7 Flashcards
What are the features of insects gaseous exchange system ?
- Very active in their short life cycles
- Have high metabolic demands/ demands for oxygen
- They have a tough exoskeleton so little to no gaseous exchange can take place through it
What are spiracles ?
They are small openings along the thorax of the insect
What is the role of spiracles ?
They allow air to enter and leave through these openings
What is a problem that insects face due to their gaseous exchange system ?
While air enters/leaves through the spiracles, water is also simultaneously lost
What is the role of sphincters ?
Sphincters open/ close spiracles
How do insects maximise efficiency of gas exchange while minimising water loss ?
Sphincters keep spiracles closed as much as possible to prevent water loss
What are trachea ( in insects ) ?
- Leading away from spiracles are trachea
- They are the largest tubes in the system that carry air into the body
What are the features of trachea ? What does this do ?
- They are lined by spirals of chitin
- This ensures they are kept open/ dont collapse
What are tracheioles ?
- Trachea branch to form narrower tubes until they divide into tracheioles
- These are single elongated cells with no chitin lining so they are freely permeable to gases
How do tracheioles maximise gas exchange ?
The vast/ large number of tracheioles results in a large surface area over which diffusion can take place maximising gas exchange
Explain how the tracheal system works ( when Ov2 is used up ) ?
- As Oxygen is used up by respiring cells, oxygen concentration towards the ends of tracheioles falls creating a diffusion gradient
- This causes oxygen to diffuse from the atmosphere along the trachea and tracheoles into the cells down the concentration gradient
- Towards the ends of tracheioles there is tracheal fluid, which limits the penetration for diffusion
Explain how the tracheal system works ( When Ov2 demands build up ) ?
- When oxygen demands build up ( Insects is flying/ being active ), this results in a build up of lactic acid as a result of anaerobic respiration
- This lowers the water potential of muscle cells/ tissue which causes water/ tracheal fluid to move out of the tracheioles into muscle cells via osmosis down the concentration gradient
- This increases the surface area of tracheioles for gaseous exchange
How do insects increase the levels of gaseous exchange ?
- Mechanical ventilation of the tracheal system
- Collapsible enlarged trachea or air sacs that act as air reservoirs
Explain how insects increase the levels of gaseous exchange through mechanical ventilation of tracheal system ?
- Air is actively pumped into the system by muscular pumping movements of the thorax/ abdomen
- These movements change the volume of the body changing the pressure in the trachea/ tracheoles
- As a result, air is drawn in and forced out of the trachea/ tracheoles as pressure changes
Explain how insects increase the levels of gaseous exchange through collapsible enlarged trachea or air sacs that act as air reservoirs ?
- These are used to increase the amount of air moved through the gas exchange system
- They are usually inflated and deflected by the ventilating movement soft the the thorax and abdomen
What are features of fishes gaseous exchange system ?
- Bony fish are large animals with a small surface area to volume ratio
- They are highly active
- They have high metabolic demands/ oxygen demands
What problems do fish face with regards to their gaseous exchange system ?
Water is more dense, viscous ( thick ) and has lower oxygen content than air so fish have specialised respiratory systems
What problems do fish avoid with regards to their gaseous exchange system ?
Fish that get Ov2 from the water don’t need to prevent water loss
What are the features of gills ?
- They have a large surface area
- Good blood supply
- Thin layers
What is the role of gills ?
- They are the organ of gas exchange
- They take oxygen from water and get rid of carbon dioxide into the water, maintaining a flow of water in one direction over the gills
How are gills arranged ?
They are contained in a gill cavity and covered by a protective operculum ( bony flap ) also involved in maintaining a flow of water over the gills
Label the features of the fish ?
What is the role of the bony gill arch ?
The bony gill arch supports the structure of the gills
What is the role of gill lamellae ?
- They have a rich blood supply and large surface area
- They are the main site of gas exchange in fish
What are gill filaments ?
They are large stacks of gill plates
What is the role of gill filaments ?
They need a flow of water to keep them apart exposing a large surface are needed fro gas exchange
What is the role of the efferent blood vessel ?
It carries blood leaving the gill sin the opposite direction to incoming water, maintaining a steep concentration gradient
What is the role of the affront blood vessel ?
It brings blood into the system
Explain how activity/inactivity effects the gaseous exchange system ?
- When swimming/ during activity, fish can keep a current of water flowing over their gills simply by opening their mouths and operculum ( ram ventilation )
- When fish stop moving/ become inactive, the flow of water also stops
Explain how gas exchange occurs during inactivity ( mouth opening ) ?
- The mouth is opened and the floor of the buccal cavity (mouth) is lowered
- This increases the volume of the buccal cavity causing the pressure in the cavity to drop and water to move into the buccal cavity
- Simultaneously, the opercular valve is shut and the opercular cavity containing the gills expands. This lowers the pressure in the opercular cavity containing gills
- This causes the floor of the buccal cavity starts to move up, increasing the pressure so water moves from the buccal cavity over the gills
Explain how gas exchange occurs during inactivity ( mouth closing ) ?
- The mouth closes, the operculum opens and the sides of the opercular cavity move inwards
- This causes the pressure in the opercular cavity to increase and forces water to move over the gills and out of the operculum
- The floor of the buccal cavity moves up, maintaining a flow of water over the gills
What are the additional two features of gills that maximise gas exchange ?
- The tips of adjacent gill filaments overlap
- Water moving over the gills flows in the opposite direction to the flow of blood in the gill filaments
Explain how the tips of adjacent gill filaments overlapping maximises gas exchange ?
- This increases the resistance to the flow of water over the gill surfaces and slows down the movement of water
- As a result, there is more time for gas exchange to occur
Explain how water and blood flowing in opposite directions maximised gas exchange ?
- Since the blood and water flow in opposite directions, a countercurrent exchange system is set up
- This ensures a steeper concentration gradient is maintained which means more gas exchange can take place
Explain what occurs in a parallel system ?
- In a parallel system, blood and water flow in the same direction
- This creates an initial steep concentration gradient over which diffusion of oxygen takes place until the oxygen concentration of the water and blood are in equilibrium
- This means no further net diffusion/ movement of oxygen in the blood takes place
Explain what occurs in a countercurrent system ?
- When blood and water flows in opposite directions an oxygen concentration gradient between the blood and water is maintained along the entire gill
- This means oxygen diffuses down the concentration gradient so a much higher level of oxygen saturation of blood is achieved
