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Question 1

What are the features of insects gaseous exchange system ?

Answer 1

• 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

Question 2

What are spiracles ?

Answer 2

They are small openings along the thorax of the insect

Question 3

What is the role of spiracles ?

Answer 3

They allow air to enter and leave through these openings

Question 4

What is a problem that insects face due to their gaseous exchange system ?

Answer 4

While air enters/leaves through the spiracles, water is also simultaneously lost

Question 5

What is the role of sphincters ?

Answer 5

Sphincters open/ close spiracles

Question 6

How do insects maximise efficiency of gas exchange while minimising water loss ?

Answer 6

Sphincters keep spiracles closed as much as possible to prevent water loss

Question 7

What are trachea ( in insects ) ?

Answer 7

• Leading away from spiracles are trachea
• They are the largest tubes in the system that carry air into the body

Question 8

What are the features of trachea ? What does this do ?

Answer 8

• They are lined by spirals of chitin
• This ensures they are kept open/ dont collapse

Question 9

What are tracheioles ?

Answer 9

• 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

Question 10

How do tracheioles maximise gas exchange ?

Answer 10

The vast/ large number of tracheioles results in a large surface area over which diffusion can take place maximising gas exchange

Question 11

Explain how the tracheal system works ( when Ov2 is used up ) ?

Answer 11

• 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

Question 12

Explain how the tracheal system works ( When Ov2 demands build up ) ?

Answer 12

• 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

Question 13

How do insects increase the levels of gaseous exchange ?

Answer 13

• Mechanical ventilation of the tracheal system
• Collapsible enlarged trachea or air sacs that act as air reservoirs

Question 14

Explain how insects increase the levels of gaseous exchange through mechanical ventilation of tracheal system ?

Answer 14

• 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

Question 15

Explain how insects increase the levels of gaseous exchange through collapsible enlarged trachea or air sacs that act as air reservoirs ?

Answer 15

• 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

Question 16

What are features of fishes gaseous exchange system ?

Answer 16

• Bony fish are large animals with a small surface area to volume ratio
• They are highly active
• They have high metabolic demands/ oxygen demands

Question 17

What problems do fish face with regards to their gaseous exchange system ?

Answer 17

Water is more dense, viscous ( thick ) and has lower oxygen content than air so fish have specialised respiratory systems

Question 18

What problems do fish avoid with regards to their gaseous exchange system ?

Answer 18

Fish that get Ov2 from the water don’t need to prevent water loss

Question 19

What are the features of gills ?

Answer 19

• They have a large surface area
• Good blood supply
• Thin layers

Question 20

What is the role of gills ?

Answer 20

• 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

Question 21

How are gills arranged ?

Answer 21

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

Question 22

Label the features of the fish ?

Answer 22

Question 23

What is the role of the bony gill arch ?

Answer 23

The bony gill arch supports the structure of the gills

Question 24

What is the role of gill lamellae ?

Answer 24

• They have a rich blood supply and large surface area
• They are the main site of gas exchange in fish

Question 25

What are gill filaments ?

Answer 25

They are large stacks of gill plates

Question 26

What is the role of gill filaments ?

Answer 26

They need a flow of water to keep them apart exposing a large surface are needed fro gas exchange

Question 27

What is the role of the efferent blood vessel ?

Answer 27

It carries blood leaving the gill sin the opposite direction to incoming water, maintaining a steep concentration gradient

Question 28

What is the role of the affront blood vessel ?

Answer 28

It brings blood into the system

Question 29

Explain how activity/inactivity effects the gaseous exchange system ?

Answer 29

- 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

Question 30

Explain how gas exchange occurs during inactivity ( mouth opening ) ?

Answer 30

- 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

Question 31

Explain how gas exchange occurs during inactivity ( mouth closing ) ?

Answer 31

- 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

Question 32

What are the additional two features of gills that maximise gas exchange ?

Answer 32

- 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

Question 33

Explain how the tips of adjacent gill filaments overlapping maximises gas exchange ?

Answer 33

- 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

Question 34

Explain how water and blood flowing in opposite directions maximised gas exchange ?

Answer 34

- 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

Question 35

Explain what occurs in a parallel system ?

Answer 35

- 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

Question 36

Explain what occurs in a countercurrent system ?

Answer 36

- 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