3.3.1 surface area to volume ratio Flashcards
smaller/larger organisms and surface area to volume ratio
smaller organisms have a higher surface area : volume ratio than larger organisms
how do you calculate the volume of a cylinder?
pi * r squared * height
how do you calculate the volume of a sphere?
4/3 * pi * r cubed
how do single celled organisms supply its cells with products/remove waste products
substances can diffuse directly in or out of the cell across the cell surface membrane
what is the diffusion rate like in small organisms?
diffusion rate is quick because of the small distances that the substances have to travel
what is too slow in multicellular organisms to supply its cells with products/remove waste products?
in multicellular organisms, diffusion across the outer membrane is too slow
what is one reason why diffusion across the outer membrane is too slow in multicellular organisms (distance)?
some cells are deep within the body - large distance between them and the outside environment
what is one reason why diffusion across the outer membrane is too slow in multicellular organisms (sa:v ratio)?
larger animas have a low sa:v ratio - difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface
how do multicellular organisms supply its cells with products/remove waste products (organs)?
instead of using diffusion to absorb and excrete substances, multicellular organisms need specialised exchange organs e.g. lungs
how do multicellular organisms supply its cells with products/remove waste products (mass transport)?
they need an efficient system to carry substances to and from their individual cells - called mass transport
what does mass transport usually refer to in mammals?
in mammals mass transport usually refers to the circulatory system - uses blood to carry glucose/oxygen around the body. also carries hormones/antibodies/waste like CO2
what does mass transport usually refer to in plants?
mass transport in plants involves the transport of water and solutes in the xylem and phloem
heat exchange and body size: larger organisms
larger organisms have a large volume but smaller surface area so it is harder for it to loose heat from its body
heat exchange and body size: smaller organisms
smaller organisms have a small volume but a larger surface area so heat is lost more easily so smaller organisms need a relatively high metabolic rate to generate enough heat to stay warm
heat exchange and body shape: compact shape
animals with a compact shape have a small sa:v ratio which minimises heat loss from their surface
heat exchange and body shape: not compact shape
animals with a less compact shape have a large sa:v ratio which increases heat loss from their surface
adaptations for heat exchange
whether an animal is compact or not depends on its environments temperature, animal’s body shape is adapted to suit its environment
behavioral and physiological adaptations to aid exchange: water loss
animals with a higher sa:v ratio tend to lose more water as it evaporates from their surface
behavioral and physiological adaptations to aid exchange: water loss - why can this be a problem
particularly for animals living in hot regions where water evaporates quickly. some small dessert animals have kidney structure adaptations so they produce less urine to compensate
behavioral and physiological adaptations to aid exchange: diet
to support their heigh metabolic rates, small mammals living in cold regions need to eat large amounts of high energy foods e.g. seeds/nuts
behavioral and physiological adaptations to aid exchange:
fur
smaller mammals may have thick layers of fur or hibernate when the weather gets really cold
behavioral and physiological adaptations to aid exchange: large organisms in hot regions
larger organisms living in hot regions e.g. elephants/hippos find it hard to keep cool as their heat loss is slow
behavioral and physiological adaptations to aid exchange: large organisms in hot regions - elephant adaptations for this
elephants have developed large flat ears which increase their surface area so they can lose more heat
behavioral and physiological adaptations to aid exchange: large organisms in hot regions - hippo adaptations for this
hippos spend much of their day in the water - behavioral adaptation to help them lose heat
