B3 exam qs

Question 1

(a)  Describe and explain one feature of the alveolar epithelium that makes the epithelium well
adapted as a surface for gas exchange.

Answer 1

3. Permeable;
4. Allows diffusion of oxygen/carbon dioxide;

Question 2

Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide
between the blood and the alveoli.

Answer 2

1. Less carbon dioxide exhaled
2. (So) reduced diffusion/concentration gradient
3. less CO2 moving out of blood

Question 3

Explain the advantage for larger animals of having a specialised system that facilitates
oxygen uptake.

Answer 3

Large(r) organisms have a small(er) surface area:volume (ratio)
- Overcomes long diffusion pathway

Question 4

Suggest how the environmental conditions have resulted in adaptations of systems using
Model A rather than Model B.

Answer 4

3. Water is dense(r) (than air);
4. (So) water supports the systems/gills;

Question 5

A student studied Figure 2 and concluded that the fish gas exchange system is more
efficient than the human gas exchange system.
Use Figure 2 to justify this conclusion.

Answer 5

1. In fish, blood leaving (V) has more oxygen than water leaving (E);
2. (But) in humans, blood leaving (V) has less oxygen than air leaving (E);
3. Difference in oxygen (concentration) between artery and vein is greater in
   fish than in humans;
4. (So) fish remove a greater proportion from the oxygen they take in

Question 6

Explain how the counter-current principle allows efficient oxygen uptake in the fish gas
exchange system

Answer 6

1. Blood and water flow in opposite directions;
2. Diffusion/concentration gradient (maintained) along (length of)
   lamella/filament;

Question 7

Describe and explain the mechanism that causes lungs to fill with air

Answer 7

  1. Diaphragm contracts and external intercostal muscles contract;
2. Causes volume increase and pressure decrease;
3. Air moves down a pressure gradient

Question 8

  Describe and explain the advantage of the counter-current principle in gas exchange
across a fish gill.

Answer 8

1. Water and blood flow in opposite directions;
2. Maintains diffusion gradient of oxygen
3. oxygen concentration always higher in water
4. diffusion along length of gill

Question 9

Describe the pathway taken by an oxygen molecule from an alveolus to the blood.

Answer 9

1. (Across) alveolar epithelium;
2. Endothelium / epithelium of capillary;

Question 10

Describe and explain the mechanism that causes forced expiration.

Answer 10

1. Contraction of internal intercostal muscles;
2. Relaxation of diaphragm muscles / of external intercostal muscles;
3. Causes decrease in volume of chest / thoracic cavity;
4. Air pushed down pressure gradient.

Question 11

The people in group B were recovering from an asthma attack.
Explain how an asthma attack caused the drop in the mean FEV shown in the figure above.

Answer 11

1. Muscle walls of bronchi / bronchioles contract;
2. Walls of bronchi / bronchioles secrete more mucus;
3. Diameter of airways reduced;
4. (Therefore) flow of air reduced.

Question 12

Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange.

Answer 12

1. Tracheoles have thin walls so short diffusion distance to cells;
2. Highly branched / large number of tracheoles so short diffusion distance to
   cells;
3. Highly branched / large number of tracheoles so large surface area (for gas
   exchange);

Question 13

Explain how the presence of gills adapts the damselfly to its way of life.

Answer 13

1. Damselfly larvae has high(er) metabolic / respiratory (rate);
2. (So) uses more oxygen

Question 14

Suggest two ways the student could improve the quality of her scientific drawing of this gill.

Answer 14

1. Don’t use shading;
2. Only use single lines
3. Don’t cross label lines;
4. Add magnification / scale (bar);

Question 15

Name the structure through which gases enter and leave the body of an insect

Answer 15

spiracle

Question 16

Name the small tubes that carry gases directly to and from the cells of an insect.

Answer 16

Tracheole/trachea

Question 17

Explain the movement of oxygen into the gas exchange system of an insect when it is at
rest

Answer 17

1. Oxygen used in (aerobic) respiration;
2. (so) oxygen (concentration) gradient established
3. (so) oxygen diffuses in

Question 18

Using information from the diagram, suggest what stimulates the spiracles to open.

Answer 18

increasing carbon dioxide concentration

Question 19

) Explain what causes the oxygen concentration in the tracheae to fall when the spiracles are
closed.

Answer 19

(oxygen is used in) respiration therefore diffuses (from tracheae) to tissues;
oxygen unable to enter organism;

Question 20

The insect lives in dry conditions. Suggest an advantage of the pattern of spiracle
movements shown in the diagram

Answer 20

spiracles not open all the time;
therefore there is less water loss

Question 21

Describe how the structure of the insect gas exchange system:
*   provides cells with sufficient oxygen
*   limits water loss (5 marks)

Answer 21

1. Spiracles (lead) to tracheae (that lead) to tracheoles;
2. Open spiracles allow diffusion of oxygen from air
3. Tracheoles are highly branched so large surface area
4. Tracheole (walls) thin so short diffusion distance (to cells)
5. Tracheole walls are permeable to oxygen;
6. Spiracles close (eg.during inactivity) preventing water loss

Question 22

Describe how humans breathe in and out.

