surface area to volume ratio Flashcards
what surface area to volume ratio do smaller animals have?
large
what surface area to volume ratio do larger animals have?
small
what is the exchange surface in animals?
lungs
what is the exchange surface in single celled organisms?
cell membrane
why is diffusion rate quick in single-celled organisms?
● due to small distances substances have to travel
● directly in / out of the cell across cell-surface membrane
why do multicellular organisms need specialised exchange organs?
● diffusion across membrane is too slow
● large distance between cells deep within body and outside environment
● larger animals have lower SA:V ratios - difficult to supply large volume of animal
● so multicellular organisms need specialised exchange organs (like lungs)
how does body size affect heat exchange?
● rate of heat loss depends on surface area
● large animals - large volume so small surface area (small SA:V)
● makes it harder for it to lose heat from its body
● small animals - small volume so large surface area
(high SA:V)
● so heat is lost more easily
why do smaller organisms need a high metabolic rate?
● have high SA:V ratio
● loses heat at a higher rate
● higher rate of respiration replaces heat loss as respiration is exothermic
● respiration is a metabolic reaction
● so need high metabolic rate to generate enough heat to stay warm
how does shape affect heat exchange?
● compact animals - small surface area relative to volume
● minimising heat loss
● less compact animals - larger surface area relative to volume
● increasing heat loss
why do large animals need high metabolic rate?
● greater the mass of an organism, the higher the metabolic rate
● therefore, a larger animal has higher oxgen uptake compared to a smaller animal
