[Unit 6.1] | Exchange Between Organisms & Their Environment

Question 1

What is tissue fluid?

Answer 1

• The environment around the cells of multicellular organisms where materials are distributed.

Question 2

In what 2 ways can exchange between organisms & their environments occur?

Answer 2

• Passively: By diffusion & osmosis, requiring no metabolic energy.

• Actively: By active transport, requiring metabolic energy.

Question 3

What is the impact of having a high surface area: volume ratio?

Answer 3

Efficient gas exchange can occur across an organism’s surface.

Question 4

What is the relationship between Surface Area & Volume as the dimensions of a shape increase?

Answer 4

• Both increase, but volume tends to increase more significantly than surface area.

• (This is why large organisms cannot be sustained by simple diffusion.)

Question 5

How does a flattened shape affect the surface area: volume ratio of an object?

Answer 5

• Significantly increases surface area relative to volume.

Question 6

What are the (4) features of a specialised exchange surface?

Answer 6

• Large SA:V ratio
• Short diffusion pathway
• Selectively permeable
• Transport system for the movement of an environmental medium to retain a gradient

Question 7

What is the relationship of the factors of diffusion?

Answer 7

Diffusion = (SA*Difference in Concs) / Length of diffusion pathway