surface area to volume ratio

Question 1

what needs to be exchanged between an organism and it’s environment

Answer 1

• respiratory gases
  (oxygen, carbon dioxide)
• nutrients
  ( glucose, fatty acids, amino acids, vitamins, minerals)
• excretory products
  (urea, carbon dioxide)
• HEAT

Question 2

how are substances exchanged between organisms and their environment

Answer 2

passively by diffusion and osmosis

actively by active transport

Question 3

what are the features of specialised exchange surfaces

Answer 3

Large SA; volume

( increases the area at which materials can be transport in/out of the cell via diffusion and active transport)

thin
(short diffusion pathway meaning diffusion can occur at a faster rate)

partially permeable
(only allows certain molecules to pass through)

movement of the environmental medium
(e.g: air)

movement of the internal medium
(e.g: blood)

Question 4

why is tissue fluid important

Answer 4

allows substances to easily move through tissue fluid to the cell so less diffusion occurs therefore it is more efficient

Question 5

what does a mass transport system do

Answer 5

moves substances to/from exchange surfaces to maintain a concentration gradient

Question 6

why do organisms with a high metabolic rate need a large SA: volume

Answer 6

metabolic rate is a measurement of respiration

lots of respiration needs lots of oxygen
need large SA from exchange surfaces so it can absorb the oxygen with maximum efficiency

Question 7

how does a flattened shape aid the exchange of substances

Answer 7

all cells are near to the surface for the exchange of substances