3.1.1 - Exchange Surfaces ( Part 2 )

Question 1

What are the features of insects gaseous exchange system ?

Answer 1

• Very active in their short life cycles
• Have high metabolic demands
• They have a rigid exoskeleton with wacky coating that is impermeable to gases

Question 2

Label the gas exchange system of the insect ?

Answer 2

Question 3

What are spiracles and what is their role ?

Answer 3

They are small openings along the thorax of the insect that allow air to enter/leave the tracheal system

Question 4

What is the role of sphincters ?

Answer 4

Sphincters open/ close spiracles

Question 5

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

Answer 5

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

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 by evaporation

Question 7

What are the features of trachea in insects ?

Answer 7

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

Question 8

What are the features of tracheoles /

Answer 8

• The ends of tracheoles are filled with tracheal fluid, allowing gases to dissolve into this fluid before diffusing into cells during gas exchange
• Large number of tracheoles provide a large surface area for gas exchange

Question 9

Explain how the tracheal system works during low insect activity ?

Answer 9

• During low activity, insects have low metabolic demands meaning solely the rate of diffusion is sufficient to provide cells with Ov2/ all required nutrients and molecules
• Sphincters close spiracles to reduce water loss by evaporation

Question 10

Explain adaptations of tracheal system for gas exchange ?

Answer 10

• Many branching tracheoles results in large surface area for gas exchange
• Tracheoles are thin-walled resulting in short diffusion distance
• When cells respire, oxygen is used up and carbon dioxide is produced maintaining STEEP CONCENTRATION GRADIENT

Question 11

Explain how a rapid supply of oxygen can be achieved in the tracheal system, during high activity ?

Answer 11

• Mechanical ventilation of the tracheal system
• Removal of fluid from tracheoles

Question 12

Explain ‘mechanical ventilation of the tracheal system’ ?

Answer 12

• Contraction and relaxation of abdominal muscles causes changes in pressure inside the tracheae
• This causes air to move in and out of the spiracles into the trachea

Question 13

Explain ‘removal of fluid from tracheoles’ ?

Answer 13

• During his activity, muscle cells Strat to respire anaerobically producing lactate
• This lowers water potential of muscle ells causing water/ tracheal fluid to move into respiring cells/ tissue via osmosis
• This reduces the volume of liquid in tracheoles allowing more air to move in and provides larger surface area for gas exchange, increasing rte of diffusion

Question 14

What are features of fishes gaseous exchange system ?

Answer 14

• Bony fish have a small surface area : volume ratio
• They are highly active
• They have high metabolic demands

Question 15

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

Answer 15

Water is more dense, viscous ( thick ) and has lower oxygen content than air

Question 16

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

Answer 16

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

Question 17

What are the features of gills ?

Answer 17

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

Question 18

What are features of gill structure ?

Answer 18

• There are a series of gills on each side of the head
• Each gill arch is attached to two stacks of filaments
• On the surface of each filament, there are rows of lamellae
• Lamellae HAVE THIN WALLS and cover a bady network of cappilaries

Question 19

Where are the gill located ?

Answer 19

• A series of gills is found on each side of the head contained in a gill cavity
• It is covered by a protective operculum ( bony flap )

Question 20

Label the features of the fish ?

Answer 20

Question 21

What are gill filaments ?

Answer 21

They are large stacks of gill plates

Question 22

What is the role of the bony gill arch ?

Answer 22

The bony gill arch offers supports to the structure of the gills

Question 23

What is the features of gill lamellae ?

Answer 23

• THEY HAVE THIN WALLS producing short diffusion distance
• They cover a vast network of capillaires so have a rich blood supply
• Due to their large number, they have a large surface area

Question 24

Where does has exchnage occur in fish ?

Answer 24

Gill lamellae

Question 25

What is the role of the efferent blood vessel ?

Answer 25

It carries blood away from the gills, opposite to direction of water flow

Question 26

What is the role of the affront blood vessel ?

Answer 26

It carries blood towards the gills

Question 27

Explain how gas exchange occurs in fish ( mouth opening ) ?

Answer 27

- When the fish open their mouth, they lower the floor of the buccal cavity - This causes the volume inside the buccal cavity to increase, causing a decrease in pressure in the cavity - Pressure is higher outside the mouth, causing water to flow into the buccal cavity

Question 28

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

Answer 28

- When the mouth closes, the floor of the buccal cavity is raised - This decreases the volume of the buccal cavity and increases the pressure in the buccal cavity - This causes water to flow from the buccal cavity into the gill cavity from high to low pressure - As water enters, pressure begins to increase in the gill cavity - This causes the operculum to be forced open and water to exit the fish - The operculum is pulled shut when the floor of the buccal cavity is lowered again

Question 29

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

Answer 29

- The tips of adjacent gill filaments overlap - Water flows in the opposite direction to the direction of blood flow in the gills; counter-current system

Question 30

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

Answer 30

- 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 31

Explain the mechanism of a counter-current system and how this maximises gas exchange ?

Answer 31

- The capillary system within the lamellae ensures that the blood flow is int he opposite direction to the flow of water; a counter-current system - This ensures a steep concentration gradient is maintained along the whole length of the gill - This allows diffusion to occur along the whole gill between water and blood in gills maximising gas exchange

Question 32

Explain how you would carry out a dissection to display maximum detail of gas exchange system in fish and insects ?

Answer 32

- Remove/ move the operculum of fish out of the way - View structures/ gills under water - Place pencil into buccal cavity to display lamellae - Cut open the exoskeleton of the insect - Stain tracheoles with methylene blue