7.4

Question 1

Gas exchange in insects

Answer 1

Air moves through spiracle
into trachea
move down trachea into tracheal fluid
oxygen diffuses into calls
used in respiration.

CO₂ produced
Diffuses out of cells
into tracheal fluid
through tracheoles and trachea
leaves through spiracles.

Question 1

Ventilation in insects

Answer 1

Insects move
causes volume and pressure to change

As a result, air moves in and out through spiracles.
spiracles open and close

Sphincter muscle control opening and closing of spiracles.

Prevents water loss.

Question 2

Ventilation in fish

Answer 2

movement of water in and out

Fish open mouth
buccal cavity is lowered
volume increases
pressure decreases
causes water to enter the mouth

Fish close mouth
buccal cavity raises
volume decreases
pressure increases
water moves towards the gills
leaves fish through the operculum

Fish have a one way movement of water.
Water is more dense than air
more energy to remove water using two way.

Question 3

Gas exchange in fish

Answer 3

Water moves over the gills

Moves in opposite direction to the blood in blood vessels.

counter current flow

Maintains steep concentration between water and blood

Allows oxygen to diffuse from water to blood.

Advantage of counter current system:
water will always have higher concentration of oxygen compared to blood.