Gas Exchange

Question 1

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Question 2

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Question 3

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Question 4

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Question 5

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Question 6

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Question 7

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Answer 8

• Large multicellular organisms
• Hard exoskeleton made up of the polysaccharide chitin is impermeable to gases and minimises water loss.

Question 9

What are the spiracles?

Answer 9

Holes in the side of an insect

Question 10

What are trachea?

Answer 10

Tubes that carry the air directly to the tissues

Question 11

What are tracheae held open by?

Answer 11

Rings of chitin

Question 12

What are the tracheoles?

Question 13

Describe gas exchange in the trachea system of an insect.

Answer 13

• Air enters through the body through the spiracles (can be opened and closed by a valve).
• Tracheae carry the air directly to the tissues.
• Muscle contraction speeds up the movement of air in and out.
• Tracheae branch into tracheoles that extend into all the insects body tissues, increasing their surface area.

Answer 14

There is a short diffusing pathway between the tracheoles.

Question 15

How are the movement of gases in an insect affected by concentration gradients?

Answer 15

• Movement of gases is affected by concentration gradients.
• Faster respiration of tissues leads to low oxygen concentration in cells promoting diffusion in from the air.
• High concentrations of CO2 produced generates a height concentration gradient with the outside atmosphere.

Answer 16

• Contraction of muscles help to squeeze trachea abdominal tracheoles - pressure changes aid in the movement of gases in and out.
• Water in the fluid filled ends of the tracheoles is drawn into muscle cells.
• Muscles release lactic acid during aerobic respiration, lowering the water potential of the cells so water moves in by osmosis.

Question 17

How are insects adapted to manage the conflict between gas exchange and water loss?

Answer 17

Spiracles close to minimise water loss.

Question 18

Why do the tracheoles have thin walls?

Answer 18

So there is a short diffusion pathway to the cells.

Question 19

Why are there a large number of highly branched tracheoles?

Answer 19

• So the diffusion distance is short.
• So there is a large surface area for gas exchange.

Question 20

Why do tracheae provide tubes full of air?

Answer 20

So there is fast diffusion into the insect tissues.

Question 21

Why does fluid in the tracheoles move out during exercise.

Answer 21

So there is a lather surface area for gas exchange.

Question 22

Why does abdominal pumping of muscle move air?

Answer 22

So concentration gradients are maintained.

Question 23

What are the gill arches?

Answer 23

Support the gills and associated blood vessels.

Question 24

What are the gill filaments?

Answer 24

Increase the surface area of the gills.

Question 25

What are the gill lamellae?

Answer 25

At right angles to fill filaments further increase surface area - site of gas exchange.

Question 26

operculum?

Question 27

Describe the gas exchange system across the gills of fish.

Answer 27

- Water is taken in through the mouth and forced over the gills and out through an opening behind the gills. Water is kept moving over the gills by a ventilation system. - Oxygen dissolved in the water is absorbed by the gills. The movements of the mouth floor and operculum are coordinated to produce a stream of water, in through the mouth, over the gills and out of the operculum.

Question 28

describe the ventilation if the gills?

Answer 28

- Oxygen dissolved in the water is absorbed by the gills. - The movements of the mouth floor and operculum are coordinated to produce a stream of water, in through the mouth, over the gills and out of the operculum.

Answer 29

Countercurrent exchange system

Question 30

Why is counter current flow good?

Answer 30

- Water and blood flow in opposite directions. - So blood is always meeting water with a higher oxygen concentration. - This means a concentration gradient / diffusion gradient is maintained across the ***whole length of the gill***. - Therefore diffusion of oxygen into the blood can occur across the ***whole length of the gill***. - This ensures maximum possible gas exchange is achieved.

Question 31

Why is parallel flow not good?

Answer 31

- Water and blood flow in the same direction. - Equilibrium is reached halfway across the gill so diffusion of oxygen into the blood stops.