THE NEED FOR GAS EXCHANGE SURFACES

Question 1

What is the surface area to volume ratio?

Answer 1

Relationship between the surface area of an organism and its volume.

Question 2

Why don’t single-celled organisms and very small multi-cellular organisms have gas exchange or transport system?

Answer 2

Nutrients and oxygen can diffuse directly into the cell.

• Diffusion distance is small.
• Surface area to volume ratio is large, big surface which substances can diffuse in/out.
• Metabolic demands are low - don’t use much oxygen/don’t regulate own temp.

Question 3

The bigger an organism gets…

Answer 3

The smaller the surface area to volume ratio gets, distance from outside to inside of organism gets longer, proportionally less surface for substances to enter through.

Question 4

How do you calculate surface area of a sphere?

Answer 4

4πr²

Question 5

How do you calculate volume of a sphere?

Answer 5

4/3πr³.

Question 6

Why DO larger organisms require a specialised gas exchange system?

Answer 6

Metabolic rates of larger organisms, tends to be higher than that of smaller animals. They control their own body temp. Also to demand for oxygen & food/waste produced is much higher. So an exchange system is needed to remove the waster product and replenish oxygen.

Question 7

What factors affect the rate of diffusion?

Answer 7

• Surface area.
• Concentration gradient; maintaining the gradient makes diffusion faster.
• Distance; shorter the distance, the faster diffusion can occur.