Surface Area To Volume Ratio

Question 1

What are organisms

Answer 1

They are constantly exchanging materials with their environment

Question 2

What can microscopic/single celled organisms do

Answer 2

They can exchange all the substances it needs directly through the cell membrane

Question 3

Why can these single celled organisms do this

Answer 3

Low rate of respiration as they are not very active organisms
The surface area of the cell membrane is relatively large compared to the volume of the cell (large SA:VOL ratio)

Question 4

How is SA:VOL ratio calculated

Answer 4

SA/VOL

Question 5

What is the formula for the surface area and volume of a sphere

Answer 5

4 pi r squared - surface area
4/3 pi r cubed - volume

Question 6

What do single celled organisms have

Answer 6

A relatively large surface area to volume ratio, sot hey can transfer all the chemicals that they need across the cell membrane.

Question 7

What do larger multicellular organisms have

Answer 7

A much smaller SA:VOL ratio

Question 8

What have multicellular organisms evolved

Answer 8

They have evolved two specialised systems to compensate for

Question 9

What are the two specialised systems that they have evolved

Answer 9

A specialised gas exchange surface with a very large surface area
A specialised transport system to carry molecules around their body

Question 10

What is the first feature that all specialised exchange surfaces have in common + examples

Answer 10

Increased surface area - provides the area needed to exchange and it overcomes the limitations of the SA:VOL ratio of larger organisms
For example root hair cells in plant and the villi in the small intestine of animals

Question 11

What is the second and third feature that all specialised exchange surfaces have in common

Answer 11

Thin layers - this means that the distances that substances have to diffuse are short making the process fast and efficient

Good blood supply - which means that substances are constantly delivered to and removed from the exchange surface maintaining the steep concentration gradient for diffusion

Question 13

What is the fourth feature that all specialised exchange surfaces have in common

Answer 13

Ventilation to maintain diffusion gradient - where a ventilation system helps to maintain concentration gradients and makes the process more efficient.