Chapter 7.4 Flashcards
Ventilation and gas exchange in other organisms
Give reasons why insects need a gaseous exchange system?
This is because they have a tough exoskeleton which no or little gaseous exchange can take place
They have a high relative high oxygen requirement
They have no blood pigments that carry oxygen
= As a result need an alternative way to exchanging oxygen system
How is the gaseous exchange system of insects evolved?
It is evolved to deliver the oxygen directly to the cells and remove CO2 the same way
What are spiracles?
They are small openings along the thorax and and abdomen
How does gaseous exchange take place the insects?
1) Air enters through the spiracles (and leaves through the spiracles) which are opened and closed using sphincters
{When an insect is inactive and oxygen demands are very low….. the spiracles are closed. BUT when oxygen demand is high they open}
2) After air then passes through tracheae and little to no gas exchange take place due to the structure. They carry air in the body
3) The tracheae then branch to form narrower tubes known as tracheoles which spread throughout the tissue of the insect and run in between individual cells
{ This process from the tracheae to tracheoles to tissues tends to happen by diffusion alone. Which is done when oxygen dissolves in the moisture on the walls of the tracheoles and diffuse into surrounding cells.}
What are the three states of discontinuous gas exchange in insects? What is happening during these states?
[Closed]
Spiracles are closed and no gas move in or out of the insect
Oxygen moves into the cells by diffusion from the tracheae and CO2 diffuses into the body fluids of the insect where it is held in a process called buffering
[Open]
Happens when CO2 builds up really high in the body fluids of the insect
Spiracles open widely and carbon dioxide diffuse rapidly
Pumping movements of the thorax and abdomen when the spiracles are open, maximising gaseous exchange
[Fluttering]
Spiracles flutter and open/close rapidly
Fresh air moves into the tracheae to renew supply of oxygen
How are the Spiracles adapted for efficient gaseous exchange?
They have sphincters - that can open and close Spiracles which help minimise water loss
What is the structure of the Tracheae like?
It is 1 nm in diameter
They run into and along the body of the insect.
Tubes are lined by spiral of chitin, which keep them open if they are bent or pressed
Chitin that makes up the cuticle is relatively impermeable to gases, so little gaseous exchange takes place in the trachea
What is the structure of the tracheoles?
Narrow tube with a diameter of 0.6 - 0.8 manometer
It is single and greatly elongated cell with no chintin lining so freely permeable to gas
Spread through tissue and can pass in between cells due to it being narrow in size
what are the 2 alternative ways that insects increase their oxygen supply during very high energy demands?
By using Mechanical Ventilation of the tracheal system
Using collapsible enlarged tracheae or air sac that act as a reservoir
How does Mechanical Ventilation of the tracheal system work to supply extra oxygen during very high oxygen demand?
1st) Air is actively pumped into the system by muscular pumping movements of the thorax and/or the abdomen
2) These movements then change the volume of the body and this change the pressures in the tracheae/tracheoles
=> As a result the air is drawn into the tracheae and tracheoles, or forced out as pressure changes
How does Collapsible Enlarged Tracheae work to supply extra oxygen during very high oxygen demand?
They increase the amount of air that passes through the gaseous exchange system
And by inflating and deflating by the ventilating movements of the thorax and abdomen
Why do fish need specialised gaseous exchange?
- This is because water is much denser, 100 times more viscous and has a much lower oxygen content (low rate of oxygen diffusion)
- Further to the above, loads of energy will be required to move dense, viscous water in and out of the lung respiratory organs
- Therefore they need a very specialised respiratory system
How are gills adapted to ensuring most effective gaseous exchange in water?
They have tips adjacent gill filaments that overlap - which increases the flow of water over the gill surface and slows down the movement of the water. So more time for gaseous exchange to take place
Water that moves over the gills and the blood in the gill filaments flow in different directions. - this gives a steep concentration gradient needed for fast diffusion to take place. Further to the above, this sets up a This then sets up a counter-current system - meaning there is a constant steep concentration gradient needed for fast diffusion to take place.
They have large surface area for diffusion, rich blood supply to maintain a steep concentration gradient for diffusion and thin layers so that diffusing substances have short distance to travel.
{Allowing for faster diffusion to take place}
What are the difference between counter-current and pararell system?
[Counter-current System]
Blood and water flowing in opposite directions so an oxygen concentration gradient between the water and the blood is maintained along the gill
Oxygen continues to diffuse down the concentration gradient so a much higher level oxygen saturation of the blood is achieved
[Parallel System]
Blood in the gills and water flowing over the gills travel in the same direction, which gives an initial steep oxygen concentration gradient between blood and water
Diffusion takes place until the oxygen concentration in the blood and water are at equilibrium, then no net movement of oxygen into the blood occurs.
How do fish use the operculum to maintain water going over the gills to ensure efficient gas exchange is taking place at all times?
1) The mouth is opened and the floor of the buccal cavity (mouth) is lowered. This then increases the volume of the buccal cavity As a result pressure in the cavity drops and water moves in the buccal activity
2) At the same time the opercular valve also shuts and opercular cavity containing gills expands. This lowers the pressure in the opercualar cavity containing gills.
3) The floor the buccal cavity starts to move up, increasing the pressure there so water moves from the buccal cavity over the gills
4) The mouth closes, the operculum opens and the sides of the opercular cavity and force the water over the gills of the operculum. And the floor of the buccal cavity moves up.
{ As a result maintaining water over the gills}
