fishes

Question 1

what type of circulatory system do fishes have?

Answer 1

Closed and single circulatory system.

Question 2

what happens during ventilation of fish?

Answer 2

 The fish opens its mouth
 This lowers the floor of the buccal cavity (inside the mouth)
 This increases the volume of the buccal cavity
 This causes the pressure inside the buccal cavity to fall
 Water is then drawn into the buccal cavity due to the pressure gradient (higher
outside)
THEN;
 The fish closes its mouth
 The floor of the buccal cavity is raised
 The volume inside the buccal cavity falls
 The pressure inside the buccal cavity increases
 Water is forced over the gill filaments – where gas exchange then occurs

Question 3

How do fishes have an efficient surface?

Answer 3

• Lots of gill filaments and gill lamellae on the gill filaments, provides a large surface area.
• Lamellae is one-cell thick, which proves a short diffusion distance.
• Gills contain a large blood supply, supplies O2 removes CO2.
• Countercurrent flow, two fluids glow in opposite directions proves a short diffusion distance, maintain conc gradient.

Question 4

How does a countercurrent work?

Answer 4

• Water and blood flows in opposite directions.
• Higher percentage of oxygen in water.
• Lower percentage of oxygen in blood.
• oxygen moves down conc gradient.

Question 5

Advantages of countercurrent.

Answer 5

• There is a net movement, so oxygen is diffused into the blood.
• Maintains a favourable concentration gradient.

Question 6

smaller species of annelid do not have gills, explain why these small worms do not need gills to obtain sufficient oxygen.

Answer 6

• Large surface area, meets requirements by diffusion.

Question 7

In many of the lugworm gills, the flows in the opposite direction to the current of water passing over them. Explain the advantage of this arrangement.

Answer 7

• Maintains a concentration gradient, as oxygen can diffuse across width of gills. From water to blood.

Question 8

Explain why water is always lost from gas exchange surfaces or terrestrial organisms.

Answer 8

• Gas exchange surfaces are permeable to small molecules, there is a higher concentration of water molecules inside an animal than out, water will diffuse outwards.

Question 9

Explain how the gills of a fish are adapted for efficient gas exchange.

Answer 9

• Large surface area provided by lamellae/ filaments increase diffusion.
• Thin epithelium/ distance between water and blood - shorter diffusion distance.
• Countercurrent system maintains concentration gradient, as water is always next to blood with lower concentration of oxygen.
• Circulation replaces blood saturated with oxygen.
• Ventilation replaces water.