Size And Surface Area Flashcards
Organisms exchange substances with environment
Give 3 examples
Cells take oxygen + nutrients
Cells excrete waste products carbon dioxide, urea
Organisms balanced temperature so heat needs exchanging.
How easily the exchange of substances is depends on?
SA:VR
Smaller animals higher SA:VR
Calculating it:
Find volume
Find surface area
Place like this SA:VR and simplify ratio
Multicellular need
Why
Single celled compared to multicellular
Exchange organs + mass transport systems
Single celled: diffuse directly across cell membrane. Rate is quick small distances substances have to travel.
Multicellular: diffusion accords outer membrane too slow.
- Cells deep within body, big distance to outer environment.
Larger animals low SA:VR can’t exchange enough substances to supply large volume animal though small outer surface.
Body size and heat exchange.
Rate of heat loss depends on surface area.
Large volume small SA harder heat loss.
Large SA to small volume heat loss easy.
Small organisms need high metabolic rate: generate heat.
Shape and heat exchange
Compact shape: small SA, large V
Minimises heat loss.
Less compact (gangly sticky out pits) large SA, small volume. Increases heat loss.
Animal compact or not depends temp of environment.
Physiological adaptations to aid exchange.
High SA: VR lose more water. Evaporates from surface. Small desert animals kidney structure adaptations -> produce less urine.
Smaller animals have fur in cold environment.
Large animals in hot regions. Hard to cool. Elephants -> large flat ears to increase SA.
Behavioural adaptations to aid exchange
Small mammals in cold regions. Support high metabolic rate by eating large amounts of high energy foods.
Smaller animals in cold regions hibernate.
Large organisms in hot regions like hippos spend much of day in water to help them loose heat.
Key words and phrases
To maintain a constant body temperature
Relative
