2023 Turn over
RSA Examinations
GCEBiology AH420/03:
Unified biology A Level
with marking scheme.
, Oxford Cambridge and RSA
Wednesday 21 June 2023 – Morning
A Level Biology A
H420/03 Unified biology
Time allowed: 1 hour 30 minutes
You can use:
* 9 8 9 7 2 8 8 4 6 6 *
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 4 2 0 0 3 *
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 70.
• 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 24 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2023 [601/4260/1] OCR is an exempt Charity
DC (EF/SG) 316164/5 Turn over
, 2
1 Cats are mammals.
(a) A light micrograph of a section through the trachea of a cat is shown in Fig. 1.1.
Fig. 1.1
A
B
C
(i) Name the tissues labelled A and B in Fig. 1.1.
A ........................................................................................................................................
B ........................................................................................................................................
[2]
(ii) Name the two types of cell in the box labelled C in Fig. 1.1 and outline their functions.
1 Name ..........................................................................................................................
Function .....................................................................................................................
2 Name .........................................................................................................................
Function .....................................................................................................................
[2]
© OCR 2023
, 3
(b) Alveoli increase the surface area to volume ratio (SA:V) in the lungs of cats and other
mammals.
(i) An alveolus in the lung of a cat has:
• a spherical shape
• a diameter of 0.13 mm
• a surface area of 0.053 mm2.
Calculate the SA:V of this alveolus.
Use the formula: volume of sphere = 4 πr 3
3
SA:V = ........................................................... [3]
(ii) Explain why the large SA:V of alveoli is an advantage to mammals.
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [1]
© OCR 2023 Turn over
