3 Substance exchange- Surface area to volume ratio

Question 1

What is the surface area of an organism?

Answer 1

-The total surface over which substances and heat can be exchanged,
It cannot alone influence the rate of exchange
-More important when relative to volume

Question 2

What is the volume of an organism?

Answer 2

-Total space it occupies
-Determines the number of substances that need to be taken in and transported out
-As volume increases, more materials are needed for metabolism as there are more cells

Question 3

What is surface area to volume ratio?

Answer 3

-When an organism increases in size, its volume also increases as there are more cells
Therefore, there is less surface area for the exchange of materials because many cells are in contact with one another
-Decreases with increasing organism size

Question 4

What are the adaptations to a decrease in surface area to volume ratio?

Answer 4

-Large surface area, so more of the substance can diffuse
-Thin membrane, reducing diffusion distance
-Transport systems, moving substances around the organism or facilitating exchange (e.g. xylem), allow higher concentration gradient
-Heat transfer; adaptations allowing this to be more efficient