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6. Exchanges surface structure adaptations in other animals

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6. Exchanges surface structure adaptations in other animals

Tadpoles and aquatic worms

For their gas exchange, tadpoles and aquatic worms absorb air through their skin and external gills.

The gills are feather-like projections that produce a large surface area for gas exchange with the water - so oxygen can be absorbed for cellular respiration and waste carbon dioxide removed.

With adult amphibians the gas exchange takes place mainly through their skin and lungs.


Insects do not have a transport system and gases cannot be directly exchanged with respiring cell tissue and the external air.

Insects have tiny holes called spiracles all along the side of their body.

The spiracles open out into tiny tubes called trachea - with a moist surface, through which insects pump air in and out.

The trachea are stiffened to prevent the minute 'tubes' collapsing.

The trachea have many minute branches called tracheoles which connect to cells - this increases surface area and shortens gas diffusion distance and time.

At the end of the trachea is a tiny drop of water that connects it to the cells.

So, gases can diffuse through the trachea and water into the cells - providing the cells with oxygen for respiration.

The spiracles can close to prevent evaporation and keep the exchange surfaces moist.


The slug absorbs air through its skin and has a moderately large surface area to volume ratio.

The gas exchange surface is moist to dissolve gases which can diffuse through the moist interface.

The skin membrane is thin to give a short diffusion time.

Summary of learning objectives and key words or phrases

Be able to describe the efficient gas exchange membrane surface and structure adaptations in tadpoles, insects, worms and slugs including details such as spiracles, external gills, skin and trachea.



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