Gas Exchange Flashcards
Use Fick’s Law of Diffusion to explain the adaptations of mammalian gas exchange surfaces? (5 marks)
Rate of diffusion is proportional to the surface area - alveoli have a large surface area:volume ratio
Rate of diffusion is proportional to difference in concentration (breathing and blood flow maintain difference in gas concentration)
Rate of diffusion is inversely proportional to diffusion distance (walls of alveoli and capillaries one cell thick)
Using the diagram and your knowledge of gas exchange surfaces, explain how the structure
of a flatworm is adapted to obtain oxygen from the water.
Large surface area to volume ratio
= faster diffusion
Explain why many animals need a heart and a circulatory system, but flatworms don’t?
Heart needed to pump oxygenated blood around body
Flatworms are small so have a large surface area to volume ratio (so can use diffusion to meet requirements)
Circulatory system needed as diffusion is not sufficient to transport oxygen in a larger animal
Describe and explain how the lungs of a mammal are adapted for rapid gas exchange?
Alveolar epithelium is one cell thick
Capillary endothelium is one cell thick
Short diffusion distance = faster rate of diffusion
Large surface area (to volume ratio) provided by alveoli
Steep concentration gradient maintained by breathing and by blood flow
Suggest how the heart of a Daphnia enables organs to carry out effective gas exchange?
Blood carries oxygen
Blood moving maintains concentration gradient
= faster diffusion of oxygen
In mammals, blood passes through the heart twice for each circulation of the body.
Suggest how this type of circulation enables mammals to carry out effective gas exchange?
One side of the heart transports deoxygenated blood to lungs
The other side takes oxygenated blood around the body
There is a separation of oxygenated and deoxygenated blood
This maintains a concentration gradient
Ensures a maximum amount of oxygen is supplied to cells
Animals need lots of oxygen because they have a high metabolic rate/ are very active
Describe why single-celled organisms, such as Valonia ventricosa, do not need
a specialised gas exchange surface?
They can rely on diffusion to {take in oxygen / remove wastes}
large surface area to volume ratio (allows diffusion to occur at
a sufficient rate) (1)
short diffusion distance
