gas exchange

Question 1

SA:V ratio in small organisms

Answer 1

• larger SA:V ratio —> thin/small —> short diffusion pathway (faster heat loss per gram so faster rate of respiration & faster diffusion)

Question 2

SA:V ratio in larger organisms

Answer 2

• smaller SA:V ratio –> long diffusion pathway –> specialised system needed

Question 3

tissue =

Answer 3

group of similar cells working together to perform a function

Question 4

organ =

Answer 4

group of diff. tissues working together to perform a function

Question 5

adaptations of xerophytes to reduce H2O loss

Answer 5

• sunken stomata / rolled leaves –> traps moisture & increases local humidity
• longer/deeper roots –> reaches more water in deep ground
• shallow roots –> enables rapid uptake of rainfall

Question 6

insects

movement of O2 in trachael system

Answer 6

1. O2 moves through spiracles, trachaea & trachaeoles
2. O2 used in aerobic respiration
3. O2 conc. gradient established
4. diffuses through permeable tracheoles

Question 7

insects

adaptations for gas exchange in tracheal system

Answer 7

1) large no. of tracheoles –> large SA
2) thin tracheole walls –> short diffusion pathway
3) body moved by muscles –> maintains O2 diffusion gradient

Question 8

insects

adaptations to reduce H2O loss

Answer 8

• impermeable exoskeleton
• spiracles can open & close
• small SA:V ratio

Question 9

fish

maintaining flow of H2O over gills

Answer 9

• mouth closes & operculum shuts –> floor of mouth lowered
• H2O enters due to decreased pressure
• mouth opens & operculum opens
• floor raised –> increase in pressure
• pressure forces H2O over gills

Question 10

fish

adaptations of fish gills

Answer 10

1) lots of lamellae on gill filaments –> large SA
2) thin epithelium –> short diffusion pathway between H2O & blood
3) large no. of capillaries —> short diffusion pathway
4) counter current –> maintains conc. gradient

Question 11

fish

counter-current flow mechanism

Answer 11

1. water flow in gills in opp. direction to blood in capillaries
2. blood always passing H2O with higher O2 conc.
3. O2 diffusion gradient maintained along length of lamella
4. so diffusion occurs across entire lamella
5. more O2 diffuses into blood
6. more aerobic resp. so more energy for swimming

Question 12

ventilation/breathing =

Answer 12

movement of air in & out of the lungs

Question 13

respiration =

Answer 13

chemical reaction to release energy in form of ATP

Question 14

human gas exchange

what is the name used to describe the internal intercostal muscles & the external intercostal muscles working simultaneously?

Answer 14

antagonistic pair

Question 15

human gas exchange

inhalation

(process)

Answer 15

1. diaphragm contracts –> external intercostal muscles contract
2. diaphragm flattens, ribcage moves up & out
3. lung vol. increases —> pressure decreases in thoracic cavity
4. presure in thorax lower than outside air
5. air moves down pressure gradient

Question 16

human gas exchange

exhalation

Answer 16

1. diaphragm relaxes –> internal intercostal muscles relax
2. diaphragm curves, ribcage moves down & in
3. lung vol. decreases –> pressure increases in thoracic cavity
4. pressure in thorax higher than outside air
5. air pushed down pressure gradient

Question 17

human gas exchange

adaptations for gas exchange in lungs

Answer 17

1) large no. capillaries –> large SA –> fast diffusion
2) alveolar walls 1 cell thick –> short diffusion pathway
3) many alveoli –> large SA –> fast diffusion
4) ventilation/circulation –> maintains O2 conc. gradient (brings in air with higher O2 & vice versa)

Question 18

describe how oxygen is taken from air to blood

Answer 18

1. trachea —> bronchi —> bronchioles —> alveoli
2. down pressure & diffusion gradient
3. across alveolar epithelium
4. through capillary endothelium