6.1 Organisms and Exchange

Question 1

Name 4 substances organisms needs to exchange in their environment

Answer 1

1. Oxygen for aerobic respiration
2. Nutrients
3. Waste products such as carbon dioxide and urea
4. Heat to stay at the same temperature

Question 2

How do single-celled organisms exchange substances?

Answer 2

• diffuse directly into or out of the cells across the cell-surface area
• quick diffusion rate = short distance substances have to travel

Question 3

Why is diffusion across the membrane too slow in multicellular animals? (2 reasons)

Answer 3

• some cells are deep within the body so there is a big distance between cells and outside environment
• larger animals have a low SA:V = its difficult to exchange enough substances to supply a large volume of animal through a small surface area

Question 4

How does the SIZE of an animal influence its heat exchange?

Answer 4

• rate of heat loss is dependent on surface area of an animal
• large volume = small surface area = harder to lose heat
• small volume = large surface area = easy to lose heat
• smaller organisms need a high metabolic rate in order to generate enough heat to stay warm

Question 5

How does the SHAPE of an animal influence its heat exchange?

Answer 5

• compact shape = small surface area to their volume = minimal heat loss
• less compact shape = large surface area to volume = increases heat loss from their surface area