Many organisms have evolved specialised gas exchange surfaces to maximise efficiency. One crucial feature of these structures is their large surface area to volume ratio.
Describe how the structural features of mammalian alveoli and the insect tracheal system provide a large surface area for gas exchange.
mammalian alveoli:
insect tracheal system:
The olm, Proteus anguinus, is an aquatic, cave-dwelling salamander that retains its feathery external gills throughout adulthood. Unlike most terrestrial amphibians, it never transitions to living on land or relying solely on lungs.
Suggest why the olm has retained external gills as an adult.
Mammals have highly specialised lungs to facilitate efficient gas exchange. The following passage describes how the structural integrity of the airways is maintained and how ventilation is driven.
Complete the passage using the most appropriate words or phrases.
In the trachea and bronchi, C-shaped rings of .................................... prevent the airways from collapsing during the pressure changes of ventilation. Mucus, which traps inhaled dust and pathogens, is produced and secreted by specialised .................................... cells. During active or forced expiration, the thoracic volume is rapidly decreased when the .................................... intercostal muscles contract. This decreases the thoracic volume, causing the pressure inside the alveoli to become .................................... than atmospheric pressure, forcing air out of the lungs.
