surface area to volume ratio and gas exchange surfaces

Question 1

what does surface area to volume ratio tell us?

Answer 1

how many units of surface area we have compared to units of volume

Question 2

what is the trend for surface area to volume ratio as the size of an organism increase?

Answer 2

decreases so larger organisms have a smaller surface area to volume ratio

Question 3

why is it a benefit to single celled organisms that they have a large surface area to volume ratio?

Answer 3

they can obtain enough oxygen at a fast enough rate via diffusion over their surface to meet their metabolic requirements

Question 4

what do organisms with a smaller SA to volume ratio require?

Answer 4

a specialised gas exchange surface to obtain enough oxygen, at a fast enough rate to meet their metabolic requirements

Question 5

what do gas exchange surfaces need?

Answer 5

large surface area, short diffusion pathway and a steep concentration gradient to ensure a fast rate of diffusion of oxygen

Question 6

what does fick’s law describe the rate of diffusion as being proportional to?

Answer 6

surface area X difference in concentration/ length of diffusion pathway

Question 7

why are gas exchange surfaces often an internal structure?

Answer 7

so it can’t be easily damaged and to prevent large amounts of water loss that would lead to dehydration.

Question 8

why do animals in cold environments have smaller ears and are larger in size?

Answer 8

smaller surface area to volume ratio
so less heat energy lost to environment

Question 9

what do mammals have the ability to do?

Answer 9

control their own body temperature- thermoregulate

Question 10

why can’t mammals be smaller than a bumblebee bat?

Answer 10

smaller mammals have a higher surface area to volume ratio so greater heat loss over surface

so higher rates of respiration needed to release heat and maintain body temp

so need to intake more glucose

smaller mammals cannot eat enough to maintain this.

Question 11

why is diffusion slower for larger organisms?

Answer 11

diffusion pathways larger

Question 12

what do larger organisms require?

Answer 12

a transport system which enables large flow/ the bulk movement of substances down a concentration gradient so that a lot of oxygen is transported to all cells quickly.

Question 13

why do large organisms have a circulatory system?

Answer 13

larger diffusion pathway due to longer distances from the exchange surfaces to the respiring cells

this means diffusion is too slow

need to move oxygen from exchange surface to respiring cells quicker than diffusion

so we have a circulatory system (pressure gradient system) which allows mass flow.