3.3.2 Gas exchange

Question 1

What is the counter-current flow in fish gills and why is it important regarding gas exchange?

Answer 1

Ensures no equilibrium
Water flows in the opposite direction to the blood
Makes sure oxygen diffuses across all of the lamella maintaining a diffusion gradient

Question 2

How are insects adapted for gas exchange?

Answer 2

Insects use a tracheal system with:
Spiracles: Openings for gas exchange.
Tracheae and tracheoles: Tubes that deliver oxygen directly to tissues.
Thin, moist surfaces for diffusion.

Question 3

How does gas exchange occur in the alveoli and what adaptations do they have for effective exchange?

Answer 3

Oxygen diffuses from the alveoli into the capillaries.
Carbon dioxide diffuses from the capillaries into the alveoli.
Alveoli have a thin epithelium, large surface area, and are surrounded by capillaries to maintain a concentration gradient.

Question 4

What are the consequences of a reduced surface area for gas exchange in the alveoli?

Answer 4

Less oxygen can diffuse into the blood, leading to decreased oxygen supply to tissues and reduced energy production.

Question 5

What do larger organism have a greater demand of ?

Answer 5

Higher demand for oxygen as

Question 6

Describe how we breathe in and out ?

Answer 6

Breathe in - external intercostal muscles and diagram contract
Volume increases and pressure decreases in the thorax cavity
Breathe out - external intercostal muscles and diagram relax
Volume decreases and pressure increases in the thorax cavity

Question 7

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing are not required

Answer 7

Trachea, bronchi, bronchioles
Down the pressure and diffusion gradient
Across the alveolar epithelium
Across the capillary endothelium

Question 8

People with fibrosis often find it hard to breath out properly. Explain why

Answer 8

Loss of elasticity
Less recoil

Question 9

Explain how the waxy cuticle prevents water loss

Answer 9

Waterproof

Question 10

Explain how the stomata reduced water loss

Answer 10

Stomata can close
Reduces area for evaporation or transpiration

Question 11

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

Answer 11

Oxygen is used in respiration
Oxygen concentration gradient is established
So oxygen diffuses in