gas exchange in insects

Question 1

what is a spiracle

Answer 1

an external opening or pore that allows air in or out of the tracheae

Question 2

what is tracheal fluid

Answer 2

the fluid found at the ends of the tracheoles in the tracheal system

Question 3

what is the tracheal system

Answer 3

a system of air filled tubes in insects

Question 4

what is the problem with many active insects

Answer 4

they have high oxygen requirements but they have a tough exoskeleton through which little or no gaseous exchange can take place. they don’t have blood pigments that can carry oxygen

Question 5

how has the gaseous exchange system of insects evolved

Answer 5

to deliver oxygen directly to the cells and to remove the carbon dioxide in the same way

Question 6

what are the small openings along the thorax and abdomen

Answer 6

spiracles

Question 7

what enters and leaves via the spiracles

Answer 7

air enters and leaves the system through the spiracles but water is also lost

Question 8

what do insects need to maximise and minimise

Answer 8

maximise the efficiency of gas exchange and minimise the loss of water

Question 9

what happens to the spiracles when insects are inactive and oxygen demands are low

Answer 9

they close

Question 10

what happens to the spiracles when the oxygen demand is raised

Answer 10

most of the spiracles open

Question 11

what are the tracheae

Answer 11

the largest tubes of the insect respiratory system and they carry air into the body. they run into and along the body of the insect

Question 12

what are the tracheae lined by

Answer 12

chitin

Question 13

what does chitin do

Answer 13

keeps the tracheae open if they are bent or pressed. it makes up the cuticle.

Question 14

why does little gas exchange take place in the tracheae

Answer 14

the chitin lining the tracheae is relatively impermeable to gases

Question 15

where does most gas exchange occur

Answer 15

in the tracheoles

Question 16

what is the width of the tracheoles

Answer 16

0.6-0.8µm

Question 17

why does most gas exchange take place in the tracheoles

Answer 17

the tracheoles are single, elongated cells with no chitin lining. this means they are freely permeable to gases. the tracheoles are thin so spread throughout the tissues of the insect running between individual cells.

Question 18

how does diffusion occur in the tracheoles

Answer 18

most of the time air moves along the tracheae and tracheoles by diffusion alone reaching all the tissues. vast numbers of tiny tracheoles give a very large surface area for gaseous exchange. oxygen dissolves in moisture on the walls of the tracheoles and diffuses into the surrounding cells.

Question 19

where is the tracheal fluid located

Answer 19

at the end of the tracheoles

Question 20

what does the tracheal fluid do

Answer 20

limits the penetration of air for diffusion

Question 21

what happens when oxygen demand builds up in the insect

Answer 21

lactic acid builds up in the tissues. this results in water moving out the tracheoles by osmosis exposing more surface area for gas exchange

Question 22

how is gas exchange controlled by insects

Answer 22

by the opening and closing of the spiracles

Question 23

where does an insect get all of the oxygen it needs

Answer 23

insects possess an air filled tracheal system which supplies air directly to all respiring tissues

Question 24

do insects transport oxygen in blood

Answer 24

no

Question 25

what kind of circulatory system do insects have

Answer 25

an open circulatory system in which the body fluid acts as both blood and tissue fluid

Question 26

how is circulation affected

Answer 26

by body movements

Question 27

how does air enter the tracheal system

Answer 27

via a spiracle. the air is transportned into the body through a series of tubes called tracheae

Question 28

where does gaseous exchange occur

Answer 28

between the air in the tracheole and the tracheal fluid. some exchange can also occur across the thin walls of the tracheoles

Question 29

what do the tracheae divide into

Answer 29

smaller tubes called tracheoles. the ends of the tracheoles are opened and filled with tracheal fluid

Question 30

how is more oxygen absorbed when the insect is active

Answer 30

when tissues are active, the tracheal fluid can be withdraw into the body fluid to increase the surface area of the tracheole wall exposed to the air

Question 31

how do larger insects ventilate their tracheal systems

Answer 31

by movements of the body

Question 32

what do sections of the tracheal system have

Answer 32

they are expanded with flexible walls

Question 33

what do the flexible walls of the tracheal system act as

Answer 33

air sacs which can be squeexed by the action of the flight muscles

Question 34

what does repetitive expansion and contraction of the air sacs do

Answer 34

ventilates the tracheal system

Question 35

what does movement of the lungs do

Answer 35

alter the volume of the thorax

Question 36

what happens as the thorax volume decreases

Answer 36

air in the tracheal system is put under pressure and is pushed out of the tracheal system

Question 37

what happens when the thorax increases in volume

Answer 37

the pressure inside drops and air is pushed into the tracheal system from outside

Question 38

how can locusts alter the movement of their abdomen

Answer 38

by specialised breathing movements. these are coordinated with the opening and closing of the valves in the spiracles

Question 39

what happens as the abdomen expands

Answer 39

spiracles at the front end of the body open and air enters the tracheal system

Question 40

what happens as the abdomen reduces in volume

Answer 40

the spiracles at the rear end of the body open and air can leave the tracheal system