7.4 Ventilation And Gas Exchange In Other Organisms

Question 1

Effects of insects having an exoskeleton

Answer 1

Little or no gaseous exchange can take place

Question 2

Do insects have blood pigments?

Answer 2

Usually they do not

Question 3

What are the openings in insects’ thorax and abdomen?

Answer 3

Spiracles

Question 4

What is the function of the spiracles?

Answer 4

Air enters and leaves the system

Water is also lost

Question 5

Function of sphincters

Answer 5

Sphincters can open/close the spiracles

Kept closed as mudh as possible to reduce water loss

Question 6

Tracheae of insects

Answer 6

Largest tubes of the insect respiratory system

Run into and along the body of the insect

Question 7

What are the tracheae lined with in insects?

Answer 7

Spirals of chitin - keeps the tubes open

Relatively impermeable to gases - little gas exchange takes place here

Question 8

Tracheole of insects

Answer 8

Single elongated cell

No chitin lining - freely permeable to gases

Question 9

How does oxygen enter the insect?

Answer 9

Air moves along the trachea and tracheoles by only diffusion
Vast numbers of tiny tracheoles gives a large surface area for gas exchange
Oxygen dissolves in moisture of tracheole walls and diffuses into the surrounding cells
Towards the end of the tracheoles, there is tracheal fluid, which limits penetration of air for diffusion

Question 10

What happens when oxygen demand builds up for the insect?

Answer 10

Lactic acid builds up in the tissues
Water moves out of the tracheoles by osmosis
This exposes more surface area for gaseous exchange

Question 11

What controls the rate of gas exchange in insects?

Answer 11

The opening and closing of spiracles

Question 12

How do larger insects with high energy demands gain the extra oxygen that they require?

Answer 12

Mechanical ventilation of the tracheal system - air is actively pumped into the system by muscular pumping of the thorax and abdomen. This changes the volume and pressure in the tracheae and tracheoles.

Collapsible enlarged tracheae or air sacs, which act as air reservoirs, which increase the amount of air through the gas exchange system. Inflated and deflated by the movements of the thorax and abdomen

Question 13

Difficulties of gas exchange in sea animals

Answer 13

Water is 1000 times denser than air
100 times more viscous
Much lower Oxygen content

Question 14

Adaptations of gills

Answer 14

Large surface area
Good blood supply
Thin layers required for gas exchange

Question 15

Blood flow in bony fish

Answer 15

Efferent blood vessel carries the blood leaving the gills in the opposite direction to the incoming flow of water

Question 16

Operculum

Answer 16

A bony flap that covers the gills

Maintains a flow of water across the gills

Question 17

Bony gill arch

Answer 17

Supports the structure of the gills

Question 18

Gill lamellae

Answer 18

Rich blood supply and large surface area

Main site of gas exchange

Question 19

Gill filaments

Answer 19

Occur in large stacks and need a flow of water to keep them apart, exposing large surface area needed for gas exchange

Question 20

What is ram ventilation?

Answer 20

Ramming water past the gills by continuously moving

Question 21

Gas exchange in fish

Answer 21

Mouth is opened and floor of buccal cavity is lowered
Volume of buccal cavity increases and pressure decreases
Water moves into the buccal cavity
At the same time, the opercular valve is shut, and the opercular cavity containing the gills expands
This lowers the pressure in the opercular cavity
Floor of buccal cavity moves up and increases the pressure, so water moves from the buccal cavity over the gills
The mouth closes, operculum opens and sides of the opercular cavity move inwards - increasing pressure
Water is forced over the gills and out of the operculum
Floor of buccal cavity is steadily moved up maintaining water floor over the gills

Question 22

How do the gill filaments increase the rate of gas exchange?

Answer 22

The tips of adjacent gill filaments overlap, which increases resistance to the flow of water
Water is slowed down and there is more time for gas exchange to take place

Question 23

Movement of water over the gills

Answer 23

The water moving over the gills is in the opposite direction to blood flow in the gills
This creates a steep concentration gradient for efficient diffusion

Question 24

What is the system when the blood and water flow in opposite directions?

Answer 24

Countercurrent systems

Question 25

What is the system when the blood and water flow in the same direction?

Answer 25

Parallel system

Question 26

Difference in ventilation between bony fish and cartilaginous fish

Answer 26

Bony fish - countercurrent system

Cartilaginous fish - parallel system