surface area to volume ratio

Question 1

do small organisms have a small or large surface area: volume ratio?

Answer 1

• very large surface are in comparison to their volume

• big surface for exchange of substances
• smaller distance from outside of organisms to middle of it
• so organism can simply exchange substances across their surface

Question 2

do large organisms have a small or large surface:volume ratio?

Answer 2

• larger an organism, smaller its surface area compared to its volume

largeer the distance from middle to the outside

Question 3

key ideas:

Answer 3

1) large animals/organisms/cells have a smaller SA:V ratio
2) large animals/organims/cells have a longer diffusion pathway
3) water has a lower oxygen concentration than air –> SO gills/in fish, SA:V ratio will be maximised to increase exchange of oxygen
4) larger animals in general will use up more oxygen BUT they use less per unit of body mass/they use it more efficiently
5) smaller animals have a higher metabolic rate per body mass, because they have a larger SA:V ratio so lose heat more easily, so require increased areobic respiration to provide energy to maintain body temp
6) when doing calculations, if in doubt round to 3 or less S.F never more than 3