3.3.1 Surface area to volume ratio Flashcards
Relationship between size of organism and surface area to volume ratio
- small animal = high SA:V ratio
- larger animal = low SA:V ratio
EQ: Explain how a larger body size is an adaptation to a colder climate.
-lower SA:VOL ratio
└so less heat lost/more heat retained
Fick’s Law
Rate of diffusion is proportional to surface area x difference in concentration / length of diffusion path (membrane thickness)
Why single-celled organisms generally have a larger surface-area to volume ratio
-living cells need to take in oxygen/ nutrients and remove waste
└via diffusion
-the rate of diffusion too slow if SA:V ratio too small
Why is the diffusion rate of substances quick in prokaryotes?
-substances are able to diffuse directly into / out of the cell across the cell surface membrane
└short diffusion path of substances= fast rate of diffusion
Why is diffusion across the outer membrane slow in eukaryotes?
-some cells are deep within the bod
└=a large distance between the cell and the outside environment
-large animals have a low SA:V ratio
└= difficult to exchange substances
Surface area to volume ratio
-why large, active organisms need a specialised surface for gaseous exchange
-large/ active, organisms have higher demand for oxygen / need to remove CO2
-smaller surface area to volume ratio
└=surface area too small / distance too large so diffusion takes too long to supply needs
Explain how differences in SA:V ratio have influenced the need for transport systems in mammals
-diffusion not adequate
└as not enough area relative to volume
└so distance too great
-mass flow system needed
└to transport blood and link the parts of the body
└ substances need to be transported e.g. oxygen
-as the demand is higher due to the high metabolic rate of mammals
EQ: Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins.
-smaller mammal =greater surface area to volume ratio
└=more heat lost
└=greater rate of respiration/metabolism
└oxygen required for respiration
└haemoglobin releases more oxygen more readily (haemoglobin has lower affinity)
What factors affect heat exchange?
- body size
- body shape
How does body size affect heat exchange?
-larger animals = smaller surface area
└=harder for the animal to lose heat from its body
└SO smaller organisms need to have a relatively high metabolic rate
└to generate enough heat to stay warm
How does body shape affect heat exchange?
-compact shape = small SA:V ratio
└= minimising heat loss from the surface
-animals in a hotter environment will have a less compact shaper
└= increase the SA:V ratio and heat loss
What increases heat in the cell
- metabolic rates
- creating waste products
What behavioural adaptations can organisms have in order to aid exchange?
-mammals in cold regions=l eat a lot of high energy foods
└to support their high metabolism
-cold weather, smaller mammals hibernate
-e.g. hippos spend much of their day in the water to help them lose heat
What physiological adaptations can organisms have in order to aid exchange?
-small animals = high SA:V ratio
└in hot climate, reduce water loss by producing less urine
└due to adaptation in kidney structure
-cold weather, smaller mammals
└=thick layers of fur
-e.g. Elephants
└large flat ears to increase their surface area
