features of efficient exchange surface

Question 1

how many alveoli in each lung?

Answer 1

300 million

Question 2

what are alveoli surrounded by?

Answer 2

capillaries

Question 3

4 adaptions of alveoli

Answer 3

moist surface for oxygen to dissolve, many alveoli, epithelium is one cell thick, ventilation supplies oxygen rich air and removes carbon dioxide

Question 4

How does moist surface speed up diffusion?

Answer 4

makes it easier for oxygen to diffuse as it is dissolved

Question 5

How does a high number of alveoli increase the rate of diffusion?

Answer 5

large number means a larger total exposed SA, so diffusion is faster

Question 6

How does a thin epithelium help diffusion?

Answer 6

decreases distance over which diffusion occurs, so it’s a quicker process

Question 7

3 adaptations of capillaries

Answer 7

lots of capillaries wrapped over alveoli, endothelium is one cell thick, circulatory system constantly moves blood through the capillary

Question 8

How does a large number of capillaries increase diffusion?

Answer 8

Good blood supply and diffusion gradient

Question 9

How does endothelium being one cell thick help diffusion?

Answer 9

decreases distance over which diffusion occurs, which increases rate

Question 10

How does movement of circulatory system help diffusion?

Answer 10

maintains a diffusion gradient as blood with high O2 concentration moves away

Question 11

What is meant by SA:volume ratio?

Answer 11

-ratio between an organism’s surface area and volume, dictates how easy the exchange of substances is

Question 12

How do you calculate SA: Volume ratio?

Answer 12

divide SA by volume

Question 13

What kinds of animals have higher SA:volume ratios

Answer 13

small animals, eg a mouse

Question 14

Why is SA:vol ratio important?

Answer 14

all animals need to exchange substances with the environment (eg. take in oxygen and glucose for aerobic respiration and other metabolic reactions, and excrete waste products such as CO2

Question 15

What is SA:vol like in unicellular organisms?

Answer 15

-high SA:vol
-substances can diffuse directly and quickly into/out of cell across plasma membrane

Question 16

What is diffusion like in multicellular organisms?

Answer 16

-diffusion is slower
-low SA:vol ratio makes it heard to exchange enough substances to supply large animal volume via small animal surface
-some cells can be deep within the body
-higher metabolic rate means multicellular organisms use up oxygen and glucose faster

Question 17

What type of organisms are better at conserving heat?

Answer 17

organisms with a low SA:vol ratio as diffusion happens slower