Gas Exchnage In Insects

Question 1

What is a tracheae in insects? Explain its structure and function

Answer 1

• An internal network of tubes which are used for gas exchange directly into respiring cells.
• The insects circulatory system does not transport oxygen
• Tracheae have rings in their structure to keep the airways open, to resist negative pressure
• subdivided into smalller tracheoles which extend through the tissue of the insect, allowing oxygen in the air entering the tracheoles to diffuse to body cells, since the distance between the many tracheoles and each body cell is small

Question 2

How do gases move in and out of the tracheal system?

Answer 2

Gas enters and leaves the trachea through tiny pores called spiracles. It moves through the trachea and into the tracheoles

Question 3

What 3 methods does gas move in and out of the tracheal system by?

Answer 3

1. Gases diffuse down a concentration gradient
2. Abdominal muscle contraction during movement
3. Loss of water by osmosis from the ends of tracheoles during anaerobic respiration

Question 4

Explain how gases move in and out of tracheal system by diffusing down a conc gradient

Answer 4

• at the tissue aerobic respiration uses up oxygen, so oxygen levels are low at the respiring tissue but higher in the tracheae, so oxygen diffuses down the tracheole to the respiring tissue.
• carbon dioxide is higher at the respiring tissue and lower in the environment so carbon dioxide diffuses from the respiring tissues where the concentrations are higher down the conc gradient through the tracheoles and out of the spiracles

Question 5

Explain how gas moves in and out of tracheal system using abdominal muscle contraction method

Answer 5

Squeezes the tracheae and so moves air in and out through the spiracles

Question 6

Explain how gas moves in and out of the tracheal system by loss of water by osmosis during anaerobic respiration

Answer 6

• end of tracheoles are filled with water
• when insects carry out a lot of activity, anaerobic respiration occurs producing lactate
• lactate is soluble and lowers water potential in the respiring cells
• water from the tracheoles moves into the muscle cells by osmosis, this loss of water volume from the tracheoles draws more volume of air into the tracheoles
• loss of water now means that diffusion occurs through a gas to the muscle cells and not liquid and this is much quicker

Question 7

How is the tracheole system adapted for efficient gas exchange?

Answer 7

1. Thin walls so short diffusion distance
2. Highly branched/ large number of tracheoles so short diffusion distance to cells
3. Highly branched/ large number of tracheoles so large surface area
4. Tracheae provide tubes full of air so fast diffusion into insect tissues
5. Fluid in the end of the tracheoles that moves into tissues during exercise so larger surface area for gas exchange
6. abdominal muscle contraction to move air so maintains concentration gradient for oxygen/carbon dioxide

Question 8

How do insects reduce water loss?

Answer 8

• small SA:Vol - minimises surface area over which water is lost
• waterproof covering - insects have a rigid outer coving of chitin which is covered with a waterproof cuticle
• spiracles- valves closing (when at rest) tracheae to reduce water loss but opening when insects are active since often is required for aerobic respiration and for the removal of CO2

Question 9

Why is the size of insects limited?

Answer 9

Larger insects will have larger surface area so rate of water loss will be greater, this will limit the maximum size of the insect. If insects were too large it would take too long to oxygen to reach the tissues rapidly enough to supply their needs