Exchange In Unicellular And Multicellular Organisms

Question 1

Describe the gas exchange in unicellular organisms (single celled)

Answer 1

• gases + dissolved substances can diffuse directly into or out of cell across cell membrane
• coz they have a large SA:V
• so enough substances can be exchanged across membrane to supply volume of cell

Question 2

Describe gas exchange in multicellular organisms?

Answer 2

• these have a smaller surface area to volume ratio
• so not enough substances can diffuse from their outside surface to supply required volume
• so they need some sort of exchange surface for efficient diffusion
• these allow the surface structure to allow enough nescessary substances to pass thru

Question 3

How are exchange surfaces adapted to maximise effectiveness?

Answer 3

• thin membranes = substances have a short distance to diffuse
• large surface area = so lots of substance can diffuse at once
• lots of blood vessels = to get materials in and out of blood quickly
• ventilation = to assist in gas exchange for animals