GAS EXCHANGE IN INSECTS

Question 1

what does the exoskeleton do

Answer 1

prevents water from evaporating off of surfaces

Question 2

what are spiracles

Answer 2

holes in the exoskeleton with a pair of valves which open and close

Question 3

trachea in insects

Answer 3

network of tubes with rings of chitin

Question 4

tracheoles

Answer 4

dead end tubes with smaller diameters
ends filled with water
end at body cells
contain air sacs where gas is stored

Question 5

4 steps of gas exchange in insects

Answer 5

1. spiracle valves open, air enters the trachea
2. air passes into the tracheoles which have thin walls
3. going directly into body cells
4. tracheoles also contain air sacs where gases can be stored

Question 6

diffusion gradient in insects

Answer 6

oxygen is used so the oxygen concentration at the tracheole decreases meaning there’s a concentration gradient of oxygen and so oxygen diffuses down the concentration gradient from the atmosphere along the trachea and tracheoles into body cells

carbon dioxide is produced so carbon dioxide concentration at the tracheole ends increases so there’s a concentration gradient of carbon dioxide and so carbon dioxide diffuses down the concentration gradient from cells , along the tracheoles and trachea and into the atmosphere

Question 7

advantages of gas exchange in insects

Answer 7

short diffusion pathway for gases
maintains diffusion gradient

Question 8

disadvantages of gas exchange in insects

Answer 8

when spiracle valves open, water can evaporate which can cause dehydration but this can be overcome as spiracles remain closed most of the time as air stored in air sacs can be used
relies on diffusion as the pathway has to be short so the size of the insect is limited

Question 9

why is this insufficient for larger insects

Answer 9

longer diffusion distance
more active so needs more energy
needs more oxygen

Question 10

how are larger insects adapted

Answer 10

ring of muscles that can contract and relax (rhythmic abdominal movement) allowing for a large movement of air in and out of the trachea which increases the concentration gradient

Question 11

another adaptation in larger insects

Answer 11

water in trachea
muscle cells carry out anaerobic respiration producing lactate
water potential decreases in muscles
osmosis occurs from tracheoles into muscle cells
increasing the exposed surface area to air
gases diffuse faster through air than water so greater volume of oxygen is supplied