Size and Surface Area

Question 1

Organisms need to exchange substances with their ————-

Answer 1

environmnet

Question 2

what are the three main things a cell needs to do regarding substance exchange?

Answer 2

1. cells need to take in oxygen and nutrients for aerobic respiration
2. they need to excrete waste products like carbon dioxide and urea
3. heat needs to be exchanged too, as most organisms need to maintain the same temperature

Question 3

what affects gas exchange?

Answer 3

the Surface area: volume ratio

Question 4

what SA:V ratio do small animals have?

Answer 4

higher SA: V ratio

Question 5

what SA:V ratio do large animals have?

Answer 5

lower SA: V ratio

Question 6

how can substances diffuse in single celled organisms?

Answer 6

they can diffuse straight in and out of cells due to the short diffusion pathway

Question 7

describe substance exchange in multi-cellular organisms

Answer 7

in multi- cellular organisms diffusion across the outer membrane is slow

Question 8

why is diffusion/ gas exchange slow in multi-cellular organisms?

Answer 8

1. the cells deep inside the body mean a large pathway
2. large animals have a lower SA:V ratio

Question 9

what do multi-cellular organisms need in order to make gas exchange more effective?

Answer 9

• specialised exchange organs
• mass transport systems

Question 10

what adaptations can organisms have to aid exchanges?

Answer 10

Behavioural and Physiological Adaptations

Question 11

describe an example of a physiological adaption

Answer 11

i.e. an elephant
a larger organism in a hot climate, means slow heat loss
an elephant has adapted to have large, flat ears which increase the SA to make exchange more efficient

Question 12

describe an example of a behavioural adaptation

Answer 12

i.e. a hippo
a large organism in a hot climate
it spends most of its time in cool water to aid heat loss
a behavioural adaptation