Exchange Surfaces - Gas Exchange in Other Organisms Flashcards
why do bony fish have a lower metabolism
they are ectotherms
why do boney fish have gills
gas exchange
why do boney fish have a ventilation system
to maintain a flow of water in one direction over their gills
how many pairs of gills do most fish have
four
what is the operculum
bony flap that covers and protects gills
what does each gill consist of
two rows of many gill filaments attached to a bony gill arch
what do the filaments consist of
- the surface of the filaments is folded into many lamellae, giving a very large surface area
- blood capillaries take deoxygenated blood close to the surface of the lamellae where gas exchange occurs
how are the gills adapted for efficient gas exchange
- many filaments and lamellae (large surface area for diffusion to take place over
- rich blood supply (maintains a diffusion gradient)
- thin layers (short diffusion pathway)
describe the flow of water over the gills and blood in the gill filaments
they flow in opposite directions (counter current flow)
why is the counter current flow the most efficient for gas exchange
blood flows across the lamellae in the opposite direction to the movement of water. this maintains a concentration gradient across the whole gill surface so that a maximum volume of oxygen can be absorbed
what is the effect of the mouth opening (operculum is closed)
- floor of the buccal cavity is lowered
- volume in the buccal cavity increases, which decreases the pressure compared to the outside
- water moves into the buccal cavity down a pressure gradient
- the opercular cavity expands
what is the effect of the mouth closing
- floor of the buccal cavity is gradually raised
- the pressure inside the buccal cavity is now higher than in the opercular cavity pushing water over the gills
- the operculum opens
- the sides of the opercular cavity move inwards, increasing the pressure
- water flows out the fish through the operculum
what specific problems with gas exchange may insects face
- active so high demand for oxygen
- tough exoskeleton
what is the name of the gas exchange system in insects
tracheal system - delivers oxygen directly to cells
they have many tiny pipes called tracheae
how does air enter the tracheae
through spiracles in the thorax and abdomen
how and why are the tracheae kept open
by spirals of chitin to allow air to move through them
what do the tracheae branch into
many microscopic tubes called tracheoles (approx 0.7 micrometres in diameter)
describe tracheoles
fully permeable to gases, so gas exchange takes place between the cells and the tracheoles
what enters or leaves the insect via the spiracles
air can enter or leave
water can be lost
how can water loss via the spiracles be reduced
hairs around the spiracles
how can spiracle sphincters increase efficiency of gas exchange but minimise water loss
they can open or close the spiracles
what is the function of tracheal fluid
limits the penetration of air
- during vigorous muscular activity lactic acid builds up in the insect’s tissues
- this causes water to move out of the tracheoles by osmosis
- more air enters the tracheoles increasing the area for gas exchange
Describe mechanical ventilation
- In some insects, movement of the wings/ muscular pumping of the thorax alters the volume of the thorax and therefore the pressure
- When volume decreases, pressure increases pushing air out of the tracheal system
- When volume increases, pressure decreases and more air is pushed in from outside
Describe collapsible air sacs
- Many insects have air sacs which store a reserve of air.
- These can be squeezed by the action of the flight muscles or by movements of the abdomen/thorax.
- This helps to push air through the tracheal system
