A-Level Biology OCR A H420

the need for specialised exchange surfaces

To include surface area to volume ratio (SA:V), metabolic activity, single-celled and multicellular organisms.

$\text{Ratio} = \dfrac{\text{Surface Area}}{\text{Volume}}$

the features of an efficient exchange surface

*To include,

• increased surface area – root hair cells
• thin layer – alveoli
• good blood supply/ventilation to maintain gradient – gills/alveolus.*

the structures and functions of the components of the mammalian gaseous exchange system

To include the distribution and functions of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli. PAG1

the mechanism of ventilation in mammals

To include the function of the rib cage, intercostal muscles (internal and external) and diaphragm.

the relationship between vital capacity, tidal volume, breathing rate and oxygen uptake

To include analysis and interpretation of primary and secondary data e.g. from a data logger or spirometer. PAG10

the mechanisms of ventilation and gas exchange in bony fish and insects

*To include:

• bony fish – changes in volume of the buccal cavity and the functions of the operculum, gill filaments and gill lamellae (gill plates); countercurrent flow
• insects – spiracles, trachea, thoracic and abdominal movement to change body volume, exchange with tracheal fluid.*

the dissection, examination and drawing of the gaseous exchange system of a bony fish and/or insect trachea

PAG2

the examination of microscope slides to show the histology of exchange surfaces

PAG1