Specilaised Exchange Surfaces

Question 1

Why do multicellular organisms need exchange surfaces ?

Answer 1

• An organism needs to supply every one of its cells with substances like glucose and oxygen ( for respiration )
• Also needs remove waste products from every cell to avoid damage itself

Question 2

Transport in single celled organism

Answer 2

• Diffuse directly into / out the cell across the cell surface membrane
• Quicker rate of diffusion given to short distance to travel.

Question 3

Transport in multicellular organisms

Answer 3

• Slow rate of diffusion
• Greater distance to between them and the outside environment
• Larger animals = larger SA:V
• Higher metabolic rate , they take up oxygen and glucose faster

Question 4

What are the 3 special futures for exchange surfaces ?

Answer 4

• Large surface area
• thin layer
• Good blood supply and/or ventilation

Question 5

How to improve the efficiency of a hair root cell?

Answer 5

• A lot of this long “hairs” along the roots
• Large surface area which helps to increase the rate of absorption of water (osmosis) and mineral ions (active transport)

Question 6

How to improve the efficiency of alveoli ?

Answer 6

• one cell thick
• thin layer made of alveolar epithelium
• this helps to decrease the diffusion distance of oxygen and carbon dioxide .
• increasing the rate of diffusion .

Question 7

How do alveoli have a good blood supply/ventilation ?

Answer 7

• Surrounded by a large capillary network .
• giving each alveolus its own blood supply
• The air in each alveolus is constantly replaced because lungs are also ventilated.
• helps maintain CONCENTRATION GRADIENT of O2 and CO2

Question 8

How do fish gills have a good blood supply/ventilation ?

Answer 8

• Large network capillaries.
• keeps them well-supplied with blood .
• Well ventilated , fresh water passes through them .
• maintains a good concentration of O2.