Exchange Between Organisms And Their Environment

Question 1

What does tissue fluid do in the body

Answer 1

Once absorbed, materials are rapidly distributed to the tissue fluid and the waste products returned to the exchange surface for removal.

Question 2

What does the mass transport system do

Answer 2

This maintains the diffusion gradients that bring materials to and from the cell surface membranes

Question 3

What will affect the amount of each material that is exchanged

Answer 3

The size and metabolic rate of an organism

Question 4

How are things such as respiratory gases, nutrients, excretory products interchanged between an organism and its environment

Answer 4

Passively- diffusion and osmosis

Actively - active transport

Question 5

What characteristics do they show to allow effective transfer of materials across specialised exchange surfaces by diffusion or active transport

Answer 5

A large SA to volume ratio - increases rate of exchange

Very thin - so that diffusion distance is short and therefore materials cross the exchange surface rapidly

Selectively permeable to allow selected materials to cross

Movement of the environment medium - to maintain a diffusion gradient

Transport system - to ensure movement of the internal medium

Question 6

What’s the formula for diffusion

Answer 6

SA x difference in concentration/length of diffusion path