7.4 Ventilation and gas exchange in other organisms Flashcards
What do insects have that makes it harder for gas exchange
tough exoskeleton where no gaseous exchange can take place
- no blood pigments that carry oxygen
How do insects breathe?
small openings known as spiracles allow air & water to enter and leave
–> these can be opened or closed by sphincters (kept close to minimise water loss)
–> spiracles open when the oxygen demand increases/ CO2 levels build up
From the spiracles, where does air travel in an insect?
itno the tracheae (largest tubes of their respiratory system
–> run into and along body of insect
–> tubes lined by spirals of chitin (keeps them open)
How is chitin useful for insects
chitin is same material that makes up waxy cuticles
–> relatively impermeable to gases so little gaseous exchange occurs
–> good as the muscles mainly need the oxygen
After the tracheae where does air travel into
tracheoles: single, greatly elongated cell with no chitin lining (are freely permeable to gases)
–> these spread into the tissues of insects, running between individual cells (most gaseous exchanges here)
what substance is there towards the end of tracheoles?
tracheal fluid
–> this limits the penetration of air for diffusion
e.g. when oxygen demand builds up, lactic acid builds up in tissues, causing water to move out of the tracheoles via osmosis
–> exposes more surface area for gaseous exchange
Because certain insects have very high energy demands, what alternative methods are there to increase the level of gaseous exchange?
- mechanical ventilation of tracheal system ( air actively pumped in via muscular pumping of thorax & abdomen= change in volume and pressure= air is drawn in more/forced out more)
- collapsible enlarged tracheae or air sacs (increase amount of air moved through system)
–> usually inflated and deflated via ventilation movement
What difficulty is there respiring under water?
1000 times denser than air= 100 times more thick= lower oxygen content
What are the organs for gaseous exchange in a fish?
Their gills: they maintain a flow of water in one direction over the gills
Why are gills good for gaseous exchange?
- large surface area
- good blood supply
- thin layers
In bony fish, where are the gills found?
in a gill cavity, covered by a protective operculum (bony flap)
What is the structure of gills?
series of bony gill arches, each containing two stacks of gill filaments
–> gill filaments have protruding rows of very thin lamellae (perpendicular to filaments)
What happens when a fish opens its mouth?
(1 & 2 occur at same time)
1.floor of buccal cavity (mouth) lowers, increasing the volume of the buccal cavity
–> pressure in cavity drops and water moves into buccal cavity
- opercular valves shut & opercular cavity containing gills expands
–> reduces pressure
Floor of buccal cavity moves up, increasing the pressure
–> water moves over the gills
What happens when a fish closes its mouth?
operculum opens and sides of opercular cavity move inwards
–> increases pressure to force water over gills and out of operculum
floor of buccal cavity moves up, maintaining flow of water over gulls
2 other adaptations of gills for efficient gaseous exchange
- tips of adjacent gill filaments overlap
–> increases resistance to flow of water over gills & slows down movement of water = more time for gaseous exchange to occur - counter-current flow: water flowing over gill filaments moves opposite to the flow of blood through capillaries
–> ensures steeper conc gradient= more gaseous exchange can occur
