Gas Exchange

Question 1

How does oxygen move through an insect?

Answer 1

Diffuse in through spiracles
Spiracles close
Down trachea and into tracheoles
Then into respiring tissues

Question 2

Explain three ways in which an insects tracheal system is adapted for efficient gas exchange.

Answer 2

Many tracheoles so large surface area
Tracheoles have thin walls so short diffusion distance
Body can be moved by muscles to move air which maintains the concentration gradient of oxygen

Question 3

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

Answer 3

Blood and water flow in opposite directions
Which maintains the concentration gradient of oxygen
Along the entire length of lamellae

Question 4

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

Answer 4

Many lamellae so large surface area
So increased diffusion
Blood and water have little distance between them
And uses the counter current system
Which maintains concentration gradient of oxygen
Water passes blood with lower concentration of oxygen
Circulation replaces blood saturated with oxygen
Ventilation replaces water

Question 5

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

Answer 5

Trachea, bronchi, bronchioles, alveoli
Breathing in- diaphragm and external intercostal muscles contract
Volume increases and pressure within thoracic cavity decreases
Breathing out- diaphragm relaxes and internal intercostal muscles contract
Volume decreases and pressure within thoracic cavity increases

Question 6

Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside a leaf.

Answer 6

Enters through stomata
Opened by guard cells
Diffuses into air spaces
Down diffusion gradient

Question 7

Explain why plants grown in soil with little water grow slowly.

Answer 7

Stomata remains closed
So less carbon dioxide so less photosynthesis