L6 - Respiration and Homeostasis

Question 1

How do insects carry out gas exchange?

Answer 1

Via a tracheal system

Question 2

Give 2 reasons why the tracheal system is efficient at delivering O2 to respiring tissues

Answer 2

1) Gas exchange occurs via diffusion, O2 diffusion is 10000 times faster in air than it is in water
2) the tracheal system presents a very large surface area for gas exchange; the trachae divide from 1mm diameter to 0.1um = 1000x increase in surface area

Question 3

What are the 4 patterns of spiracle arrangement and where in the segments are the spiracles found in each?

Answer 3

1) Holopneustic = ancestral condition (cockroaches)
Spiracles in:
- 2 + 3 thoracic
- 1-8 abdominal

2) Hemipneustic = short bodied insects
Spiracles in:
- 1 +2 thoracic
- 1-7 abdominal

3) Metapneustic = mosquito larvae
Spiracle only in the 10th abdominal segment

4) Apeunstic = no spiracles - through the skin or gill respiration (dragonfly larvae)

Question 4

What is meant when an aquatic insect has an open system?

Answer 4

Insects protrude their spiracles beyond the surface film - mosquito larvae and hematocean fly larvae

OR

They inset their spiracles into air bubbles which the carry with them - water boatman and water beetles

Question 5

Give the order, family, genus and species of water boatman

Answer 5

O = Hemiptera
F = Notonectidae
G = Notonecta
S = glauca

Question 6

What is meant when an aquatic insect has a closed system?

Answer 6

this means they either diffuse O2 from water by either:

1) A very thin cuticle overlaying a fine network
2) Tracheal gills
3) Rectal gills - jet propulsion from the rectal cavity

Question 7

Describe O2 transfer from in the tubes into the respiring tissues

Answer 7

O2 is constantly being used at the distal ends of tubes, this creates a partial pressure difference which causes O2 from the proximal end to move down.

Question 8

How does CO2 diffuse out the insect?

Answer 8

CO2 diffuse through tissues more readily than O2, 25% of the CO2 produced by respiring tissues is lost through the cuticle, 75% via the trachae

Question 9

How much O2 can water at these temperatures (Celsius) hold?

a) 0
b) 10
c) 20
d) 30

Answer 9

a) 0 = 4.9%
b) 10 = 3.8%
c) 20 = 3.1%
d) 30 = 2.6%

Question 10

what are the 4 ways in which respiration is controlled in insects?

Answer 10

1) secondary respiratory centres - stimulated by a lack of O2, or accumulation of CO2
2) Diffusion control (brain) - level of fluid in tracheoles can be varied - spiracles can be opened or closed
3) Ventilation control (thorax) - vary intensity or frequency of movements
4) o-ordination by ganglion of each segment

Question 11

What muscles hold the heart of an insect in place?

Answer 11

Alary muscles