FISH

Question 1

A fish uses its gills to absorb oxygen from water. explain how the gills of a fish are adapted for efficient gas exchange (6)

Answer 1

• Large SA provided by lamellae which increases diffusion
• thin epithelium which decreases distance between the water in the blood water and -water and blood flow in opposite direction
• which maintains the concentration gradient along with the girl
• circulation replaces blood saturated with oxygen
• ventilation replaces water (as oxygen removed)

Question 2

The concentration of oxygen is higher in the surface waters than it is in water close to the seabed. suggest y (2)

Answer 2

• Air and water mix at surface

- air has higher concentration of oxygen than water

Question 4

A scatter graph can be used to look for a correlation but in this investigation it was not appropriate for the data explain why

Answer 4

• There’s only one DV

- water temperature plus breathing rate are not both properties of fish

Question 5

Describe the relationship between temperature of water and oxygen and water invite a ventilation

Answer 5

As temp of water increases the oxygen conc in water decreases and the ventilation rate increases

Question 6

Use fig 1 and fig 2 to explain the advantage to the fish of the change in its rate of ventilation

Answer 6

• As concentration of oxygen falls, less oxygen flowing over gills
• blood oxygen lowers
• an increase in ventilation rate maintains the flow of oxygen

Question 7

Describe and explain how fish maintain a flow of water over their gills (4)

Answer 7

• mouth opens, operculum valve shuts -floor of mouth lowered
• water enters due to decreased pressure
• mouth closes, operculum valve opens

Question 8

Describe and explain how the structure of the mammalian breathing system enables uptake of oxygen into the blood . ( 6 marks )

Answer 8

1. alveoli provide a large area
2. Walls of alveoli thin to provide a short diffusion pathway
3. Walls of capillary are thin between the alveoli so provides a short diffusion pathway
4. Walls capillaries/alveoli have flattened cells;
5. Cel membrane permeable to gases
6. Many blood capillaries provide large SA
7. Intercostal muscles &diaphragm muscles used to ventilate lungs to maintain a diffusion gradient

Question 9

The volume of water passing over the gills increases if the temperature of the water increases. Suggest why.

Answer 9

There is increased respiration so less oxygen is dissolved in the water hence the increase in volume of water passing over the gills

Question 10

Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish.

Answer 10

Water and blood flow in opposite direction this means that a diffusion gradient is maintained and a equilibrium is not reached. Water will always be next to blood with a lower concentration of oxygen this happens along the whole length of the gill lamellae.

Question 11

The volume of water passing over the gills increases if the temperature of the water increases. Suggest why.

Answer 11

There is increased respiration so less oxygen is dissolved in the water hence the increase in volume of water passing over the gills

Question 12

Amoebic gill disease is caused by a parasite that lives on the gills of some species of fish. The disease causes the lamellae to become thicker and to fuse together. AGD reduces the efficiency of gas exchange in fish. Give two reasons why

Answer 12

The thicker lamellae leads to a greater diffusion distance

The fused lamellae reduces the surface area