Ventilation and gas exchange in other organisms 7.4

Question 1

what about an insects anatomy/physiology provides a challenge to gasesous exchange and how has it evolved to overcome this

Answer 1

• have a tough exoskeleton, no gaseous exchange can take place here
• They don’t have any blood pigments that can carry oxygen
• has evolved to deliver the oxygen directly to the cells and to remove the carbon dioxide in the same way

Question 2

• where are spircales found on the anatomy
• what is there function

Answer 2

• small openings along thorax and abdomen of insect
• respiratory openings where air can diffuse into and out of body of insect

Question 3

How is water loss minimised by the insect related to spiracles

Answer 3

• sphincters at the end of the spiracles can open and close
  ^ allows water loss to be minimised and gas exchange to be maximised

Question 4

When would the spiracles on an insect be open and when would they be closed

Answer 4

• during periods of high metabolic activity they will be open
  ^open when CO2 levels rise
• during periods of low metabolic demand they are closed

Question 5

along what does air travel as it makes it way past the spircales and into the body of the insect

brief description of structure and function

Answer 5

• tracheae
  ^ the largest tubes in insect respiratory system
  ^ carry air into the body.

Question 6

Where would you find the tracheae in an insect

Answer 6

They run both into and along the body of the insect

Question 7

what is the structure of tracheae in insects

Answer 7

• tubes lined with spirals of chitin (chitin makes up the cuctile)
  ^keep it open if bent or pressed.
• relatively impermeable to gases (little gaseous exchange takes)

Question 8

What does the tracheae divide into further into the respiratory system

Answer 8

• tracheoles (narrower tubes)

Question 9

What is the structure of tracheoles and how does this aid there function

Answer 9

• narrow tubes
• single, greatly elongated cells
• no chitin lining so they are freely permeable to gases.
• due to small size they spread throughout the tissues/cells of the insects

Question 10

Where does the majority of gas exchange actually take place in the insect

Answer 10

Most gas exchange takes place in the tracheoles that run throughout the insects tissues, along each cell

Question 11

How does air usually move into the insects body for gas exchange

Answer 11

In most insects, for most of the time air moves along the tracheae and tracheoles by diffusion alone, reaching all the tissues

Question 12

What can be done within the tracheoles in order to satisfy a high oxygen demand

Answer 12

At stable metabolic demand tracheal fluid limits surface area in tracheoles for gasesous exchange
At high metabolic demand, the presence of lactic acid causes fluid to move out via osmosis freeing up surface area to allow for greater gaseous exchange

Question 13

How is the extent of gas exchange controlled in most insects

Answer 13

the extent of gas exchange in most insects is controlled by the opening and closing of the spiracles by the sphincters

Question 14

What alternative methods of increasing the level of gaseous exchange have evolved in insects

Answer 14

air is pumped into tracheae via movements of the thorax and/or the abdomen.
These change the volume and so presusre of the respiratory system.
Air is drawn into the tracheae and tracheoles, or forced out as the pressure changes

This only evolved in insects with high energy demands such as bees and grasshoppers

Question 15

what does DGC stand for

Answer 15

Discontinuous gas exchange cycles
they are relativly common for many species of insect

Question 16

What are the 3 states of spircales in DGC

Answer 16

Open
Closed
Fluttering

Question 17

what occurs in the closed state of the DGC

Answer 17

no gases move in or out of the insect.
Oxygen moves into the cells by diffusion from the tracheae and carbon dioxide diffuses into the body fluids of the insect (buffereing)

Question 18

What occurs in the fluttering state of DGC

Answer 18

When the spiracles flutter, they open and close rapidly. This moves fresh air into the tracheae to renew the supply of oxygen, while minimising water loss.

Question 19

what happens in the open state of DGC

Answer 19

When carbon dioxide levels build up really high in the body fluids of the insect, the spiracles open widely and carbon dioxide diffuses out rapidly. There may also be pumping movements of the Thorax and abdomen when the spiracles are open to maximise gaseous exchange

Question 20

what do fish not need to worry about with there respiratory system

Answer 20

water loss since they live in water

Question 21

what are the organs of gaseous exchange in fish

Answer 21

gills

Question 22

in how many directions does water flow over the gills

Answer 22

water only goes in 1 direction over the gills

Question 23

what adaptions do gills have that make them good exchange surfaces

brief

Answer 23

• large surface area
• good blood supply ( as to maintain a high concentration gradient)
• thin layers
• counter current system
• mucus coating to help trap oxygen

Question 24

Where are the gills in most bony fish

Answer 24

In bony fish they are contained in a gill cavity
covered by a protective operculum (a bony flap)

Question 25

What do fish need to do in order to allow efficient gas exchange at all time

Answer 25

maintain a continuous flow of water over the gills

Question 26

what is ram ventilation

Answer 26

maintaining a constant flow of water over the gills to allow for the most efficent gas exchange in water via constant moving forward with your mouth open

Question 27

what type of fish has to keep moving and cannot do the alternative method of water flow

Answer 27

The more primitive cartilaginous fish such as sharks and rays

Question 28

what is the process of the alternative method of gill ventilation

part 1

Answer 28

mouth is opened and the floor of the buccal cavity (mouth) is lowered.
increasing volumemdecreasing pressure
water moves in
opercular valve is shut and the opercular cavity containing the gills expands.
This lowers the pressure in the opercular cavity containing the gills.
The floor of the buccal cavity starts to move up
increasing pressure so water moves over the gills

Question 29

what is the process of the alternative method of gill ventilation

part 2

Answer 29

The mouth closes, the operculum opens and the sides of the opercular cavity move inwards. All of these actions increase the pressure in the opercular cavity and force water over the gills and out of the operculum. The floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills.

Question 30

what unique adaptaions do gills have that allow them to best complete their function

Gill tips

Answer 30

tips of adjacent gill filaments overlap.
increasing resistance to flow of water over the gill surfaces so there is more time for gas exchange to occur

Question 31

explain the countercurrent system and why it works

Answer 31

blood and water flow In opposite directions so an oxygen concentration gradient between the water and the blood is maintained all along the gill
allows frish to remove 80% of oxygen from water

Question 32

what is the parallel system

Answer 32

opposite of current count system, blood and water move in same way so uptake of oxygen is less as concentration gradient is not maintained for long time are eventually is equalled