Answer 22

Breathing in
1. Diaphragm (muscles) contract and diaphragm flattens;

2. External intercostal muscles contract and ribcage pulled up/out;
3. (Causes) volume increase and pressure decrease in thoracic cavity

Breathing out
4. Diaphragm (muscles) relaxes and internal intercostal muscles contract;
5. (Causes) volume decrease and pressure increase in thoracic cavity

Question 23

Describe and explain how the countercurrent system leads to efficient gas exchange
across the gills of a fish

Answer 23

1. water and blood flow in opposite directions
2. maintains concentration gradient
3. oxygen concentration always higher in water
4. diffusion along length of whole gill

Question 24

The volume of water passing over the gills increases if the temperature of the water
increases. Suggest why.

Answer 24

1. Increased respiration
2. Less oxygen dissolved in water

Question 25

Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.

Answer 25

1. Many lamellae / filaments so large surface area; 2. Thin (surface) so short diffusion pathway

Question 26

Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills.

Answer 26

1. water and blood flow in opposite directions 2. maintains diffusion gradient of oxygen 3. oxygen concentration always higher in water 4. diffusion along whole length of gill

Question 27

A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange.

Answer 27

1. Large surface area provided by lamellae / filaments increases diffusion 2. Thin epithelium / distance between water and blood; 3. Water and blood flow in opposite directions / countercurrent; 4. (Point 4) maintains concentration gradient (along gill) as oxygen always has higher concentration in water 5. Circulation replaces blood saturated with oxygen; 6. Ventilation replaces water (as oxygen removed);

Question 28

The concentration of oxygen is higher in the surface waters than it is in water close to the seabed. Suggest why.

Answer 28

Mixing of air and water (at surface); Air has higher concentration of oxygen than water; Diffusion into water; Plants / seaweeds near surface / in light; Produce oxygen by photosynthesis

Question 29

Describe and explain the mechanism that causes forced expiration

Answer 29

1. Contraction of internal intercostal muscles; 2. Relaxation of diaphragm muscles / of external intercostal muscles; 3. Causes decrease in volume of chest / thoracic cavity; 4. Air pushed down pressure gradient.

Question 30

The people in group B were recovering from an asthma attack. Explain how an asthma attack caused the drop in the mean FEV shown in the figure below.

Answer 30

1. Muscle walls of bronchi / bronchioles contract; 2. Walls of bronchi / bronchioles secrete more mucus; 3. Diameter of airways reduced; 4. (Therefore) flow of air reduced.

Question 31

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs.

Answer 31

1. Trachea and bronchi and bronchioles; 2. Down pressure gradient; 3. Down diffusion gradient; 4. Across alveolar epithelium.

Question 32

Explain how the body shape of a Weddell seal is an adaptation to living in a cold environment.

Answer 32

Small SA:VOL retains more heat

Question 33

what causes the thoractic cavity to increase

Answer 33

external intercostal muscles contract ribs move up and out diaphragm contracts and moves down

Question 34

what causes the thoractic cavity to decrease

Answer 34

external intercostal muscles relax ribs move down and in diaphragm relaxes and moves up

Question 35

what happens to the pressure inside the thoractic cavity when inhaling

Answer 35

decreases

Question 36

what happens to the volume of the thoractic cavity when exhaling

Answer 36

decreases

Question 37

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.

Answer 37

1. Many alveoli and alveoli walls folded provide a large surface area; 2. Many capillaries provide a large surface area; 3. So fast diffusion; 4. Alveoli and capillary walls are thin so short distance between alveoli and blood; 5. Flattened epithelium; 6. So short diffusion distance so fast diffusion; 8. Ventilation / circulation maintains a diffusion gradient so fast diffusion;

Question 38

Describe the gross structure of the human gas exchange system and how we breathe in and out.

Answer 38

1. trachea, bronchi, bronchioles, alveoli; 2. Breathing in - diaphragm contracts and external intercostal muscles contract; 3. Causes volume increase and pressure decrease in thoracic cavity to below atmospheric, resulting in air moving in; 4. Breathing out - Diaphragm relaxes and internal intercostal muscles contract; 5. Causes volume decrease and pressure increase in thoracic cavity to above atmospheric, resulting in air moving out;

Question 39

what happens to the volume of the thoracic cavity when INHALING

Answer 39

increases

Question 40

what happens to the pressure inside the thoractic cavity when EXHALING

Answer 40

increase

Question 41

whats tidal volume

Answer 41

vol of air taken into the lungs during each breath when at rest

Question 42

what is pulmonary ventilation rate how do you calculate it

Answer 42

volume of air taken into the lungs during 1 min pulmonary rate (dm3min-1) = tidal volume (dm3) x breathing rate (min-1)