7.4 Flashcards
where does air enter and leave an insect?
through spiracles
why are spiracles kept closed as much as possible
to reduce water loss
what follows the spiracles?
the tracheae
what is the insect tracheae lined with?
chitin
can the insect tracheae undergo gas exchange?
no because chitin is impermeable
what does the insect tracheae divide into?
tracheoles
do the insect tracheoles contain chitin?
no so they can undergo gas exchange
what gives the tracheoles a large surface area?
there are so many of them which gives a large surface area
how does tracheal fluid increase the surface area of the tracheoles?
when lactic acid builds up in insect cells, water moves out of the tracheoles by osmosis which exposes more area for gaseous exchange
how do fish keep a constant flow of water?
they keep their mouth open while swimming
what happens to the buccal cavity when the mouth is opened?
the floor is lowered which increases the volume of the cavity and lowers the pressure in the cavity which allows water to move in
how does the water move from the buccal to the gills?
the operculum is closed which causes a low pressure in the operculum cavity where the gills are found. this causes water to move from high to low pressure, over the gills
how does water leave the operculum?
the mouth is closed which causes the buccal cavity to be raised which increases the pressure in the buccal, forcing more water over the gills. the operculum opens which allows water to leave.
what are the properties of gills which allow for efficient gaseous exchange?
- large surface area
- rich blood supply
- thin layers
-overlapping gill filaments - countercurrent flow
how do overlapping gill filaments allow for more efficient gas exchange?
increases resistance to water which slows the water down allowing time for gaseous exchange to take place
