1.10 Exchanging Materials

Question 1

What happens to the surface area to volume ratio as the organism gets bigger?

Answer 1

It decreases

Question 2

How is it more difficult for larger and more complex organisms to exchange materials with the outside world?

Answer 2

• Gas and food molecules can no longer reach every cell inside the organism by simple diffusion
• Metabolic waste cannot be removed fast enough to avoid poisoning the cells

Question 3

What are some adaptations to make exchange more efficient?

Answer 3

• Having a large surface area over which exchange can take place
• Having a thin membrane to provide a short path for diffusion
• In animals, an efficient blood supply moves diffusing substances away from the exchange surfaces to maintain a steep concentration gradient
• Being ventilated makes gas exchange more efficient by maintaining a steep concentration gradient

Question 4

What adaptations does the Australian Fitzroy river turtle have for exchange of materials?

Answer 4

• Inside the rear opening are two large sacs lined with folds to provide a large surface area and a rich blood supply for gas exchange
• The muscular opening pumps water in and out, ventilating the folds and maintaining a steep concentration gradient for gas exchange

Question 5

How is the human body adapted to make the exchange of materials more effective?

Answer 5

• Air is moved into the lungs when you breathe, ventilating millions of alveoli (tiny air sacs)
• Alveoli have a large surface area and a rich blood supply for effective gas exchange
• Vili of the small intestine provide large surface area, short diffusion paths and rich blood supply

Question 6

What adaptations do fish have to make gas exchange more effective?

Answer 6

• They have gills which are made up of stacks of thin filaments with a rich blood supply
• They get a constant flow of water pumping over the gills by pumping water over the gills using a flap that covers them called the operculum
• This maintains the steep concentration gradient

Question 7

How are plant roots adapted for exchange of materials?

Answer 7

• Have root hair cells for a larger surface area to make the uptake of water and mineral ions more efficient
• Water constantly moves away from the roots to the transportation stream, maintaining a steep concentration gradient

Question 8

How are plant leaves adapted for exchange of materials?

Answer 8

• Flat, thin leaves
• Presence of air spaces in the leaf tissues
• Stomata
• Help to provide a large surface area and maintain a steep concentration gradient