Ventilation And Gas Exchange In Other Orgaisms - Module 3

Question 1

Why can’t insects receive oxygen by diffusion?

Answer 1

They have a tough exoskeleton which prevents diffusion

Question 2

Why can’t insects receive oxygen like mammals?

Answer 2

Their blood does not have pigments that can carry oxygen

Question 3

How does air enter and leave the system of an insect

Answer 3

Through the spiracles - small openings along the thorax and abdomen

Question 4

How are spiracles in insects opened and closed and why?

Answer 4

Spiracles in insects are closed using sphincters, and are often closed to minimise water loss

Question 5

What is the structure and function of Tracheae in insects?

Answer 5

The tracheae is made up of spirals of chitin to keep airways open
They take air form the spiracles into the body

Question 6

What is the structure and function of tracheoles in insects?

Answer 6

Tracheoles are made up of a single greatly elongated cell which is entirely permeable to gases
As they are small they run between tissues and cells within the insect - this is where most gaseous exchange occurs

Question 7

What is tracheal fluid?

Answer 7

Tracheal fluid is is found towards the end of the tracheoles which limits the penetration of air for diffusion and stops dehydration of tracheal system

Question 8

When does water move out of the tracheoles by osmosis in an insect?

Answer 8

When oxygen demand is high to expose more surface areas for gaseous exchange

Question 9

What controls the extent of gas exchange in insects?

Answer 9

The opening and closing of the spiracles

Question 10

What two other methods of gas exchange do insects use if they have high energy demands?

Answer 10

1. Mechanical ventilation of tracheal system
   Air is actively pumped into the system by muscular pumping movements of the thorax and abdomen
2. Collapsible enlarged tracheae or air sacs

Question 11

What is the organ called that bony fish use for gaseous exchange?

Answer 11

Gills

Question 12

What are the 3 properties of gills that make them successful surfaces for gas exchange?

Answer 12

1. Good blood supply
2. Large surface area
3. Thin layers

Question 13

What is the role of the operculum in bony fish? [2]

Answer 13

1. Protect the gill cavity
2. Maintains a flow of water over the gills

Question 14

What are gill filaments?

Answer 14

Gill filaments occur in stacks and require a flow of water to keep them apart to expose large surface area needed for gaseous exchange

Question 15

What supports the structure of the gills?

Answer 15

Bony gill arch

Question 16

What are gill lamellae?

Answer 16

Lamellae have high blood concentration and large SA and are the main site of gas exchange in fish

Question 17

What do fish need to maintain to allow for sufficient gas exchange?

Answer 17

Continuous flow of water over the gills

Question 18

What is ram ventilation?

Answer 18

The way primitive fish maintain water flow over the gills - using continuous movement

Question 19

How do fish maintain continuous water flow over the gills?

Answer 19

1. Mouth is opened, lowering floor of buccal cavity
2. This increases volume and drops the pressure, meaning water will move into the cavity
3. Flow of buccal cavity moves up increasing pressure so water moves into opercular cavity
4. Operculum opens increasing pressure and water is forced over gills and out operculum

Question 20

What 2 adaptations do gills have to ensure the most effective gas exchange occurs?

Answer 20

1. Tips of adjacent gill filaments overlap
   This increases resistance to flow of water over gill so more time for gaseous exchange to occur
2. Countercurrent system
   Water and blood flow in opposite directions maintaining steep concentration gradient - rather than a parallel system