3.3.1 Surface Area To Volume Ratio

Question 1

What substances do organisms exchange with the environment?

Answer 1

• Oxygen and nutrients
• waste products e.g. co2 and urea
• heat (most organisms need to stay around the same temperature)

Question 2

Large animals have a…

Answer 2

Small SA:V ratio

Question 3

Small animals have a …

Answer 3

Large SA:V ratio

Question 4

Exchange in Single-Celled Organisms

Answer 4

• Substances can diffuse directly in and out of the cell across the cell membrane
• quick diffusion rate (short diffusion pathway)

Question 5

Exchange in multicellular organisms

Answer 5

• need exchange organs or mass transport systems
• diffusion across the outer membrane is too slow
• cells are deep within body (large diffusion pathway)
• small SA:V ratio

Question 6

How does body size affect heat exchange

Answer 6

• Large animals have small SA, harder to lose heat
• small animals (mouse) large SA, heat lost more easily and therefore need a high metabolic rate, in order to generate enough heat to stay warm

Question 7

How does shape affect heat exchange?

Answer 7

• compact shape= small SA, minimises heat loss

- less compact shape= large SA, increases heat loss

Question 8

Small dessert animal adaptations to aid exchange

Answer 8

Adapted kidney structure, produce less urine to minimise water loss

Question 9

Small mammals in cold regions adaptation

Answer 9

Have high metabolic rate so they need to eat large amounts of high energy foods( seed and nut)

Question 10

Small mammals in cold regions

Answer 10

Thick fur or hibernate

Question 11

Large organisms in hot regions

Answer 11

Elephant- large flat ears to increase SA, to lose more heat

Hippo- spend most the day in water, to lose more heat