3.3.1 surface area to volume ratio

Question 1

smaller/larger organisms and surface area to volume ratio

Answer 1

smaller organisms have a higher surface area : volume ratio than larger organisms

Question 2

how do you calculate the volume of a cylinder?

Answer 2

pi * r squared * height

Question 3

how do you calculate the volume of a sphere?

Answer 3

4/3 * pi * r cubed

Question 4

how do single celled organisms supply its cells with products/remove waste products

Answer 4

substances can diffuse directly in or out of the cell across the cell surface membrane

Question 5

what is the diffusion rate like in small organisms?

Answer 5

diffusion rate is quick because of the small distances that the substances have to travel

Question 6

what is too slow in multicellular organisms to supply its cells with products/remove waste products?

Answer 6

in multicellular organisms, diffusion across the outer membrane is too slow

Question 7

what is one reason why diffusion across the outer membrane is too slow in multicellular organisms (distance)?

Answer 7

some cells are deep within the body - large distance between them and the outside environment

Question 8

what is one reason why diffusion across the outer membrane is too slow in multicellular organisms (sa:v ratio)?

Answer 8

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

Question 9

how do multicellular organisms supply its cells with products/remove waste products (organs)?

Answer 9

instead of using diffusion to absorb and excrete substances, multicellular organisms need specialised exchange organs e.g. lungs

Question 10

how do multicellular organisms supply its cells with products/remove waste products (mass transport)?

Answer 10

they need an efficient system to carry substances to and from their individual cells - called mass transport

Question 11

what does mass transport usually refer to in mammals?

Answer 11

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

Question 12

what does mass transport usually refer to in plants?

Answer 12

mass transport in plants involves the transport of water and solutes in the xylem and phloem

Question 13

heat exchange and body size: larger organisms

Answer 13

larger organisms have a large volume but smaller surface area so it is harder for it to loose heat from its body

Question 14

heat exchange and body size: smaller organisms

Answer 14

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

Question 15

heat exchange and body shape: compact shape

Answer 15

animals with a compact shape have a small sa:v ratio which minimises heat loss from their surface

Question 16

heat exchange and body shape: not compact shape

Answer 16

animals with a less compact shape have a large sa:v ratio which increases heat loss from their surface

Question 17

adaptations for heat exchange

Answer 17

whether an animal is compact or not depends on its environments temperature, animal’s body shape is adapted to suit its environment

Question 18

behavioral and physiological adaptations to aid exchange: water loss

Answer 18

animals with a higher sa:v ratio tend to lose more water as it evaporates from their surface

Question 19

behavioral and physiological adaptations to aid exchange: water loss - why can this be a problem

Answer 19

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

Question 20

behavioral and physiological adaptations to aid exchange: diet

Answer 20

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

Question 21

behavioral and physiological adaptations to aid exchange:
fur

Answer 21

smaller mammals may have thick layers of fur or hibernate when the weather gets really cold

Question 22

behavioral and physiological adaptations to aid exchange: large organisms in hot regions

Answer 22

larger organisms living in hot regions e.g. elephants/hippos find it hard to keep cool as their heat loss is slow

Question 23

behavioral and physiological adaptations to aid exchange: large organisms in hot regions - elephant adaptations for this

Answer 23

elephants have developed large flat ears which increase their surface area so they can lose more heat

Question 24

behavioral and physiological adaptations to aid exchange: large organisms in hot regions - hippo adaptations for this

Answer 24

hippos spend much of their day in the water - behavioral adaptation to help them lose heat