Size and Surface Area

Question 1

SA:V ratios

Answer 1

Smaller animals = larger ratio

Question 2

Single-celled organisms

Answer 2

substances can diffuse directly into/out of cell across cell membrane.
diffusion rate increased due to short diffusion pathway

Question 3

Multi-cellular animals

Answer 3

diffusion across outer membrane too slow
cells too deep within body for substances reach in time (big distance between cells and outside environment)
smaller SA:V ratio means it’s difficult to exchange enough substances to supply large volume animal through relatively small outer surface
TF they have specialised exchange organs i.e. lungs, circulatory system

Question 4

Body Size

Answer 4

Larger SA:V ratio = easier to lose heat from body = relatively higher metabolic rate required to generate enough heat to stay warm

Question 5

Body Shape

Answer 5

compact shape = smaller surface area relative to volume = minimised heat loss
and vice versa

Question 6

Behavioural and Physiological Adaptations

Answer 6

small desert mammals have kidney structure adaptations to produce less urine to reduce water loss in hot environment
small mammals in cold regions eat high energy foods to support high metabolic rate
small mammals have thick fur or hibernate during cold winter months
Larger organisms in hot regions have increased surface area/bathe in water to keep cool