SIZE AND SURFACE AREA Flashcards
What do most cells need to exchange with the environment (3 points)
1) take in oxygen for aerobic respiration and nutrients
2) excrete waste products (e.g. C02 and urea)
3) heat - to stay at the same temperature
What 2 main factors affect the rate of exchange of substances
1) surface area: volume ratio
2) surface thickness
How does surface area: volume ratio affect the rate of exchange
bigger SA:V ratio = faster rate of exchange
How do you find the volume
the area of the surface of one side times the volume
How do you find the surface area
surface areas of all sides added
Why do multi-cellular exchange via mass transport rather than diffusing directly
diffusion is too slow
Why is diffusion too slow in multi-cellular organisms (2 points)
1) some cells are deep within the body so theres a large distance to travel for diffusion
2) larger animals have a smaller SA:V ratio
What is mass transport
an efficient system
What is mass transport usually in mammals
circulatory system
What does the circulatory system use to transport materials
blood
What does the blood in the circulatory system transport (5 points)
1) glucose
2) oxygen
3) hormones
4) antibodies
5) waste - e.g. C02
What does the mass transport in plants involve
transport of water and solutes
Where does mass transport in plants occur
xylem and phloem
What 2 main factors affect heat exchange
1) surface area: volume ratio
2) shape
How does body size affect the rate of heat loss
large SA:V ratio = heat lost more easily
What do smaller organisms with a larger SA:V ratio need to stay warm
faster metabolic rate
How does shape affect the rate of heat loss
1) compact = small SA:V = minimal heat loss
2) less compact = larger SA:V = more heat loss
What decides if an animal is compact and give an example
its environment , eg fox - arctic fox (cold temp)=small ears, european fox (warm temp)=large ears
What other types of adaptations are there (other than physical)
behavioural and physiological
What do animals with a high SA:V ratio tend to lose more of, and what do some do to adapt to this
water
they have kidney structure adaptations so that they produce less urine
What do animals living in cold regions do to support their higher metabolic rates
eat lots of high energy foods
What do some smaller mammals have/do when the weather gets cold
layers of fur or hibernate
Give 2 examples of large animal adaptations to increase surface area and lose heat
elephants have large flat ears (physical ) , hippos spend lots of time in water (behavioural)
