6.1 Exchange between organisms and their environment

Question 1

What is the environment around the cells of multicellular organisms

Answer 1

Tissue fluid

Question 2

What are the features of a specialised exchange surface

Answer 2

1. A large surface area relative to the volume of the organism which increases the rate of exchange
2. Very thin so that the diffusion distance is short and therefore materials cross the exchange surface rapidly
3. Selectively permeable so allow selected materials to cross
4. Movement of the environmental medium, e.g. air, to maintain a diffusion gradient
5. A transport system to ensure the movement of the internal medium, for example blood, to maintain a diffusion gradient

Question 3

What is the relationship between certain factors of diffusion

Answer 3

Diffusion proportional = Surface area X different in concentration/ length of diffusion path

Question 4

Why are specialised exchange surfaces easily damaged

Answer 4

Because they are thin, so they are located inside the body.