Module 3- Exchange Surfaces

Question 1

the larger the organism….

Answer 1

….the smaller the SA:V

Question 2

what are the limitations of the agar cube practical?

Answer 2

-inconsistency with SA,, cubes may not be cut to desired length on every side
-subjective results,, how much has pigment actually gone through?

Question 3

why do larger organisms need specialised exchange systems?

Answer 3

-smaller SA:V ∴ oxygen cannot diffuse quick enough (due to long diffusion distance) to meet metabolic needs deep in body
-higher metabolic activity ∴ lots of CO₂ production

Question 4

why do single-celled organisms not need specialised exchange systems?

Answer 4

-low metabolic activity ∴ O₂ demand low and CO₂ production low
-SA:V high

Question 5

how does an increase in surface area create an efficient exchange system?

Answer 5

-provides area for gas exchange to take place
-overcomes limitations of small SA:V in large organisms
EXAMPLES: root hair cells

Question 6

how do thin layers create an efficient exchange system?

Answer 6

-distance substances needed to diffuse are short so process is fast and efficient
EXAMPLES: alveoli

Question 7

how does good blood supply create an efficient exchange system?

Answer 7

-creates steep concentration gradient=faster diffusion
-ensures substances are constantly delivered+removed from exchange surface which maintains a steep concentration gradient for diffusion
EXAMPLES: gills in fish

Question 8

how does ventilation to maintain a diffusion gradient create an efficient exchange system?

Answer 8

-for gases ventilation system maintains a concentration gradient + makes process more efficient
EXAMPLES: alveolus