4. Gas exchange in fish and insects Flashcards
Why do fish have special adaptions for gas exchange? and what is the gas exchange in fish?
Theres a lower concentrations of oxygen in water than air and they are called gills
Describe the structure of the gills
> Water, containing the oxygen, enter the fish through its mouth and passes out through the gills.
Each gill is made up of lots of thin plates called the gill filaments and lamellae, which increases the surface are for the exchange of gasses (the rate of diffusion is increased)
The gill filaments is covered in gill plates and secondary lamellae, which increases the surface area even more
The gills is supported by a gill arch
The gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion between water and the blood.
Describe the counter-current system in fish
> In the gills of a fish, the blood flows one directions and the water in the opposite direction - this is called the counter-current system
The counter-current system means that the water with a highly relative oxygen concentrations flows next to the blood with a relatively low concentration of oxygen.
This in turns means that it has a steep concentration - so as much oxygen as possible diffuses from the water into the blood
How does ventilation happen in fish?
> The fish open its mouth, which lowers the floor of the buccal cavity. This increase the volume of the buccal cavity, decreasing the pressure inside the cavity.
Water is then sucked into the cavity.
When the fish closes it mouths, the buccal cavity is rated. This decrease the volume of buccal cavity, increasing the pressure inside the cavity and the water is forced out through the gill filaments.
Each gill is covered by a flap called the operculum, when the pressure increase the water is forced out of the operculum.
How does gas exchange and ventilation occur in insects
> Insects have microscopic air-filled piped called tracheas which they use for gas exchange
Air moves into the trachea through the pores on the surface called spiracles.
Oxygen travels down its concentration gradient towards the cells.
Carbon dioxide from the cells travel down its own concentration gradient to the spiracles where they can be released into the atmosphere
The trachea branches off into smaller tracheoles which have thin, permeable walls and go to individual cells. The tracheoles also contain fluid where oxygen is dissolved
The oxygen then diffuses from this fluid into the body cells & carbon dioxide diffuses in the opposite directions.
What do insects use to change the volume of their bodies
Insects use rhythmic abdominal movements to change the volume of their bodies and move air in and out of the spiracles. When larger insects are flying, they use their wing movements to pump their thoraxes too.
