Ventilation in Fish

Question 1

What are the features about the Gills?

Answer 1

• fish have 4 gills on each side of their head
• they have a large SA, good blood supply & thin surface area for gas exchange
• found within the gill cavity covered by a flap called the operculum
• helps maintain one way flow of water over the gills
• this brings water in with fresh oxygen, carries water away that has picked up carbon dioxide.

Question 2

What is the structure of the gills?

Answer 2

• each gill made up of 2 rows of gill filaments
• attached to a bony gill arch
• each filament is thin, surface is folded into lamellae (gill plates)
• provides a big surface area

Question 3

What is a counter- current system?

Answer 3

• blood flows through the gill plates in one direction and water flows in the opposite direction.
• means water with a relatively high oxygen concentration gradient always flows next to blood with a lower concentration of oxygen.
• a steep concentration gradient is maintained between water and blood.

Question 4

How does water flow over the gills?

Answer 4

• fish use their mouth and operculum flap to maintain a flow of water over their gills.
  tips of the adjacent gill filaments overlap.
  Increases the resistance to the flow of water and slows down water movement

Question 5

How does Ventilation in bony fish occur when the fish opens its mouth?

Answer 5

• fish opens its mouth
• lowers the floor of the buccal cavity
• increases volume of buccal cavity
• pressure inside the buccal cavity to fall
• water is then drawn into the buccal cavity due to the pressure gradient

Question 6

How does Ventilation in bony fish occur when the fish closes its mouth?

Answer 6

• Fish closes its mouth
• floor of the buccal cavity raises
• volume of inside the buccal cavity falls
• pressure inside the buccal cavity increases
• water is forced over the gill filaments - where gas exchange occurs

Question 7

How is the structure of a fish gill adapted?

Answer 7

• Gills have a large SA - diffusion
• Rich blood supply - maintain steep concentration gradient
• Tips of adjacent gills overlap- shows water flow
• thin layers - short diffusion pathway

Question 8

How do you dissect a fish?

Answer 8

• Place your chosen fish in a dissection tray or on a cutting tray.
• Push back the operculum and use scissors to carefully remove the gills. Cut each gill arch through the bone at the top and bottom.
• You should be able to see the gill filaments
• then draw the gills