Gas exchange

Question 1

What is the broad composition of gases in air?

Answer 1

79% N2

21% O2

Question 2

What is the air pressure at sea level?

Answer 2

101 kPa

Question 3

What is Dalton’s Law?

Answer 3

Each gas in a mixture contributes to the pressure in direct proportion to its percentage

Question 4

What are the broad partial pressures of gases in air?

Answer 4

N2 79 kPa

O2 21 kPa

Question 5

What is anoxia?

Answer 5

No oxygen

Question 6

What is hypoxia?

Answer 6

Low oxygen levels

Question 7

What is normoxia?

Answer 7

Normal oxygen levels

Question 8

What is hyperoxia?

Answer 8

High oxygen levels

Question 9

What is Fick’s Law?

Answer 9

Q=ΔP x A x D/ΔX

Question 10

How have respiratory organs in animals been enhanced to increase the efficiency of diffusion?

Answer 10

High diffusion coefficient 
Low diffusion distance
Large surface area
Vascularisation
Conversion of gas to non-diffusable substance

Question 11

How is the diffusion distance lowered?

Answer 11

Thin epithelia

Question 12

How is the surface area increased?

Answer 12

Invaginations

Question 13

How is gas converted to a non-diffusible substance?

Answer 13

Using respiratory proteins such as haemoglobin and haemocyanin

Question 14

Is the viscosity and density of water high or low?

Answer 14

High

Question 15

Why don’t aquatic organisms use tidal flow?

Answer 15

Too much energy is required to accelerate and decelerate a bulk of water

Question 16

What do aquatic organisms use instead of tidal flow?

Answer 16

Flow-through system and a countercurrent

Question 17

Describe an octopuses ventilation system

Answer 17

Water enters through the slit and exits through the siphon
The pressure in the upper mantle is higher than in the lower mantle
This gives a constant one-way ventilation

Question 18

Describe a fishes ventilation system

Answer 18

One way water flow is achieved by the sequential opening of the mouth and operculum
This sets up an almost continuous pressure difference between the 2 cavities
This ensures the water will flow through the dense sieve-like arrangement of lamellae

Question 19

How do animals keep their respiratory systems moist?

Answer 19

They themselves remain in moist areas

Have covered/ internal structures

Question 20

Describe the insect tracheal system

Answer 20

Discontinuous ventilation where the valves of the trachea open and close allowing gas to enter the tracheal system and the frequency of opening is varied depending on the oxygen requirement

Question 21

What is discontinuous ventilation?

Answer 21

The trachea are not ventilated constantly

Question 22

Describe the first step in aerial gas exchange in lungfish

Answer 22

The mouth opens, the buccal cavity expands and air enters the buccal cavity

Question 23

Describe the second step in aerial gas exchange in lungfish

Answer 23

The mouth closes, the buccal cavity compresses and air enters the anterior chamber of the air-breathing organ

Question 24

Describe the third step of aerial gas exchange in lungfish

Answer 24

The mouth is closed, the anterior chamber is closed and the posterior chamber contracts, and the spent air is exhaled from the posterior chamber through the operculum

Question 25

Describe the fourth step in aerial gas exchange in lungfish

Answer 25

The mouth is closed, the anterior chamber opens, the posterior chamber contracts and air flows into the posterior chamber, and gas exchange occurs

Question 26

What is the name for how frogs respire?

Answer 26

Buccopharyngeal pump

Question 27

Describe the mammalian respiratory system

Answer 27

Air enters the lungs from the oral cavity or nasal passages via the trachea and bronchi The air then enters the alveoli In the alveolus, the air is very close to the blood flowing through the capillary network surrounding them The alveolar walls and capillary walls are very thin thus the diffusion distance is lowered to ~2mm

Question 28

Describe the process of inhalation

Answer 28

``` The diaphragm contracts The thoracic cavity expands The intrapleural pressure becomes negative The lungs expand Air enters the lungs ```

Question 29

Describe the process of exhalation

Answer 29

``` The diaphragm relaxes The thoracic cavity contracts The intrapleural pressure becomes less negative The lungs contract Gas is expelled from the lungs ```

Question 30

What method of gas exchange do mammals use?

Answer 30

Tidal ventilation

Question 31

Describe bird lungs

Answer 31

Small Rigid No alveoli Connected to air sacs

Question 32

What do birds use instead of alveoli?

Answer 32

Vascularised tubes called parabronchi

Question 33

What do air sacs do?

Answer 33

Penetrate viscera and many bones (pneumatisation) | They are poorly vascularised and play no role in air exchange

Question 34

Describe unidirectional flow in birds

Answer 34

Air travels through the lungs in one direction from the posterior to anterior air sacs

Question 35

How many cycles of inhalation/exhalation is required for the air to travel all of the way through a bird's respiratory system?

Answer 35

2 but in reality, these 2 breaths happen simultaneously

Question 36

What system of gas exchange do fish gills use?

Answer 36

Countercurrent system

Question 37

What system of gas exchange do mammalian lungs use?

Answer 37

Tidal flow

Question 38

What system of gas exchange do bird lungs use?

Answer 38

Crosscurrent system

Question 39

What system of gas exchange does amphibian skin use?

Answer 39

Cocurrent system

Question 40

Describe the cocurrent system

Answer 40

Blood and medium flow in the same direction and gradually approach equilibrium with each other

Question 41

Describe the countercurrent system

Answer 41

Blood and medium flow in opposite directions so oxygen always diffuses from the medium into the blood

Question 42

Describe the tidal flow system

Answer 42

Fresh medium mixes with the stale medium in the lung so the partial pressure of oxygen at the exchange surface is lower than the environmental medium Oxygen diffuses into the blood so the partial pressure increases in the blood but remains lower than the exhaled medium do won't diffuse backward