gas exchange in fish and insects

Question 1

what is a spiracle

Answer 1

an external respiratory pore / opening

Question 2

how doe insects (eg. crickets) exchange gases

Answer 2

• air moves into trachea which divides until it reaches the cells in tracheoles
• diffusion occurs between body cells and tracheoles, exchanging gases via tracheal fluid

Question 3

what are the 4 adaptations of the gills

Answer 3

• increased surface area
• rich blood supply to max. amount of blood that can be oxygenated by diffusion
• countercurrent flow (maintains concentration gradient)
• ventilation

Question 4

explain how the gills can increase surface area?

Answer 4

each gill filament is covered by lamellae

Question 5

explain why the gills need a rich blood supply

Answer 5

to maximise the amount of blood that can be oxygenated by diffusion

Question 6

why is it important that the gills work under a countercurrent flow?

Answer 6

so the concentration of oxygen is always higher in water than the blood - maintains concentration gradient

Question 7

explain the importance of ventilation over fish gills

Answer 7

ventilation increases water flow over gills so increases rate of diffusion

Question 8

describe the counter current system in fish

Answer 8

• blood in capillaries flows in opposite direction to water flowing over them
• this maximises gas exchange (compared to concurrent system)

Question 9

how do fish ventilate the gills

Answer 9

increase and decrease volume of buccal cavity + opening and closing of the operculum