4.1 Surface area to volume ratio

Question 1

How does SA:V affect transport of molecules in small organisms?

Answer 1

• small organisms have a high SA:V
• diffusion distance is small
• single celled organisms usually have low metabolic demands

Question 2

How does SA:V affect transport of molecules in large organisms?

Answer 2

large organisms have small SA:V
larger organisms have:
- high metabolic rate
- substances have to travel long distances

simple diffusion is not fast enough for nutrients and oxygen to get to cells

Question 3

Why do larger organisms need specialised gas exchange surfaces?

Answer 3

-they have smaller sa:v
- high metabolic rate
- used for exchange of carbon dioxide and oxygen between a body and environment.

Question 4

What factors affect rate of diffusion and why?

Answer 4

surface area
- bigger SA, the more particles can be exchanged at the same time

concentration gradient
- diffusions happens at high conc to low conc
- steeper concentration gradient, faster diffusion

diffusion distance
- shorter diffusion distance, faster diffusion can occur

Question 5

Why do larger organisms need mass transport systems?

Answer 5

internal substances in the body need to transported

mass transport systems - effective ways of moving substances around the body

Question 6

What are the features of a mass transport system?

Answer 6

• system of vessels that carry substances
• a way to make sure substances are carried in the right direction
• means of moving the material
• suitable transport medium