Exchange Surfaces

Question 1

Give the three reasons why multicellular organisms need specialised exchange surfaces

Answer 1

• High metabolic activity
• Multicellular organisms
• Small surface area: volume ratio

Question 2

Explain why the high metabolic activity of multicellular organisms means that they need specialised exchange surfaces

Answer 2

• High demand for oxygen
• A lot of CO₂ is produced
• So they need a specialised exchange surface for gas exchange

Question 3

Explain why being multicellular organisms means that they multicellular organisms need specialised exchange surfaces

Answer 3

• The diffusion distance of oxygen is too far
• So they need a specialised exchange surface for gas exchange

Question 4

Explain why the small surface area:volume ratio of multicellular organisms mean that they need specialised exchange surfaces

Answer 4

• The diffusion of gases is too slow for enough oxygen to be supplied
• and to remove CO₂ to prevent build-up
• So they need specialised exchange surfaces for gas exchange

Question 5

Explain why the metabolic activity of unicellular organisms means that they don’t need specialised exchange surfaces

Answer 5

• The relatively low metabollic activity of unicellular organisms means that their oxygen demand is relatively low and the amount of CO₂ produced is relatively low
• This means that they can rely on diffusion alone to meet their needs for gas exchange

Question 6

Explain why the being unicellular means that unicellular organisms don’t need specialised exchange surfaces

Answer 6

• The diffusion distance of oxygen is short
• So they can rely on diffusion alone to meet their needs for gas exchange

Question 7

Explain why the large surface area:volume ratio of unicellular organisms means that they don’t need specialised exchange surfaces

Answer 7

• Diffusion is fast enough to supply enough oxygen and to remove CO₂ to prevent build-up.
• So they can rely on diffusion alone to meet their needs for gas exchange

Question 8

What are the four features that make a gas exchange surface efficient?

Answer 8

1. Large surface area
2. Thin layers
3. Good blood supply
4. Good ventillation

Question 9

How does large surface area make a gas exchange surface efficient?

give an example of where this is in plants and animals

Answer 9

It overcomes the limitations of the SA:V of larger organisms by increasing thhe rate of diffusion so that it is fast enough to supply muscles with enough oxygen and remove CO₂ to prevent build-up

root hair cells and villi

Question 10

How does thin layers make a gas exchange surface efficient?

give an example of where this is in plants and animals

Answer 10

• It decreases the diffusion distance of substances
• This increases the rate and efficiency of gas exchange and diffusion

alveoli and villi

Question 11

How does good blood supply make a gas exchange surface efficient?

give an example of where this is in plants and animals

Answer 11

• Increases the concentration of carbon dioxide in the blood so that its higher than in the alveoli
• It decreases the concentration of oxygen in the blood so that it is lower than in the alveoli
• This creates a steep concentration gradient
• This increases the rate and efficiency of diffusion

alveoli and gills

Question 12

How does good ventilation make a gas exchange surface efficient?

give an example of where this is in plants and animals

Answer 12

• It increases the concentration of oxygen in the alveoli so that it is higher than in the blood
• It decreases the concentration of carbon dioxide so that it is lower than in the blood
• This creates a steep concentration gradient which increases the rate and efficiency of diffusion

alveoli and gills