Gas Exchange

Question 1

What type of SA : Volume ratio do larger organisms have?

Answer 1

Smaller SA:Vol

Question 2

What do the efficiency of gas exchange systems depend on?

Answer 2

1. Higher surface Area
2. Short Diffusion distance
3. High Concentration Gradient

Question 3

How does gas exchange take place in insects?

Answer 3

1. Air enters through holes called spiracles
2. O2 diffuses down the concentration gradient along the trachea
3. Trachea are closely surrounded by cells
4. O2 diffuses into cells -> Ventilation helps to maintain a high concentration gradient.

Question 4

How do insects reduce water loss?

Answer 4

1. Body is covered in a waxy cuticle which reduces evaporation
2. Insects can also close their spiracles

Question 5

How does gas exchange take place in fish?

Answer 5

1. Filaments and lamellae have a large surface area
2. This increases efficiency of diffusion
3. Thin epithelium provides a short diffusion
   4.Counter current flow
   
   • Maintains a high concentration gradient
   • Water is always next to blood that has a
     lower concentration of O2
4. Circulation of blood replaces blood that is saturated with O2
5. Ventilation

Question 6

Describe Gas Exchange in Dicotyledenous Plants.

Answer 6

1. Mesophyll is where gas exchange of CO2 for photosynthesis happens
2. Gases diffuse in and out
3. Guard cell can open and close stomata to control water loss

Question 7

What are some xerophytic adaptations of plants?

Answer 7

1. Curled lead
2. Stomata sunken in pints
3. Hairs on epidermis
   
   • Water vapour builds up
   • Decreases the diffusion gradient
4. Thick waxy cuticle
   
   • reduces evaporation
5. Fewer stomata

Question 9

Describe the general path of Oxygen from the air to the lungs.

Answer 9

1. Air goes down the trachea
2. Down the bronchus
3. Down the bronchioles
4. Into the alveoli

Question 10

How is the surface area in lungs increased?

Answer 10

1. There is lots of them
2. They have folded membranes

Question 11

What is tidal volume?

Answer 11

The volume of air breathed in or out per breath at rest

Question 12

What is breathing/ventilation?

Answer 12

Number of breath per minute

Question 13

What is pulmonary ventilation?

Answer 13

The total volume of air breathed in one minute

Question 14

Describe the method of inspiration.

Answer 14

1. Diaphragm contracts (flattens)
2. External intercostal muscles contract - ribs move up and out
3. This increases thoracic volume
4. Atmospheric pressure is higher than thoracic
5. Air moves in from a high to low pressure

Question 15

Describe the method of expiration.

Answer 15

1. Diaphragm relaxes (domed)
2. External intercostal muscles relax - ribcage moves down and in
3. This decrease thoracic volume
4. Increases the pressure of the thorax
5. Thoracic pressure is then higher than atmospheric pressure
6. Air moves out

Question 16

Describe the method of forced expiration.

Answer 16

1. Internal intercostal muscles contract - pulling the ribcage down and in