topic 4.1 & 4.2

Question 1

how does the size of an organism relate to their surface area to volume ratio

Answer 1

• as the size of an organism increases, the SA:V ratio decreases

Question 2

how does SA:V ratio affect transport in molecules

Answer 2

• the lower the SA:V ratio, the greater the diffusion distance hence there is a greater distance travelled by molecules to reach parts of the organism

Question 3

explain why single celled organisms do not have a gas exchange system

Answer 3

• they have a larger surface to volume ratio
• hence there is a short diffusion distance

Question 4

why do larger organisms require mass transport and specialised gas exchange surfaces?

Answer 4

• they have a small SA:V ratio hence substances cannot easily enter the cells
• mass transport and specialised gas exchange surfaces facilitate the exchange of substances

Question 5

why do cells have a membrane

Answer 5

• to regulate movement of substances into and out of the cell
• to protect organelles inside