Ventilation in fish and insects

Question 1

what is the counter-current exchange system and how does it work ( 3steps)

Answer 1

• it is the gas exchange system in fish
  1) water containing oxygen enters the through the fish’s mouth and passes out through the gills

2) each gill is made up of lots of thin branches called gill filaments, which give a LARGE SA for gas exchange
- gill filaments are covered in gill plates which increase the SA even more . Each gill is supported by a gill arch

3) Gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion

Question 2

what is the counter current system ( simple def)

and why is it good?

Answer 2

where water flows through the gill plates in one direction, and blood flows through the gill plates in the opposite direction

• This is good because it helps to maintain a large concentration gradient between water and the blood
• concentration of O2 in the water is ALWAYS higher than in the blood

Question 3

Fish Gill ventilation process

and what does the operculum do ( bony flap on the fish’s head)

Answer 3

1) Fish opens its mouth, which lowers the floor of the buccal cavity. volume of buccal cavity increases, decreasing pressure inside the cavity
2) When the fish closes its mouth, the floor of the buccal cavity is raised again, decreasing the volume of the cavity and increasing the pressure inside the cavity., causing water to be forced out of the cavity across the gill filaments.
- The operculum protects the gill

Question 4

what do insects use for gas exchange

Answer 4

tracheae ( microscopic air filled pipes)

Question 5

Gas exchange in insects process

Answer 5

1) Air moves in to the tracheae through spiracles in the insect’s surface
2) oxygen travels down a concentration gradient towards the cell, whereas CO2 travels down ITS OWN concentration gradient towards spiracles to be released into the atmosphere
3) tracheae then branch off into small tracheoles, which have thin permeable walls
4) tracheoles contain fluid which oxygen dissolves in , oxygen, then oxygen THEN DIFFUSES from this fluid into body cells. CO2 diffuses from the body cells into the fluid.
5) Insects use rhythmic abdominal movements to change the volume of their bodies and move air in and out of their spiracles.

Larger insects can use wing movements to pump their thoraxes too