OCR 2023 Biology A H420/03: Unified biology A Level Question Paper & Mark Scheme (Merged)

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] 3 OCR 2023 Turn over 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 0.13mm • a surface area of 0.053mm2 . Calculate the SA:V of this alveolus. Use the formula: volume of sphere = 4 πr 3 SA:V = .......................................................... [3] (ii) Explain why the large SA:V of alveoli is an advantage to mammals. ........................................................................................................................................... ........................................................................................................................................... .............................................................................................