3.2.3: Gas exchange in insects

Question 1

What is the function of spiracles in an insect’s body

Answer 1

air enters through a series of openings called spiracles - these can be opened and close using valves to help prevent valuable water loss

Question 2

what is the function of the trachea in an insect’s body

Answer 2

the air passes through the spiracles into the trachea which keeps air passages open, and then the air passes into narrower tracheoles

Question 3

what is the function of the tracheoles in an insect’s body

Answer 3

the air passes from the trachea into the tracheoles so that no cell is more than a short diffusion distance from a tracheole, these penetrate between cells and right into muscle fibres, here gas exchange takes place

Question 4

how is the insect’s tracheal system adapted to provide a large surface area

Answer 4

there are many tracheoles giving a large collective surface area

Question 5

how is the insect’s tracheal system adapted to provide a short diffusion pathway

Answer 5

tracheoles penetrate between cells and right into muscle fibres

Question 6

how is the insect’s tracheal system adapted to maintain a steep oxygen concentration gradient

Answer 6

ventilation of tracheoles - the muscles in the thorax and abdomen contract/relax causing rhythmic movements, when oxygen is needed, thorax spiracles open, abdomen expands, decreasing internal pressure, drawing air inward and the opposite for pushing air out, abdomen spiracles open

Question 7

is ventilation in insects tidal or unidirectional

Answer 7

unidirectional

Question 8

whats the difference between tidal and unidirectional

Answer 8

tidal = air goes in one way and out the same way
unidirectional = air goes in one way and out another way

Question 9

in which direction is air flowing through the spiracles in insects

Answer 9

in thorax spiracles - inward
in abdomen spiracles - out

Question 10

what adaptations do insects have from having a branched, chitin-lined system of tracheae with openings called spiracles

Answer 10

branching = large SA
chitin = structural integrity
spiracles = they have valves allowing them to close and open to reduce water loss

Question 11

what adaptations do insects have from having their tracheoles lined with fluid in contact with every tissue

Answer 11

lined with fluid = oxygen can dissolve and diffuse
contact with every tissue = short diffusion pathway, no need for a respiratory pigment (Hb)

Question 12

what adaptation do insects have from having muscles in their thorax and abdomen that contract/relax causing rhythmic movements

Answer 12

ventilation of tracheoles maintains high oxygen and low carbon dioxide - steep concentration gradient of oxygen