Chapter 7// Exchange surfaces + breathing

Question 1

Why is diffusion alone enough to supply the needs of single-celled organisms? (e.g. amoeba)

Answer 1

Diffusion alone supplies single-celled organisms cuz :

🦠 LOW metabolic activity— oxygen demand and co2 production of cell is low

🦠 LARGE SA:vol ratio meaning enough substances can travel into cell because of short diffusion distance

Question 2

Why can diffusion alone not supply the needs of large multicellular organisms?
(e.g. lion)

Answer 2

Large multicellular organisms need specialised exchange surfaces cuz:

🦁HIGH metabolic activity— high o2 demands and production of co2 high

🦁SMALL SA:vol ratio meaning distance substances need to travel to reach cells is longer making it hard to absorb enough o2 through available surface

Question 3

What are the features of an efficient gas exchange surface

Answer 3

• INCREASED SA
• GOOD BLOOD SUPPLY
• THIN LAYERS
• VENTILATION TO MAINTAIN DIFFUSION GRADIENT