Exchange between organisms and their environment

where does the transfer of gases take place

exchange surfaces

what is the name of the environment around multicellular cells

tissue fluid

what type of system is gaseous exchange

mass transport system

describe the simple movement of waste products and materials

materials are distributed to tissue fluid and waste products to exchange surfaces to be removed

what will affect the amount of each material exchanged

the size and metabolic rate of an organism

what does it mean to have a high metabolic rate

exchange more materials and so require a larger surface area to volume ratio

what are examples of things that are exchanged

• respiratory gases

• nutrients

• excretory products

• heat

why is the lowest oxygen concentration inside the mitochondria

oxygen gets used up by respiration

why does mitochondria have a high concentration of co2

this maintains a diffusion gradient

what happens when organisms become larger

their volume increases at a faster rate than their surface area

how have organisms evolved

• flattened shape so short diffusion distance

• specialised exchange surfaces with large areas to increase sa:v ratio

characteristics of exchange surfaces

• high sa:v for increase in rate of exchange

• thin so diffusion distance is short

• selectively permeable to allow selected materials to cross

• movement of environmental medium to maintain diffusion gradient

• a transport system to ensure movement of internal medium to maintain diffusion gradient

relationship for diffusion

surface area * concentration /diffusion distance