Surface area to Volume ratio

Question 1

Why do small organisms need resources

Answer 1

• Must continusouly carry out chemical reactions
• Need to absorb resources and get rid of waste products

Question 2

What is the rate of exchanging substances dependent on

Answer 2

• Surface area to Volume ratio

Question 3

Why can small organisms rely on diffusion to exchange substances

Answer 3

• High surface area to volume ratio
• Small / little diffusion distance

Question 4

What happenes to an organisms SA to V ratio as it gets larger

Answer 4

• The SA to V ratio decreases

Question 5

What is the diffusion distance

Answer 5

• The distance that molecules have to diffuse across to get into the body

Question 6

What happenes to the diffusion distance as an organism gets larger

Answer 6

• The diffusion distance increases massively
• The time it takes for the diffusion to take place also increases
• Large organisms cannot solely rely on diffusion to gain / lose their required substances

Question 7

How do large organisms combat their low SA to V ratio and their high diffusion distance

Answer 7

• Have exchange systems to increase their overall surface area and therefore to get substances in and out of the body
• Have transport systems to transport substance to the part of the body that need them

Question 8

What is a large organism

Answer 8

• Anything that can be seen by the naked eye

Question 9

Examples of exchange surfaces in humans

Answer 9

• Alveoli = allow oxygen and CO2 to diffuse in and out of the bloodstream
• Villi (small intestines) = allow nutrients to be absorbed from the small intestines into the bloodstream