7.4 Ventilation and gas exchange in other organisms

Question 1

Why do insects struggle with gas exchange?

Answer 1

-have an exoskeleton
-don’t have blood pigment

Question 2

Spiracles

Answer 2

-along thorax and abdomen
-air enters/leaves
-can be opened or closed by sphincters to minimise water loss
-inactive/active or CO2 builds up

Question 3

Tracheae

Answer 3

-carry air into body
-largest tubes of insect respiratory system
-run along and into body
-lined by spirals of chitin=keep open if bent or pressed
-chitin=relatively impermeable=little gaseous exchange in tracheae

Question 4

Tracheoles

Answer 4

-branch from tracheae
-single, greatly elongated cell with no chitin=permeable to gass
-run between individual cells
-most gaseous exchange takes place
-vast number=large surface area

Question 5

Tracheal fluid

Answer 5

-limits penetration of air for diffusion

Question 6

Larger insects

Answer 6

mechanical ventilation of tracheal system=air actively pumped into system by muscular pumping movements of thorax/abdomen
-movements change volume of body and changes pressure in tracheae and tracheoles=air drawn into tracheae and tracheoles or forced out as pressure changes
-collapsible enlarged tracheae/air sacs= air reservoirs= increase amounts of air moved through gas exchange system=inflated and deflated by ventilating movements of thorax and abdomen

Question 7

Why is respiration different in bony fish?

Answer 7

-cope with a higher viscosity of water and density
-active=high O2 demand
-scaly outer covering= x allow gaseous exchange

Question 8

Gills

Answer 8

-large surface area
-good blood supply
-thin layers
-in gill cavity covered by operculum
-need to maintain a continuous flow of water over the gills (opening mouth and operculum)
-tips of adjacent gill filaments overlap=increases resistance to flow of water over gill surfaces and slows movement of water=more time for gaseous exchange to take place
-counter-current system

Question 9

Ram ventilation

Answer 9

-continual movement to ventilate gills, ram water past gills

Question 10

Opening of mouth

Answer 10

1.Mouth is opened and floor of buccal cavity is lowered
2.Increased volume of buccal cavity
3.Pressure in cavity drops and water moves into buccal cavity
4.Opercular valve is shut and opercular cavity containing gills expands
5.Lowers pressure in opercular cavity containing gills
6.Floor of buccal cavity starts to move up, increasing pressure so water moves from buccal cavity over gills
7.Mouth closes, operculum opens and sides of opercular cavity move inwards
8.Increased pressure in opercular cavity and force water over the gills and out of the operculum
9.Floor of buccal cavity is steadily moved up, maintaining flow of water over the gills

Question 11

Counter-current system

Answer 11

-water moving over gills and blood in gill filaments flow in different directions
-counter current exchange system
-ensures that steeper conc gradients are maintained than if blood and water flowed in same direction
-more gaseous exchange can take place