3.1: Surface area to volume ratio

Question 1

Why can small organisms simply exchange substances across surfaces?

Answer 1

Large surface area to volume ratio - smaller distance from outside to middle of organism

Question 2

Adaptations to increase surface area:volume

Answer 2

1) Villi and microvilli - absorption of digested food

2) Alveoli and bronchioles - gas exchange

3) Spiracles and tracheoles - Gas exchange

4) Gil filaments and lamellae -gas exchange

5) Thin wide leaves - Gas exchange

6) Many capillaries - Capillary network

Question 3

What is the relationship between size of organism and the surface area to volume ratio?

Answer 3

Size of organism increases, surface area to volume decreases

Question 4

SA:Volume ratio in relation to small organisms

Answer 4

• Large surface area to volume ratio
• Big surface area for exchange of substances
• Small distance from outside of organism to middle so simple exchange across surfaces

Question 5

SA:Volume ratio in relation to large organisms organisms

Answer 5

• Small surface area to volume ratio
• Large distance from middle to outside
• Larger organisms have higher metabolic rate so they have adaptations to make exchange of substance efficient to remove waste