2.2.1 Exchange and Transport

Question 1

SA:V

Answer 1

Surface area to volume ratio

-surface area per unit of volume of an object

Question 2

Organisms SA:V

Answer 2

• larger organism, lower SA:V
• most multicellular organisms cannot use diffusion to live as diffusion cannot occur fast enough to meet cell’s demand because of big distances
• multicellular organisms have adapted to increase SA:V at exchange surfaces

Question 3

Tapeworm

Answer 3

• large SA:V ratio
• nutrient diffuse directly into organism=quickly enough to sustain life
• diffusion distances are small

Question 4

Alveoli

Answer 4

-lungs
-max rate of diffusion of oxygen into bloodstream
-increases SA of lungs
-blood supple maintains gradient by removing oxygen and taking CO2
-spherical shape = larger SA
Thin walls = short distance for diffusion
-ventilation system moves air in and out=concentration gradient

Question 5

Villi

Answer 5

• finger-like structures
• increase SA of small intestine wall
• microscopic microvilli increase SA more
• max diffusion rate of digested food molecules absorbed into blood from small intestine
• Rich blood supply=concentration gradient for efficient diffusion
• thin one cell wall = short distance for diffusion

Question 6

Animal main transport system

Answer 6

Circulatory system

-blood carries materials to required areas

Question 7

Plant transport system

Answer 7

Xylem tubes:
-carry water and mineral ions
Phloem tubes:
-transport sugars and amino acids