module 3 - 7.4 ventilation and gas exchange in other organisms Flashcards
what is the top part of an insects anatomy called?
head
what is the middle part of an insects anatomy called?
thorax - (legs and wings attached to thorax)
what is the end part of an insects anatomy called?
abdomen
where are the tracheal tubes located in an insect?
the thorax
why does an insect have a problem overcoming losing water with their gas exchange organs?
- they are land dwelling with high demand of O2 and CO2 removal
- SA:V too small for diffusion for removal
- hard exoskeleton prevents diffusion to outer surface
- separate circulatory and gas exchange systems
what are spiracles?
- holes in the thorax and abdomen walls - a pair for each segment of body
- often with valves
what are tracheae?
tubes that lead into the body from the spiracles, form branching pattern of smaller diameter tubes
what are tracheae strengthened by?
hoops or spiracles of chitin called taenidia
what are tracheoles?
- single, greatly elongated cells that form minute tubes
- found at ends of smallest tracheae
- site of gas exchange with body cells
what is tracheal fluid?
fluid in the very end of tracheoles
what are valves?
they have control over gas exchange surfaces
what is the movement of air in insects?
- air enters & leaves insects through spiracles
why can spiracles be opened/closed?
to reduce water loss by contracting muscles surrounding spiracle that opens valves in the spiracle
why are spiracles surrounded by hairs?
to minimise bulk air movement around the opening to reduce water loss
when are spiracles opened/closed?
depending on metabolic demands of the insect
- when inactive, spiracles are mainly closed as demand for oxygen is lower
what happens after the air has passed through the spiracles?
it enters an air complex, branching network of tracheal tubes that divides into smaller diameters - reaches every part of the body
what prevents collapse of trachea under pressure?
a thin, reinforcing ‘wire’ of chitin winds spirally through wall or hoops in wall
what does the spiral of chitin allow for the tracheal tubes?
gives ability to flex and stretch without developing kinks that may restrict air flow
why do tracheoles penetrate into the spaces between body cells?
creates large SA so gas exchange can meet metabolic demands
why do tracheoles have no chitin and thin walls?
to create a smaller diffusion distance
why is the inside wall of tracheoles moist with water?
so oxygen can dissolve into liquid phase along moist lining & diffuse into body cells, CO2 follows reverse path
where does tracheal fluid fill and what happens to the air because of this?
fills very ends of tracheoles, air cannot penetrate further, gas exchange by diffusion still occurs in body cells
what do small insects entirely rely on to ventilate the tracheal system?
- passive diffusion of gases
- physical movement of the insects body
what do larger insects require to ventilate the tracheal system?
- active ventilation
- done by opening some spiracles and closing others while using abdominal muscles to expand/contract body volume
what does the opening of some spiracles and closing others while using abdominal muscles create?
creates pulsating movements that fresh air from one end of the body to the other through the tracheal system
what are the main limiting factors affecting ventilation?
- rate of gas diffusion
- weight of exoskeleton (limits size of insects)
what do the air sacs in some insects act as?
reservoirs of air and conserve water during drought period
- aquatic insects use them to regulate buoyancy
when do discontinuous gas exchange cycles occur?
when insects are at rest and may help insects by preventing entry of pathogens through spiracles
what are the 3 phases of discontinuous gas exchange cycles that reflect the behaviour of spiracles?
- closed phase
- open phase
- flutter phase
what is the closed phase (CP)?
- spiracles shut tight
- reduces ventilation with external environment
- O2 consumed, concentration decreases
- CO2 buffered at haemolymph - leads to negative pressure and starts flutter phase
what is the flutter phase (FP)?
- spiracles open slightly & close rapidly
- negative pressure in CP causes little air from environment to enter respiratory system when spiracles open
- fresh air brought into tracheal system to increase conc. of O2 & release CO2 (still buffered by lymph)
what is the open phase (OP)?
- flutter phase continues until CO2 production surpasses buffering capacity of haemolyph (builds up within tracheal system)
- rapid release of CO2
- complete exchange of gases with environment by diffusion
why do insects have discontinuous gas exchange cycles?
to stop them losing water
how many gills do fish typically have?
5
why do bony fish have no difficulty losing water with their gas exchange organs?
because they are in water
why is the SA:V too small in fish?
they tend to be large, active animals, SA:V too small to allow to supply their need of O2 & removal of CO2
what do fish scales and their outer slime layer prevent?
- diffusion
- slime layer adds protection, allows faster movement
what type of flow do fish gills employ?
counter current flow
what are 3 evolutionary strategies to gas exchange in fish?
- obligate air breathers (have to breathe)
- facultative air breathers (mainly use gills but can breathe air)
- gills (cannot breathe air)
what is the operculum (gill cover)?
- a series of bones that act as facial support and protective gill covers
- it adjusts pressure of water inside pharynx to allow ventilation
what is the buccal cavity?
- bony fish inhale water through their mouth by lowering floor of buccal cavity & closing opercular valves
- exhale by closing mouth, raising floor of buccal cavity, and open opercular valves to get water out
what are gill arches?
series of bony loops that support gills
what are gill rakers?
bony or cartilaginous processes that project from the branchial arch
what are gill filaments?
occurs in large stacks, each stack is a gill plate
what are gill lamellae?
- main site of gas exchange in gills
- very large SA
- good blood supply
- thin, moist walls
what are the standard exchange surface features of fish?
- large SA to allow enough O2 & CO2 exchanged with water
- good blood supply to maintain concentration gradients of O2 & CO2
- thin walls so diffusion pathway is short
what 2 extra features allow gills to overcome problems of gas exchange in water?
- tips of adjacent gill filaments overlap to slow flow of water, allows more time for gas exchange
- water moving across and through gills & blood flowing in gill filaments go in opposite directions
what is counter current flow?
when water moving across and through gills & blood flowing in gill filaments go in opposite directions
what is the parallel system?
- occurs in cartilaginous fish
- blood in gill filaments and water across & through gills move in same direction
- oxygen diffuses down steep conc. gradient, equilibrium reached at some point
- surface area of gill filaments not being fully utilised for O2 exchange between water and blood
- less efficient than counter current flow
what is the counter current flow system?
- occurs in bony fish
- blood in gill filaments and water moving across gills goes in opposite directions
- oxygen diffuses down conc. gradient along whole length of gill filaments, equilibrium never reached
- entire surface of gill filaments fully utilised
