7.4 - Ventilation and Gas Exchange In Other Organisms

Question 1

Name and describe the two main features of a fish’s gas transport system

Answer 1

Gills - located within the body - supported by arches along which are multiple projections of gill filaments which are stacked up in piles
Lamellae- at right angles to the gill filaments give an increased surface area - blood and water flow across them in opposite directions- countercurrent exchange system

Question 2

What needs to be maintained in order for efficient gas exchange in fish?

Answer 2

A continuous flow of water over the gills even when they’re not moving

Question 3

Explain the process of gas exchange in fish

Answer 3

• buccal cavity volume increased to enable water to flow in - reduced to increase pressure
• water is pumped over the lamellae by the operculum - oxygen diffuses into the bloodstream
• waste carbon dioxide diffuses into the water and flows back out the gills

Question 4

What are the adaptations for effective gaseous exchange in water?

Answer 4

• large surface area for diffusion
• rich blood supply to maintain a steep concentration gradient for diffusion
• thin layers so that diffusing substances have only short distances to travel

Question 5

Explain what happens when water enters the gills of a fish?

Answer 5

• the mouth is opened and the floor of the buccal cavity is lowered
• this increases the volume of the buccal cavity
• as a result the pressure in the cavity drops and water moves into the buccal cavity
• at the same time the oppercular valve is shut and the oppercular 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 the pressure so water moves from the buccal cavity over the gills

Question 6

How does the countercurrent exchange system maximise oxygen absorbed by the fish?

Answer 6

• blood flows one way and water flows the other way
• do that the concentration gradient of CO2 and oxygen is maintained throughout the gill
• thus maximising the efficiency of diffusion

Question 7

Why can’t fish breathe in and out via ventilation?

Answer 7

water is denser, more viscous and has a lower oxygen content than air so requires too much energy to be efficiently moved by a 2-way ventilation system

Question 8

What happens when a fish closes its mouth?

Answer 8

• cheeks move inwards - causing pressure in the mouth to increase and forcing water over the gills
• causing the opercular valve and operculum to open

Question 9

Why do the tips of the adjacent filaments overlap?

Answer 9

increases the resistance to the flow of the water over the gill surfaces - slows down the movement of water - thus more time for gaseous exchange to take place

Question 10

What is a parallel system?

Answer 10

• blood in the gills and water flowing over the gills travel in the same direction
• gives a initial steep oxygen concentration gradient between blood and water
• diffusion occurs until the oxygen concentration of the blood and water are in equilibrium
• no net movement of oxygen into the blood occurs

Question 11

What is a spirecal?

Answer 11

A small opening in the exoskeleton of an insects abdomen and thorax, which it uses to exchange gases with the atmosphere

Question 12

What is a spiracle sphincter?

Answer 12

The things an insect uses to open and close its spiracles, allowing it to close them when oxygen demands are low to reduce water loss

Question 13

What are trachea ( in insects ) ?

Answer 13

Small tubes which lead away from spiracles

Question 14

How are insect spiracles kept open?

Answer 14

By spirals on the tough polysaccharide chitin

Question 15

What diameter are insect tracheoles?

Answer 15

0.6-0.8 micrometers

Question 16

What is tracheal fluid?

Answer 16

•Fluid found near the end of the tracheoles
• gases can dissolve into it and then diffuse across to cells
• however it can also move out of the tracheoles by diffusion if necessary by osmosis to expose a greater surface area in them for diffusion to occur across

Question 17

What 2 adaptations do insects with high energy demands have to maximise gas exchange?

Answer 17

• some can actively pump air in and out of their body by moving hey thorax and pt abdomen
• some have internal air sacs which can be inflated and deflated by movement of the thorax and abdomen in order to increase the volume of air which moves

Question 18

Name and describe the three main features of an insects gas transport system

Answer 18

• spiracles- holes on the body’s surface which may be opened or closer by a valve for gas or water exchange
• tracheae - large tubes extending through all body tissues - supported by rings to prevent collapse
• tracheoles - smaller branches dividing off the trachea

Question 19

Name the exchange system in single called organisms

Answer 19

Tracheal system

Question 20

What is different about the tracheal system?

Answer 20

They can exchange oxygen and carbon dioxide directly through their plasma membrane via diffusion

Question 21

What is the function of the trachea in insects?

Answer 21

Air filled tubes -they run from spiracles to tracheoles and has rings made of chitin

Question 22

Do insects have blood pigments that carry oxygen?

Answer 22

No so thus the gaseous exchange system of insects has evolved to deliver the oxygen directly to me cells and to remove carbon dioxide the same way

Question 23

Explain the gaseous exchange system in insects

Answer 23

• along the thorax and abdomen there are spiracles
• air enters and leaves the system via spiracles but water is also lost
• the tubes are lined by spirals of chitin
• the trachea branch to form narrow tubes until they divide into tracheoles
• each tracheole is single - greatly elongated cell with no chitin lining so they are freely permeable to gases
• most gaseous exchange takes place between air and the respiring cells

Question 24

What happens when an insect is inactive?

Answer 24

Oxygen demands are low so the spiracles will be closed

Question 25

Why are the tubes lined by spirals of chitin?

Answer 25

As they can keep them open if mey are bent or pressed chitin is the material that makes up the cuticle

Question 26

What influence does the vast number of tracheoles have?

Answer 26

• very large surface for gaseous exchange
• oxygen dissolves in moisture on the walls of the trachea led and diffuses into the surrounding cells
• towards the end of the tracheoles there’s tracheal fluid which limits the penetration of air for diffusion

Question 27

What happens when an insect is flying?

Answer 27

•Oxygen demands builds up
• lactic acid builds up in the tissues which results in water moving out of the tracheoles by osmosis
• this exposes more surface area for gaseous exchange