properties of gas exchange Flashcards
what are the properties of a gas exchange surface
1) large surface area to volume ratio
2) thin diffusion pathway
3) permeable to respiratory gases (moist)
4) maintained conc gradient
why can a small organism use its cell membrane for gas exchange
- large surface area to volume ratio
- thin cell membrane so diffusion is rapid
- small organism have shorter diffusion distances
therefore enough oxygen can be absorbed across the cell membrane to meet respiratory demands
carbon dioxide can be removed fast enough to prevent the build up of large concentrations creating an acidic environment
why do larger organisms need a specialised gas exchange surface
- cells are aggregated together decreasing surface area to volume ratio
- diffusion across their surfaces is not efficient enough for their respiratory demands
outline gas exchange of the organism amoeba
- large surface area to volume ratio
- thin diffusion pathway (one cell thick)
- aquatic environment- moist allowing movement of gases ect
oxygen diffuses across the cell membrane and as the organisms is only one cell thick it gas exchange is efficient enough to meet respiratory demands
outline gas exchange of a flatworm
- larger surface area to volume ratio due to shape being flat so no part of the body is too far from the surface
- this means short diffusion path
- cells are aggregated together so the surface area to volume ratio is smaller than an amoeba
- aquatic organims= permeable to gases etc
outline the gas exchnage of an earth worm
- cylindrical so smaller surface area to volume ratio but better than a compact organism
- secretes mucus on the skin to create a moist respiratory surface
- low metabolic rate so low oxygen requirement therefore enough oxygen diffuses across the skin to meet demands
- maintained conc gradient from the presence of hemoglobin carrying oxygen away in blood vessels
explain why larger organisms need a ventilation system
larger organisms tend to have
- a higher metabolic rate so require more oxygen
- tissues and cells become interdependent
- a steep con gradient must be maintained across the respiratory surface to allow oxygen to meet demand and allow aerobic respiration so a ventilation mechanism is needed
outline the structure of a fish gill
- fish have gills that are supported by a gill arch
- along each gill are projections called gill filaments which contain further projections called lamellae which participate in gas exchange
- these projections are held apart by water preventing them from sticking together
how are fish gills adapted for gas exchange
- large surface area provided by the separation of many projections of gill filaments and lamellae
- maintained conc gradient from a one way current of water
outline ventilation in fish
1) the mouth opens and the mouth floor lowers increasing volume and decreasing pressure causes water to move into the buccal cavity
2) the mouth closes and the mouth floor raises increasing pressure and decreasing volume forcing water over the gills
3) pressure forces water over the gills and out the operculum slits
what is the difference between parallel and counter current flow
parallel- water and blood move in the same direction as one another, therefore a conc gradient is only maintained halfway across the lamellae before an equilibrium is reached and gas exchange cant occur
counter- water and blood move in opposite directions to one another therefore gas exchange can occur the entire length of the lamellae and equilibrium is never reached
what are the advantages of counter current flow
gas exchange occurs across the entire length of the lamellae so is a more efficient system as around 80% of the oxygen is removed from the water
compare bony and cartilaginous fish
C= no special mechanisms to force water over gills so must keep swimming, parallel flow, gas exchange only over part of the lamellae
B= specialized system, counter-current flow, gas exchange over entire length
