Size, surface area and gas exchange systems

Question 1

Why do cells need to exchange substances with their environment?

Answer 1

To take in oxygen and nutrients
To excrete carbon dioxide and urea
To exchange heat

Question 2

What size animals have a higher surface area to volume ratio?

Answer 2

Smaller animals

Question 3

What factors affect heat exchange?

Answer 3

Size and shape

Question 4

How does size affect heat exchange?

Answer 4

A larger volume to surface area ration means it is harder to lose heat (means that small animals have a high metabolic rate in order to stay warm).
A smaller volume to surface ratio means heat is lost more easily.

Question 5

How does shape affect heat exchange?

Answer 5

Compact shape = lower surface area to volume ratio = minimises heat loss
Less compact shape = higher surface area to volume rate = heat lost more easily

Question 6

Why is diffusion in single celled organisms quick?

Answer 6

Substances diffused directly into the cell
Large surface area
Thin surface
Short diffusion pathway

Question 7

Why do multicellular organisms need a specialised gas exchange system?

Answer 7

Diffusion across outer membrane is too slow as some cells are deep within the body and larger animals have a low surface area to volume ratio

Question 8

How do you calculate the surface area volume ratio?

Answer 8

Surface area / volume

Question 9

What are the two adaptation of a gas exchange system?

Answer 9

Large surface area
Thin