3.1 Exchange Surfaces

Question 1

What are the three methods of transport?

Answer 1

Osmosis
Active Transport
Diffusion

Question 2

What happens to the SA:V ratio as the organism increases in size?

Answer 2

It decreases

Question 3

What happens if there is a large SA:V ratio?

Answer 3

It’s easier for substances to diffuse across outer surfaces

Question 4

How do single celled organisms exchange substances?

Answer 4

• Across outer surfaces because they have a large Surface Area:Volume ratio and a low metabolic rate

Question 5

How do multicellular organisms meet demands via exchange surfaces?

Answer 5

• They have a smaller Sa:V and a higher metabolic demand
• So have specialised exchange surfaces and a circulatory system

Question 6

What is the definition of a specialised exchange surface?

Answer 6

Surfaces over which materials are exchanged from one material to another

Question 7

How do you calculate SA:V?

Answer 7

SA divided by V

Question 8

What are the features of a good exchange system?

Answer 8

• Increased surface area to overcome small SA:V
• Thin layers to reduce diffusion difference
• Good blood supply to maintain a steep concentration gradient
• Good ventilation to maintain a steep concentration gradient