7.4 Ventilation And Gas Exchange In Other Organisms Flashcards
Why has the gaseous exchange system of insects evolved to deliver oxygen directly to the cells and remove co2 in the same way
They have a tough exoskeleton where little gas exchange can take place
They don’t have blood pigments that can carry oxygen
What are spiracles
Small openings along the thorax and abdomen That air enters and leaves
What opens and closes spiralcles and why do they need them
Sphincters
They are kept closed as much as possible to minimise water loss
What leads away from spircales in insects
Thracheae - large tubes of the insect respiratory system that carry air into the body
What are tracheae in insects lined with
Spirals of chitin which keep them open if they are bent or pressed
It’s impermeable to gases so little gaseous exchange takes place
What do trachea divide into in insects
Tracheoles that are minute tubes
They are a single elongated cell with no chitin lining so they are freely permeable to gases
They spread throughout the tissues of insects and it’s where most Geseous exchange takes place
What is tracheal fluid
It’s towards the end of the tracheoles
It limits the penetration of air for diffusion
What happens to the tracheoles when oxygen demand builds up in insects
Lactic acid build up results in water moving out of them by osmosis and this exposes more surface area for gaseous exchange
What alternative methods of increasing levels of gaseous exchange do larger insects like wasps use
Mechanical ventilation of the tracheal system - air is actively pumped into the system by muscular pumping movements of the thorax
Collapsible enlarged tracheae or air sacs which act as air reservoirs - these increase the amount of air moved through the gas exchange system
How are gills adapted in fish to be the organs of gaseous exchange
Large surface area
Good blood supply
Thin layers
What happens with fish open their mouths
The floor of the buccal cavity is lowered which increases its volume
As a result the pressure in the cavity drops and water moved into the buccal cavity
At the same time the opercular valve is shut and the opercular cavity contain the gills expands which lowers the pressure
The floor of buccal starts to move up, increasing the pressure so water moved out of buccal cavity and over the gills
What happens when the mouths closes in fish’s
The operculum opens and the sides of the opercular cavity move inwards
Thus increase the pressure in the opercular cavity and doves water over the gills and out of the operculum
The floor of buccal cavity slowly moves up, maintaining a flow of water Over the gills
What extra adaptations do gills have to ensure the most effective possible gaseous exchange
Tips of adjacent gill filaments over lap
- this slows down the movement of water allowing more time for gaseous exchange
Why does water and the blood in the gill filaments flow in opposite directions
To allow a steep concentration gradient for fast efficient diffusion a countercurrent exchange system is needed
It maintains the steep concentration gradient and more gaseous exchange takes place
