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 structures of mammalian alveoli and insect tracheoles provide a large surface area for gas exchange.
mammalian alveoli:
insect tracheoles:
The lungless salamander, Desmognathus ochrophaeus, is a terrestrial amphibian that completely lacks lungs and gills, relying entirely on its skin and the lining of its mouth for gas exchange.
Suggest how this salamander is able to obtain sufficient oxygen without specialised internal lungs or gills.
Mammals have highly adapted ventilation systems to maintain a steep concentration gradient. The following passage describes how the mammalian gas exchange system is protected and ventilated.
Complete the passage using the most appropriate words or phrases.
To prevent the airway from collapsing under low pressure, the trachea is supported by C-shaped rings of .................................... . Throughout the trachea and bronchi, specialised goblet cells secrete .................................... to trap inhaled dirt and microbes. During inspiration, the contraction of the external intercostal muscles pulls the ribcage .................................... and outwards to increase thoracic volume. In contrast to quiet breathing, forced expiration is an active process that requires the contraction of the .................................... intercostal muscles.
